A STUDY 0? "T!“IE PREVENTEON
OF ‘BRO‘NMNG %N FROZEN SLICED
APPLES FQR USE 3N PIE

Thesis for {‘59 313m“ of M. S.
MECHSGAM SKATE SGLLEGE
Maw Kath-Mine (Sc-ad

1948

               

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9390073 6599

Thisistooertifgthatthe

thesis entitled

"A Study of the Prevention of
Browning in Frozen Sliced Apples
for Use in Pie."

presented by

MARY KATHERINE GOOD

has been accepted towards fulfillment
of the requirements for

-__ln_s_c_degree mFoodg and Nutrition

Major professor

 

 

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A STUDY OF THE PREVENTION OF BROWNING IN
FROZEN SLICED APPLES FOR USE IN PIE

BY
MARY KATHERINE §9g9~

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

l9h8

I‘HESIS

ACKNOWLEDGEMENT

The writer wishes to acknowledge her deep gratitude

to Dr. Pauline Paul for her invaluable guidance and counsel
throughout this study; to Dr. R, E. marshall, Horticulture,
for advice in planning the problem.and assistance in
obtaining the apples used in the study; to Professor

D. E. Wiant, Agricultural Engineering, for the use of zero
storage space; and to Betty I. Cole, Louise Kelley, Mhry
Herr, Dr. Pauline Paul, Da-hwei Peng, and Helen L. Tobey,

who served on the scoring panel.

TABLE OF CONTENTS

INTR ODUC T I ON 0 0 O O O O O O O O O O O O O O O O O 0
DISCUSSION OF LITERATURE . . . . . . . . . . . . . .

Enzymatic browning . . . . . . . . . . . . . . .
Quality of pack . . . . . . . . . . . . . . . . .
Methods for prevention of browning . . . . . . .
Sodium chloride . . . . . . . . . . . . . . .
Sulfur dioxide . . . . . . . . . . . . . . . .
Ascorbic acid . . . . . . . . . . . . . . . .
Ascorbic acid with citric acid . . . . . . . .
Federal Food and Drug Administration regulations
Vacuum.treatment . . . . . . . . . . . . . . . .
Addition of sugar to frozen pack . . . . . . . .
Pies from frozen apple slices . . . . . . . . . .
pH value . . . . . . . . . . . . . . . . . . . .

Color measurement . . . . . . . . . . . . . . . .

EXPERIMENTAL PROCEDURE . . . . . . . . . . . . . . .

Preparation for freezing . . . . . . . . . . . .
Selection of fruit . . . . . . . . . . . . . .
Peeling and slicing . . . . . . . . . . . . .
Treatments used to prevent browning . . . . .

Sodium.chloride . . . . . . . . . . . . . .

Sodium bisulfite . . . . . . . . . . . . .

Page

\INIOWF‘P'

10
12
13
13
ll»
15
15
15
l7
l7
l7
17
18
18
18

Ascorbic acid . . . . . . .

Potassium.metabisulfite . .

Ascorbic acid-citric acid mixture

Vacuum method used. . . . . . .
Packaging . . . . . . . . . . .
Freezing and storage . . . . .
Testing . . . . . . . . . . . . .
Baking procedure . . . . . . .
Crust . . . . . . . . . . .
Filling . . . . . . . . . .
Assembling and baking pies .
Tests on pies . . . . . . . . .
Scoring panel . . . . . . .
Firmness test . . . . . . .
Color measurement . . . . .
Tests on raw fruit . . . . . .
Ascorbic acid determination
Sulfur dioxide determination
pH values . . . . . . . . .
Statistical methods . . . . . .
DISCUSSION OF RESULTS . . . . . . . .
Preparation . . . . . . . . . . .
Preparation waste . . . . . . .
Vacuum treatment . . . . . . .
Appearance of fruit . . . . . .

P168 0 O O O O O O 0 O O O O O

Page
. l9

. l9
. l9
. 2O
. 20

. 21
. 21

. 22
. 22
. 23

027
. 27

. 27
. 27
. 28

. 28

. 28

. 29
. 32

Page
Palatability scores . . . . . . . . . . . . . . . 32

Color . . . . . . . . . . . . . . . . . . . . . 32
Consistency . . . . . . . . . . . . . . . . . . 35

Odor . . . . . . . . . . . . . . . . . . . . . 36
Flavor . . . . . . . . . . . . . . . . . . . . 36
Tenderness of fruit . . . . . . . . . . . . . . 37
Texture of fruit . . . . . . . . . . . . . . . 37
Texture of lower crust . . . . . . . . . . . . 37
General conclusion . . . . . . . . . . . . . . 38
Acceptability . . . . . . . . . . . . . . . . . 38
Analysis of variance of scores . . . . . . . . 39
Objective tests on baked fruit . . . . . . . . . . #2
Penetrdmeter . . . . . . . . . . . . . . . . . #2
Color measurement . . . . . . . . . . . . . . . L5
Objective tests on raw fruit . . . . . . . . . . . A7
Ascorbic acid . . . . . . . . . . . . . . . . . A7
Sulfur dioxide . . . . . . . . . . . . . . . . 48

pH value . . . . . . . . . . . . . . . . . . . A9
SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . . 51
LIST OF REFERENCES . . . . . . . . . . . . . . . . . 5h
APPENDIX . . . . . . . . . . . . . . . . . . . . . . 59

LIST OF TABLES

Number Title Page

1. Mean scores for each scoring period 33 - 3h

2. Results of analysis of variance of scores AC

3. Penetrometer readings on apple slices from A3
baked pies

4. Correlation coefficients between an

penetrometer readings and judges' scores on
consistency, tenderness of fruit, and
texture of fruit

5. Objective color data on apple slices from A6
baked pies

6. Ascorbic acid content of raw, frozen apple A7
slices

7. Sulfur dioxide content of raw, frozen apple A8
slices

8. Volume of solutions used in treating apple 61
slices

9. Areas of MMnsell color discs - averages for 62

each test period
10. pH values of frozen apple slices 63

Number

1.

2.
3.
LP.

LIST OF FIGURES

Title

Neutrals and hues used in objective color
tests

Disc spinning assembly for color measurement
The apple slices before and after baking

Changes in pH values of frozen apple slices
during storage at zero F.

Page
25

26

30
50

INTRODUCTION

The production of apples is an important source of
agricultural income in Michigan. The United States Census
Bureau (1945) reported a yield of 8,0h5,236 bushels in 1945
at a value of $15,321,829. There are numerous apple storage
buildings in the state, but many varieties do not keep over
long periods of time even though they are kept under the
proper storage conditions. The Jonathan, a leading variety
in Michigan, should not be held in storage after the first
of January because it is often attacked by Jonathan spot.

The problem of preserving the quality of apples and keeping
them.as nearly like the fresh product as possible can be
solved to a certain extent through the process of freezing.
The Jonathan apple has been rated as being one of the best
for freezing by Tressler (1946) and Masterson and Lee (l9h3).
Pfund (1939) reported Jonathan among the species most often
receiving favorable ratings on ”texture, meltiness, Juiciness,
and firmness". However, she found the flavor and the texture
were less agreeable after January. Variety is an important
consideration because certain ones do not retain their fresh
flavor, odor, and texture during freezing. Johnston (l9h5)
has noted that "selected apples of good quality are such
that they will cook fairly soft in pies but the slice will

2
maintain its shape, will hold juice and absorb added water.
In addition to this they must maintain their good flavor."

The use of frozen sliced apples in the commercial pie
trade increased decidedly during World War II. Tin was not
available for canning and another means of preservation had
to be used. Lee (l9hh) and Short (l9hh) report that the great-
est outlet for frozen apples is for pie stock. Cruess and
Seagrave-Smith (l9h6) report that the apple pie is still "king
of restaurant desserts, especially a la mode". In a survey
made in manhattan and Brooklyn in 1946, it was found that 40
percent of the men and 50 percent of the women preferred apple
pies over peach, blueberry, or apricot pies. Frozen apple slices
have qualities which make them.desirable for use in pies if care
is used in the preparation of the slices before freezing.

The frozen apple pack gives bakers the assurance of an
uninterrupted supply of pie apples throughout the year. It
also furnishes sliced apples to the baker in a convenient form
which assures uniform quality, color, and flavor closely
approaching those of the fresh fruit. The prepared fruit saves
the labor of peeling, coring, and slicing on the part of the
baker. Large inventories of fresh fruit are not necessary for
relatively small amounts of frozen fruit can be ordered when
needed so that costs may be calculated more accurately.

