JUICE AND JELLY QUALITY FROM GRAPES
GROWN IN WEST TEXAS
by
DONNA E. HUFFINGTON, B.S.
A THESIS
IN
FOOD TECHNOLOGY
Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for
the Degree of
MASTER OF SCIENCE
Approved
August, 1979
//^, 77 ACKNO^^^EDGMENTS
The author wishes to express sincere appreciation to
Dr. Robert C. Albin for serving as chairman of her graduate
committee.
The author also wishes to thank Dr. R. Max Miller for
his help and support in directing this research project.
Thanks are extended to Dr. M. L. Peeples for reading this
manuscript. Grateful acknowledgment is also due to Pro
fessor Robert R. Reed, Department of Plant and Soil
Science, for his helpful suggestions in carrying out this
research project.
Appreciation is extended to the Food Science and
Nutrition Institute for the financial support provided to
me for this work toward the Master of Science degree.
11
TABLE OF CONTENTS
ACKN0V7LEDGMENTS ii
LIST OF TABLES iv
LIST OF FIGURES v
I. INTRODUCTION 1
II. BACKGROUND 3
Grape Storage 5
Juice Extraction and Clarification 7
Spectroscopy 9
Jelly 9
Conclusion 12
III. MATERIALS AND T IETHODS 13
Juice 13
Jelly 21
IV. RESULTS AND DISCUSSION 23
Jelly 43
Conclusion 44
REFERENCES 45
111
LIST OF TABLES
1. °Brix of Grapes at the Time of Harvest 24
2. Weight Loss During the Washing and Destemming Process 25
3. Weight of Grapes, Juice, and Percent Yield of Juice from These Grapes Using Different Enzymes, Pectinol R-10, and Irgazyme 27
4. Ranking of Grape Varieties Combined with Enzymes Based on Percent Yield of Juice . . . . 29
5. pH and % Titratable Acidity of Purple Grape Juice Before and After Centrifuging and Before and After Treatment with Fining Agents Albumin, Bentonite Clay, and Casein 31
6. pH and % Titratable Acidity of Red Grape Juice Before and After Centrifuging and Before and After Treatment with Fining Agents Albumin, Bentonite Clay, and Casein 32
7. pH and % Titratable Acidity of White Grape Juice Before and After Centrifuging and Before and After Treatment with Fining Agents Albumin, Bentonite Clay, and Casein 33
8. Ranking of Treatments of Juices Based on Differences in Mean pH Before and After Centrifuging 35
9. Absorbance of Purple Grape Juices Before and After Centrifuging and Before and After Addition of Fining Agent; Mean , Standard Deviation and Variance of Absorbance of All Juices and All Juices Except Grand Noir 38
10. Absorbance of Red Grape Juices Before and After Centrifuging and Before and After Addition of Fining Agents 3 9
11. Absorbance of White Grape Juice Before and After Centrifuging and Before and After Addition of Fining Agents 40
IV
LIST OF FIGURES
1. Processing Steps from Grapes to Juice Extraction 16
2. Processing Juice with Fining Agents 18
3. Absorbance Scan of Commercial Grape Juices--Purple (1:10, Juice:Water), Red (1:10, Juice: Water), and White (1:2, Juice:Water)—in the Visible Light Spectrum 37
CHAPTER I
INTRODUCTION
Climatic conditions on the High Plains of West Texas
have been proven to be conducive to the production of grapes
Grape vines have grown well and produced good crops during
relatively moist seasons and very dry seasons in this area.
Rainfall is usually adequate for production of a grape crop
without requiring the use of irrigation water. These West
Texas conditions vary greatly from the conditions in the
primary grape growing areas such as California and New York.
Grapes are one of the most universally grown agricultural
products because they do seem to adapt well to most cli
matic conditions. However, these different conditions do
cause differences in the grapes.
Currently, several varieties of grapes are being grown
in West Texas in order to determine which ones are most
productive in the area. Many acres of land have been put
into grape production in the last few years and, if current
trends continue, there will be increasing acres of grapes
planted in West Texas in order to provide another source of
agricultural income for farmers of the area. Most of these
grapes are presently going into the wine industry in the
area. However, if grape production continues to increase,
it may be necessary to find another outlet for the grapes
which the wine industry in the area cannot use.
1
Therefore, this study has been designed to determine
how the growing conditions in West Texas, which are so dif
ferent from conditions in the primary grape-growing areas
of the country, will affect processing characteristics of
the grapes and whether an acceptable juice and jelly can be
made from West Texas grown grapes. In doing this, another
potential outlet for grapes will be shown to both growers
and industry.
CHAPTER II
BACKGROUND
Originally, grapes were grown only for home use. About
1900, the first plantings of grapes for commercial use were
established (Fisher, 1976). The processing of grapes into
juice for commercial use began in 1869 when a dentist. Dr.
Thomas B. Welch, and his son gathered grapes from their
trellis in New Jersey, prepared juice and pasteurized it in
hot water long enough to kill the yeasts (Pederson, 1971).
This was the beginning of an industry which has had a gradual
increase since 1869. The USDA has conducted extensive re
search with grapes beginning about 1900 (Magness, 1976).
Concord grape juice was the first to be preserved by pasteur
ization (Tressler, 1971). The procedure invented by Welch
involved hot pressing the crushed grapes, filling hot juice
into carboys which were then closed with paraffined corks.
The carboys were stored in a cool cellar for three months or
longer. During this period the pulp and other suspended
matter settled. The clear juice was siphoned off and filled
into bottles. The bottles were capped and placed in racks.
The racks of bottled juice were held in hot water, at 180 to
190° F for pasteurization. Dr. Welch was using the princi
ples expressed in Louis Pasteur's theory of pasteurization
(Pederson, 1971).
1
Grape juice is defined as the unfermented liquid ex
pressed from suitably ripened fruit of the grape (Pederson,
1971). Grape juice is essentially a solution of all soluble
ingredients of the fruit (Tressler and Joslyn, 1971). The
period during which grapes can be harvested is relatively
long; however, the juice extracted from these grapes will
not be the best unless they are harvested at the proper
times (Shoemaker, 1978). The refractometer is widely used
to give a quick sugar test for maturity. The sugar of
the berries consists of the invert sugars glucose and
fructose (components of sucrose). The optimum sugar level
differs with variety of grape but is commonly 20 percent
for processing into juice. Grapes do not increase in sugar
content after they are picked, therefore they must be
allowed to ripen to full maturity on the vine (McEachern,
1978). Time of ripening is dependent upon variety, geo
graphic location and climatic conditions (Flora, 1977).
Juice yield from ripe grapes is about 5 percent higher
than from unripe grapes (Pederson, 1971).
Grape juice differs little in chemical composition from
the grape berry except in crude fiber content and oils which
are primarily present in the seed (Pederson, 1971). Pederson
(1971) stated that in extracting juice, hot pressing of grapes
is essential in order to bring into solution the color and
other ingredients of the fruit. Hot-pressed juice is higher
in total solids, nonsugar solids and tannins than is cold-
pressed juice. The juice extracted does depend for composi
tion on variety of grape from which it is extracted, region
of production of the grape, cultural practices, weather fac
tors, and maturity (Sistrunk and Cash, 1974).
The method of extraction of the juice from the grape has
a marked effect on the composition of the prepared juice
(Tischer, 1951). The principal flavor components are sugars,
acids, and volatile esters, acids, alcohols, and aldehydes
(Pederson, 1971). Analysis by the Welch Grape Juice Company
has shown that grape juice contains potassium, sodium, cal
cium, phosphorus, iron, copper, magnanese, biotin, niacin,
panthothenic acid, pyridoxine hydrochloride, thiamin, folic
acid, ascorbic acid, choline, and trace amounts of riboflavin
and vitamin B,~. Sastry and Tischer (1952) found that grapes
contain anthocyanin pigments, chlorophyll, carotenes, and
water soluble yellow pigments.
