THE EFFECT OF THE F‘RGPC’RWON OF
SUCRQSE 9N THE VifiCOS-ETY 0F
CORNSTARCH WASTES MADE WiTH
DEFFERENT mum MEDIUMS

Thain for 1410 MM cf M. S.

WIGAN STATE COLLEGE

Marie ioswphfim Fame
”55

'1 H LENS

WWII!“ HWIWHMH

300870 5273
I
This is to certify that the
. thesis entitled

The Effect of Propertion of Sucrose on the
Viscosity of Gornstarch-Pestes Made with 0*
Different Linuid Mediums.

presented by

Marie J. Ferree

has been accepted towards fulfillment
of the requirements for

lie .ster of Sci..nce degree in_Ins_ti..11£ion Athtiristretlon

{dé/fl//f4

ajor professor

Date December 20, 1951+

 

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MSU Is An Affirmative Action/Equal Opportunity Institution
acumen-m

THE EFFECT OF ThE PLOVWRTlUN Uh SUCROSS ON THE VISCOSITY

OF CORNSTAKCH PASTLS MADE WITH DIFFEhLNT LIQUID HEDIUMS

By

Marie Josephine Ferree

A TdESIS

Submitted to the School of Graduate Studies of Michigan
State College of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of

MASTER OF SUILNCE

Department of Institution Administration

Year 1955

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oath was 1300 C. All replications oi the starcn slurries in the inves-
tigation were cooked to a final temperature of 950 C.

In this limited study it was ftutc that the maximum viscosity of
unsweetened and sweetened pastes made with tap water were hither than
were those of similar pastes mace rith other liquid mediums with the
exception of the pastes made with reconstituted whole dry milk solids
containin: 21 per cent sucrose. The maximum viscosities of the control

and all sugar levels of passes made with reconstituted nonfat dry milk

U)

solids were lover than those of sinilar pa tes Wade with the other liquid
mediums. The maximum viscositiss of the control and sweetened iastes

oiids

U)

with all three sugar levels made with reconstitutec whole dry milk

were appreciaoly higher than we?“-" those of sinilar pastes made With dis-

tilled water with the exception of the paste containing 27 per cent sucrose.
In this investigation it was found that the variations of pastes

made with tap water were sore unscatle than were pastes made with the

other liquid neniuns. The paStes made with reconstituted nonfat dry milk

' ‘ . wx fl " ‘ 'P ‘- ’ P ('1 v'r‘“ 7V. ~~ “. .3
solids were Lore stable than were other pastes haoe nlth other illhid

‘ I
”1861 LURE? o

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from the data oi this investigation, it sheared that sucrose, in
concentrations from U to Cl per cent did not show any consistent effect
on the length or cookin" time required to reach initial viscosity rise,
maximum Viscosity, and initial viscosity breakdown of the pastes made
with the four liquid mediums. The addition or 27 per cent sucrose to

the hasic starcn slurries made with all liquic mediums increased the

length of time required for the pastes to reach maximum Viscosity. The

additions of 13 and 21 per cent sucrose did not always alter the cooking

time required for the pastes to reacn maximum Viscosity. however, ad-

ditions of sucrose to the basic slurries appeared to decrease the break-

dewr in viscosity of the pastes as cooking time increased.

A

The tempsrature at raximum viscosity was angreciaely increased by

additions of 2? per cent sucrose to the resit slurries made with the

II' ." \"' ’i. 7.0 $ vv‘f": " . " F ‘i. ' P‘ I ‘ VN“ r‘ I V
iour ll;Uld neciums. ras es name with adfilthnc e: 15 aha Ll per cent

1 in relation to tengeiatnre of

-

sucrose did not snow any eetinite setter.

pastes at initial Viscosity rise or at maximum viscosity.

M‘ o ‘- ‘ . 1 “ Ar‘ -1-< «54— M‘ '.-
The daua irom this limite stunJ Suhiibt that

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tiratios needs to x r‘we lu titer to send: more lull, the e-i4

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cookies tire and paste temierattre on the viscosity of sweetened corn-

" ‘ ~ '0 2“ 1‘...\ '_‘ o - .‘ - r r)-.. ‘7‘ ‘
starcn pastes H308 'w'lth (.liltIC’uC ll’aald 119‘....ilif.:2o

ii

The writer wishes to exyress her siLcere appreciation to
Dr. Pearl Aldrich for encouragement and guidance durizg the
preparation of this thesis.

She wishes to thank Dr. William Baten ior assistance in
statistical analysis of the data, and Dr. Elizabeth Osman and
Professor Katherine Hart for their interest and helpful sugges-
tions. She also wishes to thank the Corn Products Refining
Company for the cornstarch which was used in this investigation

and for the use of the Corn Industries Viscometer.

iii

TABLE OF COKTENTS

INTRODUCTIOE
REVIEW OF LITERATURE.

Chemical Fractions. . . . . . . . . .

Effect of Swelling on Physical Characteristics

Viscosity. . . . . . . . . .

Inherent Starch Characteristics . . .

Treatment of Starch During Manufacture . . .

Concentration of Starch . . . .

Presence of Electrolytes. . . . . .

Effect of Time and Temperature.

Effect of Fatty Acids and Glycerides. . . .

Effect of Sucrose . . .

Gel Properties . . . . . .

Objective Tests for Cooked Starch Pastes .

Viscosity measurements. . . . .
Scott test for hot paste viscosity .
Stormer viscosimeter. . . . .
Brookfield viscosimeter. . . . .
Caesar consistometer. . . . . .
Prabender amylograph. . . . .
Corn Industries viscometer. .
Line-spread tests. . . . . .

Grawemeyer and Pfund test . . . .

iv

TABLE OF COhTEKTS (contd.

Gel strength tests . . .
Exchange Ridgelimeter.
Tarr-Baker Jelly tester .
Fuchs penetrometer.
PROCEDURE. . . . . . . . .
Ingredients . . . . . . . . .
Formulas . . . . . . . . . .
Starch concentration. . . . . .
Sucrose concentration . . . . .
Liquid mediums. . . . . . .
Series A . . . . . . .
Series B . . . . .
Series C . . . . . . . .
Series D . . . . . . . .
Treatment . . . . . . . . . . .
Preparation of the slurries .
Series A . . . . .
Series B . . . . . . . .
Series C . . . . . .

Series D . . . . .

Cooking procedure and viscosity tests .

DISCUSSION AND RESULTS . . . . . . .
Viscosity Tests . . .
Torque values . . . . . . .

Proportion of sucrose . . .

50
5o
50
51

TABLE or comams (contci.)

Effect of liquid medium .

Time and paste temperature

SUMD'ARY . .

CONCLUS IONS . .

LITERATURE C I'l‘ED

55
59
77
80
82

I N IRS}: UC ’I I i} ii

Cornstarch is ingortent in quantity iood production because of
its extensive use as a thickening agent in sauces, gravies, pie
fillings. and cream puddings. Preparat on of these iOOiS involves
relatively sihple methods of combining Lnfl cookirr the ingredierts.
However, difficulties in the preparation of starch mixtures are en-
countered frequently enough to suggest the need of study of the
behavior of such nixtures during cooking. The flflhl consistency of
cooked starch rixtures is nit always predictable; this variation in
consistency of the cooked product is frequently observed in starch
nixtures which cont in relatively high pchentages of sugar.

In cream pudding the cornstarch may fail to thicken the liquid
completely; or, although the desired thickening appears to have
occurred, the pudding may become thin during the cooling period. This
erratic behavior of cream pudding is usually attributed to careless
measuring and handling of the ingredients. However, starch chemists
have also suggested that temperature of cooking, rate of heating, the
presence of electrolytes, and the proportion of sugar to cornstarch
in the mixture may also be contributing factors.

Instructions for making cream puddings and pie lillings presunahly
consider all of the factors mentioned above. Slow heating of the
combined mixture is recommended. The instructions further state that

excessive sugar concentrations will prevent thickening of the final

product. The exact sugar concentration wkich may be expected to cause

this lack of thickening is not mentioned in the literature. nor is
information available which adequately eXplains the increased thick—
ening effect of starch in mixtures containing relatively low concen-
trations of sugar as c~ntrested with control pastes without sugar.

he puroOse of this investigation is to study the effect of the
pronortion of sucrose on the viscosity of cornstarch pastesmade in
four diiferent liquid mediums. The sugar concentrations used lie
within the lower range of tho 9 found in cream tgpe puddings ann pie
iillings. The liquid medium used in the first study is distilled
water. Electrolytes ere pre~ent in the second medium in the form of
the minerels commonly ;ound in unso;tened tap water. fihe liquid
mediums used in the third and fourth series are solutions of dry milk
solids in distilled water. These dry milk solids are of the spray
dry type most frequently used in quantity food production. It is
hoped that the results of tile study will be useful to those interested
in the preparation of cream type puddings and pie fillings of high

quality.

 

REVIEW OF LITERATURE

Prior to 1900, little was known of the chemistry and production
of starch. In a review or the history of starch, Brantlecht (13)
stated that starch and starch flour, manufactured exclusively from
wheat, was known to the ancient Greeks and Egyptians. Potato starch,
first made in Eur0pe during the sixteenth century, was used to stiffen
and give finish to linen. Late in the nineteenth century, Frankel (20)
observed that commercial starches could be manufactured from potatoes,
wheat, maize, and rice. Since that time, carbohydrate chemists have
contributed such to the progress in the many phases of the study of
starch. Since 1930, starch research has clarified the organization
of the starch granule and the structure of the starch molecules and

their behavior in uncooked suspensions and cooked pastes.

Chemical Fractions

In 1881, in the earliest record of starch behavior published in
English, Frankel (20) stated, "Starch belongs to chemically indifferent
substances, 1. e., to the so-called hydrates of carbon, or to that
group of organic bodies which, besides carbon, contains hydrogen and
oxygen in such proportions that they could form water when combined
with each other."

Schoch (42), in a review of starch research, reported that as
early as 1834, the behavior of starch in warm water was interpreted

as evidence that starch wasimޣuogeneous in composition, that it

contained two or more different carbohydrate substances. Frankel (20)
indicated trat e starch and water mixture, heated to 103° C temperature,
contained no starch in solution and that the paste forned in this way
should be regarded as a product of the swelling of the separate starch
granules.

In 1994, Alsberg and Raek (2) experimented with cereal starches
and found that certain varieties of the starchrs gave a blue color
with iocine and thrt other varieties gave a red color. After treat—
ment of the various starches in a hot water bath, Alsberg and Rask
concluded that the starches which gave a red color with iodine produced
more viscous pastes than did the starches which gave a blue color.

Two years later,AJ£berg (1) reported thmt the power of starch to

form pastes might be dependent upon a starch constitutent, anyIOpectin.
He attributed this to the ability of the amyIOpectin to preserve the
suspensoii character of the boiled starch.

Brimbgll and Hixon (15) tested the rigidity of cornstarch pastes
made with nine diflerent kinds of cornstarch. Results Of the tests
showed no defizite relationship between the elasticity and the breaking
strength of the cooked pastes. hicroscopic observations railed to
show noticeaole change in the granules at the temperature of maximum
viscosit" of the pastes. Erinball and hixon concluded that the lack
of correlation between rigidity and viscosity values indicated that
they measured different properties of the pastes. The findings of
Knowles and Harris (33) subst :tiated this theory. By 1947, other
research had given a conclusive answer to the problem of authentic

fractions of starch molecules.

According to Schoch (b2), the two starch fractions were first
isolated by leaching them from a starch solution. The soluble com-
ponent, called amylose,had a linear structure and gave a brilliant blue
color-with iodine. The residue from the starch solution was termed
amylopectin. This fraction had a branched chain structure and gave
only a red or violet color with iodine.

As a result of later research, Schoch (45) proposed that the
linear chain fraction be called A-fraction and that the branched chain
fraction be called B—fraction. He considered the terms amylose and
amylopectin to be too indefinite. Kerr (32) stated that in expressing
the components as A— and B- fractions, it would be necessary to denote
the starch used, name the alcohol used in fractionation. and to state
the conditions under which the fractionation was made. Kerr and other
authors (18, 28, 48) refer to Schoch's proposed A-fraction as amylose
and to his B-fraction as amylopectin.

The properties of the two starch components have been generally
agreed upon by starch chemists. Amylose is a linear polymer which is
composed of glucopyranoside units Joined at the first and fourth carbons
by alpha-glucoside linkages. A solution of amylose in hot water shows
an exaggerated tendency to retrograde or revert to an insoluble state
on cooling. When a hot solution of 5 per cent amylase from corn is
cooled to room temperature. it immediately sets up to a rigid. irre-
versible gel. At concentrations below 1 per cent. the amylose separates
from solution as an insoluble precipitate. This tendency of amylose to

retrograde is often an undesirable feature because it impairs the

stability of starch pastes. Rxanples of this effect can be found in
the formation of insoluble skins on the surface of starch pastes and
in the tendency of starch adhesives to thicken and becone less soluble.
The behavior of any ose in solution is of practical value especially
in those rixtures where gel forration is desired.