' A prefreezing treatment is necessary to prevent the

normal darkening that occurs in apple slices. When certain

3

fruits are cut and exposed to the air, they turn dark and
become unattractive in both color and flavor, due to the
oxidation of catechol tannins and other easily oxidized
substances. In preparing such fruits for freezing, the
peeled and sliced fruit must be treated or else the cut
surfaces are affected to such an extent that the product

is very inferior. Another problem.with apple slices concerns
the darkening from the inside as well as from.the outside.
This darkening or browning is objectionable when the product
is marketed to the bakery trade. The discoloration occurs
not only during the preparation of the fruit but continues
slowly during the freezing and zero storage. In order to
give the fruit correct prefreezing treatment, it is necessary
to understand how each variety responds to the different

treatments for the prevention of browning.

DISCUSSION OF LITERATURE

gnzzmatic browning

It is a generally accepted fact that the darkening
which takes place in the flesh of the apple is due to
enzymatic oxidation. Plagge (1938) states that fruits and
vegetables are living parts of plants and that the processes
common to plant life continue after harvesting. Joslyn (1930)
reports that the enzymatic oxidation is due in a great part
to the activity of the oxidase enzyme system present in the
fruit tissues. This system.is not inhibited by storage at
temperatures as low as zero degrees Fahrenheit. While fresh
fruit is resistant to oxidation, the injury of the tissues
on freezing allows mixing of the cell contents with consequent
rapid oxidation on exposure to air. Darkening occurs more
rapidly when the fruit is exposed to air during thawing than
during freezing or storage.

Onslow (1920) reports that the apple contains an oxidase
system including an oxygenase, a peroxide, and an aromatic
substance with the catechol grouping which produces a brown
color. Balls and Hale (1935) believe that the first step
in the formation of the brown pigment is the production of
hydrogen peroxide by the normal action of an enzyme of direct

oxidation. Onslow also states that most of the aromatic

5

cdmpounds of fruit appears to be in the form of catechol
tannin. Joslyn (19h1) says that flavanols and tannins in
fruit turn brown upon oxidation. Balls and Hale (1935)
note that besides peroxidase and peroxide, there is present
in apple tissue a chromogenic substance capable of rapid
oxidation by the peroxidase-peroxide system. This chromogen,
considered to be of a tannoid nature, is brown when alkaline
and colorless when acid. Natural tannins are powerful
reducing agents and exhibit a marked tendency to absorb
oxygen, particularly in alkaline solutions.

Overholser and Cruess (1923) found that a solution of
sodium chloride lessens or checks browning by inhibiting
the activity of the peroxidase and peroxide, but does not
destroy either. Cruess, Samisch, and Pancoast (1933) note
that the action of sulfur dioxide is on the organic peroxide
or oxygenase fraction of the oxidase enzyme system. Peroxidase

is not affected by sulfur dioxide.

Quality 9: pack

Senn and Bisno (19h?) report that there is an opportunity
for considerable improvement in the quality of frozen fruit
for use of bakers. They believe that the sooner emphasis is
laid upon definite standards acceptable to users, the faster
the volume of such products will increase. Woodroof (l9h6)
states that the biggest problem is not in the development of
a workable procedure or technique, but in getting the

processors to follow it.

6

Winter (l9a5) reports that the quality of any frozen
fruit at the time it is used is controlled by a long chain
of factors beginning with the selection of variety, culture,
harvesting, and subsequent handling. Masterson and Lee
(l9h3), Sparkes (l9hh), and Tressler, Evers, and Long (1946)
agree that apples to be frozen should be firm-ripe and of
a variety suited for pie.

The tentative U. S. standards for grades of frozen
apples (l9h5) states that U. S. grade A, or U. S. fancy,
must have similar varietal characteristics; practically
uniform, bright, typical color; practically uniform in
size; practically free from defects; uniform, tender texture;

and normal odor and flavor.
Iethods for prevention 2; browning

In 1923 Overholser and Cruess reported the results of
their studies on the browning of apple tissue. They found
that Yellow Newtown apples immersed for three days in five
percent solutions of sodium chloride, hydrochloric acid,
sodium sulfite, and sugar were white at the end of the test
period. The fruit treated with the sodium chloride solution
gave a faint positive reaction for peroxidase and a moderately
pronounced test for organic peroxide. Negative tests for
organic peroxide were obtained with the fruit frdm the

hydrochloric acid and sodium.sulfite solutions.

7
DuBois and Colvin (l9h5) mention that a number of

materials have been suggested for preventing discoloration,
but that none have been universally adopted for one or more
reasons. Luther and Cragwall (l9h6) point out the desir-
ability of using an enzyme inactivating method which does
not have the disadvantages of "cooking" the fruit.

Sodium chloride: Joslyn and mrak (1933) found that the
minimum.concentration of sodium chloride that would prevent
darkening of apples was five percent. The apples were
treated for one hour. Lower concentrations of brine and
treatment for shorter periods resulted in browning which
increased in intensity with decrease in concentration of
brine and time of exposure. Sodium.chloride will inactivate
the oxidase enzyme system.at low temperatures but not at
room.temperatures. The salt will not bleach apples which
have darkened.

Sulfur digzide: Sulfurous acid, sodium bisulfite, and
potassium.metabisulfite can be used interchangeably for the
prevention of browning in fruits. They all yield sulfur
dioxide when in solution. A sulfur dioxide content of about
100 parts per million in treated apples inhibits the browning
of fresh and frozen apples.

Reports frmm the Western Regional Research Laboratory
(l9hh-l9h7) indicate that sulfurous acid can be used as a
prefreezing treatment and will penetrate much.more rapidly

than sodium.bisulfite solution, but, due to its obnoxious

8
odor which is strong enough to be very disagreeable to
workers, this acid is not generally used. Sodium.bisulfite
has the advantage of being almost odorless and provides a
practical method for treatment. The penetration is stopped
by freezing and is not resumed quickly enough on defrosting
to prevent browning in areas not penetrated. A delay of
at least eight hours should be allowed between dipping the
fruit and freezing, regardless of the concentration of
sulfur dioxide. Sulfur dioxide not only prevents darkening
but will bleach apples which have darkened. Woodroof and
Cecil (1944) report that all varieties do not bleach the
same amount with sulfur dioxide. Wiegand (1946) reports
that a treatment with sodium bisulfite, leaving 50 to 100
parts per million of sulfur dioxide in the fruit, was
effective. Sorber (1943) recommends a five minute dip in
a solution containing 2000 to 3000 parts per million (0.02
to 0.03 percent). They also report that there is an
indication that sugar tends to retard penetration.

Joslyn and mrak (1933) observed a peculiar browning in
apple slices due to incomplete penetration of sulfur dioxide
into the apple. These apples were found to have a dark brown
crescent-like ring in the flesh at the line of demarcation
between the flesh that absorbed sufficient sulfur dioxide
and that not penetrated by sulfur dioxide.

In studies made by MacArthur (1945), it was found that

potassium.metabisulfite not only prevented browning, but

9

that no other discoloration occurred and the slices retained
their shape on cooking. No sulfur dioxide flavor was found
in any of the cooked samples and they had a better flavor
than the samples treated with sodium.bisulfite. macArthur
used a one-minute dip in 0.5 percent potassium.metabisulfite
and held the apples in open containers at least two hours

to permit penetration of the solution into the interior of
the slices.

Joslyn and mrak (1933) report that sulfur dioxide will
prevent darkening due to its reducing action. It exerts a
strong inhibiting action on darkening caused by oxidation
of the natural color bases in addition to its bleaching
action on anthocyan pigments. Overholser and Cruess (1923)
believe this bleaching may in some cases depend upon the
union of the color with the sulfur dioxide, because the color
returns if the fruit is warmed and the gas expelled. In
other cases, the bleaching action apparently depends upon
the absorption of oxygen from the coloring matter. Hohl and '
Swanburg (1946) explain that because of the strong reducing
or antioxidant properties of sulfur dioxide, oxygen which
would otherwise take part in the browning reaction, is used
by the antioxidant.

Lee (1944) reports that a minor objection to sulfur
dioxide is found in the persistence of a slight foreign flavor
in many cases, even after the product is cooked. A number

of people are unable to detect this flavor. Tressler and

10

DuBois (1944) report that sulfur dioxide and sulfites give
an undesirable flavor to the fruit unless used in very small
amounts. Cruess and Seagrave-Smith (1946) found that in
taste tests, the consumer preferred the sulfited fruit over
blanched fruit.

Winter and Hustrulid (1944) estimated that two ounces
(11 teaspoons) of sodium bisulfite in five and one-half
gallons of water will treat five bushels of apples at a cost
of about five cents per bushel. They found that the same
solution could be used to dip four to five lots of apples.