Grape Storage
Methods for storage of grapes prior to processing have
been studied in order to allow grapes to be harvested at peak
maturity and held until processing is possible. .Storage tech
niques have been based on high humidity cold storage with
regular sulfur dioxide (SO2) 9^^ fumigations (Ryall and Harvey,
1959). Winkler and Jacob (1925) showed that several
preservatives could be used to prevent spoilage of grapes
under refrigeration (Winkler and Jacob, 1925) . Those pre
servatives included boric acid, formic acid, formaldehyde,
benzoate of soda, salicylic acid, and sulfur dioxide.
Sulfur dioxide in concentrations of 0.06 to 0.12% showed
indications of controlling alcoholic fermentation and the
production of acetic acid and retarded the activity of
microorganisms generally associated with grape spoilage.
Methods have been developed for applying sulfur dioxide to
commercial shipments of grapes (Smit et al., 1971) . In 1940,
tablets containing a mixture of sodium and potassium
bisulfite, sodium metabisulfite, alum, and silica gel were
used in shipping. Nelson and his co-workers (1966, 1968,
1970) reported the use of specially designed envelopes con
taining sodium bisulfite for rapid, then slow release of
sodium dioxide in grape containers. In 1968 and 1969, Smit
et al. (1971) experimented with the use of different packaging
materials and different concentrations of sulfur dioxide. An
acceptable product could be maintained for about two months
with sodium bisulfite in cellophane containers and storage
at 32°F (0°C).
In 1977, Hedberg reported a marginal reduction of mold
development in stored grapes to which field applications of
benomyl had been made during the growing season. He also
found that in-container sulfur dioxide generators produced
a level of sulfur dioxide suitable for long-term storage of
grapes. Also, perforated polyethylene liners act as a mois
ture and sulfur dioxide barrier without causing undesirable
condensation.
The use of freezer temperatures to extend storage life
of grapes has been studied by Siewart et al. (1951) and
Woodroof et al. (1956) . Both of these described the use of
frozen deseeded grapes for use in pastries and other products.
However, these grapes had been heat-processed prior to freez
ing which resulted in a cooked flavor. In 1971, Harris
reported the pressing of good quality juice from crushed un
cooked grapes which had been held at -18°C for periods up
to 15 months. Woodroof et al. (1956) described juice pressed
from previously frozen grapes as superior in color and flavor.
Freezing grapes prior to juice extractions has been shown to
give increased yields and pigment extraction (Flora, 1976).
Varietal and processing differences will affect the accept
ability of the product pressed from frozen grapes. Freezing
whole grapes requires minimum preparation and will maintain
quality much better than other methods over extended storage
periods.
Juice Extraction and Clarification
Juices may be extracted from either cold or heated fruit
(Shoemaker, 1978). The conventional method of juice prepara
tion used by the industry is to heat grapes to 58-61°C
8
followed by enzyme hydrolysis (Sistrunk and Cash, 1974). At
higher temperatures excessive tannins and harsh flavor are
extracted from the seeds (Cruess, 1958).
Freshly expressed grape juice is supersaturated with
potassium acid tartrate (argols) (which gives the juice a
harsh acid flavor) and tannins and colored substances which
give the juice a cloudy appearance (Lopez, 1969). The heat
ing process brings these substances into solution (Shoemaker,
1978; Sistrunk and Cash, 1974; Tufail and Bhatti, 1973; Ishii
and Yokotsuka, 1972; Neubeck, 1959). According to Smock and
Neubert (1950) this material constitutes mucilagenous hydro-
philic gums and pectinous materials. The pectic substances
are widely distributed in grapes and in the natural state are
insoluble in water (Neubeck, 1959). The pectin in juice tends
to keep small insoluble particles suspended in a colloidal
system resulting in a cloudy or hazy juice (Neubeck, 1959;
Smock and Neubert, 1950). Clarification of the juice requires
the splitting of the colloidal system by aid of chemical or
mechanical fining agents (Tufail and Bhatti, 1973). Cruess
(1958) describes a fining agent as a substance which when
added to the liquid to be clarified, will form a precipitate
which settles and carries with it the finely divided particles
responsible for the cloudy appearance. In order to break
down the colloidal system produced by the pectin, pectolytic
enzymes have been used (Joslyn et al., 1952; Neubeck, 1959;
Tufail and Bhatti, 1973; Ishii and Yokotsuka, 1972; Flora,
1976; Sistrunk and Cash, 1974). Flora (1976, 1977) described
the use of Pectinol (Rohm and Hass, Co) and Sistrunk and Cash
described the use of Irgazyme (Ciba Geigy Corp.) pectinase
enzymes in clarifying grape juice.
Spectroscopy
A spectrometer may be used for determining clarity of
juice by measuring the amount of light dispersed by suspended
matter (Cruess, 1958). All spectroscopy instruments contain
the same basic components: a source, an attenuating device,
a monochromater, a cell to hold the sample, a detector and
amplifier, and a meter or recorder to observe the signal
(Pomeranz and Meloan, 1978). The simplest is a single beam
instrument. However, double beam instruments are more ac
curate and reliable. This instrument splits the source radia
tion into two beams. Half the time the beam passes through
the reference cell containing everything except the sample
and half the time the beam passes through the sample cell.
Any fluctuations in source or solvent will be registered both
by the sample and the reference. The detector will measure
the difference between the signals which will be .due entirely
to the sample.
Jelly
Jelly is defined in the United States as the semi-solid
food made from not less than 45 parts by weight of fruit juice
10
ingredient to each 55 parts by weight of sugar (Desrosier,
1970). Jelly is one of the most popular uses for fruit by
products because it can be made from under-ripe, undersize,
and off-grade fruit (Woodroof, 1975). The fruits used are
of good quality but are not attractive to the sight, there
fore cannot enter the fresh market channels (Desrosier, 1970).
Jelly is prepared by combining fruit juice, sugar, pec
tin, and acid in the proper amounts and concentrating by
evaporation to such a consistency that gelatinization takes
place on cooling and microbial spoilage cannot occur (Cruess,
1958; Desrosier, 1970). Of these ingredients, pectin is the
most important in forming a gel. In jelly preparation, the
sugar disturbs the pectin-water equilibrium and causes the
pectin to precipitate as a hydrated colloid which forms a
network of fibrils throughout the mass binding the sugar
syrup into a gel. The density of this network and, there
fore, the strength of the gel depends on the concentration of
pectin. Also, the more concentrated the sugar solution, the
less water there is for the gel to support producing a stiffer
texture. If the sugar content is too low, the jelly will be
tough; if the sugar content is too high, the jelly will be
soft (Woodroof, 1975). Acid causes the jelly to'be firmer,
probably by toughening the fibrils. Too much acid causes
inelasticity of the fibrils and too little acid causes weak
fibrils. Neither of these will support the gel structure
11
and result in syneresis (weeping) of the final product
(Cruess, 1958).
Federal Standards require jelly to be made on the basis
of 45 parts-standard fruit juice per 55 parts sugar (Lopez,
1969). Standard grape juice contains 14.3 percent soluble
solids. This is concentrated by cooking to not less than
65 percent soluble solids in the finished product. Maximum
jelly strength is attained at 65-69 percent soluble solids.
During the boiling, it is necessary to skim off the foam
which forms on the top in order to produce a product with a
good appearance (Woodroof, 1975). A refractometer enables
the determination of the soluble solids content. The boil
ing point of a 65 percent sugar solution is 219-221^ F and
may be used as an indication of proper concentration of the
jelly.