In 1934, Hixon and Rundle (30) reported the amylose cortent of

the conron starches as follows:

Tapioca 17%
Rice 1??
Corn 21%
Potato 22%
'1‘”? e F :_ t 24%

Schoch (#3) found that hy renoving the free fatty acids from
cornstarch, the erylose precipitated by fractionation could be increased
from 91 per cent to 28 per cent. Schoch concluded that this treatment
would produce sinilar increases of amylose from other starches which
contained free fatty acids.

Whistler and Weatherwax (52) presented evidence that the znyloSe
content of 39 different sarples of uninprcved Indian corn from New
Mexico, Arizona, and South America varied from 22.2 to 28.3 per cent.
Starches from 7 standard corn belt corns averaged 26 per cent snylose.

Amylopectir is the starch component of most practical value in
the comron uses of starch as thickening agents, as emulsifying agents,
and as sizirg natwrials for paper and textiles. Anylopectin is a
brarched chain fraction of gluCOpyrenoside linkages, Joired at the

first and fourth carbons by alpha—glucosice units. In ad ition, at

 

\)

frequent intervals throughiut the structure, a glucOpernoside unit

*Jo

is do ned at the sixth c rbon by a glucoside unit. A: lapectin con-

stitutes the xejor proportion 03 the connon starches, corn, petsto,

p.
U}

wheat, and rice. Amylcpectin soluble in water at concentrations of
5 and 10 per cent, and such solutions are relatively stable (42).
Accordirg to Schoch and Elder (36), e 30 per cent cookrd paste of the
branched frrction will harden to a gel on standing but the gel can be
readily dissolved by heating to 600 C temp reture.

Schcch and Elder (“6‘ observed that the stzling of bread was be-
lieved to be due to crystallization of the branched chain fraction.
This theory was supported by eViGence th;t ccnred breed, completely
steled by storing for 10 months, could be regenerated to a fresh and
edille condition by brief heating to 1000 C. Schoch 2nd Elder attri-
buted the regeneration to the properties of any epectir since emyIOse
he: a tendency to retrsrrwde. They stated th't the linear starch
fraction was almost cor“leiely retrograded curing the baking and cooling
of breed and that the hzrdening of the bread crumb seemed to represent
the slow association of the branched chain fraction. Heating of the
stale bread caused disassocietion of the branched chain which resulted
in the breed returning to its freshly baked state. Kerr 32) attributed
the staling of bread to the hydrogen bonding of the hydroxyl groups of
both emyloce and amylopectin. This related bondixg, Kerr comncnted,
probably eliminates water molecules. Kerr pointed out that the physio-

chemistry of refreshened breed has not been proved to be identical with

that of freshly baked breed.

Chemists from the National Starch Products Laboratory (3%) re-
ported that a corn known as waxy maize was brought from China to the
United States in 1908. Since that time, plant geneticists have re-
ported waxy strains of potato. rice. sorghum, and barley starches.
These waxy or glutinous starches are entirely devoid ox‘anylose and
consequently give the red iodine color typical of amylopectin. Schoch
and Elder (46) stated that a 5 per cent paste of waxy maize starch
would remain clear and fluid for long periods of time. Schoch and
Elder (#6) concluded that the stability of the waxy starches indicated
they have specific application \here complete freedom from retrograde—
tion is desired.

In 19F1, Hanson and co—uorkers (?4) tested starches fron various
sources for their values in stabilizing precooked frozen gravies and
sauces. The investigators found that the mixtures thickened with
starch from the waxy cereals renained more stable after frozen storage
than the mixtures thickened with starch or flour from other sources.
In addition to these findings, Hanson and co-workers discovered that
sauces and gravies thickened with waxy rice flour were more stable
than those thickened with flours from other waxy cereals. The use of
waxy rice flour produced sauces and gravies which renained completely
stable for almost a year under commercial froren storage conditionS.
In a later study. Hanson and co-workers (25) used waxy'rice flour to
thicken cornstarch pudding-type desserts for frozen storage. The
desserts remained stable after six to nine months of storage at -?3.50 C

temperature. Hanson and co-workers reported that both plain and chocolate

\i')

puddings which were thickened with waxy rice flour showed no visible
change in appearance when thawed for one hour at 25° C temperature after

1Q months of storage at -23.5° C temperature.

Effect of Swelling on Physical Characteristics

The changes which occur in starch granules during cooking have
been the subject of great intere:t and controversy among starch chemists.

On the basis of microscopic observations, Alsberg and Rask (2)
reasoned that each starch granule was enclosed in a menbrane or sac
and that thergranulesfirst swelled and then burst whin a suspension
of starch granules was heated. Brimhall and Hixon (1F) decided that
heat caused starch granules to lose their rigidity and collapse,
giving a wrinkled appearance to the granule walls. A few years later,
the sane investigators (1L) presented evidence that cooked starch
pastes contained granules which had swollen sufficiently to become
deformed under pressure and as a resujt, the pastes were made up of
empty granule sacs and soluble veterinls which had diffused from the
granules and changed the composition of the disptrsing medium.

Bear and Sense (6) explained the changes in potato starch granules
during cooking by comparing them with gas bubbles which had swelled
rapidly in size and then collapsed. Bear and Sansa reasoned that in
the initial stages of hea ing the starch suspension, the granules
expanded more rapidly than fluid could penetrate through them. There-

fore, the investigators conclufied, a low pressure area developed in

10

the interior of the granule with the result that the cell walls col—
lapsed. Hixon and Bundle (3%) reported that evidence indicated there
was no separate menbrane or layer surrounding the starch granules.
These authors suggested that enormous forces within the granule were
released by the swelling of the granule, and the tangled starch dole—
culer, moving outward in the swelling process, created the illusion
of the sec or nenhrare which was observed under the microscope.

In 1950, Bechtel (5) measured the viscosities of diiferent starch
pastes. He established the fact thst the changes which occurred during
the cooking of starch pastes were con,lex. Bechtel described the
changcs as swelling of the starch granules, collapse of the cell wells,
8 lution of the constituen 9; and final disintegration of the granules.
The findings of Cnrpbell and co-work rs (19) substanti ted the con-
clusions of Bechtel. By deans of photonicrogrephs, Campbell ens co-
workers showed that little or no change took place in the starch
granules prior to a rapid increose in the visc0sity of the starch
paste. After exaninlng the shotomicrographs of the swollen starch
granules, the investigators suggested thht the rapid rise in viscosity
of a starch paste could be attributed to the congestion of the swollen
granules. Camptell and CO-workers con luded that a decrease in vis-
cosity could be attributed to rupture of the starch granules and

dispersion of the starch.

ll

Viscosity

Kerr (32) stated that most starch pastes do not possess viscosity
in the sense in which the term is applied to the more perfect fluids
such as water: he suggested that instead they possess anomalous vis-
COsity. A number of authors (5, 10, 18) use the term "apparent
viscosity" to describe the consisteLcy of starch pastes. Kerr (32)
stated that apparent viscosity is shear-dependent viscosity which is
established by the ratio of shearing to the rate of shear. Alsberg
(1) reported thst the viscosity of a starch paste could be attributed
to the Jostling of the swollen granules. The findings of schoch (44)
substantiated the conclusion of Alsberg. Observations of Sjostrom(u7)
indicated that starch paste is a suspension cf whole and disintegrated
granules and the degree of visc0sity is a me sure of the extent to
which they crowd each othwr in passing through a narrow glass tube.

Reports of early starch research were confused by a lack of
agreement of descriptive terninology. A survey of the mire recent
literature shows that much of the confusion has been eliminated.

Kerr (3?) reported that the terms, viscosity and consistency are used
interchangeably by modern starch chemists. In the recent literature,
gelatinize is the term used to describe the changes which occur in

a suspension of starch as it cooks. The term gelation is used to
describe the cooling and solidifying of cooked starch p steS. Gel

is defined as the jelly-like material forned by the coogul tion of

a starch paste when it has cooled.

12

It has been mentioned previously in this investigation that the
final viscosity of a starch paste is affected by the time and tenper-
ature of cooking, the presence of an electrolyte, and the presence
of materials other than starch. According to Kerr (3?), other factors
which may affect paste viscosity are inherent starch chzracteristics,
treatment of starches during manufacture, mechanical injury of the

particles, concentratiwn of the starch, and pH of the cooking medium.

Inherent Starch Characteristics

Kerr (32) commented that it has long been known that the larger
granules of any pzrticmlar type of starch gelatinize more easily than
the smaller granules from the same starch. However, Kerr continued,
it now appears that there may be some correlation between the dis-
persibility of a type of starch and its average granule size.

In a comparison of corn, wheat, tapioca, and potato starches,
Caesar (16) found that the pastes made with wheat starch thickened
more slowly but were more stable than the pastes made with other
starches. After microscopic examination of the starches, Caesar
concluded that the stability of the wheat starch could be attributed
to the fact that the cell walls of the wheat starch granules were
thicker than the cell walls of the other starches.

langels and Bailey (3b) tested the swelling power of hard spring,
hard winter, soft winter, and durum whests in cold gelatinising reagents.

From the results of the tests. the investigators concluded that the

13

chemical differences which cause differences in physical properties
of starch are complex in nature and may be attributable to morpho-
logical differences in the starch granule.

Taylor and Beckman (48) commented that the characteristics of a
cornstarch paste are functions of the physical nature of the starch
granules rather than functions of the chemical nature of the amylases.
When a starch paste is made in the ordinary way, the investigators
commented, a few of the starch granules rupture easily but the majority
of them rupture only with great difficulty after maximum viscosity is
reached.

In a study of physiochemical prOperties of unmodified starches.
Harris and Jesperson (28) found little difference in the viscOsity and
swell of wheat, rice, and barley starches. However, they reported that
the viscosity and swell of potato starch was higher than that of the
cereal starches. Later in the same year, Harris and Jesperson (27)
reported data which showed significant differences in granule swelling
among commercially prepared wheat, barley, and corn starches.

Campbell and co-workers (18) gave an account of methods of eval-
uating starch for specific uses. They stated that the importance of
starch for practical application is closely related to water absorpton.
swelling, and rupture of the granules. Viscosity and gel formation
are characteristics which affect the practical use of starch pastes,

according to Campbell and co-workers.

14

Treatment of Starch During Manufacture

During the manufacturing process, native starches are frequently
modified or altered in some way to make them suitable for particular
uses. According to Kerr (32), the modification of starch may be a
relatively simple process of bleaching, or it may involve extreme
alteration of the chemical and physical properties of the starch
granules. Alteration of the physical characteristics is the most
common modification of starch for food use. Starches which have been
subjected to this type of modification are classified as heavy boiling,
thin.boiling, and mobile starches.

Mobile or dry starch is sold for use as a dusting agent for
pastries and confections. It is characterized by its ability to create
dust. the ability to spread evenly. and great volume per unit weight.
Kerr (32) reported that it is not clearly understood why some starches
possess mobility and others do not. Heavy boiling starches possess
unusually high viscosity. Kerr (32) mentioned that treatment with
chlorine gas is one of the most acceptable methods of increasing the
viscosity of native starch. According to Kerr (32), most of the modi-
fied starches which are marketed have a reduced viscosity below that of
native starch. These are called thin boiling starches. The amount of
thin.boiling starch required to thicken a unit volume of liquid must be
increased beyond the amount of native starch needed to thicken the same
volume of liquid. This is an important factor because the binding
power and other desirable characteristics of starch increase as the

amount of starch per unit of volume of liquid increases.

Caesar and Moore (17) tested the consistency Charges of pastes
thickened with commerci;lly prepared chlorinated and acid-treated thin
boiling starches. They found that the acid-treated thin boiling starch
produced heavy, plastic pastes. As heating was continued beyond the
temper ture of maximum viscosity, thinning or the pastes and dispersion
of the starch appeared to occur simultaneously. The investigators also
h ated the pastes of the chlorinated starch beyond the temperature of
maximum viscosity. They reoorted that in these pastes, the physical
eifect of starch dispersion :ppeared to be me‘e pronounced than did
the Che ical effect of degeneration of the pastes.

SJOstron (b7) COmmcnted that the space occupisd by the suspended
granules of a thin boiling starch was smaller than the space occupied
by granules of he vy boiling starch. Sjostrom reasoned that other
factors affected the difference in fluidity of pastes of he vy and
thin toiling starches; but he suégested that this relation in volume
was, without doubt, the most important.

Campbell and co-workers (1?) reported that chemical and heat
treatment during manufacture affected the characteristics of starch.

They pointed out that starch which had been dried by heat had gelatinized
slightly. The gelatinization increased the power of the starch to absorb
water and also inereised the viscosity of the pastes made with the starch.

The findinbs of Canobell and co-workers were substantiated by
Bechtel (8). In addition, Bechtel stafed, "With increasing modific~tion
of the starch, the consistency of the hot pastes of ucid-modiiied corn—

starches decreases to a gre ter extent than do the rigidity and treaking

l6

stren-tn of their gels." Alsherg (1) reported thst grinding natural,
untreated stsrch granules in a peblle mill decreased their power to
prodice pastes when they were mixed with water in normal concentrations.
Resorts of other starch chemists (44, 32) substantiated the findings

of Alsherg. Harris and Jesperson (2C) studied the effect of various
factors on the swelling of laboratory-extracted cereal starcheS. They
concluded that data on starch research was of no value unless the method

of starch manufscture was reported also.

Concentration of Starch

Anker end Geodes (f) experimented with starch pastes thickened
with diiferent concentrations of corn, wheat, ‘nd potsto starches.
They found thrt en increase in the conCentrction o‘ starch resulted
in an initial rise in vi coeity at a lower tenperstu e, a more rapid
rise in viscosity, and s more extensive bre kdown in the body of the
paste after maximum viscosity was reached.

The observations of Bechtel end Fischer (10) substantiated the
findings of Anker and Geddes. In addition, Bechtel and Fischer found
that incrersed concentretions of tapioca and acid—modified cornstarch
produced the sane effects as incret‘ed concentrations of unmodified
corn, vhe t, enc potato starch s. Brimball and Hixon (If) established
the fact thit each increase beyond the point of a critical concentra—

tion of starch produced enormous increases in viscosity and rigidity

of the resulting pastes.

17

Presence of Electrolytes

The presence of ingredients other than starch and liquid medium
affect the behavior of starch granules during cooking. Gelatinization
and subsequent viscosity breakdown during prolonged cooking of starch
pastes are accelerated by the addition of some ingredients and retarded
by the addition of others.

Kerr (32) demonstrated the effect of salts on the sedimentation
of starch granules. He washed a starch sample thoroughly with distilled
water and then used the washed sample to prepare a starch suspension
to which he added a few drops of a strong solution of sodium chloride.
Kerr reported that the starch from this sample settled more rapidly
than did the starch from an identical suspension which contained no
sodium chloride. He concluded that the rate of starch sedimentation
is increased by the presence of an electrolyte. Richardson and
Higgenbotham (#1) reported that starch had greater swelling power in
the presence of any salt.

Harris and Banasik (26) investigated the effect of electrolytes
on the swelling of cereal starches. One commercial wheat starch and
several laboratory-extracted wheat starches were studied. The starches
were treated with.’lé$03, NaOH, and HCl. The investigators found that
IIOH raised the pH of the dry starch and greatly increased the swelling

of the starch granules during cooking. Treatment with.:3250 lowered

3
the pH of the starch and increased the swelling very slightly. Cooking

in the presence of an acid markedly increased the swelling of the

18

starch at 90° C temperature and above. Harris and Banasik also tested
the swelling power of starch in a solution of water, NaOH, and acid.
They found that the two variables tended to counteract each other and
the swelling of the starch during cooking was decreased. They con-
cluded that the problems of cooking starch in the presence of elec-
trolytes are complex and that the results are not always predictable.
Bechtel (9) adjusted the pH of modified and unmodified starch
slurries with HCl and NaOH. He found that differences in pH altered
the temperature of initial viscosity rise and the temperature at
maximum viscosity. He stated that the pastes with pH value which fell
within the range of 1+ and 7 showed no breakdown after maximum vis-
cosity was reached but the pastes made from alkaline solutions showed
a definite tendency to break. Bechtel used distilled water in the
erperiments which he conducted because he found that tap water produced
unreliable results. Schoch (Mt) stated that the solubility of starch
could be raised by certain chemical modifiers. He mentioned that the
peptizing of starches by alkalies or salts resulted in mushy pastes.
Anker and Geddes (5) reported that maximum paste viscosity de-
creased with an increase in pH value of 5.2 to 6.8. Chapman and
Buchanan (19) found that inorganic acids hasten syneresis of starch
8818. They stated that the inorganic acids caused a'decrease in the
Viscosity of starch pastes after maximum viscosity had been reached
and that the gels formed from these pastes showed definite syneresis.
white (51) presented evidence that starch gelatinized quickly in

suspensions of pH value below ’4 or above 7. He said that both

l9

égelatinization and paste breakdown took place more slowly in pastes of

pi! value which fell within the range of u to V

According to Bisno (1?). variations in the water supply used in
Inaficing pie fillings altered the viscosity of the fillings. He SuntEd
truat a change from tap water to softened water frequently produced

'vitsible changes in the consistency of pie fillings. Bisno observed

truat oie fillinrs made with ta water were more viscous than were the
l L

fiflllings made with softened water. Raine (23) reported that the addi-

txion of a solution of citric acid at the beginning of the cooking of
snvectened cornstarch pastes made it possible to obtain maximum viscosity
:in.en appreciably shorter time than was required for similar sugar-

starch pastes without acid. Rains further reported that additions of

Citric acid to cornstarch pastes decreased the viscosity of the pastes

containing 20 per cent sucrose and of the control pastes made without

sucrose. Hovevcr, citric acid solution did n»t alter the viscosity

of the cornstarch pastes which contained Q0 and 60 per cent sucrose.

.According to Rains, there was no decrease in gel strength of any of

the pastes to which citric acid solution was added.

Effect of Time and Temvcrature

The chenists from the National Starch Products Laboratory (3%)

ireported that the gelatinization tenper tures of starches are not

‘Physical constants. The gelatinization process t kes place gradually

OVer a wide rarge of te peratures. The chenists attributed the lack

oj‘ definite gelatinivation temper tures to the fact thet starch gr rules
riiiler in size. In general, the chemists Stated, the large granules
sgtrxt to swell at a lower terperature th~n do the small granules. when
time tezper:ture of maximum viscosity as been reached, White (‘1)

o
st;fit~d, further cooking, even at a constant temp r ture will result in
a.‘breakdown in the viscosity of the paste.

Alsberg and Rask (2) used the Stormer viscometer to test the con-
szistency of h.5 and 5 per cent concentrations of wheat and corn starches.
Tile starch suspensions were cooked in a water bath which was heated at
srich a rate that the temperature of the suspensions was raised from
2?50 C to above 303 C in the course of #0 to 45 minutes. The investi5a'ors
zreport d no ch :58 in the viscosities o the suspensions below 650 C.

{The viscosities of the p ctes began to rise at 650 C to 68° C and con-
tinued to rise until the to per ture of maximum viscosity was reached.
(reaperwture of maximum viscosity was 910 C for cornstarch and 95° C
for wheat starch, according to Alsberg and Rash. The investigators
concluded that the viscosity changes were caused by gradual changes

in the stgrch granules which took place over a temperature range of
2?0° C to 30° C. From the results of their experiments, Alsberg and
Pkigc concluded also that the gelatinization process of suspended starch
éSr'nules is a gradual one. They the the following ohserVations con-
<2erning the gelatinizatiOn of starch: (l) s.arply drying or thoroughly
‘Netting the starch granules altered the gelatinization tenperzture,

(2) gelatinization was incomplete unless wdequste quantities of water

‘were present. (3) the rate of heating had a definite effect on the

Solstinieation terpernture of starch.

The findin

the extent to

ease with which the granules were softened b;

inherent swelling

granules. After considering

different starches woudd

when boiled and that indiv:

which heet caused

power of the

(l) inlic: ed thwt three f ctors affected

starch granules to swell: (l) the
moi t heet, 2) the
{raniles, (3) the .urface area of the

these fictors, Aloberg concluded that

incre: se their volumes to different degrees
unl granules, even in the same sarple,

would swell to r different extent.
Peckford and Sardstedt (ll) used a spectrophotometer to study
the eelatinizat on Droyerties of Ct rch graniles. Their findings
cor irned tie otservations of Alsberg. In ad'itio , they stated that
within the limits of 2.50 C, the rete oi “Eutlr‘ had no effect on the

viscosity rise of corn end

Bechtel and lischer (10)

peared to attain a plateau in viscosity

whe t st rch susoensions.

reported thpt most types of

after one hour or cooking at

90° C to 92° C. Vigorois agitn ti or produced a rapid decrease invis-
cosit" hut differences in the rete of "gitation did not appe r to
alter the pasting process of the starch.

Bechtel (9) used the Corn Incustries viscom‘ter to nee ure the
p stin3 ch 18 teristics of different starches. He found that both
tine and tenper ture affected the viscosity of st rch pastes. Rapid
heating of the paste lowered the tetper»ture 0f iriti l viscos it;’
rise, decreased the length of time the starch pastes needed to be

heldz

of the pastes.

t 300 C to re ch m ximum vis co s tv

Bechtel concluded that

:nd increased the viscosity

0 9

thvre appeared to he a definite

22

temperature at which each type of starch gelatinized at a uniform rate
and at which the paste could be held for a reasonable length of time
without excessive breakdown of paste viscosity. For unmodified cornr
starch. this temperature was 90° C, according to Bechtel. The findings

of Bechtel have been confirmed by other investigators (17, 16, 6).

The Effect of Fatty Acids and Glycorides

It has been known for many years that some starches contain fatty
acids (32). During purification, rice, tapioca, and corn starches
yield relatively large amounts of combined fatty acids. However. the
tuber starches appear to have no fatty acids associated with them.
Schoch (#4) stated that the short, Opaque characteristics of the pastes
made from cereal starches are attributable to the presence of fatty
acids. Schoch (db) found that the pasting characteristics of starch
from which the fatty acids had been extracted were different from the
pasting characteristics of natural starch. He reported that dofatting
unmodified cornstarch lowered the maximum viscosity to about one-half
that of the original starch. Later research by Bechtel (9) substantiated
the findings of Schoch.

Mitchell and Zillman (35) studied the effect of fatty acids on
the viscosity of nonwaxy starches. Among the factors which influenced
the physical properties of the starch and fatty acid mixtures were the
preportion of starch to water and the amount of fatty acids present.
The investigators concluded that soaps, fatty acids, and perhaps natural

fats increased the viscosity of starch pastes.

23

In.practical usage, glycerides in the form of milk fats are fre-
quently present in starch pastes. The Brookfield viscosimeter was
used by Jordan and co-workers (31) to measure the viscosity of corn-
starch puddings made with homogenized and nonhomogenised milk. Nine
different levels of cornstarch were used to thidken puddings made with
each type of milk. The levels of cornstarch ranged from 2.bl to 5.63 per
cent, based on the weight of the milk. The puddings were cooked over
boiling water to 91.50 0 temperature. Analysis of variance for the
puddings showed no significant difference in the consistencies of the
puddings which.contained less than.3 per cent cornstarch. However.
the analysis of variance for all the puddings containingnore than 3 per
cent cornstarch showed that those made with homogenized milk were signi-
ficantly thicker than were those made with nonhomogenized milk. The
investigators suggested that the differences in viscosities might be
attributable to the relative surface area of the fat globules in the
two kinds of milk. They reasoned that the increased surface area of
the fat globules in homogenized milk increased the amount of fat exposed
for colloidal reaction. They further reasoned that the increased
availability of the fat in homogenized milk might be considered equivalent
to an increase in the amount of fat in the starch paste.

In a second part of the study, Jordan and co-workers prepared
cornstarch puddings with.skim milk to which they added varying amounts
of clarified butterfat and refined cottonseed 011.. Jordan and co—
workers stated that the results of the second group of tests supported

the belief that the higher viscosity and greater firmness of puddings

24

made with homogenized milk were associated with the greater surface
area of the fat globules.

Morse and associates (36) tested the effect of nonfat dry milk
solids on the viscosity and gel strength of starch pastes. In the
first part of the tests. slurries were made of flour, nonfat dry milk
solids, and water. The amount of flour was kept constant and the
amount of nonfat dry milk solids was varied. The investigators dis-
covered thzt increased amounts of nonfat dry milk solids increased
the viscosity and gel strength of the starch pastes.

Morse and associates also studied the effect of fat and salt on
the viscosity and gel strength of starch pastes made with additions
of nonfat dry milk solids. They reported that additions of fat ap-
peared to have no effect on the viscosity of thin pastes. However,
additions of fat caused significant decreases in the viscosity of the
thick pastes. Increases in the amount of salt only slightly decreased
the gel strength of any of the pastes, according to Morse and associates.

In a report on the use of starch in pie fillings, Trempel (50)
stated that large amounts of eggs. fat, dry milk solids, and sugar
interfered with the swelling of starch granules during the pasting

process.

The Effect of Sucrose

Nevenzel (39) used the Stormer viscometer to study the effect of
varying concentrations of sugar on starch gels. She found that the

cold gel of a 5 per cent cornstarch paste containing 5 per cent sugar

25

concentration did not hold its shape when turned out of the.mold. With
additions of 15 and 30 per cent sugar, the gel strength of the corn-
starch pastes gradually increased. However, Nevenzel reported that

the cold gel from the paste containing 30 per cent sugar was weaker

than the gel from the paste containing 15 per cent sugar. When the
sugar concentrations were increased to 50 and 60 per cent, the resulting

gels were soft or liquid. From the studies of photomicrographs of the

 

starch pastes, Revenzel concluded that, at a specific temperature, the
starch granules in the pastes containing sugar had swelled less than
the starch granules in the pastes without sugar.

Woodruff and Nicoli (53) cooked 5 per cent slurries of corn, wheat,
rice, potato, and cassava starches with four different concentrations
of sucrose. The samples were cooked, poured into molds, and allowed to
stand for 2h hours before they were tested for firmness. With additions
of 10 and 30 per cent sucrose, the root starches formed increasingly
softer gels. The additions of 50 and 60 per cent concentrations of
sucrose produced syrups instead of gels. The same percentages of sucrose
were added to 5 per cent slurries of cereal starches.?§Each addition of
sucr0se produced an increase in transparency and tenderness of the cold
gels. The addition of 50 per cent sucrose formed a gel which would not
hold the shape of the mold and the addition of 60 per cent sucrose to
the cereal starch slurry produced a syrup.

Trempel (50) stated that sugar raised the gelatinization tempera—
ture of starch and interfered with the swelling of the starch granules.

For making pie fillings, Trempel suggested that the amount of sugar in

the mixture should not be more than three and one-half times the amount
of starch in the mixture during the pasting process. If increased sugar
is needed for palatability, it should be added after the pasting of the
starch is completed.

The findings of Morse and associates (36) indicated that the

r'"

viscosity of thin starch pastes was increased by additions of sucrose.
However, the investigators stated that pastes made from flour and water
,were preportionntely more viscous wit added sug:r than were pastes
containing flour, water, nonfat dry milk solids, and sugar.

J{faster (29) reported the effects of increasing concentrations of
sucrOse on the paste and gel strength of several types of starches.
She stated that a paste containing 6.5 grams of cornstarch and 100
grams of water formed a paste which was considered standard. The
additions of 15.9 grams of sucrose to the standard paste produced an é
increase in viscosity. However. further increases in the level of
sucrOse progressively decreased the maximum viscosity of the pastes.
Increases in the level of sucrose also increased the temperature of
the initial viscosity rise and the temperature of maximum viscosity
of the pastes. Hester found that the gels of the standard pastes
containing 15.5jgrams of sucrose were slightly less firm than those
of the standard paste without encrose. Further increases in sucrose
concentrations produced gels which wOUld not hold the shape of the
molds. The highest sucrose concentrations, 31.6 grams and 39.5 grams,

)/
formed thin pastes.

27

Rains (93) tested the maximum viscosity of 12 per cent cornstarch
pastes in which sucrose constituted 20. b0, and 60 per cent of the
weight of the liquid. #Bhe found that the pastes containing 20 per cent’
sucrose were thicker than were the control pastes without sucrose.

With additions of MO and 60 per cent sucrose, the maximum viscosity of
the pastes progressively decreased. Hains stated that higher tempera-
tures and much longer cooking periods were required to obtain maximum

viscosity of starch pastes when increased proportions of sucrose were

added.

Gel Properties

It has been mentioned that Erimball and Hixon (15) reported dif-
ferences in the properties of hot and cold starch pastes. Further
studies by other investigators have emphasized these differences.

In experiments with various root and cereal starches, Voodruff
and Nicoli (53) reported that maximum gel strength was obtained from
the starches which had been cooked to a temperature of 90° C or above.
The report of Bisno (12) confirmed the findings of Woodruff and Nicoli.
Maximum gel strength, Bisno reported. was produced by rapidly heating
the starch paste to 900 C and then renoving it immediately from the
cooking container. The findings of Bechtel (8) indicated that the
effect of temperature of cooking on the gel prOperties of starch
pastes varied with the degree of modification of the starch. The

rigidity and breaking strength of the starch increased with increased

28

modification of the starch, according to Bechtel. These conclusions
were supported by the evidence that acid-modified starches which had
been cooked to 91° C and then cooled to room temperature showed greater
increase in rigidity and breaking strength than did the unmodified
starches which had been given the same treatment. Bechtel (8) cooked
other pastes to temperatures of 9h° C and above. He found that gel
strength of pastes cooked to 94° C was greater than the gel strength
of pastes cooked to lower temperatures but gel strength decreased if
the pastes were cooked to temperatures above 94° 0.

According to Knowles and Harris (33). environmental conditions
during growth of wheat affected the gel strength of pastes made from
hard and soft wheat starches. Knowles and Harris also indicated that
the stage of maturity of the wheat affected the gel strength of the

starch pastes.

Objective Tests for Cooked Starch Pastes

The characteristics which determine the usefulness of starches
for practical application are viscosity, plasticity. gel strength, and
rigidity (32). Measurements of these characteristics are made in

terms of hot paste viscosity and cold paste body.

Visc0§itz‘m§asugements

Objective measurements of viscosity are made on both hot and cold
pastes. Several accepted tests of this kind are described on the

following pages.

29

§£gjt test forghot paste viscosity (3;). The Scott test is widely
used for determining hot paste visc0sity. A slurry is made of 280
cubic centimeters of distilled water and a quantity of starch of
known pH value. The slurry is leed in a German—silver beaker and
then the beaker and contents are placed in a boiling water bath. The
starch mixture is heated for 15 minutes with constant stirring. Two
minutes prior to the end of the cooking period, 200 cubic centimeters
of the paste are transferred to a Scott viscosity cup which is also
in the water bath. At the end of the 15 minute cooking period, the
orifice on the bottom of the cup is raised and the time, in seconds,
is noted for a given volume of the paste to fall into a graduated
cylinder. The time, in seconds, is the specific Scott viscosity value
of the starch.

The viscosity may also be considered as relative viscosity in the
sense thrt standard starches are used to set up permissable limits of

variation in the viscosity of other starches to be tested by this method.

§jormer viscgggmeter (32). This instrument is used to measure cold
paste body. The viscosimeter consists of a cylinder immersed in the
test paste which is held in a metal cup surrounded by a water bath.

The imLersed cylinder is rotated by a free—falling weight acting
through a gear and pulley system. For the test, the starch is gel—
atinized in the manner described for the Scott viscosity test. Heating
is continued for the full 15 minute cooking period without transferring

the paste to the Scott viscosity cup. Instead, the paste is placed in

30

a closed container and immediately put into a 250 C constant tenpera-
ture bath. At the end of a definite aging period, the surface skin on
the paste is carefully removed. The remaining paste is gently stirred
with a spatula and then transferred to the cup of the Stormer visco-

meter. The viscosity of the prste is noted at 25° C temperature.

Brookfield viscosimeter L32). This torsional viscometer contains
spindles of various capacities which are driven by a synchronous motor.
Viscosity, in terms of poises, is recorded as the force which the

thickening paste exerts on the spindles.

gassar consistonetergfilé). This continuous recording instrument gives
a complete history of the consistwncy changes of starch pastes. The
recorded changes include the gelatinization tenperature of the starch,
peak viscosity which is obtained.with a definite cooking procedure,
specific viscosity after a prescribed cooking operation, rate of in—
crease in paste body with decreased tenperatures, and cold paste body
after a specified cooling period. For the test, the starch suspension
is poured into a cooking beaker which is surrounded by a heating bath.
As the temper ture of the heating bath is raised at a regular rate,
the starch suspension is stirred by a paddle. The paddle is connected
by a sh ft to a.const2nt speed electric motor. Changes in viscosity
or paste body are indicated by the difference in the electrical input
needed to maintain a constant motor speed. When the cooking of the
starch paste is completed, cold water may be put into the bath to

cool the paste. To obtain significant differences in observed viscosity

values, it is recommended that relatively high starch concentrations

be used.

31

Brabe e o a h . The Brabender amyIOgraph is used to measure
the pasting characteristics of starches. With this instrument, the
paste is held in a cup surrounded by an air bath for temperature control.
The cup is revolved at a constant speed. The measuring device consists
of a disc to which are attached several short rods extending into the
paste. This mechanism serves as a stirring unit also. The torque
impressed on the measuring unit is transmitted to a torsion balance.

A continuous, graphical record is traced by the instrument over the
entire period of the test. The temperature may be increased at a

fixed rate and may be held at any level by a thermostatic control. By
switching off the heating unit, the paste may be cooled to any desired
temperature. A cooling coil is provided for circulating cold water and

accelerating the cooling of the paste.

Corn Industries viscometer. Bechtel (7) tested various cornstarches
with this instrument and showed its suitability for research. The

Corn Industries viscometer measures and records the viscosity of starch
pastes for any desired cooking period. The slurry to be tested is
poured into a stainless steel cooking beaker which is set in a ther-
mostatically controlled liquid bath. The operating temperature of the
liquid bath is usually 92° C to 96° C. The cooking paste is stirred

at a constant rate by electrically driven paddles which remove the
layer of pasted starch from the walls of the cooking beaker. This con-
stant removal of the pasted layer improves the efficiency of the heat

transfer to the body of the paste and results in a nearly uniform paste

temperature. A seprrately mounted propeller, driven through the gear
differential, stirs the center of the paste and also serVes as a means
of measuring viscosity changes. The force which the propeller enr
counters is continuously balanced by a dynamometer, consisting of a
weighted arm which moves through a vertical arc. A series of inter-
changeable weights are provided for the dynamometer so that it covers
a relatively wide range of torques between 950 and 2000 gram-centimeters.
Attached to the dynanometer is a pen which automatically records the
continuous viscosity cha ges of the paste. Evaporation of moisture
from the cooking paste is prevented by the cover of the beaker which
acts as a condenser. The viscosity changes of the paste are recorded
in terms of torque which is the me sure of the force the propeller en-
counters as it turns through the thickening paste. The apparatus can

be adjusted for a cooling period if desired.

Line spread tests

w

Grawemeyer and Pfund (22) have developed an objective test for
measuring the flow characteristics of hot or cold starch pastes. This
method, or its modification, is often used to determine the spread of

cream pudding or pie filling.

Grawemeyer and.Pfund test (22). In this test, a flnt glass plate is
placed on a surface which has been checked for evenness with a spirit
level. A diagram of concentric circles is placed beneath the glass.

The smallest circle has a diameter of two inches and the surrounding

33

circles are graduated at intervals of one-eighth inch. A hollow cylinder,

the exact diameter of the innermost circle, is put in place over the

center circle and filled with the material to be tested. The material

in the cylinder is leveled with a spatula and the cylinder is carefully

lifted. The product is allowed to spread for two minutes and readings

are taken at 1+ widely separated points which mark the limits reached

by the product. The average of the four readings is recorded as the

line-spread of the sample.

Ge; strength te sts

The gel strength of starch pastes has been measured by a variety

of instruments embodying different principles. Kerr (32) reported that

several of the instruments are the rigidometer, Terr-Baker Jelly tester.

blunt plunger type penetrometer, and the tube type penetrometer. The

rigidometer measures the rigidity of a gel or its lack of elasticity;

the {Parr—Baker Jelly tester gives a value which is preportional to

the force necessary to rupture the gel. The results of tests with the

blunt plunger type penetrometer are a combination of plastic and

alei-stic effects. The tube type of plunger measures the resistance of

gels to cutting action.

We Ridgelimeter (22). For this test, the starch pastes are

atoned in Jelly glasses provided with sideboards. At the end of a

8Pecific aging period, the sideboards are removed and the excess gel

18 sliced off even with the rim of the glass. Each gel is removed

from the glass by inverting it on a glass plate. The gel is allowed

31+

to stand on the plate for two minutes and then a micrometer screw is
adjusted and the per cent of sag is read. The rigidity of the gel is

interpreted in terms of the per cent of sag.

Tarr—EL'J-cer ell ter ($22. For this test, the starch suspension

     

is placed in a porcelain cup and cooked in a boiling water bath for
30 minutes. The cooked paste is cooled and immediately covered with
a. film of mineral oil. After the paste has aged in a water bath at
25° C for one hour, the mineral oil is poured from the "pa ste and the
paste is then placed under the plunger of the tester. With 500 cubic
centimenters of water in the Jelly tester, the flow of water is ad-
justed so that it raises in the manometer column at the rate of 60
centimeters per minute. The manometer is read when the gel breaks.
The gel strength is recorded as the height in centimeters reached by

the water column in the manometer at the breaking point of the gel.

”AchsJenetrometer. Kerr (52) stated that the Fuchs penetrometer
Provided a sensitive and accurate method of determining the gel
Strength of a starch paste. ,xFor this test, the cooked starch paste
is aged for a definite period of time and then the surface skin of
the gel is removed. The plunger of the penetrometer is adjusted so
that it rests on the t0p surface of the prepared gel. A weight is
it41posed on the plunger in a receptacle on top of a vertical rod which
is attached to the top of the plunger. The plunger consists of a
Sh'Eu'pened, hollow tube that is highly polished. This tube resembles
a. large cork borer. The plunger is released, and the time, in seconds,
reQuired for the hollow tube to cut into the gel up to a certain depth

18 noted.

PROCEDURE

Ingredients

Four different liquid mediums were used in making the starch
slurries in this study. The four mediums were distilled water, a
ssingle sarple of tap water with a value of 16 grains hardness, a
scilution of nonfat dry milk solids in distilled water, and a solution
c>f whole dry milk solids in distilled water.

The cornstarch for this project was supplied by the Corn Products
Ileafining Company of Argo, Illinois. The lot used was taken from a
regular run of their commercial starch prepared for food uses. Ac-
chrding to Bechtel (8) the standard Scott viscosity for this type of
starch is 76.

The entire lot of cornstarch, packaged in polyethylene bags, was
sstcbred in a covered, stainless steel bin at room temperature.

Superfine granulated sugar was obtained from the College Food
Stores. The sugar was kept at room temperature in a covered, water-

t1glut container.

The supply of nonfat dry milk solids for this investigation was
Obtained from the Michigan Milk Producers Association of Adrian,
Michigan. The nonfat dry milk solids were manufactured by the spray
dry process and were sold for home and institution food preparation.

COmposition of the nonfat dry milk solids was as follows (3):

36

Butterfat 1.00%
Minerals 8.00%
Moisture 3.00%
Protein 37.00%
Lactose 51.00%

The supply of whole dry milk solids was purchased from the Borden
Chompany of New York City, New York. These dry milk solids were manu-
.f£1ctured by the spray dry process and sold under the trade name, Parlac.

Composition of the whole dry milk solids was as follows (1+0):

Butterfat 28.00%
Minerals 5.80%
Moisture 2.00%
Protein 26.50%
Lactose 37.70%

Because the mineral content of tap water varies from day to day,
the entire volume of tap water used in this study was drawn from the
faucet at one time. The water was stored at room temperature for a
period of two days in a covered glass bottle. A sample of the tap
“Eitexr was analyzed for hardness by the college sanitarian.

The distilled water used in this investigation was freshly distilled
arni stored at room temperature in a covered glass bottle for a period

01' not more than three days.

Formulas

S tare conc en trat ion

As a preliminary step in this study, cream pudding recipes for

h“Dine and institution use were checked. The percentage of cornstarch

in these recipes was found to vary from 8.3 to 13 per cent of the
weight of the liquid (N, 71, U9). Eleven per cent cornstarch was
selected for this study after tests with 11 and 12 per cent cornstarch
Ipastes. In these tests. it was found that 12 per cent cornstarch
gr;stes made with the solutions of dry milk solids in distilled water
unare too viscous to be handled by the instrument used to record vis-
ccasity. The prOportion of cornstarch to‘water was kept constant in

all replications of the starch slurries in this study.

Sucrggg concentration

In the cream pudding recipes which were checked, sugar content
varied from 25 to 55 per cent of the weight of the liquid. Sucrose
(reticentrations of 15, 21, and 27 per cent of the weight of the liquid
awarwa arbitrarily selected for this study. These low ranges of sucrose
vwsrws chosen because information concerning the effect of the prOportiQn
Of‘ smicrose on the thickening of starch pastes is limited and because
t1¥e increased thickening effect of st rch in mixtures containing
Péilaitively low concentrations of sucrose has not been adequately ex-
PlfiiJned. A basic starch paste without sucrose was used as the COLtTOl
f0]? teach liquid medium. Because the beaker of the viscometer was
d981gned to cook and stir a total volume of one liter, the weights of
starch, sucr0se, and liquid medium, based on the desired percentage
relationships, were calculated to yield a total volume of one liter of
each mixture. Allowance for the displacement of the dry ingredients
111 'the liquid medium of each replication was based on actual measure-

n‘edlt of the starch slurries in a preliminary step in the investigation.

L.)
(D

L iguid mediums

Series . The purpose of this series was to determine the effect of
the proportion of sucrose on the viscosity of cornstarch pastes made
with distilled water. Table llists the ingredients and the quantities

of each used for Series A of the study.

Series B. To study the effect of the proportion of sucrose on the
viscosity of cornstarch pastes made with tap water, Series A t-ras
repeated with tap water substituted for the distilled water. Table 2

lists the ingredients and the quantities of each used for Series B.

Series C. Series A was repeated with addition of 8.52 per cent non-
fat dry milk solids, 'based on the weight of the liquid. The purpose
Of this study was to determine the effect of the proportion of
sucrose on the viscosity of cornstarch pastes made with a solution of
nonfat dry milk solids in distilled water. The percentage of nonfat
dry milk solids was consistent with the amount of nonfat dry milk
solids found in fluid skim milk. The formulas for Series C are

1 isted in Table 3. Allowance for the displacement of the dry milk
sOlids in distilled water was based on actual measurement of the dry
iIlgredients and the solution of nonfat dry milk solids in distilled

Water.

aeries D. To study the effect of the proportion of sucrose on the

VisCOsity of cornstarch pastes made with a solution of whole dry milk

BOlids in distilled water, Series A was repeated with addition of

39

12.01 per cent whole dry milk solids, based on the weight of the

liquid in the formula. The concentration of whole dry milk solids

used in the liquid medium for this series was consistent with the

whole dry milk solids found in whole fluid milk. Table 4 lists the
ingredients and quantities of each which were used in Series D. Allow-
ance for the displacement of the whole dry milk solids in distilled
water was based on actual measurement of the dry ingredients and the

solution of whole dry milk solids in distilled water.

to

Table 1. Formulas for Series A, distilled water medium.

 

 

__Cornstarch Sucrose Distilled Water
Variation Gm. % Gm. s Ml.
I 106.7 11 0 0 970
II 100.3 11 136.8 15 912
III 97.5 ll 186.1 21 886
IV 9Q.6 11 232.2 27 860

 

..

 

Table 2. Formulas for Series B, tap water medium.

 

 

 

Cornstarch Sucrose Tap Water
Variation Gm. if Gm. % M1.
I 106.7 11 0 0 970
II 100.3 11 136.8 15 912
III 97.5 11 186.1 21 886
IV 94.6 11 232.2 27 860

 

H!

 

Table 3. Formulas for Series C, nonfat dry milk solids plus distilled
water medium.

 

Cornstarch Sucrose Distilled Water Nonfat dry milk

 

 

solids
Variation Gm. % Gm. % M1. Gm.
I 102.1 11 0 0 927.8 79.0 8.52
II 95.6 11 130.“ 15 869 74.0 8.52
III 92.1 11 175.8 21 837 71.3 8.52
IV 89.5 11 239.6 27 813.3 69.3 8.52

‘_.

_..__ W

 

 

Table 4. Formulas for Series D, whole dry milk solids plus distilled
water medium.

Cornstarch Sucrose Distilled Water Whole dry milk

 

 

_~ solids ¥__
Variation Gm. % Gm. % M1. Gm. %
I 100.7 11 0 0 915 109.9 12.01
II 9h.3 11 128.6' 15 857 102.9 12.01
III 90.8 11 173.3 21 825 99.1 12.01

IV 88.2 11 216.5 27 802 96.3 12.01

1+1

Treatment

Preparation of the slurries. All the ingredients for the starch
slurries were weighed on a Torsion balance. Glazed weighing paper
unas used to line the balance pens for weighing the starch, sucrose.
aund dry milk solids to minimize losses in transferring materials to
laeakers for blending the ingredients. The water was weighed in a
ln-litcr glass beaker. A narrow rubber scraper was used to remove the
ruesidue of the dry ingredients from the weighing papers. The quantities
CLf ingredients needed for the three replications of each starch slurry
vnere weighed at the beginning of each testing period but were not
xni.xed together until immediately before starting the testing procedure.

Because investigators have established that maximum viscosity of
ccooked starch pastes is affected by the length of time the starch
slsurry stands before cooking, care was taken to mix the slurries
Qtrickly and to keep the mixing time constant for each replication.

111 the preliminary tests, technique was developed so that total mixing
time approximated one and one-hr-lf minutes.

Temperature of the ingredients is another factor which has been
fVDILnd to affect the maximum viscosity of a cooked starch paste. The
tennperature of the uncooked starch slurries in this study was 26° 0,
1L 31° C when the slurries were poured into the preheated, steel cooking

b e 83:9? 0

uz

Series A. For the control slurry, without sucrose, the starch was

'gilaced in a l-liter glass beaker. One-third of the distilled water

‘vxas added to the sterch, and the mixture was stirred with a narrow

Ivuhber scraper until it was free from lumps; then half of the remaining

snater was added to the slurry. The-slurry was then poured quickly into

tihe cooking beaker of the viscometer. The remaining one—third of the

1.1QU1d.vaa used to rinse the gl:ss beaker, and this rinse was added

immediately to the mixture in the cooking container.

The addition of sucrose to the starch made it more difficult to

Ioroduce a slurry which was free from lumps. For the variations with

ssucroSe, the starch and sucrose were placed in the glass beaker and

aware thoroughly blended in the dry form. Only enough distilled water

to moisten the ingredients was added and the mixture was stirred vig—

<>rously to produce a smooth paste. With increase in the level of

sucrose, the first liquid addition was gr dually decreased to produce

a smooth slurr‘. When the slurr wzs free from lumps all but one-
A I

t ird of the remaining water was added. The remainder of the water

was used to rinse the beaker and this rinse was then added to the

slurry in the cooking beaker.

Series B. Tap water at 26° C tenper ture was sutstituted for the

distilled water in the uncooked st rch slurry. Proportion of ingredi-

ents and mixing procedure was the same as described for Series A.

Series C. Series A was repeated with the addition of 8.52 per cent

nonfat dry milk solids, based on the weight of the water. In the

43
trial studies the starch,

sucrose, and nonfat dry milk solids were

3gilaced in a glass beaker and thoroughly mixed in the dry state. The
tuaater was added to the dry ingredients and the slurry was mixed in

‘tlne manner described for Series A. It was found that this method of
<3c3mbinin5 and mixing the ingredients did not produce a smooth slurry

Viithln the time limit established for total mixing in Series A and B.

flTherefcre, the inVestig tor decided to reconstitute the nonfat dry

nailk solids for use in the repli“utloxs in this s<ifcs instead of com-

}:ining the milk solids with the other dry ingredients.
The nonfat dry milk solids were reconstituted in individual

szoluticns immediately before the mixing time of each slurry. One-

tLhird of the distilled water needed for each replication was set aside

:for use in the final rinsing procedure. The remaining two-thirds of

1;he distilled water was used to reconstitute the noniat dry milk solids.
I3ecause dry milk solids dissolve mush more easily in warm water, the

(distilled water was heated to a U50 C temperature in a hot water bath.

'When the desired temperature was reached, the distilled water was
removed from the heat and the nonfat dry milk solids were sprinkled

over the surface of the water. The mixture was stirred with a narrow

rubber scraper only enough to moisten all the dry milk solids and was

then allowed to stand for 20 minutes. During the standing period,

the solution was stirred occasionally with a narrow rubber scraper.

At the end of the 20-minute period, the solution of nonfat dry

milk solids in distilled water was placed in a cold water bath and

cooled to a temperature of 26° C, i_lo C. Total cooling time was

44

ealgrnxndrmtely 10 minutes. In the replications in this series, treat-

:niernt of the other dry ingredients and mixing of the slurries were the

sseume as described for Series A except that the solution of reconstituted

milk solids replaced distilled water.

The beaker which had held the solution of dry milk solids in

C35.stilled water was rinsed with the water set aside earlier for this

IDILTPOSG. The rirsings were poured into the beaker in which the starch

sslgurry had been Hiled and these total rinsings were added immediately

‘t<) the mixture in the cookirg container.

Sieqjgs D.

Series A was repeated with addition of 19.01 per cent whole

Cirjrnfllk‘solids, based on the weight of the water. Heating of the

éiistilled water rad recorstituticn of the whole dry milk solids were

';e as descrited for Series C. Treatrent of the other dry ingre-

Ciients and Hiring of the slurries were the sane as described for Series

It except that the solution of reconstituted dry milk solids replaced

tiuadistilled water. Rinsing of the beakers was the same as described

for Series C.

‘onhingppfccedure and viscosity tests. The Corn Industries Viscometer,

described in the review of literature, was used for cooking the starch

slurries and for measuring the visco:ity of the hot pastes. Figure 1

.sas a cross section 61L???“ of the viscometer. Bechtel (7) reconnends

that the stirrer of the viscometer be operated at standard speed during

general laboratory testing of starch pastes. For this reason, standard

speed was used throughout the investigation.

“5

When highly viscous mixtures are tested in the visconeter, it is

Iiezcessar; to extend the range of the weight arm of the dynamometer.

Irc>r testirg 11 per cent star

ch mixtures, Bechtel (7) suggests that the

215300 gram-centimeter veight be used. This SUpplenentery weight wee

gilficed on the weight arm and was kept there for the duration of the

estudy.

The viscometer has a hot water bath (Fig. 1) which is thermo-

sataticelly controlled. Distilled water is used as the bath liquid

innless a cooking tezperature of 1000 C is desired. When the bath is

tised at boiling terpersture. steaming may cause excessive evaporation

:fzmm the bath which makes it advisable to use antifree7e or glycerol

. O U n I
Insating mediums with b0111n5 p01nts above 100‘ C. Pecause the investi-

égator wished to cook the st rch slurries at the boiling temperature

(of water in this study, a glycerol-type permanent cntifreese was used

Eis the bath liquid. Before sttrting the tests described in this in-

‘vestig tion, the temperature of the bath was adjusted. A thermometer

‘was inserted into the liquid, the he.ting element was turned on, and

the thermostat was adjusted to hold the bath at a constant temperature

of 1000 Cti l0 C. The temperature of the bath was kept constant

throughout the investigation.

When the bath temperature had been adjusted, the stainless steel

beaker and the stirrer were pleced in position (Fig. 1). The confenser

cover (Fig. l) was put on the beaker and the air inside the beaker was

heated to 700 C terpersture. Then the motor which controlled the

stirrer was started and the slurry was mixed. The front hnlf of the

Iigure 1. Sectional drawing of the Corn Industries Viscometer (7)
l. Recorder and dynamometer (Dynamometer not shown)
2. Cable from viscometer to recorder.
3. Cable drum
4, 5, 6, 7. Gears of sun and planet differential
8. Worm, turned by synchronous motor (not shown)
9. Norm gear
10. Spring pins for holding center shaft

11. Coupling to attach stirrer

 

12. Condenser cover

13. Liquid bath

14. Overflow

15. Drain cock

16. Starch beaker

1?. Electric heater, therm0statica11y controlled
18. Scraper blades

19. Propeller

20. Thermometer in paste

21. Thermometer in bath

 

 

 

 

 

 

HI?

’1 HIM]
T

 

 

 

 

 

 

 

 

 

 

1+7

 

 

 

 

 

 

 

 

 

@J
) §m
2mm /rHy m a

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

§§ x]
n
We

a
AW /
AEZZZZZZQvazfllgfl

a? n z
T Ntk HNHHNHHH H > . [I
l 4 . i ., A. if I
A r .r/4 A . 4 4 A ,

rj/

4%
Q:
j

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

-—) unmnn 1111111]

 

 

 

 

Sectional Drawing of the Corn Industries Viacometor.

 

Figure 1.

48

c:ondenser cover was removed and the slurry was poured into the cooking
c:3ntainer. The condenser cover was replaced immediately. Simultane-
czusly with the start of the pouring procedure. the chart recorder
(Fig. l) was started. On the chart of the viscometer. the continuous
iriscosity changes during the cooking of the starch pastes were auto-
rnatically recorded. The measurement of viscosity with the Corn Indus-
‘trdes Viscometer is made on the basis of force which the propeller
(encounters as it turns in the paste. This force on the propeller is
'transmitted by a cable to the recorder pen which moves from left to
Jright across the chart as the viscosity of the paste increases. The
:force or torque can be calculated, or Bechtel's tables (7) can be used
:for transpoeing chart readings into torque values. Bechtel's tables
Vuere used for determining the torque values in this study.

Figure 2 shows a sample chart with a record of a viscosity curve
(bf a starch paste. In this study, the chart was operated at rapid
speed. At this speed, the chart moves downward at the rate of one
horizontal arc per minute.

Because the rate of temperature rise is a factor which may affect
the rate of thickening and the final visc0sity of a cornstarch paste,
the investigator decided to cook all the pastes in this study to a
temperature of 95° C. Paste temperatures were recorded at 1-minute
intervals throughout the cooking period from a thermometer inserted

into the starch paste through the cover of the cooking container.

49

 

:22x22/2/

/////:/g.//

 

m/222/2/J

 

///////

 

2/2///////

2..- /

 

 

244/

K!
O

a

 

 

 

 

 

 

 

 

 

. a h

 

 

 

 

 

 

 

 

 

N _

 

\\\\\\\\\a

\\\\\\

 

\\\\\\\\R\

\\\\\\

 

 

\\ _ \ x \ ,-\ \ .\ \..

li’nav ‘ii‘!:‘. ll.n
i.‘ I ‘

 

 

Sanple chart with record of a visc0sit
curve of a

Fimue ?.

ste.

starch pa

50

DISCUSSION AND RESULTS

Viscosity Tests

Torggg values

The torque values of the three replications of each starch paste
in this investigation did not vary more than 35 gram-centimeters at
maximum viscosity. The range in torque values in the viscosity tests
of the three replications of each variation is shown in Table 5.

The averages of the torque values at maximum viscosity for the three
replications in each series are shown in Table 6.

Table 5. Range in torque values in the three replications of
each series.

 

Liquid Sugar level in terms of percentage of total liquid
Series Medium 0 15 21 27

 

 

A distilled
water 1325-1358 1358-1391 1358-1391 1306-1341

B tap water 1454-1U85 lh5fl-lh70 1391-1QO7 lQO7~1439

C nonfat dry

milk solids

in distilled

water 1222-1257 1257-1391 1222-1257 1222-1257
D whole dry

milk solids
in distilled
water 1bo7—1u39 1357-1u07 1ho7-1h23 1291

 

51

Table 6. Summary of average torque readings of the three
replications of each series at maximum viscosity.

 

Sugar Concentrations
Series Liquid Medium ‘rv

 

 

o 15 21 2?
A distilled water 1335 1371» 137a 1329
3 tap water luau 1461+ 1396 1428
C nonfat dry milk
solids in dis-
tilled water 1239 1274 1233 1239
1). whole dry milk
solids in dis-
tilled water 1u23 1385 1417 1291

 

 

Proportion of sucrose

The effect of the proportion of sucrose on the viscosity of corn-
starch pastes made with distilled water is shown in Figure 3. Analysis
of variance for the starch pastes made with distilled water, Table 7,
showed there was no significant difference in.maximum viscosity of the
control paste and maximum viscosity of the starch paste containing
27 per cent sucrose. However, the maximum viscosities of the pastes
which contained 15 and 21 per cent sucrose were significantly higher
than the maximum viscoSity both of the control and of the paste con-
taining 27 per cent sucrose. This is in agreement with results of
other investigators (23, 29, 39) who indicated that additions of
relatively low concentrations of sucrose to cornstarch suspensions
produced pastes with higher viscosities than obtained from starch

and water suspensions alone.

DJ

E
J

   

 

 

 

TORQUE CHART
2l°l. sucrose
'39' r- _.._.__.~‘.--. _. 7O
\
t l .°°
IZZZ _ con ro ‘e‘::‘ -60
~e
|5°/. sucrose
I0395 "50
l e
a : \.
o . ‘.
l , ~e
I .'
s45- } : —40
l O
' I
l .
l .
l e
’5'
__ I _
64| ' . 30
I O
' .’
' .
432 r— — 20
2|? - - l0
0 l l l l l J l 0
MIN 0 6 l2 IO 24 30 36 42 45
Effect of proportion of sucrose on the initial
viscosity rise, maxinum viscosity, and final

Figure 3 .
viscosity of cornstarch pastes made with distilled

Water 0

53

Table 7. Analysis of variance for Series A, distilled water
medium, and Series D, reconstituted whole dry milk
solids medium.

 

 

Source of variance D. F. M. S. F.
Total 23

Between the series 1 h00h.2 u.6*
Between % of sucrose 3 8801.1 10.0‘*
Interaction:series x sucrose 3 894.6 1.01
Error 16 877.6

 

Viscosity curves for the pastes made with tap water are shown in
Figure b. Analysis of variance for the pastes, Table 8, showed there
was no significant difference in the maximum viscosity of the control
pasusand the maximum viscosity of the paste containing 15 per cent
sumrose. However, the maximum viscosities of the control paste and
the paste containing 15 per cent sucrose were significantly higher than
the maximum viscosity of each of the other pastes. There was no signi-
ficant difference between the maximum viscosities of the pastes containing

21 and 27 per cent sucrose.

Table 8. Analysis of variance for Series B, tap water redium.

 

Source of variance D. F. M. S. F.
Total 11

Between % of sucrose 3 3586.3 56.8"
Error 8 63.1

w

 

l'Signii‘icant at Eilevel of probability
‘*Significant at 1% level of probability

 

  
  

 

  

 

 

 

 

 

TORQUE CHART
I544r- ‘ 180
I575 sucrose
I39lh- -70
i 27 ‘7. sucrose
'222F- I :l ‘60
.l
C ‘I
1 n
.l
l 2;
l in
IOSOF | :n' --so
0 .l
! :I .
I :-'
e l e
I :,- ‘
846— U: 2|°/. sucrose . -40
I q /"‘0~ ..°‘e
' J
l : control
I 1
o
64I— 1 . -30
a
1 :
l t
.' E
I k
432— ..'§ -20
» § .
I :
ans I! 3 -IO
l 5
l '.
o L, l l l J l l 0
MIN 0 6 l2 I8 24 3O 36 42 45
Figure 4. Effect of proportion of sucrose on initial viscosity
rise. maximum viscosity, and final viscosity of

cornstarch pastes made with tap water.

55

The effect of the proportion of sucrose on the viscosity of corn-
starch pastes made with a solution of nonfat dry milk solids in dis-
tilled water is shown in Figure 5. The analysis of variance for the
pastes showed that the maximum viscosity of the starch paste containing
15 per cent sucrose was significantly higher than the maximum viscosities
of the control and the pastes containing 21 and 27 per cent sucrose.

Table 9. Analysis of variance for Series C, nonfat dry milk
solids in distilled water medium.

 

Source of variance D. F. M. S. 1.
Total 11

Between.% of sucrose 3 1023.0 3.68‘
Error 8 277.5

Analysis of variance for the cornstarch pastes made with a solur
tion of whole dry milk solids in distilled water, Table 7, showed
there was no significant difference between the maximum viscosity of
the control paste and the maximum viscosities of the starch pastes
containing 15 and 21 per cent sucrOse. However, the maximum viscosity
of the paste containing 27 per cent sucrose was significantly lower
than the maximum viscosities of all the other pastes. Viscosity

curves for the pastes are shown in Figure 6.

Liguid mediums

Although the difference was not calculated statistically, data

suggest a probable significant difference between the maximum

__._

"Significant at 3‘ level of probability. according to Fair (37).

 

 

 

 

   
 

56

 
 

 

 

 

 

 

 

TORQUE CHART
|3Q|F 170
control
.222 _ “jfi'fztfi‘: :I'.‘£:E: '21; 4 50
46 +
’e
I: \
f ZIWQ sucrose
|039 r- ’ - 50
O
.'
I
1
846 _ I .3 - 40
e lo
I K
I '0
I "
.0
o \
’ 27°]
6‘“ _ OI e4———— 0 sucrose --30
l
O
432 r- 1 |5°Io sucrose .. 20
Zl7h— D '—|°
1 ~1 L 1 l 1 1 0
MIN 0 6 l2 18 24 30 36 42 45
Figure 5. Effect of pro ortion of sucrose on initial viscosity
rise, naxinum viscosity, and final viscosity of corn-

starch pastes made with a solution of nonfat dry milk

solids in distilled water.

57

 

 

 

 

 

TORQUE CHART
l544 " 180
control
I39I I— - 70
I222— 160
|O39 — '1 50
845 i- , -I 40
IL 2|°lo sucrose
I
I
I
l
l
64| - ,’ 1 30
I
6
432— —20
2|7 — — l0
0 L L L - l l l l 0
MIN 0 6 I2 I8 24 30 36 42 45
Effect of proportion of sucrose on initial viscosity

Figure 6.
rise, maxinum viscosity, and final viscosity of corn-
starch pastes made with a solution of whole dry milk

solids in distilled water.

58

viscosities of the pastes made with tap water and the maximum viscosities
of the pastes made with the other liquid mediums. The peak viscosities
of the pastes in each variation made with tap water were higher than
were the peak visc0sities of the comparable pastes made with the other
liquid mediums. The exception was the paste made with a solution of
whole dry milk solids containing 21 per cent sucrose.

The viscosity curves for the pastes made with tap water indicated
that they were more unstable than were the pastes made with the other
liquid mediums. According to the findings of this study, cornstarch
puddings or fillings made with tap water could be expected to thicken
very quickly. However, such mixtures may tend to be unstable and
these pastes could be expected to start to show a decrease in.viscoeity
within 2 to 6 minutes after reaching maximum viscosity. From the data
of this study, thinning of the pastes, after they have reached maximum
viscosity, could be expected to continue as the length of cooking time
was increased .

The maximum viscosity of the starch pastes in each variation made
with a solution of nonfat dry milk solids in distilled water was lower
than that of the comparable pastes made with the other liquid.mediuls.
This is in agreement with the findings of Horse and associates (36) who
reported that sweetened flour and water pastes were prOportionately
more viscous than similar sweetened flour and water pastes to which
nonfat dry milk solids were added. The viscosity curves for the
pastes made with reconstituted nonfat dry milk solids indicated that
they were more stable than were the pastes made with the other liquid

medias e

59

The analysis of variance for Series A.and D showed that there
was a significant difference in the maximum viscosities of the pastes
attributable to the difference in liquid mediums. The peak viscosi-
ties of the pastes made with distilled water were lower than were the
peak viscosities of the pastes made with reconstituted whole dry milk
solids except for the paste containing 2? per cent sucrose. The peak
viscosity of the paste made with distilled water containing 27 per
cent sucrose was higher than the peak viscosity of the paste made
with reconstituted whole dry milk solids containing 27 per cent sucrose.

The differences between the maximum viscosities of the starch
pastes made with solutions of two types of dry milk solids were probably
attributable to two factors. First, the total amount of milk solids.
including butterfat, in Series D was greater than the total amount of
nonfat dry milk solids in Series 0, although the total amount of nonfat
dry milk solids in each series was calculated to be the same. Second,
according to Mitchell and 2111121811 (35), fatty materials such as soaps,
fatty acids, and perhaps natural fats increase the viscosity of starch
pastes. The effect of liquid medium on the viscosity of starch pastes

is shown graphically in Iigures 7, 8, 9, and 10.

Time‘ggg paste temperature

The viscosity curves for the cornstarch.pastes made with distilled
water, Iigure 3, showed that the increases in sucrose concentration
caused no appreciable difference in the time required for initial

viscosity rise. However, as the sucrose concentrations increased, the

60

  
    

 

 

 

 

TORQUE CHART
l544~ ‘80
tap water
distilled water and whole
dry milk solids
I39| r-
IZZZ-
IO39-
840r—
I ; d'lllt! l d
III e we er on
64'b 1" nonfat dry milk solids 3°
' I
l e
l
.I
‘1'
° ‘ — 20
‘32P [4—_ distilled water
0
1
1
2”" "lO
0 L_ l l l I l l 0
MIN 0 6 I2 I8 24 30 36 42 45
Figure 7. Effect of liquid medium on the initial v1500sity

rise, maximum viscosity, and final viscosity of
cornstarch pastes without sucrose.

 

 

 
 
   
   
  
   
   

61

 

 

 

TORQUE CHART
l544r 180
tap water
distilled water and whole
I 9|—
3 dry milk «lid. " 7°
i k-*-‘.“-
: ‘1‘ **+'.--.-
'222 h : If \‘e. ‘ _ 60
e 1‘ ‘.e...
\ ".
e\°e...
e..
e 0.
l039 - \ \ -l so
\.\
846 h- - 4O
distilled water and
nonfat dry milk solids
644- -*30
432 - '- 20
l
l
3“
2'7 __ I‘L—distilled water _ ‘0
o l J J l l l l 0
Figure 8. Effect of liquid medium on the initial viscosity
rise, maximum viscosity, and final viscosity of

cornstarch pastes with addition of 15 per cent

sucrosee

62

        
   
    

 

 

 

 

TORQUE CHART
I544 F‘ — 80
distilled water and whole dry milk solids
..ee.eo......
um - ,;-.o,.;..-...\ —70
.0 e... e\.
3 g \k
2 Q
: / ‘3‘ “c.
'222__ : ffm-e e-e—e-e-e7;:e-e-e—t“.h‘z: -+60
: '
: "
E distilled water and nontot
: dry milk solids
I039 l- 3 -— so
: idp voter
e45 — : 1 so
641 — 5 - 30
E ! distilled water
' i
432% I -20
an — l. —l no
0 l l 14, l l J l 0
MIN 0 6 l2 IS 24 3O 36 42 45
Figure 9. Effect of liquid medium on the initial viscosity
rise, maximum viscosity, and final viscosity of

cornstarch pastes with addition of 21 per cent

SUCI‘OSB.

63

     
 

 

 

 

 

 

TORQUE CHART
I544 - 1 80
tap water
distilled water.
l39l *- ~70
NWW-O-C-O'".
ll.
~emq\
Ce.‘.. \
e~
1222 — """'"""{"’“‘---o 4 so
...ee.
distilled water and whole
dry milk solids
i
846 - Ll " 40
l
:l
l
l
:i distilled water and nonfat
6 ' dry milk solids
64| - I -+30
432 r— . - 20
e'
2l7- —-IO
l.
O J l l l l l, J 0
MIN 0 6 l2 l8 24 3O 36 42 45
Figure 10. Effect of liquid medium on the initial viscosity
rise, maximum viscosity, and final viscosity of

cornstarch pastes with addition of 27 per cent

SUCTO 88 .

time required for the pastes to reach maximum viscosity progressively
increased. The exception was the paste containing 21 per cent sucrose
which reached maximum viscosity in the same length of cooking time as
that required for the paste containing 15 per cent sucrose. The addi-
tions of 15, 21, and 27 per cent sucrose to the pastes made with dis-
tilled water caused a progressive decrease in breakdown of paste vis-
cosity as the cooking time extended beyond 22 minutes.

The temperature-viscosity curves for the pastes made with distilled
water are shown in Figure 11. The curves showed that each increase in
the preportion of sucrose caused a progressive increase in the paste
temperature at initial viscosity rise and.at maximum viscosity. There
was also a progressive increase in the temperature at initial viscosity
breakdown except in the paste containing 15 per cent sucrose. The con—
trol paste without sucrose and the paste containing 15 per cent sucrose
showed initial viscosity breakdown at 91° C. It appeared that progres-
sive increases in the concentration of sucrose produced a stabilizing
effect on viscosity of the pastes at 95° C.

Viscosity curves for the starch pastes made with tap water,

Figure 4, indicated an extremely rapid rise in viscosity of each
variation of the series. Maximum viscosity of each variation was
maintained for a very short time and a rapid decrease in viscosity
followed. The increases in sucrose concentration caused no appreciable
difference in the time required for initial viscosity rise in the
pastes made with tap water. The control paste without sucrose, the

paste containing 15 per cent sucrose, and the paste containing 21 per

TORQUE

I39”-

l222"

|O39 '-

846 '-

64l

«432

2|7

 

°C

65

CHART
2| °lo sucrose

'5 ‘70 sucrose _ 7o

       

e— J—e—e—O'v‘q °
I {a

Id ,0. \

    
  
  

“‘60

 

-‘ 40
control
- 30
.. 20
X: one reading only .1 .0
o : two readings only
e = three readings
1 l J o

 

 

85 90 95

Figure 11. Effect of proportion of sucrose on the temperature

rise of cornstarch pastes made with distilled water.

66

cent sucrose required the same length of cooking time to reach peak
viscosity: only the paste containing 27 per cent sucrose required a
longer time to reach peak viscosity. The control paste without sucrose
showed the greatest breakdown in viscosity after 16 minutes of cooking
time. As sucrose concentration increased in the sweetened pastes made
with tap water, the rate of paste breakdown progressively decreased.

The temperature-viscosity curves for the starch pastes made with
tap water are shown in Figure 12. The increases in sucrose concenr
tration influenced the temperature at which initial viscosity rise
was noted in the pastes. Increases in sucrose concentration also
influenced the temperature of the pastes at maximum viscosity except
in the paste containing 21 per cent sucrose. At maximum viscosity
the temperature of the paste containing 21 per cent sucrose was the
same as that of the paste containing 15 per cent sucrose. The addi-
tions of sucrose made no appreciable difference in the paste tempera-
ture at the initial breakdown of any of the pastes. The breakdown in
viscosity of all the pastes took place rapidly after a temperature of
87° C was reached; at a temperature of 94° 0 there was no apparent
difference in the extent to which the pastes had thinned.

The viscosity curves for the pastes made with reconstituted non-
fat dry milk solids showed that increases in sucrose concentrations
made no appreciable difference in the time required for the initial
viscosity rise and the time required for the pastes to reach.maximum
viscosity. The length of cooking time required for the pastes made
with reconstituted nonfat dry milk solids to reach initial viscosity

breakdown was as follows:

 

 

6?

 

 

TORQUE CHART
I544 - 1 80
,e—e
IO ' \
e .""\”‘ .
__ / --e-- -e. -. ..
use! . ,r'f "\ ,. 7o
/ ’ ' q t
0 .’ e. . e
I II 3 \. \0
.l I ,o' \ :.
/ 0’ g. \ \:e.
0 g e e .
1222 — / a .' \ u. — so
‘. ' '. . ‘0‘
conlrol / {‘0' \ l \ '.
. \ \ e.
N sf 27". sucrose \ “o
e I, O .0
e
|O39P ./ ,‘ \ \‘g ‘50
/ I \ 5‘0.
. I ’ \.
I II \. \.e
e
J I \. ‘s‘
I \ °..
I
846 l— .l I \\ a 40
l ' I
0 I .e
l I '-
° I
l , 2|"lo sucrose
6“ - l I’ J 30
. I
l I
I
° I
l [I
432 - l .I -+ 2°
i l/ISV/e sucrose
9
l X = one reading only
2'7 _ L O: {we readings only _+ l0
0: lhree readings
o W J l l l 0
°C 0 75 80 85 90 95
Figure 12. Effect of proportion of sucrose on the temperature
rise of cornstarch pastes made with tap water.

68

control paste without sucrose 36 minutes
paste with addition of 15% sucrose 28 minutes
paste with addition of 21% sucrose 38 minutes
paste with addition of 27% sucrose 34 minutes

The effect of the sucrose concentrations on the time required to
reach initial viscosity breakdown.was not consistent: but after the
initial breakdown, the control paste showed greater decrease in vis-
cosity than the sweetened pastes as cooking time increased.

The temperature-viscosity curves for the pastes made with recoup
stituted nanfat dry milk solids are shown in.ligure 13. The additions
of sucrose to the starch suspensions made with a solution of nonfat
dry milk solids caused a progressive increase in the temperature of
initial viscosity rise and the temperature at maximum viscosity of the
pastes. There was no appreciable difference in the temperature at
initial viscosity breakdown of the pastes. Breakdown of the pastes
did not occur until a temperature of 93° 0 had been reached.

The viscosity curves for the pastes made with reconstituted whole
dry milk solids, Figure 6, showed that the control paste and the pastes
containing 15 and 21 per cent sucrose reached maximum viscosity in the
same length of cooking time. The paste containing 27 per cent sucrose
required a longer cooking period to reach peak viscosity. The increases
in sucrose concentration had no consistent effect on the length of
cooking time required to reach initial viscosity breakdown. The time
required to reach initial viscosity breakdown was as follows:

control paste without sucrose 20 minutes
paste with addition of 15% sucrose 20 minutes

paste with addition of 21% sucrose 16 minutes
paste with addition of 27% sucrose 22 minutes

TORQUE

I39”-

Izzzk

 

|O39

846'-

SM

432

 

69
CHART

70

IS °Io sucrose

      
 

~60

   

“L7. - .E¥£été1.-
I‘, 3.0

    

Z7 °/o sucrose

 

 

/
r -u20
! .: X: one reading only
I .° 0: {we readings only .1“)
I. i 0=fhree readings
I
e
.__JWL l i l l J 0
75 80 85 90 95
Figure 13. Effect of proportion of sucrOSe on temperature rise
of cornstarch pastes made with a solution of nonfat
dry milk solids in distilled water.

70

The temperature-viscosity curves for the pastes made with recoup
stituted whole dry milk solids. Figure 14, showed that the increases
in sucrose concentrations only slightly increased the temperature at
initial viscosity rise. The temperatures at initial viscosity rise

were as follows:

control paste without sucrose 75° C
paste with addition of 15% sucrose 76° C
paste with addition of Zlfi sucrose 77° 0
paste with addition of 27% sucrose 77° C

The increases in sucrose concentration had no consistent effect
on either the temperature at maximum viscosity or on the temperature
at initial breakdown in viscosities of the pastes.

The temperature-viscosity curves for the control pastes made with
each of the four liquid mediums is shown in Figure 15. The temperature-
viscosity curves for the variations of the starch pastes made with each
of the four liquid mediums are shown in Figures 16, 17. and 18.

In the control pastes without sucrose and in all the sweetened
pastes. the pastes made with tap water and the pastes made with recon-
stituted whole dry milk solids showed more rapid increase in viscosity
than did the other sweetened and unsweetened pastes. In similar varia-
tions of the starch pastes. there was no appreciable difference in the
temperature at initial viscosity rise attributable to the different
liquid mediums. In similar variations of the pastes, there was no
appreciable difference between the temperatures at maximum viscosity
of the pastes made with tap water and those made with reconstituted
whole dry milk solids. Temperatures at maximum viscosity in the varia-

tions of the pastes made with each liquid medium are shown in Table 10.

 

C HART

        
   

 

 

71
TORQUE
l544r ‘80
arr-33:9.- :r-x'
|39I b ./ , 4 7o
/ “
O—e—J ....e.oe.00.oo.ee..o.eo\.
conlrol I , 0° .
e ’ .0
I222 #- j X I .' - so
/x I, .0. 27". sucrose
l039 '- /° X I, .°. -150
I .‘
0 ’ .0
I 9
l5°l. sucrose I, 5
I .'
I O
846 P I : — 40
I I
I .’
0 I :
I e
’ I
Zl'l. sucrose I, .'
__._._._..L’ .
64| - I .' “ 30
I, e.
e .'
432 - .o' - 20
.'
; X: one reading only
2l7 L- O: lea readings only _ '0
= three readings
0 _ML J l l l L 0
°C 0 75 80 85 90 95
Figure 14. Effect of proportion of sucrose on temperature rise
of cornstarch pastes made with a solution of whole
dry milk solids in distilled water.

CHART

 

 

 

 

 

 

 

72
TORQUE
l544F‘ '180
top waler
0
d. {H d * XeeQeeQeeOeeQee ee.eeXee.e..
isi e we er J .
— ‘ ° -‘70
I39. and whole dry .0. °..
mflk: soflds 3' “O” “0”‘Wh&
OOeee O /‘ ‘.\
l222l- ,-o—.j""'I’ """"' g."‘\ 160
: 1’ I ‘5 \
0 .’ e e. \t
: I I A ~
e I . e
e I, g \e
e. I .
l039 — ,° ' I . ?" 450
° /° . dislilled waler \
,’ I and nonfal ‘\
,’ ,' dry milk solids .
z \
I ‘ e
I, / 40
J '
I’ !
,’ “41 distilled waler .
’ /
64l ’- I , "" 30
I, ./
I, *.d
I
I /
I e
432- f / -20
I
, /
I O
I J .
I /. X: one reading only
‘ : lwo readings only
2'7P 10' f e: ilIree readings "0
Il ‘
I!
I
O
ClLJVL~ 1 l 1 4L ll 0
°C 0 75 80 85 90 95
Effect of liquid medium on temperature rise of

Figure 15.
cornstarch pastes without sucrose.

 

CHART

  
 

 
 

   
 

 

 
   
   

 

 

 

 

 

73
TORQUE
I544 80
F- tap water -i
__ distilled water 470
'3“ and whole '°.".".".“.. "' e...‘°‘\
. . e
dry null: solids '\
IZZZ" .'\ 460
. \\
O. .\
. \
e. .0
O..\
C 0..
8 '.
l039— .0 -50
: distilled water
: 9' and nonfat
.' I dry milk solids
see —- -i 40
I
i I I
I, L distilled water
0 .'
l
l / “J -*30
64. [I I?
9’ -’
I e/
I /
977'"
432- ,‘I ‘20
.I
I
. [I
I” X: one reading only
'I 0: two readings only
2|? __ é 0: three readings .4 l0
.’
i!
OLJNki 14 l l |
°C 0 75 80 85 90 95
Effect of liquid medium on temperature rise of

Figure 16 .

cornstarch pastes with addition of 15 per cent

sucrose 0

 

74

 

 

80

'IO

60

50

4O

30

20

IO

 

 

rosauc CHART
I 44-
5 1
distilled water and whole dry milk solids
...00..'..'.0e....
|39|I- .° "0.. _
I. 0 e+e$';:e‘.
/. \.
e '3 \
e I .° e
'222" .: ’0‘-.-7-. .-.-.'-.-.‘..\..e-I
. ,II ..
I -.
I O
I /
.' I 9
l039- . I / "
: I, 0 distilled water
.° ‘ and nonfat dry
,' 'I I. mill: solids
e I
.- . I
._ I .I
846 I .I
I, I4 distilled water
I I.
I
I I
I O
64J- , j I.
I
I!
tap water ',
I,"
436h- /‘ '—
e/;k
/ .
x X: one reading only
2:7— d° O=two readings only _
I s: three readings
!
I
e
OLA/L L L l l 1
°C 0 75 80 85 90 95

Figure 17.

Effect of liquid medium on temperature rise of
cornstarch pastes with addition of 21 per cent
sucrose.

CHART

 

 

 

 

 

75
TORQUE
I544 - ‘80
tap water
l39lr-
l222-
distilled water
and whole dry
milk solids
l039—
845 I-
.° / . . .
. / J1 distilled water
.° ’ .
e /
.- I.‘ .’
54I- E 'I o distilled water _30
o , I and nonfat dry
: I ° llllk solids
I I I
a I °
. , oI
.' I °
432~ . , / -I20
I . .
.° I /
e I 0
.' I /
e I, .
s’ 1' x:.-one reading only
I _ .
2|7_ ,/ 0.. two readings only -IIO
f '3 three readings
/
e
0 LNL I 1 l I I 0
°C 0 75 so , as so 95
Figure 18. Effect of liquid medium on temperature rise of
cornstarch pastes with addition of 27 per cent

sucrose e

Table

Temperatures at maximum viscosity for pastes made
with four different liquid mediums.

76

 

 

Liquid Control paste Paste with Paste with Paste with
Medium no sucrose 15% sucrose 21% sucrose 27$ sucrose
0 o o o
C C O C
distilled
water 86 87 88 91
tap water 82 8b 8b 85
reconsti-
tuted whole 81 83 85 84
dry milk
solids
reconsti-
tuted nonfat 85 86 87 88
dry milk
solids

In all liquid mediums the pastes containing 27 per cent sucrose

showed higher temperatures at initial viscosity rise than did the control

pastes.

the pastes made with each liquid medium are shown in Table 11.

Table

Temperatures at initial viscosity breakdown in the variations of

11. Temperatures at initial viscosity breakdown for pastes
made with four different liquid mediums.

 

 

Liquid Control paste Paste with Paste with Paste with
Medium no sucrose 15% sucrose 21% sucrose 2?}: sucrose
°C 00 0 o 00

distilled

water 91 91 93 94
tap water 85 86 87 8?
reconsti-
tuted whole 89 89 8? 91
dry milk
solids
reconsti-
tuted nonfat 9h 93 93 93

dry milk
solids

77

SUMMARI

The maximum viscosities of 11 per cent cornstarch pastes containing
15 and 21 per cent sucrose made with distilled water were significantly
higher than the maximum viscosity of the control paste without sucrose.
However. the maximum viscosity of the paste containing 27 per cent
sucrose was not significantly different from that of the control paste.

Data on pastes made with tap water showed that addition of 15 per
cent sucrose produced a paste with maximum viscosity comparable to the
control. However. additions of 21 and 27 per cent sucrose resulted in
pastes with maximum viscosities significantly lower than that of the
control paste.

Additions of 21 and 27 per cent sucrose to pastes made with re-
constituted nonfat dry milk solids resulted in.maximum viscosities
similar to that of the control paste. However. the additions of 15 per
cent sucrose produced a paste with greater maximum viscosity than that
of the control paste.

The maximum viscosities of 11 per cent cornstarch pastes. con-
taining 15 and 21 per cent sucrose. made with reconstituted whole dry
milk solids were not significantly different from the maximum viscosity
of the control paste without sucrose. The maximum viscosity of the
paste containing 27 per cent sucrose in this series was significantly
lower than that of the control paste.

The maximum viscosities of the control and all sugar levels of

cornstarch pastes made with tap water were significantly higher than

78

those of similar pastes made with the other liquid mediums with the
exception of the paste containing 21 per cent sucrose made with re-
constituted whole dry milk solids.

The maximum viscosities of the control and pastes with all three
sugar levels made with reconstituted nonfat dry milk solids were lower
than were those of similar pastes made with other liquid mediums.

The maximum viscosities of the control and pastes with all three
sugar levels made with reconstituted whole dry milk solids were signi-
ficantly higher than were those of similar pastes made with distilled
water with the exception of the paste containing 27 per cent sucrose.

The control and pastes with all three sugar levels made with tap
water were the most unstable of the comparable pastes made with other '
liquid mediums in this investigation. The variations of the pastes
made with reconstituted nonfat dry milk solids were the most stable
pastes in the study.

The control and pastes with all three sugar levels made with tap
water and those made with reconstituted whole dry milk solids showed
a more rapid rise in viscosity and attained maximum viscosity at lower
temperatures than did similar pastes made with other liquid mediums.

At a specific sucrose concentration, the difference in liquid
mediums did not appear to influence the paste temperatures at initial
viscosity rise of any of the pastes. .

There was no consistent effect of time on initial viscosity rise,
maxim-n viscosity. and initial breakdown in paste viscosity attribut-

able to sucrose concentration of the pastes in this investigation.

79

The addition of 27 per cent sucrose appeared to increase the tem-
perature at initial viscosity rise and the temperature at maxim- vis-
cosity of the pastes made with all mediums in this study. Pastes made
from the four mediums containing additions of 15 and 21 per cent sucrose
did not show any definite pattern in relation to temperature of pastes

at initial viscosity rise or at maximum viscosity.

80

CONCLUSIONS

The effect of the pr0portion of sucrose on the viscosity of corn-
starch thickened mixtures cannot be predicted without taking into
consideration the liquid medium in the mixtures.

In this limited study it was found that the maximum viscosity of
unsweetened and sweetened pastes made with tap water were higher than
were the maximum viscosities of similar pastes made with other liquid
mediums with the exception of the paste made with reconstituted whole
dry milk solids containing 21 per cent sucrose. The maximum viscosi-
ties of the control and all sugar levels of pastes made with recon-
stituted nonfat dry milk solids were lower than those of similar pastes
made with other liquid mediums. The maximum viscosities of the control
and pastes with all three sugar levels made with reconstituted whole
dry milk solids were appreciably higher than were those of similar
pastes made with distilled water with the exception of the paste con-
taining 27 per cent sucrose.

The stability of desserts thickened with starch is frequently an
important factor in the quantity preparation of these foods. In this
investigation it was found that the variations of pastes made with tap
water were more unstable than were pastes made with the other liquid
mediums. The pastes made with reconstituted nonfat dry milk solids
were more stable than were other pastes made with other liquid mediums.

From the data of this investigation, it appeared that sucrose.

in concentrations from 0 to 21 per cent did not show any consistent

81

effect on the length of cooking time required to reach initial vis-
cosity rise. maximum viscosity, and initial viscosity breakdown of the
pastes made with the four liquid mediums. The addition of 27 per cent
sucrose to the basic starch slurries made with all liquid mediums in-
creased the length of time required for the pastes to reach maximum
viscosity. The additions of 15 and 21 per cent sucrose did not always
alter the cooking time required for the pastes to reach maximum viscosity.
However. additions of sucrose to the basic slurries appeared to decrease
the breakdown in viscosity of the pastes as cooking time increased.

The temperature at maximum viscosity was appreciably increased
by additions of 27 per cent sucrose to the basic slurries made with
the four liquid mediums. Pastes made with additions of 15 and 21 per
cent sucrose did not show any definite pattern in relation to tempera-
ture of pastes at initial viscosity rise or at maximum viscosity.

The data from this limited study suggest that additional investi-
gation needs to be made in order to study more fully the effect of
cooking time and paste temperature on the viscosity of sweetened

cornstarch pastes made with different liquid mediums.

10.

11.

12.

13.

14.

82
LITERATURE C ITED

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1926.

Alsberg, C. L. and Rask. O. S. 0n the gelatinization by heat of
wheat and maize starch. Cereal Chem. 12107-116. 1924.

American Dry Milk Institute. Milk and its uses in the bakery.
5th ed. p. 19. Chicago. 19h9.

American Woman's Cook Book. p. 555. Garden City. Garden City
Pub. Co. 1948. .

Anker. C. A. and Geddes, W. I. Gelatinization studies upon wheat
and other starches with the amylograph. Cereal Chem.
21:335-360. 1944.

Bear, R. S. and Samsa, E. G. Gelatinization mechanism of starch
granules. Ind. Eng. Chem. 35:721:726. 1943.

Bechtel, W. G. Instruction manual for Corn Industries viscometer
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Bechtel, V. G. Measurement of properties of cornstarch gels.
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Bechtel, V. G. A study of some paste characteristics of starches
with the Corn Industries viscometer. Cereal Chem. 24:200-214.
1947.

Bechtel, V. G. and Fischer, E. X. The measurement of starch paste
viscosity. J. Colloid Sci. #:265-282. 19Q9.

Beckford. 0. C. and Sandstedt, R. M. Starch gelatinisation studies.
Cereal Chemo 2Q: 250‘2580 1947.

Bisno, L. Thickenings used in pie fillings. Bakers Digest.
25 (no. 1): 26-29. 1951.

Brautlecht. C. A. Starch. Its sources, production. and uses.
New York. Reinhold Pub. Corp. 1953.

Brimball. B. and Hixon, R. M. Interpretation of viscosity
measurements on starch pastes. Cereal Chem. 19:425-h40.
l9h2.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

28.

83

Brimball, B. and Hixon, R. H. The rigidity of starch pastes.

Caesar. G. V. Consistency changes in starch pastes. Ind. Eng.

Caesar, G. V. and Moore. E. 3. Consistency changes in starch
pastes. Ind. Eng. Chem. 27:1447;1450. 1935.

Campbell. H. A., Hollis. E. Jr., and HeAllister, H. V. Improved
methods of evaluating starch for specific uses. Food Tech.

Chapman, 0. W. and Buchanan, J. H. The properties of starch in
relation to time and formation of starch gels. Iowa State
College J. of Colloid Sci. 48441-450. 1930.

Frankel, J. A practical treatise on the manufacture of starch.
glucose. starch-sugar and dextrine. p. 1-30. Philadelphia.
Henry Cary Baird Co. 1881.

Good Housekeeping Cook Book. p. 607. Chicago. Rinehart Co.
1949.

Grawemeyer, E. A. and Pfund. M. C. Line-spread as an objective
test for consistency. Food Hes. 8:105-108. 1943.

Being. A. J. The effect of sucrose, citric acid. and temperature
on viscosity and gel strength of cornstarch pastes. Unpub.
M. S. Thesis. Michigan State College. 1953.

Hanson, H. L., Campbell, A.. and Lineweaver, H. Preparation of
stable frozen sauces and gravies. Food Tech. 5:432-435.
1951.

Hanson, H. L., Mishita, K. D., and Lineweaver. H. Preparation of
stable frozen puddings. Food Tech. 7:462e465. 1953.

Harris, R. H. and Banasik, 0. A further inquiry regarding effect
of electrolytes on the swelling of cereal starches. Food Res.

Harris. H. H. and Jesperson, F. Factors affecting some physio-
chemical properties of starch. Food Res. 11:216-228. 1946.

Harris, H. H. and Jesperson, E. A study of the effect of various
factors on the swelling of certain cereal starches. J. of
Colloid Sci. 1:479-493. 1946.

29.

3o.

31.

36.

37-

380
39.

40.

41.

42.

Hester, E. E. Some preperties of selected edible starches as
thickening agents and changes induced by sucrose. Unpub.
Ph. D. Thesis. Ithaca, New York. New York State College
of Home Economics, Cornell University Library. 1952.

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