Ascorbic ggigc Tressler and DuBois in 1938 found that
ascorbic acid in solution prevents browning and flavor loss
in easily oxidized fruits cut for use in baking or for
freezing. The treatment does not affect the flavor and adds
to the nutritive value. It was found that l-ascorbic acid
is superior to any of its isomers for this purpose. DuBois
and Colvin (1945) report that the role that ascorbic acid
plays is not thoroughly understood. It has been called an
antioxidant although it seems to reduce other substances
that produce a brown color in fruit. Observations have been
made that recently discolored fruits are returned to the
original color when exposed to ascorbic acid. Most fruits
that brown readily are low in natural vitamin C and do not
discolor until nearly all the ascorbic acid has disappeared.

Bauernfeind 32.31, (1946) report that certain active

enzymes, 1. e. polyphenolase, in the presence of air, change

ll
ascorbic acid to its first oxidation product, dehydroascorbic
acid. Dehydroascorbic acid possesses no antioxidant value in
retarding the browning action. Before all the ascorbic acid
in the package is converted into dehydroascorbic acid,
partial browning of the fruit may occur. These researchers
also found that the method of defrosting does not significantly
affect the vitamin C content of the thawed fruit. A.minimum
of 150 milligrams of l-ascorbic acid per pound of finished
pack (fruit plus sirup) is recommended, but there is greater
margin of safety with 200 milligrams. In eight to ten
months storage, about 80 percent or more of the added ascorbic
acid is retained in the thawed fruit as biologically active
vitamin C.

The merits of the ascorbic acid treatment have been
summarized by workers at the Hoffman-La Roche laboratories
(1947) as follows:

1. Does not introduce foreign substances or
unnatural flavors.

2. Is not detectable in the pack by appearance,
smell, or taste.

3. Is easily detected by applying recognized
chemical and biological tests.

4. Significantly increases the vitamin C value
of the pack.

5. Has been proven practical from.the cost and

quality angle.

12

The workers at the Merck laboratories (1948) report that
the accepted method of calculating the amounts of ascorbic
acid in frozen-fruit packs is based on the weight of the
total finished pack, including the packing mediums

Ascorbic acid with citric acid: Sorber (1943) notes
that a pH below 3.25 has the effect of stabilizing the
vitamin C and color in frozen fruits. Luther and Cragwall
(1946) report that the simple addition of a suitable acid
campletely inactivates the enzymes which are so largely
responsible for the destruction of natural and added ascorbic
acid. They state that it is this rapid destruction that has
made the use of ascorbic acid impractical in apples where
the enzymes are so active that the added ascorbic acid is
quickly destroyed and consequently affords only a lbmited
measure of protection for the treated fruit. They found
that the half-life time increases as more citric acid is
used. The use of citric acid helps reduce costs since it
permits the use of a smaller quantity of ascorbic acid to
prevent browning.

Workers at Charles Pfizer (1947) give the following
stabilizing effects of citric acid:

1. Retards the activity of the oxidation enzymes
naturally present in fruit.
2. Decreases the atmospheric oxidation of the
ascorbic acid under the more acid conditions.

3. Forms complexes with traces of iron and copper

13

and in this manner retards their otherwise destructive

effect.
They have found that if citric acid is used at a level of
0.48 percent (based on weight of fruit), the ascorbic acid
level can be reduced to 90 milligrams per pound of fruit.
Merck laboratories (1948) add that citric acid used in
combination with ascorbic acid in vacuum treatments did not

seem to prevent the destruction of the ascorbic acid.
Federal Food and Drug Administration regulations

According to Winter and Hustrulid (1944), the Federal
Food and Drug Administration permits the use of sodium
bisulfite for the purpose of preventing browning in frozen
fruits. However, Wiegand (1946) reports that some states
frown upon the use of sulfur dioxide. This points to the
advisability of seeking other antioxidants. The Adminis-
tration has questioned the use of sodium.chloride for it
sometimes affects the palatability of the fruit. The use
of l-ascorbic acid to prevent browning in fruits is entirely

unquestioned by the Food and Drug Administration.
Vacuum.treatment

The problem of combating the discoloration of frozen
apple slices is a difficult one since the color changes are
not confined to the exposed surface of the fruit. The

solution of the problem of internal browning is basically

1h
one of penetration, for if the agents used in treating are
added in such a way as to penetrate to the center of the
slices, no internal browning will result. Bauernfeind and
Siemers (1946) show that it is not practical to hold apple
slices treated with ascorbic acid at room temperature to
increase penetration. The Pfizer laboratories (1947) report
that penetration and protection of the center portion can
be obtained by the use of a vacuum.

Hoffman-La Roche technicians (1947) report that regular
apple slices can be evacuated by using a vacuum.of 24 inches
or higher for five to fifteen minutes. This removes the air
or oxygen-containing gases from.the intercellular spaces and
allows the liquid to fill these spaces when the vacuum.is
released. Mazzola (1945) points out that the temperature
and chemical characteristics of the liquid must be controlled

if this process is to be successful.

Addition 2; sugar 39 frozen pack

 

Sorber §£_§l, (1944) state that sugar need not be added
to the frozen pack unless desired by the trade. 0n the other
hand, Sparkes (1944) states that there is a general agreement
among the authorities that fruits frozen without sugar are
inferior. Winter (1942) recommends a four-plus-one pack for

apples.

15

Pics from frozen apple slices

Tressler (1946) suggests that to make pies from frozen
apples, the slices should be allowed to thaw just enough so
they can be broken apart. The slices are placed on an
unbaked pie crust, and then the regular procedure for making

pie is carried out.
211 value

Pfund (1939) found that good flavor in cooked apples is
associated with relatively high acidity (pH 3.10 to 3.39).
The Jonathan rated high in acidity. According to Morris (1946),
the average pH of raw apples is 3.35.

Q5112; measurement

Much has been done by Nickerson to standardize color
measurement so that a simple and satisfactory conversion of
color can be made into current trade terms. It is necessary
that such terms be understood in relation to some color
standard. The mnnsell method of color notation (Nickerson,
1946) has made this standardization possible. This system
uses three color dimensions: hue, value, and chroma. Hue is
the name of a color, e. g. red, yellow, or blue, and is
designated by a number and/or symbol. Value is the lightness
or darkness of a color and ranges from one (black) to ten

(white). Chroma is the strength or purity of a color. The

16
higher the chroma number, the more color is present. The
highest chroma number depends upon the maximum.chroma possible
for each color. A color notation under the munsell system
is an exact and specific color designation using symbols and
numerals written as hue/value/chroma.

Disc colorimetry using the Munsell standards provides a
simple, rapid, and direct method for making color measurements.
Any color can be matched by the proper choice of four discs,_
if the color to be matched lies in the geometric space
intermediate to the four that are chosen. The colors of the
discs are mixed by spinning and matched with the sample

through a color comparator eyepiece.

EXPERDIIENTAL PROCEDURE

Tests were made on the apples before they were prepared
for freezing and after they had been in zero storage for
two, five, ten, fifteen, and twenty weeks. Samples were
baked as pics for organoleptic scoring, firmness tests, and
color measurements. Raw samples were used in analyses for

ascorbic acid, sulfur dioxide, and pH values.

Preparation for freezing

Selection 2; fruit

Jonathan apples grown on the Michigan State College
Farms were chosen for use in this study. U. S. No. 1 grade
with a minimum.diameter of two and one-fourth inches was
used. This grade was selected to avoid interference from
bruises or off colors when the apples were scored and the
color measurements were taken. The apples had been in cold
storage approximately two months before they were prepared

for freezing. They were firm-ripe and well colored.
Peeling and slicing

The apples were weighed before peeling and the waste

was weighed after peeling in order to obtain the percent

18

waste. The fruit was peeled on a Bonanza apple peeler which
also removed the cores. The apples were dropped immediately
into a one percent sodium chloride solution to prevent
browning between peeling and subsequent treatment. The
apples were trimmed and then sliced into twelfths. The
slices were kept in a one percent salt solution until there
was a sufficient amount to be treated. This holding period
never exceeded one hour. Stainless steel knives were used
for trimming and slicing in order to prevent the development
of the blue color which forms when iron comes in contact‘
with the flesh of apples.

The slices were drained in a colander and rinsed 15

seconds under running water before further treatment.
Treatments used'pg prevent browning

One lot of apples was frozen without additional treat-
ment other than that used in preparing the slices. This lot
was used as a control.

Sodium chloride: The sliced apples were placed in a
four percent sodium chloride solution and a vacuum.drawn on
them.for 20 minutes. The remainder of the treatment is
described under Vacuum.method ppgd.

Sodium bisulfite: A 0.1 percent solution of sodium
bisulfite was made in an enamel container. The apple slices
were placed in a cheesecloth bag and immersed in the solution

for two minutes. They were then drained for 15 minutes and

19
left in a covered, enamel container for five hours to allow
for penetration before packaging.

Ascorbic acid: The apple slices were placed in a 0.08
percent ascorbic acid solution and held under vacuum.for 20
minutes. For the remainder of the treatment, see Vacuum
method ppgg.

Potassium.metabisulfite: A 0.5 percent potassium.meta-
bisulfite solution was made in an enamel container. The
prepared fruit was placed in a cheesecloth bag and dipped in
the solution for two minutes. Then the fruit was drained for
15 minutes and allowed to stand in a covered, enamel contain-
er for three hours to permit penetration before packaging.

Ascorbic gpgg-citric gpgg mixture: The apple slices
were held under vacuum in a 0.5 percent solution of an ascorbic
acid-citric acid mixture for 20 minutes. This mixture was
composed of four percent ascorbic acid and 96 percent citric
acid. For the remainder of this treatment, also, see Vacuum

method used.
Vacuum.methgd used pp facilitate penetration 9; solutions

Three kilograms of apple slices were placed in a large
vacuum.desiccator, and a weight was placed on top of the
slices in order to prevent their floating. They were well
covered (two inches above the top of the fruit) with either
of the following three solutions: sodium chloride, ascorbic

acid, or ascorbic acid-citric acid mixture. The desiccator

20
was covered and the vacuum pump turned on. Time was counted
from.the time the vacuum.became constant (approximately 27
inches). After the desired time had elapsed, the vacuum.was
broken and the contents allowed to stand for five minutes to
permit thorough penetration of the slices. The fruit was
removed from.the solution and drained for five minutes before

being packed with sugar and frozen.
Packaging

After the slices were treated, they were packed in number
two tub Nestrite containers. Each tub contained the exact
amount of fruit for one pic and was packed with four parts
apples and one part sugar. The apples and sugar were added
to the tubs alternately in order to secure a complete mixture
of the fruit and sugar. The control (no treatment), sodium
chloride, sodium.bisulfite, and potassium.metabisulfite
groups were packed with 500 grams of treated fruit and 125
grams of sugar, while the ascorbic acid and the ascorbic
acid-citric acid groups were packed with 600 grams of the
treated fruit and 150 grams of sugar. The increase in weight
was made necessary by the high.water content of the vacuumr

treated fruit.
Freezing and storage

The apples were frozen at minus 40 degrees Fahrenheit
and then held at zero plus or minus two degrees until used

in the tests.

21
Testing

Bakipg procedure

Pies were baked using fresh apples and apples frozen
for two, five, ten, fifteen, and twenty weeks respectively.

gppgp: The pastry was made in two batches, each
consisting of 650 grams of all-purpose flour, 300 grams of
lard, 17 grams of salt, and 160 milliliters of water. The
flour and salt were mixed together, using 25 light strokes
of a spoon. The fat was added to the flour and mixed at low
speed for three minutes with a Hobart Kitchen Aid mixer
(model C). At the end of the mixing time the machine was
stopped, and the mixture was scraped down from the sides of
the bowl with a rubber spatula. The water was added, and the
mixture was mixed at low speed for 40 seconds. The pastry
was turned out on a board and folded five times. One-sixth
of one batch (enough for one crust) was folded four thmes
and then rolled between cellophane. All the crusts were
rolled before the pies were assembled.

Fillipg: The frozen fruit was defrosted in a household
refrigerator (approximately 41 degrees F.) for 14 to 15 hours
before making into pies. No additional sugar or spices were
added to the apples.

Assembling Egg baking pigg: Nine-inch (top measurement)
paper pie plates were lined with pastry, and the apples were

arranged on this crust. The outer edge of the crust was

22

moistened with water and the upper crust was placed on top.
The crusts were trimmed five-eighths of an inch from.the
edge; then the edges were turned under and crimped. Three
slits (each one and one-fourth inches long) were cut in the
top to permit the escape of air and steam, The tops were
brushed with milk in order to obtain better browning.

The pics were baked at 400 degrees Fahrenheit for 65
minutes, then cooled about three and one-half hours before

tests were made.
Tests pp pies

Scoring pgpgl: The panel for scoring the apple pies
was composed of six members of the staff in the Foods and
Nutrition Department. All but one person had had experience
on scoring panels for other products. There were five test
periods of five days each and all six treatments previously
mentioned were baked each day. The pics were presented to
the judges in random order. A sector was removed from each
pie and placed on a white plate for the judges to score
color, consistency, and odor. Smaller sectors were placed
on white trays so that each judge could score flavor,
tenderness of fruit, texture of fruit, texture of lower
crust, and general conclusion. The judges were requested
to record comments concerning any outstanding features. A
sample of the score sheet used is shown on page 60 in the

appendix.

23

The scoring was done at 2:30 p.mi in the foods research
laboratory. Care was taken that there were no foreign odors
in the room.at that time. The judges were provided glasses
of cold water.

Firmness test: The penetrometer used for the firmness
test is described in the A.S,T.M§ Standards (1944). To
make the test, the upper crust was removed from the cooled
pie, and the apple slices were carefully removed and placed
in pyrex custard cups. Approximately 150 grams of fruit
wee used. This amount filled the-cups to within one-fourth
of an inch frmm the top.

The grease cone was attached to the penetrometer and
pushed up so that the dial read zero. The cup was placed
on the stage of the penetrometer, and the stage was adjusted
so that the surface of the sample was just in contact with
the point of the cone. The needle bar was released for two
seconds, the indicator bar was depressed until it reached
the top of the needle bar, and the depth of the penetration
was then read on the dial. The needle bar plus the grease
cone weigh 150 grams.

Qplpp_measurement: The color of the baked fruit was
measured objectively by the use of mnnsell color discs
according to the method given by Griswold (1944). In order
to match the color of the fruit, four discs were overlapped
by means of radial slits and spun by a motor. These discs

included two neutrals, one lighter and one darker than the

2h
sample, and two hues of strong chroma that lie on either
side of the hue to be matched. The neutrals used were N l/
and N 5/ or N 8/, depending upon the value of the color to
be matched. The hues used were 5Y 8/12 and 5 YR 6/12.
Samples of these neutrals and hues may be seen on page 25.

A diagram of the spinning assembly used is shown on page 26.
The sample of fruit was well mixed and packed in a
glass cup. Color of the discs was matched with that of the

fruit by looking through a color comparator eyepiece and
adjusting the areas of the discs. The percentage of each
disc used was measured by means of a scale which circumscribed
the discs.

The hue and chrome for each sample were determined
from.the conversion tables published by Nickerson (1935).
The value was calculated from.the following formula given by

Nickerson (1929):

 

 

(bxa2)+(dxc2)+(th2)+ilxn2)
100

Value -

¢_

value of lower neutral disc
area of neutral disc a
value of higher neutral disc
area of neutral disc c

area of lower hue number
value of lower hue number

area of higher hue number
value of higher hue number

U h'b‘H»n:o o'm
I I I I I I u u

25

color tests
trals and hues used in objective

Neu

Figure l.

N 1/

 

N 5/

N 8/

SY 8/12

5YR 6/12

26

Figure 2. Disc spinning assembly for color measurement

We

U3
I
I

1

 

 

 

 

 

 

 

 

A. Comparator eyepiece

B. Lamp

C. Motor

D. Color discs and calibrated disc
E. Sample cup

The entire assembly is covered with black sateen

27

Tests pp raw fruit

Ascorbic acid determination: Reduced ascorbic acid
determinations were made on the frozen fruit by the method
described by Loeffler and Ponting (1942). Determinations
were made on the samples which had no pretreatment and on
those treated with ascorbic acid and ascorbic acid-citric
acid mixture.

Sulfur dioxide determinations: Sulfur dioxide content
of the frozen fruit was determined according to the method
described by Ponting and Johnson (1945). The samples with
no treatment and those treated with sodium bisulfite and
potassium metabisulfite were analyzed.

p§_gg;pg: .A ten-gram.sample of frozen apples was blended
with 90 milliliters of distilled water in a Waring Blender
for two minutes. This mixture was filtered and the pH of

the filtrate determined by means of a Beckman pH meter.
Statistical methods

Correlation coefficients were calculated, and analysis
of variance made, according to methods recommended by

,Snedecor (1946).

DISCUSSION OF RESULTS

Preparation
Preparation waste

The preparation waste averaged 31.3 percent. The waste
included peels, cores, bruises, and any other unusable
portions of the fruit. This percent waste is considerably
higher than the 12 percent waste which was reported in studies
by Masterson and Lee (1943). The differences may lie in the
method of removing the peels and cores and in the amount of
trimming, since care was taken in the study to remove all
peels and discolored areas in the fruit. Also, a mechanical

peeler was used in the current study.
Vacuum treatment

Table 8 on page 61 in the appendix shows the volume of
the solutions used to treat the fruit and the volume absorbed
by the apple slices when vacuumrtreated. The slices treated
with sodium chloride absorbed the smallest amount of liquid.
This constituted seven percent of the original weight of the
apple slices. The fruit treated with ascorbic acid gained
40 percent of its original weight, and that treated with

ascorbic acid-citric acid gained 46 percent.