When boiling and concentrating is completed, the hot
liquid is poured into jars and allowed to set. The heat of
the boiling liquid is usually sufficient to eliminate spoil
age organisms. Too much agitation before the jelly has set
injures the formation of the physical structure (Prescott
and Proctor, 1937). Improper processing of grape jelly may
result in a poor product. Sugar crystallization may be
caused by too much sugar, too little acid, overcooking of
jelly or delay in sealing the jelly container. Cloudiness
is caused by using cloudy juice. An improper balance of
12
pectin, acid, and sugar may cause failure of the jelly to
jell (Woodroof, 1975). Using too little sugar or boiling
after the jellying point has been reached will cause jelly
to be tough or stringy (Thrash, 1968).
Conclusion
High costs associated with production and harvesting
and the lack of a concentrated growing area have hampered
development of a processing market for grapes (Flora, 1977).
Increased grape plantings in recent years have caused sur
pluses for the wine industry. Therefore, other processing
outlets are being sought to absorb the projected increase
from more recent plantings of grapes. Marketing of com
mercial processed juice and jelly show promise for expanded
use of these grapes.
CHAPTER III
MATERIALS AND METHODS
Juice
Grapes were gathered from two vineyards in the West
Texas area over a two-year period. Harvesting was done
during the months of August, September, October, and early
November because grapes in this area ripen and are ready
for harvest during these months. The actual time of harvest
depends on grape variety and climatic conditions during the
growing and ripening season. Varieties were chosen for
harvesting based first on availability and next on advice
of the growers. From the suggested varieties, selections
were made for color to enable the study of purple, red, and
white grape juices. For the most part, different varieties
were available each of the two harvest seasons due to the
very different conditions during the two growing and ripen
ing seasons, one of which was rather cool and moist (1977)
and the other of which was very hot and dry (1978). However,
both years it was possible to obtain samples from varieties
of the three colors.
Once the variety decisions were made, grapes of those
varieties chosen were checked twice a week near and during
the harvesting season for soluble solids content. This was
accomplished by randomly selecting 10 grapes from 3 or 4
13
14
different vines of that variety and determining the average
percent soluble solids in "Brix by use of a hand-held Abbe
refractometer (National No. 15666, 0-32% soluble solids or
°Brix). When the grapes of each variety reached at least
20° Brix, a half-bushel basket full of grape bunches was
harvested by hand randomly from several vines of that variety
and taken to the Texas Tech University Food Technology Depart
ment pilot plant for processing.
On arrival at the pilot plant, the grapes were weighed,
including adhering dirt and trash. They were then washed in
a sink of cool water. Upon removal from the water, individ
ual grapes were removed from clusters by hand, discarding
damaged and shriveled grapes along with stems and leaves.
The sound grapes were put on cheesecloth on a mesh table to
allow for evaporation of excess water. A fan was used to
circulate air more quickly and speed the evaporation process
before leakage of juice from the grapes could begin. Grapes
were put in large clear plastic bags which were then closed
and labeled. These bags of grapes were put on racks in a
freezer room which was maintained at 0°F. They remained in
the freezer room until time for further processing. The
length of storage has been shown not to affect quality of
products made from frozen grapes (Flora, 1976). The grapes
in this study were kept from one to fifteen months.
Of the varieties from which samples were harvested, the
results of ten are presented in this thesis. Samples from
15
the other varieties were used in trying methods other than
the one presented in the Materials and Methods section of
this thesis.
Before further processing, grapes were allowed to thaw
at room temperature for approximately 24 hours. The first
steps in the actual processing were to divide the grapes into
two approximately equal amounts, add an enzyme to each, and
extract the juice (Fig. 1). Two different enzymes, Irgazyme
(Ciba Giegy) and Pectinol R-10 (Rohm and Hass), were used in
this study. The portion of the grapes with which Irgazyme
was used was allowed to set for at least four hours at room
temperature after the addition of the enzyme which was added
on the basis of 0.0375 gm of enzyme per 908 gm of grapes.
At the end of this period, the grapes were put into a 5 1/2
quart china cap with wooden roller (Wearever #4700) and the
juice pressed from them by rotating the wooden roller.
As shown in Fig. 1, when using Pectinol R-10, it was
necessary first to heat the grapes to 135°F and hold at this
temperature for ten minutes. The temperature was then raised
to 145°F where it was held for another ten minutes. At the
end of this time, the Pectinol R-10 was added on the basis
of 28.4 gm of enzyme per 908,000 gm of grapes. This was
held at 145°F for an additional 30 minutes after which these
grapes were put into a 5 1/2 quart china cap and the juice
pressed from them by rotating the wooden roller.
Irgazyme (70°F - 4 hours)
Extract Juice
16
Thawed Grapes
i Heat
(135°F - 10 minutes)
Heat
(145°F - 10 minutes)
I Pectinol R-10
(145°? - 30 niinutes)
Extract Juice
Fig. 1. Processing steps from grapes to juice extraction
Further processing was accomplished as shown in Fig. 2.
The juice extracted from each variety of grape was divided
into four samples, one of which was bottled and heat pro
cessed in a hot water bath at 175°F for 30 minutes in order
to stop enzymatic activity and preserve the juice for storage.
A 2 percent egg albumin in warm water solution was added
on the basis of 5 ounces of albumin per 25 gallons of juice.
The albumin was purchased as a dry powder and dissolved in
enough warm water (approximately 100°F--not hot enough to
coagulate the egg albumin) to make a 2 percent albumin solu
tion for each sample. After adding the albumin solution to
the grape juice, this mixture was heated to 175°F to coagu
late the albumin and stop enzymatic activity. This was
allowed to settle for at least 48 hours at which time the
clear supernatant layer was poured off. This was bottled
and processed at 175°F for 30 minutes in a hot water bath.
The third sample (Fig. 2) was heated to 175°F for one
minute to stop enzymatic activity. To this juice was added
a 2 percent casein solution on the basis of 5 ounces of
casein per 25 gallons of juice. The casein solution was pre
pared by soaking the desired amount of casein powder in an
ammonium hydroxide solution prepared by diluting 1 part con
centrated ammonia in 20 parts distilled water. This casein-
ammonium hydroxide solution was heated until no more ammonia
18
Extracted Juice
Sample 1
bottle Egg Albumin (2%)
i Heat
Pasteurize to (175°F - 30 min.) 175°F
I Settle
(70°F - 48 hrs.)
Bottle
Pasteurize (175°F - 30 min.)
Sample 4
Heat to
175°F
Casein (2%)
I Settle
(70°F - 48 hrs.)
Heat to
175°F
Bentonite Clay (5%)
i Hear to
140°F Bottle I
Settle
(70°F - 48 hrs.) Pasteurize
(175°F - 30 min.) Bottle
i Pasteurize
(175°F - 30 min.)
Fig. 2. Processing juice with fining agents
19
fumes were detectable from it. The resulting material was
diluted to 2 percent casein in water. This 2 percent solu
tion was added to sample 3, mixed well and allowed to setnle
without agitation for 4 8 hours. The supernatant layer was
removed, bottled, and processed for 30 minutes at 175°F in
a hot water bath.
As indicated in Fig. 2, sample 4 was heated to 175°F
to stop activity of the enzyme. A bentonite clay suspension
was added to this juice on the basis of 3 gm bentonite clay
per liter of juice. This bentonite clay was purchased as a
dry powder and made into a suspension by placing 5 gm of clay
in a bottle and making up to 100 milligrams with distilled
water and shaking well. This was agitated frequently and
kept for at least three days prior to its use in order to
assure a good suspension. The desired amount of this sus
pension was weighed and added to sample 4, mixed well and
allowed to set for 48 hours without agitation. The clear
layer was poured from the top, bottled, and processed in a
hot water bath for 30 minutes at 175°F.
All juice samples were held at 40°F until ready for
testing.
Aliquots were taken from each juice sample for deter-
minination of pH, percent titratable acidity, and absorbance;
pH was determined by use of a Beckman Model 3 500 digital pH
Meter (Beckman Instruments, Inc., Fullerton, California).
20
Percent titratable acidity was determined by titrating an
18 gm sample with 0.1 N NaOH to the phenolphthalein end
point of pH 8.3 as determined by the use of a Beckman Model
3500 Digital pH Meter. The number of milliliters of 0.1 N
NaOH used for the titration was used in the following formula
to determine the percent titratable acidity:
ml 0.1 N NaOH x 0.0075 % Titratable Acidity = • x 100
gm Sample
All acid titrated in this juice was calculated as tartaric
acid:
COOH I
H-C-OH J eq wt 7 5
HO-C-H
k :ooH Absorbance of the samples was determined by a Beckman lodel
35 Spectrophotometer with Recorder (Beckman Instruments,
Inc., Irvine, California). Prior to running absorbance tests
on the experimental samples, samples of commercially prepared
purple, red, and white juices were each scanned to determine
the optimum wavelength settings for determination of absorb
ance on the test juices. As a result of those scans, a set-
ting of 450 nm was chosen for all samples and absorbance was
read directly from the digital display readout.
The grape juice samples were then centrifuged in a
VWR Scientific Centrifuge Model 6F-8 at 1000 rpm for 20 minutes.
21
Aliguots were again taken for pH, percent titratable acidity
and absorbance. These tests were performed in the manner
as done with the aliquots of the samples before centrifuga-
tion.
Remaining clarified juices of samples chosen on the basis
of color were stored in refrigeration storage for later
processing into jelly. No light colored juices were stored
for this purpose because there would be little commercial
value of jellies made from these juices.
Jelly
The first step in. making jelly was the determination
of the soluble solids content of the juice to be used. This
was done with the use of a Kerno No. 5532 hand-held refrac
tometer calibrated to read from 0 to 90 percent soluble
solids. By definition, standard grape juice contains 14.3
percent soluble solids and jelly production requires 45 parts
standard juice per 55 parts sugar. Therefore, the amount of
sugar needed is based on grape juice containing 14.3 percent
soluble solids. In calculating the amount of sugar required,
adjustments for soluble solids contents were made by use of
the following:
14.3 Soluble solids of juice to be used
45 _ (Weight of juice) (factor) ^ 3 ~ X
X = amount of sugar needed
= factor
22
The amount of pectin required was based on the amount of
sugar used. The pectin was 100 grade; therefore, it was
added on the basis of 1 part pectin per 100 parts sugar.
The amount of acid required was determined by titrating
a 22.7 ml. sample of each juice to pH 3.3 with a 0.25 per
cent tartaric acid solution. The milliliters of tartaric
acid solution multiplied by 200 was the milliliters of acid
required per pint (454 gm) of jelly.
Once the amounts of constituents required had been
determined, the juice was put into a steam jacketed ketrle.
The pectin was mixed with a small amount of the sugar and
stirred into the juice. This juice-sugar-pectin mixture was
heated to boiling, at which time the remaining sugar was
added. Boiling was continued until the mixture was concen
trated to contain 65 percent soluble solids as determined
by a Kerno No. 5532 refractometer. The required amount of
acid was put into pint jars and the hot jelly mixture at
65 percent soluble solids poured on top of the acid. The
jars of jelly were allowed to set without agitation for
24 hours for complete jelling to take place. They were then
kept at room temperature for one week at which time the con
tents were checked by visual observation for clarity,
syneresis, and jelling.
CHAPTER IV
RESULTS AND DISCUSSION
As shown in Table 1, all grapes with the exception of
the Veeport variety were between 20 and 25° Brix (percent
soluble solids) when checked in the vineyard at the time of
harvest. Veeport grapes were harvested at 19.9° Brix which
was considered close enough to 20° Brix to justify harvest
at that time. Stuben was the only variety from which samples
of the two growing seasons were used with the processing
method previously described in the Materials and Methods
section. These grapes had a higher percent soluble solids
during the hot dry year (1978) than when conditions were
cooler and more moist (1977) during the growing and ripening
season.
Table 2 shows the weight of grape clusters harvested
for each variety and the weight of grapes after washing,
destemming, and removing leaves and shriveled grapes.
Table 2 also shows the calculated percent weight lost during
these procedures and this is the most significant part of
this table. These percent losses in weight ranged from 2.32
with SV12-309 to 14.08 with the Grand Noir variety.. Differ
ences in percent weight loss are caused by size and there
fore, weight of stems, adhering leaves, and shriveled or
unformed grapes which must be discarded.
23
24
TABLE 1.—°Brix of grapes at the time of harvest
Variety °Brix
Buffalo 20.1
Carmen 21.8
Camay 22.8
Golden Muscat 22.0
Grand Noir 2 4.6
New York Muscat 21.7
Stuben (1977) 21.7
Stuben (1978) 23.6
SV 12-309 21.6
Veeport 19.9
25
TABLE 2.—Weight loss during the washing and destemming process
Variety
Buffalo
Carmen
Camay
Golden Muscat
Crand Noir
New York Muscat
Stuben (1977)
Sti±)en (1978)
SV 12-309
Veeport
weight of Crape Clusters
(gm)
6615
8095
12465
11085
8400
5280
6750
7390
9410
6220
Wei Aft
ght of Crapes .er Destemming
6262
7514
12012
10242
7217
4872
6352
6940
9192
5907
Percent Weight: Loss
5.34
7.18
3.63
7.60
14.08
7.73
5.90
6.10
2.32
5.03
27
t p G
• H
m :3
U3 (U D fd
s CJi
0) t/3 <U
X ! -P
e 0 M
LM
(D 0
•H ^
•r^
U-l 0
' ^ r H Q)
•H > i
+J c: Q)
o ^ 0)
a T3 C tT3
W
(U 0
- H p
•r-i
^ CO Q)
0)
e > i N (T3 <J^
u H
'd c ftj
« t
o r H
1 Cr:
f-\
0 c
•H 4-) U dJ a(
^ en CD
e a, >i (T3
u N
c 0^ 0)
M- 0
•p i =
-p G 0) ^ (U
a^y-i • H 0)
<+-! •H
1 1
^ pa < EH
0) 0) en U T3 rd -H nH s-i a oj (U ITD -H > >^
(U ^ £ U >i
•H "73 N
fT) a; cp • H 5-1
dip >H H
O rH
Q) I O «
•H \
= J ^
T3
Q)
•H >H
e o ^
-P en x : <D en Ou
• H (T3
[2 O
4-1 s 0 Gn
" - 4J
X (U ^ 0
•H -H cu :3 12 f
o r r CN
o ^ ro CN
O 00 r i n
o . H <£) ( N
O r H ^ m
LO i n r-\ CN
O
o VO CN
O " ^ m m
o <o 00 " ^
o m CN m
o o o o o o o o o o O L n < N C N o o L n o o * ^ v x ) L n r H r ^ < T t o o m v £ 5 V £ ) r ~ - ^ v . D i ^ i n . — i ^ r * ' ^ i n i n < » i n
> . 0) 4J 04 0 a -H ^ u U (T3
>
0 r-{
(T3 MH U-f
3 CQ
G OJ
s M (T3 U
> i (t3 £ (T3 U
4-> 03 U cn ^ S
C a;
T3 r H 0 o
5 •H 0 s T5 C (T3 5H O
1 )
(13
0 cn 0 S ^
u 0 >^
5 (U 2
^-^ r r-a> r H — '
r^ Q) Xi 3 ^
cn
—-, CX)
r o —1 >—'
c Q) -2 3 1 ) in
o o ro
1 CN ^
> cn
4J M
CI a; 0) >
0)
cu > <
28
the 1977 crop of Stuben grapes which had a juice yield of
47.28 percent with Irgazyme and 44.16 percent with Pectinol
R-10—a difference of 3.12 percent. The 1978 crop of Stuben
grapes exhibited a similarly close percent juice yield with
the two different enzymes with a difference of only 4.35 per
cent between the use of Irgazyme giving a juice yield of
60.14 percent and Pectinol R-10 giving a juice yield of
55.79 percent. The average difference in percent juice
yield is 14.65, with Irgazyme giving an average of 57.45
percent and Pectinol R-10 giving a juice yield of 42.80
percent. This large difference could make a substantial
difference to the grape processor who wants to extract the
largest amount of juice from the purchased grapes.
The ranking of the grape varieties and enzymes used
are shown in Table 4. Ranking is based on the percent juice
yield ranging from greatest to least percent yield. None
of the grape batches on which Pectinol R-10 was used ranked
in the top quarter (first 5) and only two ranked in the top
half. Those two were Stuben (1978), ranking number 6, and
Veeport, ranking number 9. However, Stuben (197 8), using
Irgazyme ranked number 5 and Veeport using Irgazyme ranked
number 4, both ahead of that same variety using Pectinol
R-10. The poorest ranking for a grape using Irgazyme was
Carmen which ranked 15 with a 44.07 percent juice yield.
However, when-Pectinol R-10 was used with this variety, ir
TABLE 4.—Ranking of grape varieties combined with enzymes based on percent yield of juice
Grape Variety Enzyme
SV 12-309
New York Muscat
Golden Muscat
Veeport
Stuben (1978)
Stuben (1978)
Grand Noir
Camay
Veeport
Buffalo
Stuben (1977)
SV 12-309
Golden Muscat
Stuben (1977)
Carmen
Grand Noir
Camay
Carmen
Buffalo
New York Muscat
Irgazyme
Irgazyme
Irgazyme
Irgazyme
Irgazyme
Pectinol R-10
Irgazyme
Irgazyme
Pectinol R-10
Irgazyme
Irgazyme
Pectinol R-10
Pectinol R-10
Pectinol R-10
Irgazyme
Pectinol R-10
Pectinol R-10
Pectinol R-10
Pectinol R-10
Pectinol R-10
Ranking i Juice Yield
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
67.59
67. 09
63.64
60.59
60.14
55.79
55.37
54.65
54.42
54.10
47.28
46.85
44.58
44.16
44.07
42.67
40.39
37.14
36.72
25.32
30
ranked 18 with a juice yield of 37.14 percent. With all
varieties, the batch using Irgazyme ranked higher than that
same variety when Pectinol R-10 was used which means that
the Irgazyme gave a greater percent yield than did Pectinol
R-10 with all grape varieties.
As pointed out earlier, the percent juice yield from
grapes is of great importance to the grape processor. There
fore, Irgazyme would be the enzyme chosen based on the data
thus far presented. For this reason, further data will be
presented only on juice which was extracted with the aid of
Irgazyme pectinase enzyme.
Tables 5, 6, and 7 show the pH and percent titratable
acidity of the Irgazyme-extracted purple, red, and white
juices before and after the addition of fining agents and
before and after centrifugation. There was little change
in pH shown with the largest difference in mean pH between
centrifuged and non-centrifuged samples of the same type
(i.e., bentonite non-centrifuged versus bentonite centrifuged)
being 0.08 pH change. This occurred with white grape juice
(Table 7) in which Irgazyme alone was used and when Irgazyme
was used in combination with casein. When Irgazyme alone
was used, the pH changed from pH 3.79 with a standard devia
tion of 0.07 and variance of 0.003 in the ncn-centrifuged
sample to pH 3.87 with a standard deviation of 0.09 and
variance of 0.004 in the centrifuged sample. When Irgazyme
31 cn C ^3
•H C &> (d 3
<4-l « •H > , }>l (d 4J rH c: o <D
4J S-l -H 0) C -P 0 ^-l 4-) (d c
0) 13 Xi c td *
(D -H ^ £ 0 3
iw i 2 0) rH
Si rd
0) CO O +J
•H G 3 (U
• n C7> (d
(U
(d c }-4 -H
•H (U M-l
r-^
Chs: U A-> 3 -H
a ^ 4-1 -p 0 c
> i £ +J -P •H (d TJ Q) •H J-l U -P fd
u 13) Q)
^ M-4 rd (d •p (d T3 J-t c +J fd •H 4J 0)
u <*p 0
MH fO o c C .Q -H (d 0)
•T3 W B c: <d cu (d u 1 1 •
i n
9 H
-H cn 3
M-< • H
4J fi 0)
u S>4 <u -p
<4-l <
cn c •H cn 3
M-4 •H S-l •P C (1)
U
(U u 0
0) CQ
1
0) S t3 -H N C (U (0 (d cn cn «a n u
0) 0) -P
> i -o d N C 0 nj (TJ -P cn c i^ 0) H OQ
(1) 6 C >i TS -H N C g «J (fl 3 cn ja U <-i H <
0)
> 1
(13 cn u H
(i> S c >i TS -H M C (U fd (d Ul cn (d 5 CJ M
0)
S -H >, TJ C N C 0 <d (d -P cn c M (U H CQ
>i T3 -H N C g rd Id 3
H rH H <
g > i N <d cn M H
> t
o -P cu 0) (d -H M M (J Id
>
in in <n r^
m o
iH in (T> r*-
n o
CO r* CO r
m o
in rn CO 0 0
ro O
00 ';!• 00 r-
n o
^ in 00 r-
m o
00 rn 0 0 CO
m O
r-t r-<y» r -
m o
X < cu &
<M> 0
rH (d
<4-t M-l 3 CQ
(T> O 00 in
n o
m in en in
cn o
in m o^ in
m o
\0 i-i 00 in
cn o
CO in 00 in
cn o
00 cn 00 in
cn o
m in <n in
cn o
cn 00 <n in
cn o
< X 6^ c u <*P
c 0} g ^ (d u
o cn <n ^ cn o
^ o 00 in
cn o
lO 00 00 ^
cn o
\0 <H 00 in
r ) o
r^ CO cn '3'
cn o
r 00 cn ^
cn o
00 CO <n 'a '
cn o
CO 00 cn ^
cn o
< H
ac dP cu > i
Id g Id CJ
r^ r-l cn vD
m o
cn If cn vD
cn o
vO -H cn ^
fO o
CN o O v£>
^ O
•"sr o cn vo
n o
CN cn cn in
cn o
cn CN cn vo
cn o
CO cn 0^ in
cn o
s cu u < •H EH 0 dP Z
T) c Id ^ o
o cn 00 in
cn o
o o 00 vD
m o
CN ^ CO <0
m o
O .H CO v ^
ro O
00 CO r in
cn o
r-^ O CO yD
cn o
O "^ 00 vO
m O
CO o r^ vD
n o
X < cu H
dP V u 0 Ck Q) (U >
o r o o^ O O
• • « cn o O
m 00 vO O 00 o o
• « •
m o o
cn 00 vO o 00 o o
• • • m o o
00 00 .H CO o o
• • • m o o
cn r* ^ 00 o o
• • • m o o
'3' CO vC O 00 o o
• • • m o o
^ O r* o <T» O O
• • • m o o
m <T> r-l cn o o
• • • m o o
t
• (1)
> o (U c Q Id
c: -H cd • u (U 4J Id S cn >
X
cn o -H in rH o
. . . o o o
,H O rH vD H O
• • • o o o
rH r-l rH VD rH O
• • • o o o
rH m CN VO rH O
• • • o o o
cn o rH in rH o
. . . o o o
O O rH VO rH O
• • • o o o
^ m CN VO rH O
• • •
o o o
O O rH VO rH O
• • •
o o o
. d)
> o (U c C Q Id (d -H Q) • U S -p Id
en > < EH HP
32
u c •H
>
« cn >i 3
MH •H M -P C (U u M 0) 4J
(d r-i O
0) +J •H G 0 +J c <u
iPi ;Q <d
T3 C <d
^ G
•H g 3
<D ia u 0
M-l Q) Xi
<u u
•H 3
• m
0)
rH (d
CO • p G Q) CT> (d
cn c
•H
a c <d M cn
13 <u }H
<4-l 0
•H M-l
x : + j •H ^
+J G 0)
>i e + j •H Ti •H 0 (d
0) rH
4J fd (U M + j
u <D 4J
J3 MH (d +J
fd
(d TJ iH +J •H +J
OP
T3
c: (d
0) c M -H 0 0)
MH CO (U (d
c: i 3 0 Id
K T3 TJ C C
Oi (d (d
< EH
cn c
•H cn 3
MH •H ^ +J C 0)
u M <u 4J MH <
(U g >i T3 N C fd fd cn u H
cu g >i T3 N G fd fd cn u H
cu g >1 TJ N G fd (d cn M
rgaz
ym
e I
c •H fU cn Id U
CD 4J •H G 0 +J G (3) CQ
C •H c
3 jQ rH <
cn G
•H cn 3
ItH •H V 4J G 0)
u lU }H 0
I4H o OQ
CU g >i Tl N G Id Id cn u H
cu g >i 'C3 N G Id fd cn u H
(U g >i TJ N G fd Id cn u
rgaz
ym
e I
G •H CU cn Id U
0) 4J •H c 0 +J c cu m
G •H g 3 .Q
r-^
<
>1 cu -P cu 0) (d -H u u C3 Id
>
in in o KO
• •
^ o
m r» cn '3'
• • m o
in r^ o <^
• •
^ o
o 00 cn ^
• • m o
cN r o r-
• • "T o
o m cn ^
• • m o
00 r-\ 00 r
• • m o
o o 00 in
m o
\0 CO
m o
KO O cn in
• • m o
00 cn CO in
• t
m o
o vo
m o
CO ' I ' CO in
« •
m o
CO ON CO ^
• • m o
m o m o
Id o (0 3
O
(U
z
m
m
m in
m in
o
H in
CO
m
m 00
CN CN
o
CN
in o o
o
in in
o
in in
cn o
o
o 1-^
r-i
o o
rH
o m o
<-\ CN \0 in
m o
<T> o in in
m o
^ m lO in
• • m o
m o
O CN *^ in
m o
m o o
'i^' H ^ 00 CN O
m o o
r^ i n CN r rH o
m o o
«^ CO m 00 rH o
• t •
m o o
m o o
00 <n 00 in
• •
vO ^ 00 in
• t
O r-i KO in
00 VD CN P- H O
CN in TT o in o o
m o
X EH O4 dP
G CU
cn
cn
X EH CU dP
G fU
•P
cn
CO
cn rH
X £H CU dP
^ >,o m r* rH o
m o o
m o o
0 0 0
cn i n CN in rH o
0 0 0
r- CN rH in rH o
0 0 0
o o m o in o o • • •
0 0 0
cn 0 in in
cn p m r- rH 0
^ CN r» 0 m o o 0 0 0
i£> O
CN m o in o o
0 0 0
0 0 0
G Id <u S X Q*
• > <u Q
t
P cn
(U 0 G fd •H U Id >
G Id cu S < EH dP
• > 0) Q
• P cn
lU 0 G Id
•H u Id >
0^13 C
•H
cn 3
MH •H ^ -P G 0)
u 5H OJ -P 4-1
fd
^ c (d
Q)
u
C fd
^ > i fd
r H
u cu
4-1 • H
c 0 -p
c cu
i 2
^ G
•H 6 3
0 .Q MH 0)
jQ
Q) 0
•H 3
•r- i
OJ
r-{
Id
cn 4J C CU cn (d
cn CU C fd U
•H G
cn-H
cu -p •H ^ ^
M-l 0
MH
^ +J •H ^
-P G CU
> i s ^ •H T^ •H 0 td
(U rH
4-1 fd Q) U -P
^ CU 4-1
XH MH td -p
fd
(d ^d
u -p •H +J
dP
T3
c 03
cu u 0
MH cu G
C .Q -H (d
X CU 1 1
J CQ < EH
cu T ) CO G fd Id u
1
cn c
•H cn 3 "H • H
- p G (U u u
4-1
0) g N C (d (T3 W cn Id
(U
CU (U P g -H >. TJ c N C 0 (0 (d 4J cn c p <u
H CQ
<u g N C (d Id cn u rH
B > 1
(d cn u
cn c
•H cn 3
IM • H iH 4J c 0) u OJ p 0
MH dJ CB
CD g > i T3 N G (d (d cn p H
a; g > i tD N C (d Id CP p H
0) s > i t3 N C (d 03 cn p
Irg
azy
me
I
c • H <u en Id
u
0) p •H c 0 4J c a; CQ
c - H g 3
^ rH <
0) 4J CU (U (d -H p p (J (d
>
cn in CO m
• •
m o
00 m • •
m o
CN (Ti
CO m
m o
o o CO " ^
• • m o
r o 00 ' ^
• • m o
r-- H CO ' ^
• • m o
r- cn CO m
• •
m o
^ O CO r f
m o
o m <y\ i n
• « m o
vx> m 00 i n
• • m o
in (T> CO in
• • m o
m CO cTi in
• • m o
v£) m • fl
m o
^ <n • •
m o
' r H • •
m o
TT m
• • m o
X a,
cn o m
1 CN H
> cn
< H dP
+J (d 0 cn 3 S
G CJ
TD r- i
0 CJ
< EH ;*>
ro
O H O 0^ O O
• fl «
^ o o
33
o o o •X o o
• • • m o o
00 O
CN O o
m o o
m o
m o o
m o o
m o o
m o o
L O ' ^ ^ ^ H O
• • • O O o
_0 H ^ " ^ rH O
• • • O O O
• ^ H O t • •
O O o
"^ r- a O CD o O
c m ^ ^ ^ o
m CN CO O CO O O
f-{ <0 <-< in H o
o O o
m CN CO o CO o o
in o CN in CN o
o o o
rH GO
<n o
'^ o o
in m m in CN o
o o o
m <n r- o r- o o
cT\ m m in CN o
o o o
c (d <D S
X 1-M
• > a Q
• 4J n
V u c A!
• M
SH
-0 >
c rd (U S
< EH dP
• > CU Q
• -J cn
V a f—'
T - H P Id >
34
and casein v/ere both used, the change was from pH 3.82 with
a standard deviation of 0.08 and variance of 0.003 before
centrifuging to pH 3.90 with a standard deviation of 0.01
and variance of 0.00003 after centrifuging. As shown in
Table 8, difference in the mean pH ranged from these two
with 0.08 percent difference to purple juice with which
Irgazyme and bentonite clay were used. This juice showed
no difference in pH before and after centrifugation having
a pH of 3.88 in both sample types with a standard deviation
of 0.06 and variance of 0.003 before centrifuging and
standard deviation of 0.06 and variance of 0.002 after
centrifuging. Overall, the change in mean pH was quite
small when the juices were centrifuged with 67 percent show
ing less than 0.05 pH change (Table 8).
The mean pH's covered a relatively narrow range from
pH 3.77 to pH 3.93. Likewise, the percent titratable acidity
of these juices covered a narrow range from 0.45 percent to
0.63 percent. Since both are measures of acid, it would be
expected for both to be relatively close in value if either
is close.
When looking at individual grape varieties in Tables 5,
6, and 7, varietal differences can be seen. For example,
while Veeport and Buffalo are both purple grapes, zhe pH of
Veeport grapes was near pH 3.80 while the pH of Buffalo
grapes was near pH 3.90 (Table 5). In the red juices
35
TABLE 8.—Ranking of treatments of juices based on differences in mean pH before and after centrifuging
Percent Difference Grape in Mean pH Ranking Color Treatment
0.08 1.5 White Irgazyme w/casein
0.08 1.5 White Irgazyme
0.05 3.5 Purple Irgazyme
0.05 3.5 Red Irgazyme w/albumin
0.04 5.5 White Irgazyme w/bentonite
0.04 5.5 Red Irgazyme w/bentonite
0.03 7.5 White Irgazyme w/albumin
0.03 7.5 Red Irgazyme w/casein
0.02 9 Purple Irgazyme w/albumin
O.Ql 10.5 Red Irgazyme
Q.Ol 10.5 Purple Irgazyme w/casein
0.00 12 Purple Irgazyme w/bentonite
36
(Table 6), the juice from the 1978 crop of Stuben grapes
had a pH near 3.60 while the New York Muscat had a pH close
to 3.90. This indicates that pH and percent titratable
acidity are more variety dependent than color dependent.
As described in the Materials and Methods section,
samples of commercial purple, red, and white juices were
purchased and scanned in order to determine the proper
absorbance setting for use as a measure of juice clarity.
The results of those scans are shown in Fig. 3. It was
necessary to dilute the purple and red juices to 1:10 juice
to water in order to scan them. The white juice was diluted
to 1:2 with water. All three juices exhibited a flat ab
sorbance in the 450 nm range; therefore, this was selected
as the wavelength setting for determining the absorbance
of the test juice samples. Results of the absorbance test
ing at 450 nm for purple, red, and white juices are shown
in Tables 9, 10, and 11, respectively. These juices were
divided into the three groups for comparison of absorbance
results because of the influence of color on the absorbance
as shown by the mean absorbance of samples before centrifug
ing or adding any of the fining agents. Purple juices had a
mean absorbance of 3.63, with a standard deviation of 2.60
and variance of 5.42, red had a mean absorbance of 1.87,
with a standard deviation of 1.70 and variance of 1.93, and
white had just 0.27 mean absorbance with a standard deviation
of 0.23 and variance of 0.03.
37
• Purple
350 400 450 500 550 600
Wavelength in nm
650 700 750
Fig. 3. Absorbance scan of commercial grape juices—purple (1:10, juicerwater), red (1:10, juice:water), and white (1:2, juice:water)--in the visible light spectrum
38 T3 G 1 fd xi
fd
cu U MH 0 0
MH cu cu .Q o
c 13 fd G -H fd p
Id cn > G
•H u Cn G 3 fd
MP •H G ^ 0 4-J -H PI C P -r^ CU fd 0 U -H S
> P (U TS CU 13 G -p (d MH TJ p fd P u
fd 13 13 4-1 G G CL (d fd CU
4J U CU CO X u cu 0 -
MH G cn cu fd 0)
^ cu u e -H
en 3 cu - n U '^
•H 4J rH :2 :: r-{
•r-> cu fd cn
cu fd D a G fd Di fd U G cn-H cn
G cu (U -H U
rH MH -H a 3 p MH - n 3 0 CU rH
G r-^ MH 0 fd 0 -H
4J MH CU -H 0 U 13 G 13 cu (d Id U
Xi G p p fd 0 cu XJ cn 4-1 p
XJ MH 0 < (d cn
1 1 •
<T\
a J
9 r 1 EH
cn c
•H
cn 3 MH •H P 4-)
c (U o p (U 4J MH <
Cn C
• H
cn 3
MH • H P 4J C 0) u 0) p 0
MH (U
OQ
(U g C > i T3 -H N C (U (d fd CO CP Id P U H
(U 0) P g -H > i 13 G N G 0 (d Id 4J cn C P cu H CQ
OJ g C > i T3 - H N C g Id Id 3 cn ja P rH H < :
0) e > i N (d cn u H
<u g c > i U - H N C (U (d Id cn cn (d P CJ H
CD + J
g -H > i 'O G N C 0 Id Id p
cn c P (U H CQ
(U g c > i 13 - H N c g (d (d 3 cn X5 P rH
0) g > 1
Id
cn p M
V P Cu V fd - H p p
CJ (d >
m "^
• rH
i n •
o
H
•
o
r CN
H
CN H
• CN
vO <D
* O
rH
r o
o •
rH
0 H Id
MH MH
3 03
CO
^ •
(M
i n
• CN
m o
• CN
o CM
m
m (^
•
i n i n
• CN
i n r
CN
i n CN
• CN
G <U g P (d CJ
<D m
• CN
o m CN
CN H
• CM
i n
o CN
i£) m
* CN
H m
• CN
H
o CN
rH O
• CN
> i
(d g Id (J
CN ^
t
00
i n
« 00
CO H
« 00
i n H
CO
m 00
•
r> H
« CO
m r-
r
i n 00
t
r
P • H 0
z "5
^ 1
•d P CI
CN ^
• "^
CN ,—1
m
i n
• m
r-in
'=3'
i n r~
• m
vo o
• m
r~« CN
m
m
• -^
P p 0 CU <u (U >
o cn
• m
m
m
CO CN
• m
r-CO
• m
^ in
• m
i n m
• m
cn CN
• m
m 10
• m
c (d 0) s
00 CO
• r j
<n CN
CM
• CN
H !^
• CN
H i n
CN
'^ CO
• CN
O ^
• CN
o •
CN
• > V
• P cn
<o UD
• ^
H
t ^
CN CO
•
o cn
• i n
m o i n
i n " r
• ^
'^ ^
i n
CN
• in
<u 0 c
>4
(d >
, •—1
0 2
d p
? .—1
t? 3
0 X j j
CN r
CN
CO
CN
un
o CO
• CN
cn ^
» CN
i n H
» CN
CO r—t
, CN
t ^ i n
• CN
c fl 1) 2
^ m
, _ j
• rH
H •
rH
r 'g*
• rH
CO CO
o
"^
• H
rH f—i
H
r^ CN
t
<-{
• > V
• .H OT
^ m
i-H
cn o
o o rH
rr o
• r J
CO i n
•
o
f -H -"/
, o
m y\ 1
• o
o CM
• H
D 0
^ ! d >
G Id
cu p O
MH CU
XI
13 G fd
G • H cn 3
MH • H P
4-1 c cu u p cu 4P MH fd
1 5 G fd
cu p 0
MH CU
XX cn
cn 4J cu G u • H 3
•r—1
CU
cu cn fd
cn G
a -H fd p
G • H
cnMH
T3 CU
MH 0
cu
G O
• H 4J • H
O 13 G 'O Id Id
Xi p p O cu CO 4-1
XX MH < fd I I
PI PQ <C EH
cn H
- H
cn 3
MH •H P P c <u u p (U -p MH
<:
<u g > i t3 M C (d Id cn P H
0) g >i 13 M G Id Id CP p
H
(U g > i 13 N C Id Id en p
rgaz
ym
e I
c • H 0) tn Id U
0) •p • H
c 0 4-1
c (U CQ
c • H P
3 X5 H <:
cn c
•H
cn 3
MH • H P P c OJ u (U p 0
MH
cu CQ
(U g > i 13 N G Id Id cn p H
<u g >. u N G Id ro cn p
H
0) g > i 1 ! N G fd (d cn p
rgaz
ym
e I
G • H CU cn Id U
0) p • H G 0 P G <U CQ
C • H
£ 3 ia H
<
>1 cu -u a 1) (d -H p p
>
o m
O
m
00
m in
O i n
in
ID
i n i n
in in i n
rH vX)
o m
cn CN
CN
m H
r-H
CN
O in
CO m CN
r O
• rH
CN CO
• m
r-i
r-fl
O
j j fl u cn 3 S -i<J P 0
>H
5 0) z
^-. r-r-J^ rH
-^
.-* 5 •§ 4J
cn
-» 00 r o r — 1
'
^ <u § p CO
39
cn in
CN cn
CN
CO CO
CO
CO CN
CO
in in
CN CN
CO
r ^
o m
CO
• H
0.9
9
• -H
1.1
5
1—I
0.8
8
CO
CO 00
CM in
o m cn
c Id Z) S
• > <u Q
• 4J
cn
V D
c; fl
-•-H > H
fl >
cu P 0
MH CU XX
13 G td
cn G
• H
cn 3
MH • H P 4-) G CU u p (U
- p MH td
u G td
cu u 0
MH
cu ^
cu u
• H 3
•r—i
CU
a
cn 4-1 G cu tj^ Id
CJi G
• H G
• H td MH p (J^MH
CU 4-1 • H
x:
0
G 0
• H 5 -P
MH • H 13
0 13
CU U G fd
td
p
cu 4-1
^ MH
P 0
Id
cn 13 XX <
G Id
cn c
•H cn 3
MH • H P P G CU CJ
P lU 4J MH <:
cn c •H cn 3
MH •H P 4-) G lU
u (U p 0
MH cu CQ
0) g G > i 13 -H N C cu Id Id cn cn Id p U H
lU cu P g -H > i T : C N - 0 Id Id 4J cn G p cu H CQ
CU g c > i 'H -H N C g fd Id 3 cn j a P r-i H <
(U
g > i N fd cn p H
0) g G > i t 3 -H N G CU Id Id cn cn Id P U H
<U CU P g -H > i 13 C N C 0 Id (d -P cn G p cu H OQ
<U g G > i 13 -H M C g Id Id 3 cn ia
yme
Ir
Al
N Id cn p M
> 1 1) 4J CM CU fl -H P P CJ Id
>
CM m
• O
• o
» o
i n O
• o
r-' i ^ '
• o
«i3 O
fl
o
i n o
* o
r-i r-i
• O
m '^
• o
^ O m 1
CM H
> cn
i n cn
• o
m O
• O
r H
• O
m -^
• o
CO " ^
« o
m o
• O
m o
• o
O H
« o
Id 0 cn 3 2 C 0
•0
0 a
-^ l o
• o
•^ o
« o
<-i r-i
• o
i n '^
• o
r CN
• o
^ o
• o
r-o
• o
r»> CM
• o
>-< fl (U 2
i n • ^
• o
r-i O
• O
CO o
• o
m o
• o
o m
• o
r-i o
• o
^ o
• o
m CM
• O
fl
> CU Q
. H 'vO
O H
• O
m o o o o
• o
m o o o
o o o o
^ o
« o
r-i o o o
• o
CM o o
• o
m O
« o
• VJ fl >
40
41
In the purple juices (Table 9) the mean absorbance, the
standard deviation, and variance were greatly reduced by
the elimination of Grand Noir juice from the calculations.
This is an extremely dark juice which produced absorbance
readings which were considerably higher than the other purple
juices. Because of its dark color, this could be a good
juice to mix with other grape juice which is lacking in
color.
The mean absorbances indicate that allowing the juices
to settle for 48 hours and removing the supernatant layer
produced a clearer juice than did the centrifuging of the
juices. For example, a mean absorbance of 3.63 was obtained
when juice with Irgazyme was allowed to settle and a mean
absorbance of 3.87 was obtained with this same juice after
centrifuging (higher absorbance indicates less clear juice).
The mean absorbance of the purple juices was higher after
centrifuging with all fining agents except albumin. When the
samples in which albumin was used were centrifuged, the mean
absorbance was reduced from 3.29 to 3.28, which indicates
essentially no change in clarity.
Definite varietal differences can be seen through these
absorbance readings. For example, when bentonite clay was
used as a fining agent in the Irgazyme extracted juices of
Buffalo and Veeport grapes, the absorbance was reduced both
before and after centrifuging while that same procedure
42
increased the absorbance of Grand Noir juice. Although
there are varietal differences, it appears that the best
average method for use with purple juices would be the
addition of albumin as a fining or clarifyijg aid.
Table 10 deals with red juice absorbance which
shows that the juice from the 1977 harvest of Stuben grapes
was not clarified as well as that from the 1975 harvest.
This is the only area studied in which there was any real
difference seen between the two years harvest of this grape
variety. As with the purple juices, the mean absorbances
of the red juices indicate that the use of albumin as a
clarifying aid did produce a clearer red juice than the
other methods. The albumin-clarified juices produced a mean
absorbance of 0.89 with a standard deviation of 0.88 and
variance of 0.52 before centrifuging and mean absorbance of
0.87 with a standard deviation of 0.67 and variance of 0.30
after centrifuging. These standard deviations and variances
which are so close to the same value as the means indicate
the absorbance values are varietal dependent.
Table 11 shows that the use of bentonite clay as a clari
fying agent produced a clearer white juice than the other
methods based on absorbance. However, little difference
was observed between the absorbance when bentonite clay
was used or when albumin was the clarifying agent. The
absorbance differences are just 0.03 before cenrrifuging
43
and 0.07 after centrifuging. Therefore, either of these two
agents, bentonite clay or albumin, could be considered good
clarifying agents for use with Irgazyme-extracted white grape
juices.
Jelly
Although the primary purpose of this study was the
clarification of juices extracted from grapes grown in West
Texas, an attempt was also made to determine whether jelly
could be made from these juices. As stated in the Materials
and Methods section, no attempt was made to produce jellies
from any red or white juices. Jellies were only evaluated
visually to determine whether they met quality standards as
described in the Background section of this thesis.
No varietal differences were seen in the jellies as
long as the proper amount of juice, sugar, pectin, and acid
were used as previously described. When a portion of jelly
was removed from its container and placed on a flat surface,
the jelly retained its shape. There was no evidence of
syrupy, sticky, or gummy jelly. When cut, the jelly was
tender and left a smooth cut surface. No syneresis was
observed either in the jelly surface in the jar or after the
jelly was removed from the jar. The jelly had a clear spark
ling appearance. These statements were true of all jellies
made from the purple juices of this study. (The Grand Noir
juice was not used because of its extremely dark color.)
44
Conclusion
Results of this study have shown that it is possible
to make a clear juice from grapes grown in West Texas. In
order to do this it is necessary to use a pectinase enzyme
during the extraction process in order to break down the
pectin structure and allow the substances held in colloidal
suspension to settle out of the juice. Irgazyme was found
to be the best pectinase enzyme for this purpose. This
enzyme also allowed for the extraction of a greater amount
of juice from the grapes.
Along with the enzyme, it was preferable to use a fining
agent or clarifying aid in order to help settle the suspended
particles once the pectin structure was destroyed. Overall,
albumin was found to be the best substance for this purpose.
However, bentonite appeared to be slightly better for use
with white grape juices.
Once a clear juice was obtained, it was possible to make
a clear sparkling jelly from this juice. Purple juices were
the only ones used for this purpose. These jellies met good
visual quality standards.
Therefore, grapes grown in West Texas have been shown
to have processing potential as juice or jelly. "These could
provide another source of agricultural income to the High
Plains of West Texas.
REFERENCES
Cruess, W. V. 1958. Pectin, jellies and marmalades. In Commercial Fruit and Vegetable Products. McGraw-Hill Book Co., New York. 426.
Cruess, W. v. 1958. Unfermented fruit beverages. In Commercial Fruit and Vegetable Products. McGraw-Hill Book Co., New York. 360.
Desrosier, N. W. 1970. Preservation of food as sugar concentrates. In Technology of Food Preservation. AVI Publishing Co., Inc. Westport, Conn. 268.
Fisher, D. V. 1976. Development of fruit growing in the American States. In History of Fruit Growing and Handling in the United States of America and Canada. Regatta City Press Ltd., Kelowna, British Columbia, