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This is to certify that the
thesis entitled

COOKING QUALITIES OF SEVERAL CONCENTRATIONS OF

VARIOUS TYPES OF NONFAT DRIED MILK SOLIDS
presented by

Margaret Janet MacDougall

has been accepted towards fulfillment
of the requirements for

Jig—degree 1n_HDme_Econom1cs

2%

Major professor

 

 

Date—W3—

0-169

 

COOKING QUALITIE‘S OF SEVERAL CONCENTRATIONS OF
VARIOUS TYPES OF NONFAT DRIED MILK SOLIDS

By
margaret Janet MacDougall

A THESIS

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 SCIENCE

Department of Foods and Nutrition
School of Home Economics

1953

C," "'-”,-> .4

a?

ACKN OWLEDGELMT

The writer wishes to express her gratitude to
Dr. Pauline Paul for her invaluable guidance and counsel
throughout the study; and to Dr. Louise Kelly, Maura Bean,
Doris Kereluk and Mary Mills who served on the scoring
panel.

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TABLE OF CONTENTS

INTRODUCTION . . . . . . . . . . . . . . . . . .
REVIEW OF LITERATURE . . . . . . . . . . . . .
Nonfat dry milk solids . . . . . . . . . .
Definition . . . . . . . . . . . . . . . . .
Methods of manufacture . . . . . . . . . . .
Spray . . . . . . . . . . . . . . . . . .
AtmOSpheric roller or drum . . . . . . . .
Vacuum roller or drum . . . . . . . . . .
Characteristics of nonfat dry milk solids . .
Theory of heat coagulation . . . . . . . . . .
Effect of temperature . . . . . . . . . . .
Effect of acid . . . . . . . . . . . . . . .
Effect of alkali . . . . . . . . . . . . . .
Effect of salts . . . . . . . . . . . . . .
Effect of sugar . . . . . . . . . . . . . .

Custards as a medium of testing various types
or milk 0 O O O O O O O O O O O O 0 O O O O

Nutritive values and uses of nonfat dry
solids O O O O O O O O 0 O O O O O O O O O O

Subjective and objective measurements of baked
cuStards O O o 0 e e e e e e e e e e e e e e

Subjective tests . . . . . . . . . . . . . .

Objective tests . . . . . . . . . . . . . .

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13
13
15

TABLE OF CONTENTS (Contd.)

Syneresis . .
Gel strength .
Curd tension me
Penetrometer .
Standing index
PROCEDURE . . . . .

ter . . . . . . . . .

Design of experiment . . . . . . . . . .

Ingredients . . .

General procedure

Preliminary preparation . . . . . . . .

Preparation of cust
Custard cups . .
Baking . . . . . .
Cooling . . . .
Subjective tests .
Objective tests .
pH readings . .
Time-temperature

Syneresis . . .

ard mix . . . . . . .

curves.......

Curd tension meter . . . . . . . . . .

Penetrometer . .
Standing index .
Statistical methods

Page
15
15
16
16
17
18
18
18
22
23
24
24
24

25
26
26

27
27
28
29
29

TABLE OF CONTENTS (Contd.)

DISCUSSION OF RESULTS
Palatability Scores (Subjective tests)

Appearance .
Crust . . .
Color inside
Flavor . . .
Firmness . .
Smoothness .

Sweetnes 3 0

General acceptability

Objective tests

pH readings

Time-temperature curves

Syneresis .

Gel strength

Curd tension meter

Penetrometer . .

Standing index . .

SUMMARY AND CONCLUSIONS

REFERENCES CITED
APPENDIX 0 O O O

O

Page
31
52
52
34
57
39

43
46
48
51
51
51
56
59
59
61
66
69
72
76

LIST OF TABLES

Table
l Solubility Index and Moisture Content of
Dried Milka O O O O O O O O O O O O 0 O O O
2 Adjusted Average Scores and Analysis of
Variance for Appearance Scores . . . . . .
5 Adjusted Average Scores and Analysis of
Variance for Crust Scores . . . . . . . . .
4 Adjusted Average Scores and Analysis of
Variance for Inside Color Scores . . . . .
5 Adjusted Average Scores and Analysis of
Variance for Flavor Scores . . . . . . . .
6 Adjusted Average Scores and Analysis of
Variance for Firmness Scores . . . . . . .
7 Adjusted Average Scores and Analysis of
Variance for Smoothness Scores . . . . . .
8 Adjusted Average Scores and Analysis of
Variance for Sweetness Scores . . . . . .
9 Adjusted Average Scores and Analysis of
Variance for General Acceptability Scores .
10 Average pH Readings on the Unbaked and Baked
Custards . . . . . . . . . . . . . . . .
11 Correlation between some Subjective and
Objective Measures . . . . . . . . . . . .
12 Average Daily Scores for Appearance . . . . .
15 Average Daily Scores for Crust . . . . . . .
14 Average Daily Scores for Color Inside . . . .
15 Average Daily Scores for Flavor . . . . . . .
16 Average Daily Scores for Firmness . . . . . .
17 Average Daily Scores for Smoothness . . . . .

Page

21

33

55

58

4O

42

44

47

49

52

65
77
78
79
80
81
82

LIST OF TABLES (Contd.)

Table Page
18 Average Daily Scores for Sweetness . . . . . . 85
19 Average Daily Scores for General Acceptability. 84
20 Score Sheet for Baked Custards . . . . . . . . 85

21 Illustration of Statistical Calculations for
Flavor Scores . . . . . . . . . . . . . . . 86

Figure

LIST OF FIGURES

Average Time-Temperature Curves for Baked

Custards at Concentration Number 1 .

Average Time-Temperature Curves for Baked
Custards at Concentration Number 1%

Average Time-Temperature Curves for Baked

Custards at Concentration Number 2 . .

Syneresis (grams per hour) . . . . . .

Average Curd Tension Meter Readings on

Baked Custards (grams) . . . . . . .

Average Penetrometer Readings on Baked

Custards (millimeters) . . . . .

Average Standing Index Readings

Page

55

54

55
57

6O

65
67

INTRODUCTION

During the past few years there has been a tremendous
growth in the use of nonfat dried milk solids in commercial
food products. in.large quantity cooking and home cooking.
Dried milk solids are easily stored and cost much less than
f1uid.skim.milk.

Three methods are used in manufacturing nonfat dried
milk solids: atmospheric roller or drum.drying, vacuum
drum drying and spray drying. The latter process may be
carried out at low, intermediate or high temperatures and
such powders are called dairy, intermediate and oven dried
milk solids. The different temperatures to which these
milks are subjected during the drying process cause the
dried milk solids to have certain characteristics which
are desirable for some special uses in cooking.

This study was initiated to obtain information
concerning the merits of the various processed nonfat
dried milk solids at different concentrations in baked
custards. Custards were selected because they have a
high degree of sensitivity to slight changes in egg-milk-
sugar mixtures as demonstrated by Carr and Trout (3) and
in Logue's study (22). I

REVIEW OF LITERATURE

Nonfat Dry mm: Solids

mm

The Federal Food. Drug and Cosmetic Act of March 2. 1944
has defined defatted milk solids as follows (54):

“That for the purposes of the Federal, .Drug and

Cosmetic Act of June 26, 1958 (ct. 6'75, Sec. 152.

Sta. 1040) nonfat dry milk solids or defatted milk

solids is ' the product resulting from the removal of

fat and water from milk. and contains the lactose,

milk proteins and milk minerals in the same relative

proportions as in the fresh milk from which made.

It contains not over 5 percentum by weight of moisture.

The fat content is not over 1% percentum by weight

unless otherwise specified. The term milk when used

herein. means sweet milk of cows."

"6.4.1113 0 21W

Dried milks consumed in the United States are manu-
factured by three principal processes: spray, atmospheric
roller or drum and vacuum drum. The milk is pasteurized

before or during the drying procedure in all three processes.

In some drying procedures the milk is partially concen-
trated first to increase the drying speed. This is done

by the application of heat. The concentration varies with
the method but it may be as great as 40 percent. This heat
treatment sometimes has an effect on the cooking quality

of the milk. Helm (17) stated that skim milk is usually
preheated to 185° F since the milk treated in this manner
has better baking qualities than skim milk which has

received only pasteurization.treatment.

Sara: 221.21 mm: In the spray dryinz method the
partially concentrated milk is sprayed by pressure or

centrifugal means into a chamber through which a current

of heated air is directed. The milk droplets dry instantly
to a fine powder. The force of gravity or cyclonic motion
removes the milk powder from.the air. Three different
types of Spray dried powder are produced. They differ

only in the temperature used during the process (17).

Atmosgheringzgm Ezocegs Qghfiglleg Process: In this
method revolving metal rollers or drums are coated with a

thin.film of milk which dries by steam heat as the rollers
revolve. A steel blade. which is placed parallel to the
surface of the roller or drum, removes the film of dry
milk in one complete revolution. The milk product is

then reduced to a powder by a grinding device. wright
(56) states that atmospheric roller drying causes quite
extensive heat damage.

lam m 2:293:13 This process is the same as the
atmospheric drum process except that the drumor roller is
enclosed in a chamber which is maintained under a partial
vacuum during the drying period. Vacuum.drum.processed
milk is expensive to produce and thus is manufactured only

in very small quantities (20).
Characteristics of Nonfat Dried Milk Solids

Honfat dried milk solids have many characteristics
which affect their cooking properties. Hunsiker (20)
states that the particles in spray dried milks are minute
spherical grains. each grain has one or more air cores and
consequently is susceptible to oxidative deterioration.

The lactose is present in a noncrystalline form as a very
concentrated solution or glass (55). Since lactose consti-
tutes the continuous phase it may diminish the permeability
of the milk powder particles to gases. The lactose glass
is very hygroscopic and can take up water until it is
diluted to such an extent that the molecules attain
sufficient mobility to become oriented in crystals. Dried

milk powders manufactured by the spray and vacuum.drwm
processes are 99 percent soluble and retain.many of the
properties of fluid milk (20). Maximum.protein solubility
in water occurs at 50° C (18). Choi and coworkers (8)
pointed out that lactose was nonhygroscopic in.fresh none
fat dried milk solids of low'moisture content. As the
powder absorbed moisture. the lactose changedto .(-lactose
hydrate which was much less soluble. .The critical moisture
level was 7.5-8 percent. This moisture content was ac-
companied by loss of solubility, caking, browning and
development of undesirable odors and flavors (29).
Atmospheric roller processed dried.milk powders are
composed of flakes which are irregular in size and shape
(20). No air cells are present. These powders are partially
non-hygroscopic. Due to the high drum.temperature necessary
for drying there is a slight discoloration of the product
and partial coagulation of the protein. This coagulation
is a result of the denaturation of the protein constituents,
casein and lactalbumen. which makes them insoluble. There-
fore these powders are difficult to dissolve in water.

Theory of Heat Coagulation

Custards thicken and attain a serving consistency
due to the formation of a gel. This is formed by the

coagulation of protein which holds the liquid within its
meshes. In custards egg furnishes the larger percentage

of heat-coagulable protein. since only 0.75 percent of the
protein of cow‘s milk is heat-coagulable. However this
small amount has a decided effect on coagulation of custards
(25). According to Gortner (12), heat denaturation or
coagulation of proteins takes place in three steps:

(a) the denaturation proper which is the intraamolecular
rearrangement of the molecules, (b) the flocculation of

the denatured protein and (c) the coagulation or setting.
This coagulation occurs because of polymerization of the
denatured protein molecules. Chick and Martin (4) thought
that coagulation occurred in two stages only: denaturation
and coagulation. In the language of colloid chemistry
denaturation is the change in the protein from the hydrophilic
to the hydrophobic state (24). When a protein has reached
the denatured state it is insoluble. This occurs most
readily at its isoelectric point and thus proteins are

least soluble at this pH.

Coagulation of protein.hay be brought about by a
variety of ways. One of the principal means is heat.
Acids, alkalis, salts and sugar play an important role
in coagulation. A.brief discussion of the role played
by these factors in the coagulation of custards follows.

mgwm rt

One of the most common ways that proteins are denatured
in.food preparation is by heat. Chick and Martin (5) state
that heat coagulation is a reaction between protein and
water. The effect of temperature is merely to accelerate
the reaction (4). Davies (11) indicates that the degree
of denaturation of the protein in milk depends upon the
time and temperature of heating. The rate of heating plays
an important role in the temperature at which coagulation
takes place (25).

Knife 9.1.4231

The clotting of the denatured protein by small amounts
of acid or alkali is due to the electric charge given to
the particle (5). Addition of an acid solution speeds the
second part of the heat coagulation process but not the
denaturation process itself. For every solution containing
denatured protein there is a critical temperature. depending
on the reaction, below which coagulation does not take
place. In general the coagulation temperature is higher
with an increase in acidity.

EII££&.Q£.AIKSLI

Alkali also has a definite effect on protein coagulation.
According to Chick and Martin (6), in alkaline solution the

second part of the coagulation process does not occur.
If after heating. the alkali is neutralized with acid

then coagulation occurs.

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Chick and Martin (7) indicate that coagulation is
greatly influenced by the presence of neutral salts.
Dispersion by salts appears to be caused by the adsorption
of ions on the denatured particles of protein. The ion
of the Opposite charge to that of the protein is adsorbed.
The coagulating power of the ion increases with increasing
valence. In heat coagulation of milk. the milk salts play
an important role. In general the citrates and phosphates
appear to increase stability whereas calcium decreases

the stability of milk to heat (25).

waffles;

An.increased prOportion of sugar elevates the gelation
or coagulation temperature (25). This is due to the
peptizing effect of the sugar on the protein.

Use of Baked Custards in Studying
the Properties of Driedeilk Solids

Custards were selected for use in this study to show
differences in cooking prOperties of various dry milk solids

because custards have a high degree of sensitivity to slight
changes in egg-milk-sugar mixture. This sensitivity was
demonstrated in Logue's study (22) on the cooking qualities
of different grades of eggs and in the study by Carr and
Trout (5) on the different cooking prOperties of whole and
homogenized milks.

Whole milk custards should be baked to an internal
temperature of 82° - 84° C (es). With normal baking
conditions curdling generally occurs between 85° - 87° C.
If the custards are heated rapidly they are too thin to
serve even at 87° - 890 C, and frequently curdle before
a serving consistency is reached. Carr and Trout (5)
observed that heat penetration was slower in custards
made with homogenized milk than those made with plain.milk.
Such custards could withstand higher baking temperatures
without seriously affecting the stability of the gel.

Morse and Davies (25) reported that an increase in
gel strength and gel stability occurred in baked custards
fortified with nonfat dry milk solids. Carr and Trout (5)
found that custards made from.homogenized milk also had
a more stable gel. The formation of egg gel, such as in
baked custards, depends upon the coagulation of the protein
and the ability of the precipitated protein to hold within

10

its meshes the solution from which it was precipitated (26).
Thus it would seem that in nonfat dry milk solids and homo-
genized milk the protein has been changed somewhat in nature
from that of whole milk. since custards made from dried
milk solids coagulate at a different rate and the protein
mesh retains the solution better. In Korea and Davies'
experiment (25) as the concentration of dry milk'solids

was increased the strength of the gel improved.

The curd tension meter readings in Carr and Trout's
experiment (3) indicated that homogenized milk had a timer
coagulum than nonhomogenized milk. Hollender and Weckel (16)
found Just the reverse results. In their study the serum
protein separation was greater with homogenized milk. This
separation increased when the cooking time was prolonged.
Bonogenized milk had a more critical cooking temperature
than plain whole milk.

Custards made with plain whole milk have a soft crust
which browns evenly. Custards made with homogenized milk
and nonfat dried milk solids had a tough skin which did
not brown except at the extreme edges (5. 25). A theory
of browning is set forth by Ramsey and coworkers (51).
when milk was heated for a sufficient length of time at
high temperatures (90° - 120° C) the lactose was decomposed

and acid products formed. This increased acidity inverted
some of the sucrose to dextrose. A.brownish color developed
as a result of the condensation product of the free aldehyde
group on the dextrose molecule with the protein. They found
that this did not occur when.sucrose only was present because
it contains no free aldehyde or ketone group.

Horse and Davies (25) showed that whole milk custards
had a sweeter flavor. They suggested this might have been
due to the.fact that sugar concentrates in the liquid phase
and since these custards showed greater syneresis they
seemed sweeter.

In the work, mentioned above, by Morse and his coworkers
the pH of the baked custards containing nonfat dried milk
solids ranged from.6.9 to 7.5. The acidity of the custards

increased with an increase in concentration of milk solids.
Intritive value and Uses of Nonfat Dried Milk Solids

In studying the properties of nonfat dried milk solids
the nutritive value should be considered. Coulter (9)
stated that the nutritive value of spray dried whole milk
is not inferior to that of the milk.from.which.it is
prepared, unless oxidative deterioration.or sugar protein._
interaction have occurred. Nonfat dried milk solids contain

only very small amounts of the fat soluble vitamins and
only .9 percent fat.

The type of nonfat dried milk solids to be used in
different products in cooking often presents a problem.
The solubility of the different milk solids is important
in food preparation, especially in products such as beverages,
soups and sauces which have a high water concentration (28).

O'Malley (27) recommended the following uses for none
fat dried milk solids. Spray dried milk solids should be
used in cakes and similar products. Either spray or roller
nonfat dried milk solids should be used in.yeast raised
products. When.these are used the milk must be heat treated_
before drying to inactivate the compounds in raw milk which
interfere with the development of the dough. Milk.solids
for cottage cheese should be pasteurized only. since higher
temperatures interfere with the curd.formation.*

The fact that improvement in baking quality of nonfat
dried milk solids appears to involve heat denaturation of
milk serum proteins has prompted efforts to correlate baking

 

*In a private communication, Beach states that oven
tested or high heat powder is used in the baking industry
in dry mixes and sausage manufacture. The low heat powder.
which usually is more expensive, is used for cultured butter
milk, cottage cheese, ice cream and chocolate milk.

13

qualities with the extent of denaturation. Heat treatment
(9) produces an effect similar to removal of‘a reducing
group. This heat treatment decreases the reactivity of

the majority of the -SH groups. Harland and Ashworth (14)
devised a method for determining nondenatured serum protein
by measuring the turbidity developed by acidification of the
filtrate, which was obtained by salting out the casein with
sodium chloride. From.18 samples of good quality baking
nonfat dried milk solids. 15 had nondenatured serum protein
nitrogen content ranging from..67 to 1.40 mg per gram.
Fourteen.out of 17 samples of poor baking quality dried
solids had readings ranging from 1.86 to 6.59 mg per gram.
Thus it appears that if denaturation is carried too far,

. a dried milk solid of poor baking quality results. ‘Kitzes
(21) indicated that spray drying has the distinct advantage
over roller drying of mdnimizing heat damage.

Subjective and Objective Measurements of Baked Custards

Whats.

The ultimate test for any product is its eating quality.
The best flavor. texture or eating quality is that which
people prefer in a given.food. Organoleptic tests are
conducted to decide how near the standard the unknown

samples come.

14

The validity of organoleptic tests is based on several
fundamental assumptions (50):

1. Reaction of the same judge to exactly the same food
‘will continue to be the same throughout the period of the
test.

2. Difference between two samples from two lots is
greater than the difference between.two samples from the
same lot.

5. Preferences expressed represent reliable. reproducible
decisions, not mere guesses which.may easily be reversed.

Organoleptic tests are the only means of expressing
many important qualities of food products. In the laboratory.
eating quality or palatability of a product is divided into
component parts. Trained judges are asked to discriminate
between samples by rating large and.small differences in
the various characteristics. These differences are usually
rated on the basis of their degree of acceptability. written
records of sensations and impressions are kept. An evaluation
of these records is used as a basis for determining the
relative quality of a sample.

Organoleptic tests are not sensitive enough for critical
evaluation in some cases. In order to eliminate the personal
factor, much time and thought has been spent on.the develop-
ment of objective means of testing the quality of foods.

15

The results of these tests are correlated with those

obtained by organoleptic procedures.

Objectiye Tests

Several tests have been developed to measure some of
the physical characteristics of baked custards by objective
means. The main tests are the syneresis of the custard,
the rate of heat penetration during baking and the gel

Strength.

Syneregig: After the gels are allowed to stand.
protected against evaporation, for a number of hours.
there is a tendency for the gel to separate into 2 phases.
liquid and solid. This is called syneresis. Various methods
have been devised for measuring this weeping. Some employ
the use of adsorbent paper while others use a fine mesh or
screen through which the liquid drains. Then this liquid
can be weighed. Unfortunately there is no standard method

for measuring syneresis.

fig]. m: The gel strength of a custard can be
measured by various instruments. In'this experiment three
methods were used: the penetrometer which measures the

consistency or breaking strength of the gel; the curd

16

tension meter which measures the cutting strength of the
gel and the 'standing index' which measures the ability
of a gel to hold its shape on standing.

M M 11.612923 The curd tension meter was first
used by Hill (15) to estimate the degree of hardness of the
curd in milk. This test was employed to find out the type
of milk most suitable for infants. A.milk with a soft
curd was found to be the easiest to digest. The instrument
measured the tension or force required to draw the curd
knives through the curd. Carr and Trout (5) used a modifi-
cation of the curd tension meter to measure the differences
in gel strength in.custards made from.homogenized and none
homogenized milk. The curd tension meter measures the
resistance of the custard to the cutting blades of the
instrument. The reading is in grams and is called “the

curd tension."

W: Various elaborate instruments are
available for determining the consistency of food products
by measuring their penetrability. One of these instruments
is called the penetrometer.* The instrument measures the

depression in a sample caused by a force applied over an

 

*New'York Testing Laboratory Penetrometer.

17

area for a given length of time. Hooke's law states that
the strain produced is in proportion to the stress producing
it and this is the basic principle of the penetrometer.
The average readings of such tests in millimeters penetration
is referred to as the index of 'penetrability'. The penetro-
meter was originally used for penetration tests of bituminous
materials. asphalts, petrolatum and grease. A modification
has been.used to determine the moisture content of soils
of which maximum density is produced by a specific amount
of compacting. A penetration cone, needle or disc may be
used. depending upon the type of material to be tested.

The penetrometer has been used successfully in testing
the texture of various baked products such as cake and bread,
vegetables. and the consistency of batters and cooked

nuxtures such as cornstarch puddings and applesauce.

Standing Iggggfi A.measure for the gel strength of a
custard is the ”standing index.” This measurement. used
by Carr and Trout (5). is the ratio of the height to the
average diameter. After the custard has stood for sometime
the standing index diminishes as a result of the decrease
in height and increase in spread.

18

PROCEDURE
Design of Experiment

Baked custards prepared from drum dried and from
spray dried nonfat dried milk solids were compared ob-
jectively and subjectively. The best proportions of non-
fat dried milk solids to be used in the baked custards
were determined.

The pattern selected for this experiment was the
statistical plan.known as the balanced incomplete block.
In.this design only a part of the total number of samples
is judged at the same time. The distribution of the
treatments is randomized throughout the tests.

Four variations were prepared each day. Each variation
was baked 4 times during the experiment. Skim milk was
used as the control. Seventeen custards of each replication
were made at one time. One custard was used for the temper-
ature reading. 11 for the objective tests and 5 for the

subjective tests.
Ingredients

All the ingredients were obtained at the beginning
of the study with the exception of the fresh skim milk

which was purchased as needed.

19

Fresh eggs were obtained.from.the Foods and Nutrition
storeroom. The eggs were mixed with a mechanical mixer*
using the following proportions: .75 grams of salt, 75
grams of sugar, and 288 grams of eggs. This mixture was
beaten 8 minutes at No. 1 speed. It was then strained
into a large container and the procedure repeated until
sufficient egg-sugar-salt mixture for the entire experiment
had been obtained. This large quantity was thoroughly
blended to insure a homogeneous mixture. Then the egg-
sugar-salt mixture was weighed into 565.75 gram portions
and placed in pint freezing containers, sealed, labeled
and stored immediately in the deep freezer.

The three types of spray dried milk** used in this
experiment are described by Beach (2) as:}

1. Low heat or dairy type powder which is heated to
175° F and held at this temperature for five minutes or
to 145° F and held for so minutes.

2. High heat or oven tested powder which may be
heated to a minimum temperature of 175° F and held for
50 minutes or more often heated to 195° F and held for
50.ninutes. Temperatures as high as 240° F may be used
but the holding time is reduced.

 

*Kitchen.Aid.
**Purchased.from Michigan Producers Dairy Company.

2.0

5. Normal type or intermediate spray dried powder
is heated to temperatures in between that used for oven
or dairy types of dried milk. 1

These solids were obtained in polyethylene sacks
which were tightly tied to keep out any moisture. and
stored in cold storage.

The drum dried nonfat solids* used in this experiment
were preheated to 180° F. The temperature of the roller
was 5200 F. Enough drum dried milk was purchased for the
entire experiment and stored in cold storage in.screw-top
bottles.

The figures for the solubility index and moisture
content of the dried milk solids at the beginning and end
of the experimental period are listed in Table 1. The
moisture content was determined according to the methods
recommended by the Dry Milk Institute (1) and the solu-
bility index by the method outlined by Howat and coworkers
(19).

The figures for the solubility index and moisture
content of the Spray dried milk solids fell within.the
normal range cited in the literature and thus it was
assumed that normal samples of Spray dried milk were used

 

*Lansing Dairy Company.

21

TABLE 1

Solubility Index and Moisture Content of Dried Milka

 

 

Solubility Index MoigtupeCEptept
Beginning of End 0 Beginning of End of

9": -' w 1 k 0: y‘i 530‘ “2:9 kg9‘ in‘v $=" -U‘t
percent percent percent percent

Spray, oven 100.7 98.0 5.51 4.06

Spray, dairy 94.9 97.2 2.67 2.88

Spray. inter-
mediate 99.6 96.5 4.10 5.85

Drum. 55.8 56.7 5.18 4.20

 

22

in the experiment. The first lot of drum dried milk solids
obtained had a very low solubility index and therefore a
second lot was purchased which was definitely known to be
fresh. This lot also had a low solubility index indicating
that this was characteristic for drum dried milk solids.

General Procedure

The basic custard described in Lowe (25) was used in

this experiment. The recipe was as follows:

Milk (skim) 6 cups 1464 grams
Sugar 5/4 cup 150 grams
Egg 6 288 grams
Salt . 75 grams

The nonfat dried milk solids were substituted for
skim milk into the recipe on the basis of skim milk
containing 9-1/2 percent solids and 90-1/2 percent water.
The solids were used in a:

1:1 ratio = 140.25 grams solids + 1525.75 grams water -
6 cups skim milk

1:1.5 ratio = 210.58 grams dry milk solids +-1525.75
grams water '

1:2.0 ratio = 280.5 grams dry milk solids + 1525.75
grams water

23

Preliminary Preparation

Four cartons of the egg-salt-sugar mixture were
removed from the deep freeze and placed in the refrigerator
to thaw.

The nonfat dried milk solids were weighed on cello-
phane paper on a torsion balance. To these solids was
added half of the total sugar in the recipe - the remainder
being already in the frozen egg mixture. The milk solids
and sugar were blended with a metal tablespoon.using 20
strokes. The required amount of water was heated in an
enamel pan to 50° C. This was transferred to the large
size bowl of an electric mixer.* The electric beater was
Operated at No. 2 speed and the dried milk solids were
sprinkled into the water in 4 portions as indicated below:

Time Speed
lst portion 0 minutes No. 2
2nd portion. 5/4 minutes No. 2
5rd portion li-minutes No. 2
4th portion 2% minutes No. 2

After the last addition of milk the mixture was beaten
an additional 1-5/4 minutes at No. 2 speed and than 1/2
minute at No. 5 speed. A rubber spatula was used to clean

 

*Hamilton Beach. Model G

24

off the sides of the bowl during the mixing process. The
milk was transferred to a Pyrex bowl, covered and stored

in the refrigerator over night.
Preparation.of Custard Mix

The egg mixture was blended with the milk for 1/2
minute using the electric heaters at No. 2 speed. Any

froth was removed.
Custard Cups

The custards were baked in 5 oz. Pyrex custard cups.
The cup was filled with.custard mix to within 1/2 inch of
the top. This distance was measured with a depth gauge.
All the cups contained 101:: 5_grams of custard. The cups
were numbered according to subjective and objective tests
for which they would be used. They were placed in the
baking pan in a definite pattern. This pattern varied
according to the oven in which the custards were to be

baked.
Baking

‘Water at 55° C was poured into the baking pan filling
it half full. The custards were placed in the oven and
more water was added to the baking pan until it came up

25

to the designated mark. (This mark had been previously
established so that the water reached the exact height

of the custard in the cup.) They were baked at 525° F in
gas ovens. The oven.temperatures were checked each day
with an oven thermometer. A.thermometer was placed in the
custard dish designated in the plan and a second thermometer
in the water bath. The custards were baked to an internal
temperature of 92° C. This temperature was determined by
preliminary experiments. as follows. Custards made from
all the different types and concentrations of dried milk
solids were removed from the oven at internal temperatures
ranging from 84° C to 95° C. At 84° C the gel of the
custards had not formed and at 95° C the custards appeared
slightly curdled. Custards baked to an internal temper-
ature of 92° C gave the most acceptable custard.for all

the types of dried milk solids at the various concentrations.

Cooling

The custards were removed from the water bath and
placed on a wire rack. They were allowed to cool until

they reached room.temperature (2 to 2% hours).
Subjective Tests

The custards were scored for.flavor. sweetness,

smoothness, appearance, color inside, firmness, crust.

26

and general acceptability, by 5 judges from the Foods and
Nutrition Department of Michigan State College. The
judges were requested to record comments concerning any
outstanding features noted. A sample of the score sheet

used is shown on page 85 of the appendix.
Objective Tests

The room.temperature and humidity were taken and
recorded at the beginning and end of each test period.

hammer.

The pH was taken on the fluid mixture before baking.
In order to determine the pH of the baked custard. 2 grams
of custard were mixed thoroughly with 10 ml. of distilled

water. The pH was measured by using a Beckman pH meter.

Time-Temperature 93212:

The temperature of the uncooked custard mixture was
taken before placing in oven. A second temperature reading
was taken 10 minutes after the custard had been placed in
the oven. Temperature readings were taken every 5 minutes
thereafter until the internal temperature of the custard
reached 92° C. The time-temperature curves for the 4

replications of each variable were plotted as a graph.

27

Syneresig

The rubbery crust was removed from the top of the
custard with a knife. The custard was then inverted on
a very fine screen under which a weighed petri glass was
placed. The weight of the petri dish was recorded every
hour for five hours. The amount of syneresis each hour
was obtained by taking the difference in weight. This
procedure was carried out on 2 samples for each type of
custard. The samples were covered between readings to

prevent evaporation.

Curd Tension meter

The firmness of the custard was measured by the curd
tension meter. The meter consists of a cutter and a float
assembly which floats freely in a pool of mercury. The
custard was placed in the path of the downward moving
cutter. The blade was brought into contact with the
custard and the amount by which the float was raised out
of the mercury was a measure of the resistance offered
to the passage of the cutter through the custard. This
provided a measurement of the gel strength. Three types
of readings were taken: one with the crust on the custard,

one with the crust removed and a third on the inverted

28

custard. Two samples of each type of custard were used.
The knives of the curd tension meter were unable to cut
through some of the crusts. Therefore the data collected

from the custards with the crust on were not used.

W

The penetrometer readings give the depth of penetration
within a certain time period caused by a total weight of
75.5 grams for disc and needle bar. The cup of custard was
placed on the level platform and centered under the disc,
which was in contact with the top of the custard. The
spring was released for 2 seconds allowing the disc to
penetrate the custard, giving the depth of penetration.

A.2 second period was used instead of the usual 5 second
period of penetration because with the longer period the
disc passed directly through some of the custards to the
glass plate. The strength of the crust, the strength of
the gel at the top of the custard when the crust had been
removed and a third reading on the gel strength of the
inverted custard were made on each type of custard. The
penetrometer readings reported are the average of duplicate

readings for the above tests.

29

m <11 and

The standing index was determined by removing the
rubbery crust and inverting the custard onto a flat square
glass plate. This glass was placed over a paper which had
concentric circles* drawn thereon. Quadrant readings were
taken. The height in inches was measured with a depth
gauge. The spread and height of each custard was taken
at the beginning of the test period and every hour for the
5 following hours. This test was carried out on 2 samples
of each type of custard. The custards were kept covered

between.readings to prevent evaporation.
Statistical Methods

It is well known that large day-to-day variations may
occur in studies involving food preparation, even though
the same procedures are being repeated each.day. In
addition. it is often impossible to handle many variations
in a single day because the procedures are time consuming,
and judging panels usually cannot handle more than 6 to 8
samples at one time. Since 15 variations were employed in
this experiment, the balanced incomplete block given by
Cochran and Cox (10) was used. This design permits ad-
justment of the data to allow for the.fact that not all

 

*As in Grawemeyer and Pfund's experiment (15).

30

the samples were done on the same day. The corrected mean
factors are indicated as adjusted mean scores. The complete
calculation for one scoring item (flavor) is given in the
appendix.

The least significant difference was calculated using
the corrected skim milk custard scores as a standard.
Calculation of the least significant difference designates
a range around the standard. Any score falling outside
this range is said to differ significantly from the standard.
The least significant differences were computed for proba-
bilities of l in 20 and l in 100. In this experiment all
the dried milk custard scores were lower than the scores
for the standard (skim milk). so only the negative half
of the least significant difference range was used.

Correlations were calculated between the following
pairs of items: crust score versus penetrometer reading
(crust on); crust score versus difference between penetro-
meter reading for crust on and off; firmness score versus
penetrometer reading (crust on); firmness score versus
penetrometer reading (crust off); firmness score versus
penetrometer reading (custard upside down); firmness score
versus curd tension meter readings (crust off); firmness
score versus curd tension meter readings (custard upside down).

The method of calculation given by Snedecor (52) was employed.

51

DISCUSSION OF RESULTS

The quality of baked custards containing drum dried
and spray dried milk solids at three different concentrations
were evaluated. Hereafter, nonfat dried milk solids will
be abbreviated DMS. The levels of DM3 will be designated
as concentration No. l, which is equal to the concentration
of solids in.fluid skim milk; concentration No. 1%, being
equal to one and a half times the concentration of solids
'in.fluid skim milk and concentration No. 2. which is equal
to twice the concentration of solids in fluid skim milk.
Three types of spray DMS were used which differed only in
the heat used during processing. The DMS treated at low
temperatures is called dairy DMS; the one at intermediate
temperatures. intermediate DES and the milk processed at
high temperatures, oven DMS.

The results of each subjective and objective test will
be discussed in the following manner: the results of the
analysis of variance will be given followed by an outline
of the overall picture of the results dealing with all
types of custards made; a paragraph dealing with the
differences between.custards containing the four types of
DMS will follow and finally a discussion on the effect of

concentration of DMS on the various custards.

32

Palatability Scores

.A summary of the adjusted average scores and analysis
of variance for each characteristic judged by the scoring
panel is shown in the table following the discussion of
that particular characteristic. Hereafter, the least
significant difference, from scores of Skim.milk custard
(standard). will be designated as LSD. The average judging
scores for each replication are given on page 'r70f the
appendix. The highest rating a custard might receive for
a given characteristic was seven, the lowest, one. A
rating of seven would indicate an excellent product in
that characteristic. a rating of one a very poor product.

ADEQQZQEQQ

The average scores and analysis of variance for

appearance are shown in Table 2. Analysis of variance
for these scores indicates that the chief source of
variation among the scores was the difference between
custards made from the various types and concentrations
of EMS.

Skim milk had the highest score for appearance.
The scores for oven DMS concentration No. 2 fell within

the least significant difference at the 5 percent level.

33

TABLEZ

Adjusted:L Average Scores and Analysis
of Variance for Appearance Scores

‘—‘-

__ 5113310 (Matse
Concentrat on oncentrat on oncentration

 

 

 

 

W No. i Noam: NiiL—o
Skim 5.7
Dairy Spray 4.6 4.8 5.0
Intermediate Spray 5.0 5.0 5.0
Oven Spray 4.7 4.9 5.1
Drum 4.0 2.7 2.5
Skim - LSDOl 5.0
Skim - LSD05 5.1
Analysis of Variance
£922.93. 123°”? of F

Total 51 - g.
Adjustedl Treatment 12 . 422567 3. 40*
hror for Adjusted]-

Treatment 27 .124465
AdjustedlBlocks 12 .127658 <1
Intra Block Error 27 .141504

 

*Significant at 5% level

lAdjusted according to method given by Cochran and Cox (10).

34

Custards of intermediate DMS at the three concentrations

and dairy DMS at concentration No. 2 had equal scores, and
were just at the limit of the 1 percent LSD. All the other
custards received scores less than these. In some instances
the reason for the low score was a cracking or wrinkling of
the crust.

Of all the DMS, the intermediate gave the custard of
best appearance. Custards of oven DMS had a slightly better
appearance than those made from dairy DMS. The custards of
poorest appearance were made from the drum DMS. This may
have been due to the fact that the protein of the drum.DMS
was nearly insoluble. The custards appeared granular and
bubbly.

An increase in concentration of dairy and oven DMS
improved the appearance of the custards. There was no
difference in the judges' scores for appearance when the
concentration of intermediate DMS was increased in the
custards. With drum DMS, as the concentration was increased

the appearance scores were poorer.

ngst

The adjusted average scores and analysis of variance

for the crusts are shown in Table 5. The chief source of

35

TABLE 3

Adjusted Average Scores and Analysis
of Variance for Crust Scores

R o o t
CBncentration.Eoncentration Concentration

 

 

 

 

 

 

M Nail No_:_la_____9.a_z__i N
Skim 5.2
Dairy spray 4.7 4.4 4.2
Intermediate Spray 4.7 4.5 4.2
Oven Spray 4.9 4.4 4.1
Drum 5.5 5.8 4.8
Skim - LSDOl 4.4
Skim - LSD05 4.5
Analysis of Variance
Search W W F

Total 51 - -
Adjusted Treatment 12 1.105555 6.26**
Error.for Adjusted

Treatment 27 .176290 -
Adjusted Blocks 12 .197992 1.04
Intra Block Error 27 .190152

 

“*Significant at l% level

36

variation between scores would appear to be a consequence
of the concentrations and kinds of DMS used. No significant
variance between replications appeared in the data.

The crusts were scored only for toughness or tenderness.
The crusts on the custards from drum DMS at concentration
No. 1% received the highest score. The crust on the drum
DMS at concentration No. l scored second highest and then
the score for the crust on the control custard was next.
The average score on the crusts of oven and dairy DMS at
concentration No. 1% were equal. Scores for crusts from
the three spray DMS at concentration No. 2 and intermediate
DMS concentration No. 1% were highly significantly lower
than that of the control. .

Drum.DMS gave the most tender crust of all the milks
used. The judges indicated that. though tender, the crusts
did not have a desirable consistency. They were mealy and
spongy. The crust on the control custard was the next most
tender and had a desirable consistency. Oven DMS gave the
most tender crust of the spray DMS custards. The toughness
of the crusts varied little between custards made with
intermediate and dairy DMS.

All the crusts on the skim.and spray DMS custards

were rather tough. As the concentration of DMS was increased

37

the crusts became tougher. The toughness of the crusts
appears to be caused by dry heat on the tap of the custard.
since dry heat toughens protein. Possibly the tenderness
of the crusts on.whole milk custards could be explained

by the presence of fat which tends to collect at the
surface of the custard. To test this hypothesis, a
supplementary series was done, in which a small amount

of melted butter was added to the DMS custard mix before

baking. The crusts on these custards were more tender.

Colgr Inside

Analysis of variance on the average scores for the
inside color of the custards, listed in Table 4. indicates
that the main source of variation between the scores was
due to the levels and types of DMS used. Variation due to
replications was significant at the 5 percent level.

Skim.milk custards had the highest score for color.
The scores for intermediate and oven DMS custards at
concentration No. l fell within the least significant
difference at the 5 percent level. Custards of intermediate
and oven DMS at concentration No. 1% had equal scores and
were just at the limit of the 1 percent LSD. The scores
would indicate that the color of all the other custards
were highly significantly different.from the control.

38

TABLE 4

Adjusted Average Scores and Analysis
of Variance for Inside Color Scores

 

 

 

 

lkha£L___.

 

 

5.4
5.5
5.6
2.9

F

 

115.35**

2.07*

_: Li» 0 Amo t
Concentration Concentration Concentration
W Noll M
Skim. 6.2
Dairy Spray ‘ 5.7 5.7
Intermediate Spray 6.1 5.8
Oven Spray 5.9 5.8
Drum. 4.2 5.4
Analysis of Variance
Degrees of
_._s__80 rce fascia—o Mars.
Total 51 -
Adjusted Treatment 12 4.418551
'Eiror for Adjusted
Treatment 27 .058504
Adjusted Blocks 12 .070692
Intra Block Error 27 .054250

 

wwSignificant at 1% level
*Significant at 5% level

39

The color of intermediate DMS custards was the most
acceptable to the judges of all the types of DMS custards.
Custards of oven DMS had a better color than those made
from dairy DMS. The color of custards from drum DMS had
the lowest score of all. These custards were gray in color
due to dark color of the milk solids. Probably the milk
solids had been scorched in processing.

As the concentration of DMS was increased in all the
custards the color became less desirable. The only exception
to this was the dairy DMS, which had the same score for

color at concentrations No. l and No. 1%.

Flavor

The adjusted average scores and analysis of variance
for flavor are given in Table 5. This indicates that the
chief source of variation among scores was the different
kinds and amounts of DMS. variation.due to replications
was not significant.

The custards made with Skim.milk received the highest
scores for flavor. Custards of oven and intermediate DMS
at concentration No. 1 had equal scores and were second
best. The average scores for custards of dairy DMS

concentration No. l were just at the 5 percent limit of

40

TABLE 5

Adjusted Average Scores and Analysis
of variance for Flavor Scores

—‘ __

 

 

 

 

5oncentrat§gg goncefitration Concentration

Type of Milk No.;l: No.:lé; No. a
Skim 6.0
Dairy Spray 5.5 5.1 4.9
Intermediate Spray 5.7 5.2 5.1
Oven Spray 5.7 5.4 5.2
Drum. 5.5 5.1 2.5
Skim - LSDQl 5.4
Skim - LSD05 5.5
Analysis of Variance

m 33:33:“ nag agen-g F
Total 51 - -
Adjusted Treatment 12 4.985818 55.22**
Error for Adjusted

Treatment 27 .095648

Adjusted Blocks 12 .06055 <1
Intra Block Error 27 .12527

 

**Significant at 1% Level

the LSD while the flavor scores for oven DMS concentration
No. 1% fell just at the 1 percent limit. 'All other custards
had scores below this level and were significantly different
in.flavor from the control.

Oven DMS custards had the best flavor of any of the
DMS used. The flavor of custards from intermediate DMS
were only slightly less acceptable. The scores for flavor
of dairy DMS were considerably lower. Custards from drum
DMS had a very poor flavor, tasting burnt. Probably this
DMS had been scorched in manufacture.

As the concentration of DMS was increased in all of
the custards the flavors were less acceptable. The judges

described the flavor as being “too milky”.

Firmnegs

Analysis of variance for the mean average scores,
shown in Table 6, indicates that the main source of variation
' among these scores was due to the different amounts and
kinds of DMS used in the custards. No significant differences
due to replication were evident.

The control custard received the highest score for
firmness. Oven and intermediate DMS custards at concens

tration No. 1 had equal scores, and were just at the limit

42

TABLE 6

Adjusted Average Scores and Analysis
of Variance for Firmness Scores

.—

 

 

 

 

 

EBncentratggfi goncegtration Concentration
IZE§_2§_E§J¥L N0-_le N9a_l%a N21_§____
Skim 6.2
Dairy Spray 5.5 5.1 4.5
Intermediate Spray 5.6 4.7 4.2
Oven Spray 5.6 4.9 4.6
Drum 4.1 5.9 5.6
Skim - LSDQl 5.5
Skim - LSD05 5.6
Analysis of variance

Degrees of ' -

Sogrge Freedom Mean Square ,_;E_
Total 51 - -
Adjusted Treatment 12 2. 541755 _ 16.55%
Error for Adjusted

Treatment 27 .155605
Adjusted Blocks 12 .254267 1.64
Intra Block Error 27 .142755

—

i*Significant at 1% level

43

of the 5 percent LSD. The average score for firmness of
dairy DMS custards at concentration No. I fell within the
1 percent significant range. The probability is very high
that the firmness of all the other custards were different
from the control.

Oven DMS gave the most acceptable custard as to firm-
ness. Dairy DMS in custards had a higher.firmness score
than intermediate DMS. The firmness of custards from drum
DMS scored very low.

As the concentration of DMS was increased in the
custards the firmness of the gel became less acceptable.
In scoring the custards for firmness, the judges indicated
whether a low score signified that a gel was too thin or
too stiff. With the spray DMS the low score indicated
that the gel was too stiff. This increase in stiffness
perhaps could be attributed to the increase in protein
concentration. The drum DMS had low scores for firmness
because they were thin and watery, which resulted from the
insolubility of the protein.

Smoothness

In Table 7 is shown the adjusted average scores and
analysis of variance for smoothness. As indicated the

chief source of variation among the scores was due to

44

TABLE 7

Adjusted Average Scores and Analysis
of Variance for Smoothness Scores

__‘_-

_g Rat o ounts)
Concentration Concentration Concentration

 

 

W No.11 N045 Naif...
Skim 6.5
Dairy Spray 6.2 5.9 5.6
Intermediate Spray 6.2 5.7 5.7
Oven Spray 6.0 5.8 5.7
Drum 4.1 5. 4 5.4
Skim - LSDQl
Skim - LSD05
Analysis of Variance
m $5333 of Mean Square F

Total 51 - -
Adjusted Treatment 12 4.505794 72.08**
Error for Adjusted

Treatment 27 .062485
Adjusted Blocks 12 .155517 2.46*
Intra Block Error 27 .054952

 

**Significant at 1% level
*Significant at 5% level

45

different kinds and amounts of DMS. Variation due to
replications was significant at the 5 percent level.
This difference could have been caused by some slight
variation in the experimental procedure or possibly the
judges' reaction to the result. Degree of smoothness is
difficult to judge and it is probable that variation on
the part of the judges' reaction to smoothness could
occur within replications. Also the baking time of the
custards varied from day to day and this would affect
the smoothness of the custard.

The highest scores for smoothness occurred with
custards made from skim milk. The dairy and intermediate
DMS at concentration No. 1 had equal scores for smoothness,
which were just at the limit of the 5 percent LSD. The
scores for custards from oven DMS at concentration No. l
fell within the LSD at the 1 percent level. The probability
that all the remaining custards varied significantly in
smoothness from the control is very high.

The oven and intermediate DMS gave custards which
were slightly smoother than the custards from the dairy
DMS. Custards containing drum DMS were scored very low
on smoothness. The protein of the drum DMS was very
insoluble and consequently the custards made from this

type were granular and watery.

46

As the concentration of DMS was increased, the custards
became less smooth except with drum DMS at concentration
No. 1% and No. 2, both of which had the same scores. These
custards were so poor at concentration No. 1% that there
was little difference as to the degree of poorness. The
decrease in smoothness with spray DMS could.be due to the
increased concentration which made the protein slightly
insoluble. They were described as being grainy.

fiflfififlflfiflfll

Table 8 shows the average scores for sweetness and
analysis of variance on these scores. The analysis of
variance indicates that the principal variation among the
scores was between custards made with different amounts
and kinds of DMS. Variation due to replications was
significant at the 5 percent level. This could have been
caused by inconsistent scoring on the part of the judges,
since the degree of sweetness is rather difficult to score.

The custards made with skim.milk and oven DMS at
concentration No. 1 received equal scores and had the
most acceptable degree of sweetness. The intermediate
DMS custards at concentration No. 1 and No. 1% scored

second best. Dairy DMS at concentration No. l scored

47

TABLE 8

Adjusted Average Scores and Analysis
of Variance for Sweetness Scores

 

 

 

 

 

 

-g Ratio (Amounts)_glg
Concentration Concentration Concentration
W 15111.10 No.42 1114.2...0
Skim 5.9
Dairy Spray 5.5 5.5 5.0
Intermediate Spray 5.7 5.7 4.9
Oven Spray 5.9 5.4 5.2
Drum. 5.9 5.8 5.2
Skim - LSD05 5.4
Analysis of Variance
Degrees of
Sggrce Fggegom Mean Square F
Total 51
Adjusted Treatment 12 2.980552 24.18**
Error for Adjusted
Treatment 27 .125265
Adjusted Blocks 15 2.98055 2.46*
Intra Block Error 27 .125265

wwSignificant at 1% level
*Significant at 5% level

48

next and then the oven DMS at concentration No. 1%, the
average score being just at the limit of the 5 percent LSD.
The analysis indicates that custards of the drum DMS and
the three spray DMS at concentration No. 2 were highly
significantly different from the control.

Oven DMS gave the custards with the most acceptable
degree of sweetness. Dairy DMS in custards had a less
acceptable degree of sweetness than intermediate DMS.

Drum DMS were much too sweet in custards.

As the concentration of DMS was increased the sweet-
ness of the custards became less desirable except with the
intermediate DMS custards at concentrations No. l and
No. 1%. As the concentration of DMS was increased more
lactose was present which would cause the custards to taste
sweeter. Morse (25) suggested this sweetness could be

caused by lactose dissolving in the liquid phase.

Genera; Acceptability

Table 9 shows the adjusted average scores and the
analysis of variance on acceptability. The chief source
of variation for these scores was due to difference between
custards made with different amounts and kinds of DMS.

Variation due to replications was not significant.

49

TABLE 9

Adjusted Average Scores and Analysis
of Variance for General Acceptability Scores

 

 

 

 

 

 

 

Ehncentrat%%fiigséégfi%%§%%onfaoncentration

linear—Milk Neil 494.1% iii—.110
Skim, 5.8
Dairy Spray 5.4 5.0 4.5
Intermediate Spray 5.6 4.8 4.5
Oven Spray 5.5 4.9 4.6
Drum 5.5 2.7 2.2
Skim - LSDOl 5.2
Skim.- LSD05 5.4
Analysis of Variance

Source 3:22:69; of Meg Square F
Total 51 - -
Adjusted Treatment 12 4.858645 56.09**
Error for Adjusted

Treatment 27 .086617

Adjusted Blocks 15 .112575 1.58

Intra Block Error 27 .081444

«*Significant at 1% level

50

The custards made with skim milk received the highest
score for general acceptability. The spray processed DMS
at concentration No. I scored next with the custard contains
ing intermediate DMS being best, then oven DMS and thirdly
the dairy DMS, the average score being just at the 5 percent
level of significance. All the other custards had lower
scores and probably were highly significantly different in
acceptability from the control.

Intermediate and oven DMS custards were of nearly
equal acceptability. The dairy DMS was inferior in quality.
The drum DMS was very poor in the custards. This was perhaps
caused by the effect of the insolubility of the protein and
the burnt flavor.

As the concentration of DMS was increased the custards
were less acceptable. With Spray DMS the poorer custards
were the result of an increase in protein concentration,
which gave a stiffer and slightly granular gel, a tougher
crust and a darker color. The increased lactose gave a
sweeter and a more milky flavor. Increasing the drum DMS
in custards had the same effect as the spray DMS except

that the custards became thinner in consistency.

51

Objective Tests on Baked Custards

p_I_-I_ Reading;

The baked custards were very slightly acidic, as
indicated in Table 10, with the exception of the 5 different
spray DMS custards at concentration No. 1. As the concenp
tration of DMS was increased in the custards, the acidity
increased. During the baking process the acidity of the
custards decreased, the only exception being custards made
from drum and intermediate DMS at concentration No. 1 in
which the acidity increased. The pH of fluid skim milk
custards was similar to oven DMS custards at concentration

No. 1% and custards of drum DMS at concentration No. l

Wme-T 9132159.

The time-temperature curves for the different variations
of baked custards are shown in Figures 1, 2 and 5. Baked
custards made from skim and drum DMS at concentration
No. l baked in the shortest time while custards of dairy
DMS concentration No. 1 took the longest time to bake.

The rate of heat penetration in.custards made from
the different spray DMS was very similar. Custards of
drum DMS had a slower rate of heat penetration than the

52
TABLE 10

Average pH Readings on the Unbaked and Baked Custards

I

Variation Unbaked Baked

Skim milk 6.86 6.90
Spray Processed
Dairy Type
Concentration #1 7.17 7.22
I #14 5.88 5.95
I #2 5.71 5.84
Intermediate #1 7.15 7.01
Concentration.#l% 6.91 6.95
I #2 5.77 5.85
Oven Concentration #1 7.06 7.11
I #14 5.89 5.92
I #2 5.75 5.85
Drum Processed '
Concentration #1 6.95 6.90
I #1% 5.74 5.82
' #2 6.58 6.69

 

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56

spray DMS custards until an internal temperature of 82° -
84° C was reached, when the heat penetration.was much more
rapid than in the spray DMS custards. The curve for the
rate of heat penetration of the control custards fell
between the heat penetration curves for the dairy and
drum DMS custards until an internal temperature of 80° C
was attained and then resemble closely the curves of the
custards containing drum DMS. The different rates of heat
could possibly be accounted for by the effect of the various
heat treatments on the protein in the manufacture of the
milk.

Upon increasing the concentration of DMS, the baking
time was shortened. The decreased baking time could be

accounted for by the increased protein concentration.

Smeaaaia

The syneresis shown by the different custards, at
intervals of 1 hour, for a total of a 5 hour period is
graphed in Figure 4. The protein of drum DMS was very
insoluble and these custards had the highest syneresis.

The custards of dairy and oven DMS had the least syneresis.
Some of the gels of the custards with Spray DMS were soft
and thus part of the custard passed through the mesh

8 cream.

Syneresis
(grams)

/0 Jr

  

Time

gf‘ (hours)
a ; 12 3 9 .5

(a) Dried Milk Solids

at Concentration No. 1

 

Syneresis
‘ (grams)
1b

44!

2 ,, q, .
arrwr'o‘v' "
’ t A a 4 #211715

0 l' 2 g 4 g—(hours)

(b) Spray Dairy DMS

 

 

Syneresis
(grams)

Iai

1

34
54

’1’
z..

 

 

. . ¢_Time
0 / 1 3 4 5' (hours)
(d) Drum DMS

Fimre 1]..

57
Key (a)

Oven++++4++t

Drum

Skim + +

Spray Dairy ------
Intermediate 5 o

 

 

 

Key (b, o, d, e)

Concentration Mo. 1
Concentration No. 1% -----
Concentration No. 2 ———-+

 

4’

Syneresis
64(grams)

1

41

  
 

 

 

24F --v"'
. O I 12 3 7 .{(hours)

(c) Spray Oven DMS

    

 

 

Syneresis
(Emma)

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I”"" ‘—‘+——
‘1"':. ‘: 1. 1 Time

0 I 2 3 q. 5(hours)

(8) Spray Intermediate DKS

Syneresis (grams per hour)

58

In general the greatest amount of syneresis in the
custards occurred during the first hour of testing. 'With
oven DMS the increase in syneresis per hour after this
was small but fairly constant. The increase in syneresis
after the first hour of testing in intermediate DMS custards
was slightly greater than during the three following hours.
The increase in syneresis with dairy DMS was fairly constant
for the first 5 hours of testing and then the syneresis
leveled off as indicated in Figure 4c. The amount of
syneresis in drum DMS custards was very great during the
first hour, somewhat less but constant during the second
and third hours and occurred to a lesser extent the last
two hours.

As indicated in Figures 4(b, c, d. e) an increase in
the concentration of DMS caused the amount of syneresis
to decrease. The only exception noted was the dairy DMS
custard at concentration No. 1% and No. 2, which showed
practically equal syneresis. The amount of decrease was
much greater when the level was increased from concen-
tration No. l to No. 1% than when the concentration was
increased from No. 1% to No. 2. The decrease probably
was due to increased protein content Which contributed
a larger number of protein strands to form a denser mesh

work to hold the liquid. The results indicate that when

59

a certain concentration of protein is reached. additional
protein has only a slight effect on the decrease of

syneresis.

§§;_Strength

The strength of the gel in the custards was measured
by three methods, the curd tension meter, the penetrometer,
and the standing index. The results of these tests are

discussed in the following pages.

Quad Tension E92223 The cutting strengths of the gel
at the top of the custard with the crust removed and the
bottom were measured by the curd tension meter, the results
being indicated in Figure 5. As shown in the graph, the‘
top of the custards had a less tender gel than the bottom
in all kinds of custards with the exception of drum and
intermediate DMS at concentration No. 1%, which had nearly
equal gel strengths at the top and bottom. The tougher
gel at the bottom could be caused by the protein coagulating
at the outer edges and bottom first and then at the center
and Just under the crust.

The most tender gel was in custards from.skim milk.
The dairy DMS were next most tender, then the intermediate
DMS and lastly the oven and drum DMS, which had nearly

 

60

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61

equal gel strengths. This difference in gel strength

could be accounted for by the temperature used in the

manufacture of these DMS. The data indicate. that the
gel was tougher when a higher temperature was used in

the manufacture of the DMS.

As the concentration of DMS was increased, the gels
were tougher except with custards from drum DMS concen-
tration No. 2. The increased toughness could be caused
by increasing the protein concentration which gave a
denser mesh work for the gel. The decrease in cutting
strength of gel in drum DMS at concentration No. 2 could
be the high percentage of insolubility of the solids.

With increased concentration of the solids, the difference
in gel strength of the bottom and top of the custard
increased greatly. The increase possibly could be caused
by an increased insolubility in spray DMS as their concen-
tration increased, and thus the insoluble particles“settled
to the bottom. This theory is substantiated by the Judges'
scores for smoothness, which were low due to the graininess

of the custards.

Penetrometer: The compressibility of the gel at the
tap and bottom of the custard and the breaking strength

of the crust was measured with the penetrometer. The

62

compressibility readings increase with the tenderness of
the gel.

Figure 6 shows that drum DMS in custards had the
greatest amount of compressibility. skim milk custards
slightly less and then the oven DMS custards. The readings
for compressibility were slightly higher for custards
containing intermediate DMS than for those containing
dairy DMS.

The gel at the bottom of a custard was more easily
compressed than at the top except with custards of drum
DMS at concentration No. 2. These findings are Just the
reverse of the results using the curd tension meter.

As the concentration of DMS was increased, a tougher
gel resulted. The only exception to this increase in
toughness was with the custards from.dairy DMS at concen-
tration No. 1%, which had the same gel toughness as at
concentration No. l.

The penetrometer readings for breaking strength of
the crust indicated that drum DMS custards had the most
tender crust, with the control custard next. The inter-
mediate DMS custards had the most tender crust of the
spray DMS custards and the oven DMS gave the toughest

crusts in all the custards.

 

 

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64

When the concentration of DMS was increased the
crusts became tougher. The exceptions were the crusts
on custards from drum DMS at concentration No. 2 and
dairy DMS at concentration No. 1% which were less tough
than the crusts on the custards containing a lower concen-
tration of DMS.

Correlations were calculated on the penetrometer and
curd tension meter readings to find out which agreed more
closely with the Judges' scores. There was no significant
correlation between the Judges' scores for firmness and
the penetrometer readings for compressibility as indicated
in Table 11, but a significant correlation at the 1 percent
level existed between the Judges' scores for firmness and
the curd tension readings for the top of the custards with
the crust off. A significant correlation at the 5 percent
level existed between the curd tension meter readings on
the custards upside down and Judges' scores for firmness.
These results suggest that the curd tension meter gave a
better measure of gel strength than the penetrometer.

Table ll indicates that the negative correlation
between the Judges' scores for firmness and the penetro-
meter readings on the crust was significant at the 1 percent
level. The positive correlation between the penetrometer

readings and the Judges' scores for the crusts was even

65

TABLE 11

Correlation between some Subjective
and Objective Measures

 

Crust score vs penetrometer reading (crust on) «+0.6167**

Crust score vs difference between penetrometer
reading for crust on and off +0.1522

Firmness score vs penetrometer reading
(crust on) -O.3595**

Firmness score vs penetrometer reading
(crust off) -0.0999

Firmness score vs penetrometer reading
(custard upside down) -0.0992

Firmness score vs curd tension meter readings
(crust off) -O.4777**

Firmness score vs curd tension meter readings
(custard upside down) -O.5283*

 

*fiSignificant at 1% level
*Significant at 5% level

66

more highly significant. The reason for the positive
correlation was the tougher the crust the less the
penetration and also the lower the Judges' scores.

The cause of the toughness of crusts on custards
with spray DMS could be the absence of fat which would
seem to act as a protecting agent for the protein from
the dry heat of the oven. Carr and Trout (3) found that
homogenized custards had a tougher crust than custards
of whole milk. On adding butter or cream to the custard,
the crust improved in tenderness. To test this hypothesis,
a supplementary series was done, in which melted butter
was added to the DMS custard mix before cooking. The

crusts were more tender on these custards.

Standing gaggz; The data.for the standing index of
the various custards is represented in the graphs in
Figure 7. The standing index was taken at intervals of
1 hour for a 5 hour period. A smaller ratio indicates
a weaker gel structure. As indicated by the graphs, a
considerable difference existed in the ability of the
gels of the custards to hold up at the beginning of the
test period. The results indicate that custards of drum
DMS had the weakest gels. The spray DMS custards had
gel strengths that differed only slightly: the oven DMS

67

Standing Index Key (a)
.400
' Skim (Control)
350 Spray Dairy ------ -
. Spray Intermediate —-+ -— 4-
Spray Oven ++ ++ + ++

 

 

 

300‘ Drum ‘———a-——-o
.2504

Key (b: c, d: 9)
.2004

Concentration No. 1
ISO‘ Concentration No. 1.}; + + + + +
. Concentration No. 2 - - - - -
.flm i . . JTime

 

o ) 2 é ,: Hhours)
(a) Dried Milk Solids at
Concentration No. 1

   

 

 

 

 

Standing Index Standing Index
.400
§\
'350“ zt"-
V‘ \
. **
n300‘
0150‘
-200 : 4. a : +Tim° '200 : : : : km”
0 I a 3 a 5(hour-s) o I 2 3 9 70101116)
(b) Spray Dairy DMS (0) Spray Intermediate DMS
St nding Index St nding Index
.450 ' .35

350

   

 

 

 

 

 

’3001 0200*
’1‘
1.
-250" ’.+ * ’Bb*
0200 ; : : Ar 1 Time 0/” A #_ I
a o z 3 4 {(hours) 0 I a. 3 5+ 5(hours)
(d) Spray Oven DNS (6) Drum DMS

Figure 7. Average Standing Index Readings

68

giving the custard with the firmest gel, the intermediate
DMS having the weakest gel and the dairy DMS with an
intermediate gel strength. The gel strength of skim milk
custards was between.that of the spray and drum DMS custards.

The greatest decrease in the standing index occurred
during the first hour of testing. The decrease after the
first hour in all the Spray DMS custards was small but
fairly constant. This was true also with custards made
from skim.milk. The gel of the drum DMS slumped more
between the second and third hours of testing than during
the last 2 hours. The total decrease in the standing index
over the 5 hour period for the 3 Spray DMS custards was
nearly the same and less than the drum DMS and skim milk
custards, which had practically equal decreases in the
total standing index.

As indicated in Figure 7(b, c, d. e). when the concen-
tration.of dairy and intermediate DMS were increased the
gel strength was greater. With oven DMS custards the gel
strength was weaker at concentration No. 1% than at concen-
tration No. 1. Figure 7e indicates that the gel strength
of drum DMS custards at concentration No. 2 was weaker than
at concentration No. 1%. Of all the custards. the gel
strength of drum DMS custards at concentration No. 1% is
closest to the gel strength of the control custard.

69

SUMMARY AND CONCLUSIONS

The merits of various processed nonfat dried milk
solids at 3 concentrations were compared in baked custards.
Custards were selected for this study because the literature
indicated that they had a high degree of sensitivity to
slight changes in egg-milk-sugar mixtures.

Two types of dried milk powders were used, drum and
spray processed. The spray processed powders were treated
at different temperatures during processing, low being
called dairy DMS, high, oven DMS and a third at intermediate
temperatures called intermediate DMS. The 4 dried milks
were used at'S concentrations. Concentration No. l was
equivalent to the solids in.fluid skim milk, concentration
No. 1% being equal to one and a half times the solids in
fluid skim milk and concentration No. 2 equalling twice
the concentration of skim milk solids. Custards made from
skim milk were the control for the experiment.

Objective and subjective techniques for judging the
,quality of baked custards were used. The custards were
scored subjectively for appearance, crust, color inside,
flavor, smoothness, sweetness and general acceptability.

Objective measurements included the solubility index and

7O

moisture content of the dried milks, the pH of the custard
before and after baking, the time-temperature curves for
the rate of heat penetration, a test for syneresis and
three tests for gel strength - the curd tension meter,

the penetrometer and the standing index.

The chief source of variation among the palatability
scores was due to different treatments, not variation within
replications. The preference for various baked custards
indicated by the general acceptability scores were skim
milk custards and spray DMS custards at concentration No. l
in the following order: intermediate DMS, oven DMS and
dairy DMS. The data show. that all other custards differed
significantly from the control. As the concentration of
DMS was increased the flavor and color of the custards were
less acceptable, the gel too firm, the texture too grainy
and the crusts too tough.

In general, the results of the objective tests agreed
with the palatability scores. All the custards showed
some syneresis, but the degree of syneresis varied greatly
between treatments. A.highly significant negative correlation
existed between the judges' scores for firmness and results
of the curd tension meter. No significant correlation
between the firmness scores by the judges and penetrometer

readings was evident. This indicates the curd tension

71

meter was more nearly measuring the thing the judges scored
for firmness than the penetrometer. A highly significant
positive correlation between the judges' scores on the
crust and the penetrometer readings on breaking strength
of the crusts existed. This indicates a good relationship
between the penetrometer readings and the judges' scores
for the crust._

From these results it appears that:

l. Skim milk custards were superior to custards made
of DES.

2. Spray DMS gave the most acceptable product of
the DMS used.

3. Results of this experiment did not indicate one
type of Spray DMS to be superior.

4. The best concentration of DMS to use is an amount

equivalent to the concentration of solids in fluid skim
milk.

9.

10.

ll.

72

REFERENCES CITED

American Dry Milk Institute, Inc., 1942. The grading
of dry milk solids. Rev. ed. Chicago, Illinois.

Beach, B. F., 1952. Private communication. Michigan
Producers Dairy Company, Adrian, Michigan.

Carr, E. and Trout, G. M., 1942. Some cooking qualities
of homogenized milks. I. Baked and soft custards.
Food Research 1; 560.

Chick, H. and Martin, C. J., 1910. I. On “heat
coagulation” of proteins. J. Physiol. $9; 404.

,. 1911. The action of hot water upon egg-
albumen and the influence of acids and salts upon
reaction velocity. J. Physiol. fig; 1.

. 1912. The influence of alkali upon the
reaction velocity. J. Physiol. g5; 61.

. 1912. The conditions controlling the
agglutination of proteins already acted upon by
hot water. J. Physiol. $55 261.

Choi, R. P., Totter, C. W. and O'Malley, C. M., 1951.
Lactose crystallization in dry products of milk.
1) A method for estimating the degree of
crystallization. 2) The effects of moisture
and alcohol. J. Dairy Sci. 53; 845.

Coulter, S. T., Jenness, R. and Geddes, W. F., 1951.
Physical and chemical aSpects of the product,
storage and utility of dry milk products.
Advances in Food Research g; 45. Edited Mrak,‘
E. M. and Stewart, G. F. Academic Press Inc.,
New York.

Cochran, W. G. and Cox, G. M., 1950. EXperimental
design. lst ed. John Wiley and Sons, Inc.,
New York.

Davies, W. L., 1959. The chemistry of milk. 2nd ed.
D. Van Nostrand Company, Inc., New York.

12.

15.

14.

15.

16.

17.

18.

19.

20.

21.

75

Gortner, R. A., Gortner, R. A. Jr., and Gortner,
Willis, 1949. Outlines of biochemistry. 5rd ed.
John Wiley and Sons, New York.

Grawemeyer, E. H. and Pfund, M. C., 1945. Line spread
as an objective test for consistency. Food
Research a; 105.

Harland, H. A. and Ashworth, A. 8., 1947. A rapid
method for estimation of whey proteins as" an
indication of baking quality of nonfat dry milk
solids. Food Research 12; 247.

>Hill, R. L., 1923. A test for determining the

character of the curd from cows' milk and its
application to the study of curd variance as an
index to the food value of milk for infants.

J. Dairy Sci. g; 509.

Hollender, H. and Weckel, K. C., 1941. Homogenized
milk in cookery practice. Food Research.§3 541.

Holm, G. E., 1949. Dried milks. U.S.D.A. Research
Administration, Bureau of Dairy Industry Information
Bulletin No. 25.

Howak, G. R. and Wright, N. C., 1955. Factors affecting
the solubility of milk powders. II. The influence
of temperature of reconstitution on protein
solubility. J. Dairy Res. 4; 265.

Howatt, G. B., Smith, J. A. B., Waite, R. and Wright,
N. C., 1959. Factors affecting the solubility of
mdlk powders. IV. The influence of speed and
duration of stirring on solubility, with a
description of a rapid method for solubility
determinations. J. Dairy Res. ;_; 498.

Hunziker, O. T., 1949. Condensed milk and milk
powders. 7th ed. Published by the author,
LaGrange, Illinois.

Kitzes, A. 8., 1948. Factors influencing the design
and Operation of a spray drier. Ph. D. Thesis,
University of Minnesota Library, MHnneapolis,
Minnesota. (Original not available for examination;
cited in Advances in Food Research 55 45.)

22.

23.

24.

25.

26.

27.

28.

29.

30.

31.

32.

33.

34.

35.

74

Logue, L. B., 1940. Some qualities of eggs affecting
the gel strength of custards. M. S. Thesis,
Iowa State College, Ames, Iowa.

Lowe, B., 1945. Experimental cookery. 5rd ed.
John Wiley and Sons, Inc., New York.

McBain, J. W., 1950. Colloid chemistry. D. C. Heath
and Company, Boston.

Morse, L. M., Davis, D. and Jack, E. L., 1950. USe
and prOperties of nonfat dry milk solids in.food
preparation. II. Use in typical foods. Food
Research 15; 216.

Nason, E. H., 1959. Introduction to experimental
cookery. McGraw Hill, New York.

O'Malley, C. M., 1951. Dry milk in prepared mixes.
Cereal Chem. 2; 116.

Paul, P. C. and Aldrich, P. J., 1955. USing nonfat
dry milk solids. Amer. Dietet. Assoc. J. 22; 254.

Paul, P. and Plummer, J., 1949. Home storage of.
nonfat dry milk solids. J. Home Econ. 41; 198.

Flatt, W., 1957. Some fundamental assumptions
pertaining to the judgment of food flavors.
Food Research g; 257.

Ramsey, J., Tracy, P. H. and Rhee, H. 8., 1955.
The use of corn sugar manufacture of sweetened
condensed milk. J. Dairy Sci. 16; 17.

Snedecor, G. W., 1950. Statistical methods. 4th ed.
Iowa State College Press, Ames, Iowa.

Tray, H. C. and Sharp, P. F., 1950. at and! lactose
in some milk products. J. Dairy Sci. 1_; 140.

United States Statutes at Large, 1944. 78th Congress,
2nd Session. Volume 58, Part 1, Public Laws.

Watt, B. K. and Merrill, A. L., 1950. Composition
of foods - raw, processed, prepared. Agr.
Handbook No. 8, U. 8. Dept. Agr.

75

56. wright, N. C., 1952. Factors affecting the solubility
of milk powders. I. The affect of heat on the
solubility of milk proteins. J. Dairy Sci. 4: 122.

76

APPENDIX

77

TABLE 12

Average Daily Scores for Appearance

 

 

 

IEELT
1 (4) 1.8 (6) 5.0 (7) 5.4 (8) 5.4
2 (1) 5.8 (5) 4.6 (6) 5.0 (9) 4.8
s (2) 4.2 (3) 2.8 (5) 4.8 (8) 4.8
4 (8) 5.4 (9) 4.8 (11) 4.6 (15) 5.0
5 (4) 2.6 (5) 4.6 (10) 5.2 (15) 5.8
6 (s) 2.4 (6) 4.2 (11) 4.6 (15) 4.8
7 (5) 4.2 (7) 5.0 (11) 4.6 (12) 5.6
8 (2) 3.5 (6) 5.0 (10) 5.0 (12) 4.3
9 (s) 2.8 (7) 4.6 (9) 5.0 (10) 4.8
10 (2) 4.4 (1) 5.6 (7) 4.8 (13) 4.6
11 (2) 3.8 (4) 3.0 (9) 5.2 (11) 4.8
12 (3) 5.0 (4) 2.4 (1) 5.2 (12) 4.8
13 (l) 6.0 (8) 4.5 (10) 4.8 (12) 4.8
Key
(1) Skim milk custard (control)
(2) Drum.DMS custard concentration No. 1
(5) Drum DMS custard concentration No. 1%
(4) Drum DMS custard concentration No.
(5) Dairy DMS custard concentration No. 1
(6) Dairy DMS custard concentration No. 1%
(7) Dairy DMS custard concentration No. 2
(8) Intermediate DMS custard concentration No.
(9) Intermediate DMS custard concentration No. 1%
(10) Intermediate DMS custard concentration No.
(11) Oven DMS custard concentration No. 1
(12) Oven DMS custard concentration No. 1%

(l5)

Oven DMS custard

concentration No.

Average Daily Scores for Crust

78

TABLE 13

 

 

Day
1 (4) 3.4 (6) 4.4 (7) 4.4 (8) 5.4
2 (1) 5.4 (5) 4.4 (6) 4.6 (9) 4.2
3 (2) 6.0 (3) 6.4 (5) 4.4 (8) 4.4
4 (8) 4.6 (9) 4.6 (11) 4.8 (13) 4.0
6 (4) 6.2 (6) 5.2 (10) 4.6 (13) 4.6
6 (3) 4.8 (6) 4.4 (11) 5.0 (13) 4.0
7 (6) 4.8 (7) 4.4 (11) 5.0 (12) 4.6
8 (2) 6.3 (6) 4.3 (10) 4.5 (12) 4.3
9 (3) 6.2 (7) 4.0 (9) 4.2 (10) 5.8
10 (2) 5.0 (1) 5.2 (7) 3.8 (13) 3.8
11 (2) 6.8 (4) 5.0 (9) 4.0 (11) 4.6
12 (3) 6.6 (4) 5.4 (1) 5.0 (12) 4.2
13 (1) 5.0 4.3 (10) 4.0 (12) 4.5

(8)

79

TABLE 14

Average Daily Scores for Color Inside

 

 

(om-ammewtor-IE

+4 Ia F' +4
0: ts F’ <3

(4)
(1)
(2)
(8)
(4)
(5)
(5)
(2)
(5)
(2)
(2)
(5)
(1)

2.8
6.2
4.2
6.0
3.2
3.4
5.6
3.9
3.2
4.2
4.4
3.4
6.0

(6)
(5)
(5)
(9)
(5)
(6)
(7)
(6)
(7)
(1)
(4)
(4)
(8)

6.0
5.4
3.6
5.6
6.0
5.6
5.6
5.5
5.4
6.2
3.0
2.8
5.8

(7)
(6)
(5)
(11)
(10)
(ll)
(11)
(10)
(9)
(7)
(9)
(1)
(10)

5.4
5.6
6.0
5.6
5.6
6.2
5.8
5.5
5.8
5.4
5.8
6.2
5.0

(8)

(9)

(a)
(13)
(15)
(13)
(12)
(12)
(10)
(13)
(ll)
(12)
(12)

6.2
5.8
6.2
5.8
5.8
5.4
6.0
5.8
5.8
5.6
5.8
5.4
5.8

 

80

TABLE 15

Average Daily Scores for Flavor

 

 

(om-ammpchI—JE

HHHH
Cami-Jo

(4)
(l)
(2)
(8)
(4)
(5)
(5)
(2)
(5)
(2)
(2)
(5)
(1)

2.8
5.6
3.6
5.6
2.6
3.0
5.6
2.9
2.8
3.4
3.4
3.2
6.3

(6)
(5)
(5)
(9)
(5)
(6)
(7)
(6)
(7)
(1)
(4)
(4)
(8)

5.0
5.0
3.4
5.4
5.8
5.4
4.4
5.0
5.2
6.2
2.4
1.8
6.0

(7)
(6)
(5)
(ll)
(10)
(11)
(11)
(10)
(9)
(7)
(9)
(1)
(10)

4.8
5.2
5.4
5.0
5.6
6.0
6.0
4.5
5.0
4.8
5.2
6.2
5.0

(8)

(9)

(8)
(13)
(13)
(13)
(12)
(12)
(10)
(13)
(ll)
(12)
(12)

5.8
5.4
5.4
5.0
5.0
5.2
5.6
5.5 -
5.2
5.0
6.0
5.0
5.5

 

81

TABLE.16

Average Daily Scores for Firmness

 

 

Day
1 (4) 3.4 (6) 4.6 (7) 4.0 (8) 5.8
2 (1) 6.2 (6) 4.6 (6) 6.2 (9) 4.6
3 (2) 4.2 (3) 5.0 (6) 5.6 (8) 5.6
4 (8) 6.8 (9) 5.0 (11) 4.8 (13) 4.4
6 (4) 3.6 (6) 6.0 (10) 4.2 (13) 4.8
6 (3) 3.6 (6) 6.6 (11) 6.0 (13) 4.6
7 (5) 5.8 (7) 4.6 (11) 6.2 (12) 4.8
8 (2) 4.5 (6) 4.9 (10) 4.0 (12) 4.9
9 (3) 4.0 (7) 4.4 (9) 4.6 (10) 4.4
10 (2) 4.0 (1) 6.4 (7) 4.2 (13) 4.6
11 (2) 3.8 (4) 3.6 (9) 4.4 (11) 6.4
12 (3) 3.4 (4) 3.6 (1) 6.6 (12) 5.0
13 (1) 6.5 5.5 (10) 4.3 (12) 5.0

(8)

 

TABLE 17

Average Daily Scores for Smoothness

 

 

Dav
1 (4) 2.8 (6) 6.0 (7) 5.6 (8) 6.0
2 (1) 6.2 (5) 5.8 (6) 6.6 (9) 5.4
3 (2) 4.2 (3) 3.4 (5) 6.2 (8) 6.0
4 (8) 6.2 (9) 5.6 (11) 6.6 (13) 6.6
6 (4) 3.6 (6) 6.2 (10) 5.8 (13) 5.8
6 (3) 3.4 (6) 6.0 (11) 6.2 (13) 5.8
7 (5) 6.4 (7) 5.6 (11) 6.0 (12) 6.0
8 (2) 3.3 (6) 5.5 (10) 5.5 (12) 5.5
9 (3) 3.4 (7) 5.6 (9) 6.8 (10) 6.6
10 (2) 4.6 (1) 6.6 (7) 5.8 (13) 6.0
11 (2) 4.2 (4) 3.6 (9) 6.0 (11) 6.4
12 (3) 3.4 (4) 3.8 (1) 6.6 (12) 6.8
13 (1) 6.8 (8) 6.5 (10) 5.8 (12) 5.8

 

TABLE 18

Average Daily Scores for Sweetness

 

 

w m ‘4 m) on e. on a) F4 Efl

55:38

(4)
(l)
(2)
(8)
(4)
(5)
(6)
(2)
(3)
(2)
(2)
(3)
(l)

3.8
6.2
4.0
5.8
3.8
4.0
5.2
3.9
3.8
4.0
3.6
3.4
5.5

(6)
(6)
(5)
(9)
(5)
(6)
(7)
(6)
(7)
(l)
(4)
(4)
(8)

5.4
5.6
4.0
5.4
6.0
5.8
5.0
4.9
5.4
5.8
2.8
2.6
5.5

(7)
(6)
(5)
(11)
(10)
(11)
(11)
(1o)
(9)
(7)
(9)
(1)
(10)

4.6
5.0
5.8
5.4
5.6
6.0
5.8
4.0
5.6
5.0
5.4
6.0
5.0

(8)

(9)

(a)
(13)
(13)
(13)
(12)
(12)
(10)
(15)
(11)
(12)
(12)

5.8
6.6
5.8
5.4
5.6
4.8
5.2
5.5
5.0
5.4
6.0
5.2
5.0

 

TABLE 19

Average Daily Scores for General Acceptability

 

 

tOCDQO‘aUlnhOJNl-‘E

F’ +4 )4 F'
on {O F’ c:

(4)
(1)
(2)
(8)
(4)
(3)
(5)
(2)
(3)
(2)
(2)
(5)
(l)

2.0
5.4
3.6
5.6
2.4
2.4
5.6
3.9
2.4
3.0
3.4
3.0
6.0

(6)
(5)
(3)
(9)
(5)
(6)
(7)
(6)
(7)
(l)
(4)
(4)
(8)

406

4.8
3.0
4.8
5.8
5.2
4.4
4.9
4.2
5.8
2.4
2.2
5.5

(7)
(6)
(5)
(11)
(10)
(11)
(11)
(10)
(9)
(7)
(9)
(1)
(10)

4.0
5.2
5.4
4.8
5.0
5.6
5.8
4.0
4.8
4.6
4.4
6.0
4.5

(8)

(9)

(8)
(15)
(13)
(13)
(12)
(12)
(10)
(13)
(11)
(12)
(12)

5.8
5.0
5.4
4.6
4.6
4.6
4.8
4.9
4.4
4.6
5.6
5.0
5.0

 

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86

TABLE 21

Illustration of Statistical Calculations
for Flavor Scores

First Stage

Source
Total

Treatments (unadjusted)

Blocks (adjusted)

Intra block error

Second Stage

Adjusted Treatment

Error for Adjusted

Treatment

LSD05

t 0.44

Skim '- LSD05 :

2 2.062 (0.2164)

5.54

Treatment Number

madmmPCfiNI-J

Degrees of

Freedom

51
12

27

27

LSDOl

Analysis of Variance on Flavor Data

Sum of
éknraaai 142811828281 ._li__

66.6862

61.6327
0. 7242 0. O6055(Eb) <1
3.3283 0.12527(Ee)

59.805814 53.2186**
4.983818
0.093648

t 2.771 (0.2164)
2 0.60 V '

Skim - LSDOl 3 5.58

Adjusteg Treatment Meag

5.98
3.29
3.10
2.47
5.51
5.08
4.85
5.73
5.18
5.09
5.70

5.38
5.16

87

TABLE 21 (Contd.)

 

Bt = total of all blocks within which treatment occurs

G = grand total

t = number of treatments = 15

b = number of blocks = 15

r = number of replications : 4

K = number of samples per block = 4

8t: 40

T 2 treatment totals

£31229. M=MO° 2 = 12028848

1. Correction Term: C = N 53 - '

2. Sums of squares'(total) = (x1)2+ (1:2)2'4-(1:3)2+--+(x52)2 - C
= (2.8)24-(6.6)2+»(3.6)3+--4+(6.5)2 - 1202.8848
= 66.6862 '

5. Sums of squares (Treatment totals) = $§$L§JEiL$lgeélEL2214§94Elf

- 1202.8848
: 61. 6527

4. W - found for each treatment

w = (t-k) T - (t-l) Bt + (K91) G

= 9T - 12 Bt + 5 G

ie.= 218.7 - 955.2 + 750.5 3 15.8
5. Sums of Squares for blocks (adjusted)

2.6.5.225 “284; 2.832;? 2___._ 2 = #122422

= 0.7242

6.

7.

8.

9.

10.

ll.

12.

13.

14.

15.

88

TABLE 21 (Contd.)

Mean Sq. for blocks = 11848. = .06036 ( )
(adjusted) 12 Eb

Intra block error 8 Total - (Treatment 4» Block)
66.6852 4 (61.6327 + .7242)

3.3283

Mean Square for intra block error 8 Sum 01' Squares intra

block 8 r0
(tr - 2t + 1)

 

: 303283 2 =
-—————27 .12527 (Ea)
F 3 Mean Sggare adjusted blocks = .,O6055 _ < 1
Mean Square adjusted intra block error .12527
n = Eb "’ E6 3 0006035 "" 0012327 : '00 06292 =

 

w “000267
t(k-1)Eb 15(3)(0.06055) 2.36366

Adjusted Treatment Total

T +.nW

24.3 + (-.56846) = 25.95154

Adjusted Treatment Mean = ELL-BE; W = 5.98

 

r 4
2
8.8. for adjusted treatment Means = Ell—31:312- - C
: (25.95154)2 + ---- + (20.69662)2 -.Q
4

59.805814

Mean Square for Adjusted Treatment Mean
= 59-83281 = 4.9838178

Effective Error . Mean Square per unit = E8 1 - (t-k))1
0.12327 [1 + (13-4)(-0.0267§l

0.12327 E1 - 0.2403]

0.093648__*

\

89

TABLE 21 (Contd. )

16. Standard error (Sa) for differences between 2 adjusted

means - ‘/ 2 (effective error mean sggare)
r

 

 

 

sd = V2(0.0926482192 . 0.2164

17. Least Significant Difference
LSD06 ' t06 Sa
t05 (of = 27) - 2.052

t. 2.062 (0.2164)

LSD05

i 0.44
Skim - LSDO5 = 6.64

 

“A WEN MANN