29

Appearance 9: fruit

The appearance of the raw fruit after defrosting was
recorded. The apple slices treated with the sodium.chloride
solution in a vacuum had a glassy appearance which they
maintained throughout the storage period. This was due to
the absorption of some of the salt solution. The slices
treated with ascorbic acid and ascorbic acid-citric acid
solutions under a vacuum had a transparent appearance and
looked as though they had been cooked. This transparency
was caused by the replacement of the air spaces with the
solution. The fruit treated with sodium bisulfite and
potassium metabisulfite retained the normal appearance of
raw apples.

Kodachrome pictures were made of the defrosted fruit
after 15 weeks in zero storage. Since it is difficult to
reproduce true colors in this type of picture, the colors in
the reproduction of the raw fruit on page 31 are not as true
as in the transparency. The picture does show the relative
differences in the appearance of the fruit with different
treatments. It can be seen that there was some discoloration
in the control sample, especially in the core area. None of
the other treatments showed discoloration in the raw fruit,

even at the end of 20 weeks in zero storage.

Figure 3. The apple slices before and after baking

a. Raw, defrosted apple slices

Control Ascorbic acid

Sodium.chloride Potassium
metabisulfite

Sodium bisulfite Ascorbic acid-

citric acid

b. Baked apple slices

Same arrangement as above

 

31

 

 

32

 

When pies were baked from the frozen apple slices, the
juice from the fruit treated by means of a vacuum had a
tendency to boil out onto the top crust.‘ The juice in the
sodium chloride-treated fruit boiled out very little, while
that in the ascorbic acid- and ascorbic acid-citric acid-
treated fruit boiled out enough to almost completely encircle
the outer edge of the upper crust. This boiling out was
undoubtedly caused by the high liquid content in the fruit.
The higher the liquid content in the fruit, the greater the

amount of juice that boiled out.

Palatability Scores

The mean scores for the pies in each test period are

shown in Table 1 on pages 33 and 34.
Color

The fruit in the control pies was scored lowest for
color. The judges described it as being dark and brown.
The fruit treated with sodium chloride, ascorbic acid, and
ascorbic acid-citric acid received the highest scores. The
fruit treated with sodium chloride had a pink cast after
baking. The samples treated with sodium bisulfite had a
brown tinge, while those treated with potassium metabisulfite

had a more yellow, bleached color.

.Meen scores for each scoring period

Table 1 e

 

Texture Crust General
of texture con-

Tender-
ness of

Consist-

Time

frozen Color

fruit (lower) clusion

fruit

Odor Flavor

ency

Treatment

 

weeks

5.? 5.5 4.1 5.3

5.6 5.8 5.4

5.7

Fresh

V'HDIOG
d'fl'fl'd't‘;

00:0015
donned.

cocooucc

‘id'lnd'd'

None

33

(0000b

fi'd‘tOIQN

”IDOCDN

#d'd'd'd'

”Fr-100i

Ind'lnd‘l‘)

Sodium
chloride

006205034

fi'lfld'd'd'

IOIOHI-ib

IOIOIDLO¢

”Hr-100“

IDIOlD‘d'd'

ovum—no

omens!

Od'HI-IID

Q'IOIDlofl'

Sodium
bisulfite

 

3h

 

 

0.0 H.¢ 0.0 «.0 m.w m.¢ 0.« 0.0 0«
0.0 0.0 >.0 0.0 0.¢ 0.¢ 0.0 «.0 0H
0.0 0.0 0.0 0.0 0.# 0.0 v.0 0.0 0H
0.0 H.¢ 0.0 0.0 0.0 0.0 0.0 0.0 0 Gwen oaHaHo
>.¢ 0.0 0.0 «.0 0.0 0.0 0.0 b.0 « added odnhoomd
«.d 0.0 0.0 0.0 0.0 m.¢ 0.0 0.0 0«
0.¢ ¢.¢ 0.0 0.0 0.0 5.0 0.0 0.0 0H
«.v 0.0 0.¢ b.# 0.0 0.¢ 0.0 m.¢ 0H
0.0 #.¢ H.0 H.0 H.0 0.0 0.0 «.0 0 opdhaflmdnoaoa
0.0 0.¢ H.0 H.0 H.0 0.0 0.0 0.0 « addmmopom
0.0 «.¢ «.0 «.0 0.0 «.0 0.0 m.¢ 0«
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0H
m.¢ 0.0 0.0 0.0 0.0 H.0 0.0 «.0 0H
0.¢ 0.0 0.0 0.0 0.0 «.0 «.0 b.0 0 Guam
b.¢ 0.0 «.0 0.0 H.0 «.0 0.0 0.0 « oanhoomd
mace:
downsao “Hosea“ pagan pasnu noboam Hove hone uoaoo meson“ oncogenes
loco cadence no no omen naedmuoo esaa

flamenco ausno

annexes assumes

 

aceonuvnoov .H eases

s ,Q .‘ C .v. s . I .3 O I .'_ .C U ' .‘. C I. .I II; ’15' -ieo
I

I 7 t d | I O C d I V I
e e o e
o O . O o
o 0 e D
o e O 0
v O O O
O o v . O
o e e . o
e o c e
e e O o
O O o Q
s o e e
e e o 0
o o O Q
o O o e
0 e o e

35

The color scores for the sodium.chloride-treated fruit
dropped the greatest amount with time in storage. The scores
for the fruit treated with ascorbic acid and potassium.meta-
bisulfite drOpped almost as much as did the scores for the
fruit treated with sodium chloride. The scores for the fruit
with no treatment dropped the least with storage since these
samples had low scores in the beginning.

An illustration of the range of colors obtained in the
baked fruit is shown on page 31. This picture was taken of
the pies after the fruit was stored for 15 weeks. It shows,
also, the variation in the consistency of the apple slices and
in the amount of juice, factors which affected the consistency

scores discussed in the next section.
Consistency

The fruit treated with ascorbic acid and ascorbic acid-
citric acid received the lowest scores for consistency. There
was an excessive amount of free juice in these pies which
can be accounted for by the high water content of the fruit.
This excessive juiciness might be corrected by the use of a
thickening agent. The fruit in the control and sodium
bisulfite- and potassium.metabisulfite-treated pies was
mushy and somewhat dry.

The scores for consistency changed very little with
storage except in the case of the fruit treated with ascorbic
acid-citric acid where the score dropped after the 15-week
period.

36
Odor

 

The judges made no comments concerning off odors in the
baked fruit. At no time were they able to detect the odor
of sulfur dioxide. The differences in treatment had no
effect on the odor of the fruit, but there was a gradual

decline in the scores with length of time in storage.
Flavor

The fruit treated with ascorbic acid received the high-
est scores for flavor. Although this treatment received the
highest average score, one of the judges described the flavor
as bland and tasteless. The flavor of the fruit treated with
the ascorbic acid-citric acid was occasionally described as
tart. These latter samples received the second highest
score. most of the judges commented frequently on the
saltiness of the fruit treated with sodium chloride. The
flavor of sulfur dioxide was detected only once, by one judge,
in any of the samples treated with sulfite solutions. This
was in the potassium metabisulfite sample after two weeks in
zero storage. I

The greatest drop in flavor score, with storage, was in
the sodium chloride-treated sample. The time that elapsed
between the first and last test periods made very little
difference in the flavor of the control and in the samples

treated with ascorbic acid and ascorbic acid-citric acid.

37

Tenderness p; fruit

The sodium chloride-treated sample was the least tender
of all the treated samples but received the same average
score as the control. The judges commented on the lack of
tenderness of the sodium chloride—treated fruit more than
they did on the control. They described the fruit treated
with sodium chloride as being dry, tough, and hard. The
ascorbic acid-treated fruit had the highest score for ten-
derness, and the sample treated with ascorbic acid-citric
acid was second. There was a gradual decline in the tender-

ness scores with the length of trme in zero storage.
Texture pf fruit

The texture of the fruit treated with ascorbic acid and
ascorbic acid-citric acid was most desirable. The texture of
the fruit treated with sodium chloride was coarse and disagree-
able to the tongue. This coarseness may have been brought
about by dehydration of the sample by the salt. All the

scores on texture gradually declined with storage.

Texture pg lower crust

 

The pies made from the fruit treated with ascorbic acid
and ascorbic acid-citric acid had the soggiest lower crusts.
The fact that the scores for texture of the crust and

consistency of the fruit followed the same pattern suggests

38
that the amount of liquid present in the fruit has a direct

influence on the texture of the lower crust.

General conclusion

 

The apples treated with sodium bisulfite received the
highest average score on general conclusion, and those
treated with ascorbic acid were close second. The fruit
treated with sodium chloride received the lowest average
score. The general conclusion scores appear to be influenced
most by the flavor of the fruit, except in the case of the
slices treated with ascorbic acid. The color seemed to have
some influence, except with the sodium.chloride- and ascorbic
acid-treated fruit. The salty flavor of the fruit treated
with sodium chloride was so evident that it had a great
affect on the general conclusion score. There was a steady
decline in all of the general conclusion scores with time in

zero storage.
Acceptabilipy

The pies made from.the fresh apples were acceptable to
all the judges but one who was more critical than the others
during the entire study. Except for the control and sodium
chloride samples, all the pies made from.the frozen apples
were acceptable to the judges throughout the entire test
period. The control sample was not acceptable one day in the

five-week test period and one day in the 20-week period. The

39
samples treated with sodium chloride became less desirable
with longer time in storage. They were acceptable to the
judges after two and five weeks in storage but not acceptable
two days in the 10-week test period, one day in the lS-week
period, and all five days in the 20-week period.

Analysis pf variance 2: scores

The data were analyzed to separate variation due to
replication, treatment, and time in storage. Table 2 on
page 40 gives a summary of this analysis. Calculations
showed that there was very little difference due to
replication. The only places where replication differences
did show up were in color and crust texture, the former being
significant and the latter being highly significant. The
differences in color may be accounted for by irregular light-
ing in the room.where the scoring was done. The total light
available in this room is affected by the amount of sunshine
coming through the windows. The bamboo blinds at the windows
were lowered to subdue the light on bright days and the
incandescent lamps were used on dark days. The differences
in the crust texture may have been caused by lack of uniformity
of the water distribution in the pastry. Wet or dry spots may
have made weak places in the crusts and thus may have been
responsible for leakage during baking. This leakage was
found in one or two pies each day but was no worse in one

treatment than in another. This difficulty might be remedied

40

Table 2. Results of analysis of variance of scores

 

 

 

 

“‘ Tender- TEXture ‘Crust General
Consist— ness 0f of texture con-
Factor Color ency Odor Flavor fruit fruit (lower) clusion
Average scores for each
Treatment
None (control) 5.55 5.28 4.65 4.29 4.71 4.92 4-51 4-24
Sodium chloride 5.40 5.56 5.11 5.61 4.72 4.76 4.55 3.87
Sodium bisulfite 4.91 5.65 4.99 4.87 5.02 5.10 4.51 4.81
Ascorbic acid 5.58 3.65 5.10 5.15 5.42 5.41 5.98 4.74
Potassium metabisulfite 5.16 5.54 4.98 4.82 .4.86 4.86 4.47 4.54
Ascorbic acid-citric acid 5.57 5.62 I 5.09 4.90 5.40 5.58 4.10 4-67
Average scores for each
Storage Period
2 weeks 5.55 4.79 5.07 4.85 5.19 5.22 5.99 4.74
5 weeks 5.09 4.90 5.17 4.90 5.15 5.22 4.52 4.70
10 weeks 4.95 4.91 5.00 4.55 5.17 5.16 4.59 4.51
15 weeks 4.95 5.01 4.87 4.55 4.98 5.12 4.55 4.57
20 weeks 4.51 4.45 4.81 4.20 4.65 4.80 4.52 5.97
F Values
Treatment 24.53** 7,72** 5.65** 8.86** 8.59** 5.35** 14.07** 17.07ss
Storage 122.28** ll6.04** 4.75M 50.60** 12.99’M 15.69” 12.52M 19.70M
Storage x treatment 5.78" 2.75“ 1.45 2.24“ 1.06 1.34 1.47 2.46**
Replications 1.99* 0.68 1.22 0.91 1.06 1.55 5.55** 0.70

 

* Significant
** Highly significant

   

 

41
by allowing the pastry to stand for a time between mixing

and rolling.

The differences attributable to treatment and length of
frozen storage were highly significant for all scoring
factors. These individual factors have been discussed in
detail on the pages just preceeding.

The interactions between storage and treatment were also
calculated. These were highly significant for color, con-
sistency, flavor, and general conclusion. These figures
indicate the lack of shrilarity in the response of the
various treatments to the various storage periods. The data
in Table 1 indicate this variation. The scores for the color
of the sodium bisulfite-treated fruit were relatively constant
up to the last time interval, then dropped. The scores for
the potassium.metabisulfite-treated fruit dropped through
the first three storage periods, then were constant for the
remaining time.

The scores for consistency in the control pies continued
to increase gradually through the first four time intervals
and then dropped back to the same as those of the first
period. For the fruit treated with ascorbic acid, the score
increased at the second time interval and then declined. The
scores for the ascorbic acid-citric acid-treated fruit
remained almost constant through the first four test periods
and then dropped.

The flavor scores for the fruit treated with sodium

chloride made a steady drop throughout the test periods.

42
The scores for the flavor of the fruit treated with sodium
bisulfite increased at the second time interval, decreased
at the third, increased at the fourth, and decreased again
at the fifth.

The general conclusion scores for the fruit treated
with sodium chloride dropped through the first three time
intervals, remained constant at the fourth interval, and
dropped greatly at the fifth interval. The scores for the
fruit treated with potassium.metabisulfite were the same for
the first two test periods, dropped at the third, increased
at the fourth, and decreased again at the fifth.

I An example of scores that do not show significant inter-
actions between storage and treatment are the ones for crust
texture. These scores tend to go up and then come down,

all following very much the same pattern.

Objective Tests on Baked Fruit
Penetrometer

The penetrometer readings on the apple slices from the
baked pies are listed on page 43 in Table 3. This method
for determining firmness did not work out satisfactorily.
It was hoped that this determination would show differences
in firmness of the fruit treated in different ways to prevent
browning. However, when the apple slices lacked firmness,

they cooked up into a sauce which gave very much the same

43

 

 

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resistance to penetration as did those firm.enough to hold
their shape.

Correlation coefficients between the penetrometer
readings and the scores on consistency, tenderness of fruit,
and texture of fruit were calculated. These are given in
Table 4. The correlation coefficients between the penetrometer
readings and the scores for texture and tenderness are higher
for the samples treated with sodium chloride than for any
other treatment. However, none of the coefficients were
large enough to be statistically significant.

Table 4. Correlation coefficients between penetrometer

readings and judges' scores on consistency, tenderness of
fruit, and texture of fruit.

 

Correlation coefficients between
penetrometer readings and

 

 

Treatment Consistency Tenderness Texture
None -0.028 -0.l38 0.090
Sodium chloride 0.014 0.344 0.372
Sodium bisulfite -0.083 0.046 0.093
Ascorbic acid 0.297 -0.272 -0.367
Potassium 0.014 -0.063 0.049
metabisulfite
Ascorbic acid- 0.025 0.025 -0.l88

citric acid

 

45

Color measurement

The results from the objective color tests on the baked
fruit are shown in Table 5 on page 46. The fruit treated
with sodium bisulfite had about the same hue as the fresh
fruit, but the value was lower and not as much of the color
was present. The potassium.metabisulfite-treated fruit con-
tained the greatest amount of yellow, with the fruit treated
with ascorbic acid being second, and that treated with
ascorbic acid-citric acid, third. The control contained the
smallest amount of yellow.

The figures for value show that the control group was
darkest, and that the ascorbic acid-, potassium.metabisulfite-,
and ascorbic acid-citric acid-treated samples were the
lightest, all being nearly the same. The values of the
samples treated with sodium chloride and sodium.bisulfite
were about equal.

There was very little change in hue and value with the
length of time in storage, but there was considerable change
in chroma. The highest chroma was in the fresh fruit. All
of the frozen samples showed a decided decrease in chroma
from the first time interval to the last. This shows that
there was a loss of color with storage.

The averages of the areas of the color discs required to
match the color of the baked fruit in each test period are
shown in Table 9 in the appendix. The hue, value, and chroma

notations in Table 5 were calculated from these data.

46

Table 5. Objective color data on apple slices from baked
pies, expressed according to the Munsell system

 

 

Treatment Time frozen Hue* Value** Chroma‘*‘
weeks
”Can. 0 20.58 7e02 9e36
None 2 17.59 4.94. 5.53
5 18.53 4.91 5.53
10 19.61 5.49 5.21
15 18.84 5.56 5.25
20 18.56 5.16 4.52
Sodium chloride 2 20.10 6.64 8.47
5 18.89 5.88 7.66
10 18.75 5.86 6.84
15 19.77 6.05 6.50
20 19.66 5.61 5.55
Sodium bisulfite- 2 20.57 6.65 8.21
5 20.01 5.88 6.50
10 19.60 5.85 6.00
15 20.62 6.15 6.41
20 20.44 5.86 5.16
Ascorbic acid 2 22.51 6.98 8.55
5 22.56 6.58 7.20
10 21.82 6.57 6.58
15 22.58 6.44 6.58
20 21.81 6.11 5.74
Potassium 2 25.56 7.12 8.55
metabisulfite 5 22.55 6.44 7.18
10 22.29 6.44 6.55
15 22.69 6.44 6.41
20 22.68 6.26 5.69
Ascorbic acid- 2 22.55 6.92 7.97
citric acid 5 21.01 6.24 7.22
10 20.97 6.18 6.45
15 21.85 6.24 6.10
20 21.54 6.09 5.45

 

* Hue of yellow-red is 15 and yellow is 25.
*‘ Value runs from one (black) to ten (white).

‘7‘ Chrome is the strength of the color. The maximum chroma
for yellow-red and yellow is 12.

47
Objective Tests on Raw Fruit

Ascorbic acid

Ascorbic acid determinations were made on the fruit
treated with ascorbic acid and ascorbic acid-citric acid
merely as a means of control rather than from the nutritive
value standpoint. The fruit receiving no treatment was used

as a check. The data obtained are shown in Table 6.

Table 6. Ascorbic acid content of raw, frozen apple slices

 

 

Ascorbic Ascorbic acid-
Time in storage Control acid citric acid
mg./100gm. mg./100gm. mg./100gm.
3 weeks 0.8 22.7 4.9
11 weeks 0.7 2h.8 2.8
16 weeks 0.7 16.0 3.2
21 weeks 0.7 * 5.3

 

* Sample lost.

The figures indicate’that there was very little reduced
ascorbic acid in the control samples. This amount remained
constant with time in storage. The samples treated with
ascorbic acid contained around three and one-half times as
much ascorbic acid as those treated with ascorbic acid-citric
acid. The ascorbic acid solution with which the fruit was
treated contained four times as much ascorbic acid as the
ascorbic acid-citric acid solution. The fluctuation in the

figures for the treated fruit might be accounted for by

48
variation in the amount of the solution that was absorbed

by the fruit.
gulfur dioxide

The sulfur dioxide content of the fruit treated with
sodium.bisulfite and potassium.metabisulfite was determined
to find how well the sulfur dioxide was retained in the fruit
with storage. The fruit which received no treatment was

used as a check. The data obtained are shown in Table 7.

Table 7. Sulfur dioxide content of raw, frozen apple slices

 

 

Sodium Potassium
Time in storage Control bisulfite metabisulfite
p.p.m. p.p.m, p.p.m.
6 weeks 0 17 117
11 weeks 0 32 97
16 weeks 0 20 107
21 weeks 0 2A 109

 

The control samples contained no sulfur dioxide. The
fruit treated with sodium.bisulfite contained an average of
23 parts per million throughout the entire test period as
compared to 108 parts per million in the fruit treated with
potassium.metabisulfite. This can be accounted for in the
fact that the fruit was exposed to five times as much sulfur
dioxide in the sample treated with potassium.metabisulfite

as in that treated with sodium bisulfite.

49
From these figures, it appears that the sulfur dioxide

was well retained during zero storage.

2§_va1ue

As can be seen in Figure A on page 50, all the samples
showed a slight increase in pH with time in storage. The pH
of both samples treated with sulfur dioxide dropped at the
10-week interval. This drop cannot be explained by changes
in the sulfur dioxide content. In only four cases were the
pH values of the frozen fruit lower than the pH of the fresh
fruit. None of these changes in pH was large and any

fluctuations might be accounted for in sampling errors.

50

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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SUMMARY AND CONCLUSIONS

A study was made of five methods of preventing browning
in frozen, sliced, Jonathan apples for use in pie. Fruit
frozen without additional treatment after peeling and slicing
was used as a control. A record was kept on waste in
preparation. Pies were made from the fresh fruit, and from
frozen apple slices after two, five, ten, fifteen, and twenty
weeks in zero storage. There were five replications in each
test period. The pies were scored subjectively for color,
consistency, odor, flavor, tenderness of fruit, texture of
fruit, texture of lower crust, and general conclusion. The
firmness of the baked fruit was measured objectively with a
penetrometer and color was measured by the Munsell spinning
disc colorimeter. The raw fruit from the appropriate treat-
ments was analyzed for the reduced ascorbic acid and for the
sulfur dioxide content to determine their retention with
storage. The pH of the raw fruit was also measured.

The scores for the various treatments showed sodium
chloride best for color, odor, and crust texture; sodium
bisulfite best for consistency; ascorbic acid best for flavor
and tenderness; and ascorbic acid-citric acid best for texture
of fruit. The treatments ranked in the following order for

general conclusion score: first, sodium bisulfite; second,

52
ascorbic acid; third, ascorbic acid-citric acid; fourth,
potassium.metabisulfite; fifth, control; and sixth, sodium
chloride.

The scores for color, odor, flavor, tenderness of fruit,
texture of fruit, and general conclusion dropped fairly con—
sistently throughout the storage period.

Analysis of variance of the scores showed the differences
attributable to treatment and length of zero storage were
highly significant for all scoring factors. There was little
difference due to replication. The interactions between
storage and treatment were highly significant for color, con- '
sistency, flavor, and general conclusion and not significant
for odor, tenderness of fruit, texture of fruit, and texture
of lower crust.

The penetrometer did not prove to be satisfactory for
determining firmness in the baked apple slices. There was
no correlation between the penetrometer readings and scores
on consistency, tenderness of fruit, and texture of fruit.

The Munsell color readings indicated that the fruit
treated with potassium.metabisulfite contained the greatest
amount of yellow. The value in all cases dropped (became
darker) with time in storage except in the control which
became lighter and then darker. The chroma in all frozen
samples declined steadily with storage, indicating loss of
color.

Ascorbic acid and sulfur dioxide were well retained in

53
the fruit in zero storage. There was very little change
in the pH with storage.
0n the basis of these results, it appears that:

1. Sodium bisulfite was the best treatment used
for the prevention of browning in frozen, sliced,
Jonathan apples; all treatments used except sodium
chloride were acceptable; treatment was necessary to
prevent browning.

2. The palatability of the fruit declined with
storage. However, all samples were satisfactory for
all the treatments except sodium chloride and the
control for 20 weeks in zero storage.

3. The penetrameter was not satisfactory for
determining firmness in baked apple slices.

h. The hue notations varied between treatments
but remained fairly constant with storage; the value
and chrama notatiOns declined with storage, indicating
darkening and loss of color.

5. Ascorbic acid and sulfur dioxide were well

retained in the frozen fruit.

LIST OF REFERENCES

Anon. 1944. Sulfur dip prevents browning of frozen sliced
agplez. Food Industries, vol. 16, pp. 805-806,
8 2-8 30

. 1945. Tentative U. S. standards for grades of frozen
apples. The Canner, vol. 101, no. 12, pp. 36, 38.

. 1946. Institutional uses for frozen peaches and
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. 1947. Commercial preparation, freezing preservation
of sliced apples. Frozen Food Industry, vol. 3,
1’10. 12, Ppe 12-13, 3093]..

Am. Soc. Testing Materials. 1944. Tentative method of test
for consistency of lubricating greases and petroleum.
Designation: D217-44T. A. S. T. M. Standards, Part
III, Nonmetallic Materials - General.

Balls, A. K., and W. S. Hale. 1935. Peroxidase in the
darkening of apples. Ind. and Eng. Chem., vol. 27,
PP- 335-337.

Bauernfeind, J. 0., F. W. Johns, E. G. Smith, and G. F.
Siemers. 1946. Vitamin C stability in frozen fruit
processed with crystalline l-ascorbic acid. Fruit
Products Journal, vol. 25, pp. 324-330, 347.

Cruess, W. V., R. Samisch, and H. M; Pancoast. 1933. Fruit
enzyme investigations. Fruit Products Journal,
vol. 12, pp. 323-324, 344.

, and H. Seagrave-Smith. 1946. Observations
on freezing of apples. Fruit Products Journal,
V01. 26, no. 10, PP. 36-37, 590

 

DuBois, C. W., and D. L. Colvin. 1945. Loss of added vitamin
C in the storage of frozen peaches. Fruit Products
Journal, vol. 25, pp. 101-103.

Griswold, Ruth M. 1944. Factors influencing the quality of
home-canned Montmorency cherries. Tech. Bull. 194,
Mich. St. College Agra Exp. Sta.

55

Griswold, Ruth M. 1944. Factors influencing the quality of
cooked Jonathan apples. Tech. Bull. 195, Mich. St.
College Agr. Exp. Sta.

Hoffman-La Roche, Inc., Vitamin Division. 1947. Processing
frozen fruit with l-ascorbic acid (vitamin C), 3rd
ed. Hoffman-La Roche, Inc., Nutley, New Jersey.

J___. 1947. Use of ascorbic acid with frozen
apples. Food Packer, vol. 28, no. 9, pp. 33-34.

 

Hohl, Leonora, and Joyce Swanburg. 1946. Freezing of
California fruits - apricots. The Food Packer,
vol. 27, no. 4, pp. 37-38, 68, 70, 72.

Johnston, G. E. 1945. Frozen fruit designed for use in the
baking industry. Baker's Digest, vol. 19, no. 6,
PPo 142-144.

Joslyn, M. A. 1930. Preservation of fruits and vegetables
by freezing storage. Calif. Agr. Exp. Sta. Circ.
320: PP- 1'35.

. 1941. Color retention in fruit products.
Ind. and Eng. Chem., vol. 33, pp. 308-314.

 

, and E. M. MIak. 1933. Investigations on the
use of sulfurous acid and sulfites in the preparation
of fresh and frozen fruit for bakers'use. Fruit
Products Journal, vol. 12, pp. 135-140.

 

Lee, F. A. 1944. Cold dip and scalding methods for fruits.
Quick Frozen Foods, vol. 7, no. 2, p. 35.

Loeffler, H. J., and J. D. Ponting. 1942. Ascorbic acid,
rapid determination in fresh, frozen, or dehydrated
fruits and vegetables. Ind. and Eng. Chem., Anal.
Ede, V01. lily, PP. 8146-8490

Luther, H. G., and G. 0. Cragwall. 1946. Ascorbic-citric
acids prevent browning of cut fruit. Food Industries,
vol. 18, pp. 690-692, 794, 796, 798, 800.

MacArthur, Mary. 1945. Apples: experiments in freezing
preservation. Canadian Food Packer, vol. 16, no. 4,
DP 0 17-18 0

. 1945. Freezing apples for bakers. Canadian
Food Packer, vol. 16, no. 8, pp. 13-14.

56

Masterson, Nancy K., and F. A. Lee. 1943. The home freezing
of farm products. Cornell Agr. Ext. Bull. 611,

PP 0 1-148 0

Mazzola, C. L. 1945. Fruit processing improved. Food
Industries, vol. 17, pp. 134-137.

Merck and Co., Inc. 1947. Processing frozen fruits with
ascorbic acid Merck to prevent discoloration, a
handbook of methods employed. Merck and Co., Inc.,
Rahway, New Jersey.

. 1948. Ascorbic acid Merck as an anti-
oxidant in fruit and food products. Supplement to
"Processing frozen fruits with ascorbic acid Merck”.
Merck and Co. Inc., Rahway, New Jersey.

 

Morris, F. N. 1946. Principles gkoruit Preservation. 2nd
ed. Chapman and Hall Ltd. London.

Munsell Book of Color. 1929. Standard ed. Munsell Color
Company, Inc., Baltimore, Maryland.

Nickerson, Dorothy. 1929. A method for determining the
color of agricultural products. Tech. Bull. 154,
U. S. Dept. Agr.

. 1935. Color tables for converting areas
of selected disks to terms of hue, brilliance and
chrome. Mimeo., Bur. Agr. Econ., U. S. Dept. Agr.,
pp. 1-115.

 

. 1946. Color measurement and its
application to the grading of agricultural products,
a handbook on the method of disk colorimetry. Misc.
Pub. 580, U. S. Dept. Agr.

 

Onslow, M. W. 1920. The oxidizing enzymes of some Common
fruits. Biochemical J., vol. 14, pp. 541-547.

Overholser, E. L., and W. V. CrueSs. 1923. A study of the
darkening of apple tissue. Calif. Agr. Exp. Sta.
TGChe Paper, vele 7, PP. 1-14.00

Pfizer, Chas. and Co., Inc. 1947. Ascorbic and citric acids
in fruit products. Chas. Pfizer and Co., 81 Maiden
Lane, New‘York 7, N. Y.

Pfund, Marion C. 1939. The culinary quality of apples as
determined by the use of New York state varieties.
Cornell U. Agr. Exp. Sta. Memoir 225, pp. 1-73.

57

Plagge, H. H. 1938. Freezing preservation of fruits and
vegetables. Quick Frozen Foods, vol. 1, no. 1,
Pp. 39-hogl-I'20

Ponting, J. D., and G. Johnson. 1945. Determination of sulfur
dioxide in fruits. Ind. and Eng. Chem., Anal. Ed.,
vol. 17, no. 11, pp. 682- 686.

Senn, G., and L. Bisno. 1947. What do the preservers and
bakers look for in frozen fruits? Frozen Food
Industry, v01. 3, no. 12, pp. 6-7, 19-20.

Short, R. M. 1944. Testing apple pies, sauce and baked
apples. Quick Frozen Foods, vol. 6, no. 9, p. 21.

Snedecor, G. W. 1946. Statistical methods. 4th ed. The
Collegiate Press, Inc., Ames, Iowa.

Sorber, D. G. 1943. Prefreezing apples and other fruits
for desserts. Quick Frozen Foods, vol. 5, no. 9,
pp. 18-19, 25, 40.

Sorber, E. D., J. D. Ponting, G. Johnson, and Mildred Boggs.
1944. Commercial preparation and freezing preser-
vation of sliced apples. Quick Frozen Foods, vol. 7,
no. 2, pp. 38, 75.

Sparkes, B. 1944. Zero Storage in Your Home. Doubleday,
Doran and Co., Inc., Garden City, New York.

 

Tressler, D. K. 1946. .Are you freezing autumn fruits?
American Fruit Grower, vol. 66, p. 14.

, C. F. Evers, and Lucy Long. 1946. Into the
Freezer and Out. The Avi Publishing Company, New York.

 

, and C. W. DuBois. 1944. No browning of cut
frUit when treated by new process. Food Industries,
V01. 16’ n00 9’ pp. 137-1390

 

U. S. Census Bureau. 1945. Census of Agriculture, vol. 1,
part 6, p. 7.

U. S. Dept. Agr., Western Regional Research Laboratory. 1944.
Commercial preparation and freezing preservation of
sliced apples. AIC - 57. PP. 1-7.

Wiegand, E. H. 1946. Oxidation and its control. Quick
Frozen Foods, vol. 8, no. 9, pp. 81-83, 92.

58

Winter, J. D. 1942. Quality in frozen fruits and vegetables.
U. of Minn. Agr. Exp. Sta. Bull. 362.

, and A. Hustrulid. 1944. Preparation of apples
for freezing. Locker Operator, vol. 5, no. 12, p. 39.

 

Woodroof, J. G. 1946. Quality of frozen fruits should be
improved. Quick Frozen Foods, vol. 8, no. 6,

Pp. 58-59.

, and S. R. Cecil. 1943. Preserving fruits
with sulfur dioxide solution. Fruit Products
Journal, vol. 22, no. 5, pp. 132-135, 155.

 

APPENDIX

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62

Table 9. Areas of Munsell color discs - averages for each test

 

 

 

period
Time Percent of discs showin§___
Treatment frozen YR 6/12 Y 8/12 N l/ N 5/‘ N 8/‘
weeks
None 2 58 12 45 - 8
5 52 12 58 18 -
10 26 18 21 56 -
15 50 14 21 55 -
20 26 ll 22 40 -
Sodium. 2 55 54 7 - 25
chloride 5 45 21 15 22 -
10 59 18 8 55 -
15 52 22 5 45 -
20 27 17 15 45 -
Sodium 2 52 57 7 - 24
bisulfite 5 50 25 16 52 -
10 50 20 8 42 -
15 27 26 0 46 -
20 25 21 7 50 -
Ascorbic acid 2 17 51 7 - 25
5 19 40 7 55 -
10 21 54 0 45 -
15 18 57 0 45 -
20 18 29 5 49 -
Potassium 2 ' 12 60 7 - 22
.metabisulfite 5 18 41 6 55 -
10 18 57 0 45 -
15 15 58 0 47 -
20 15 52 1 55 -
Ascorbic acid- 2 25 48 7 - 25
citric acid 5 27 55 8 52 -
10 25 28 1 45 -
15 19 51 0 49 -
20 18 26 l 56 -

 

* A darker value had to be used after the two-week storage
‘ period in order to match the color discs with the samples.

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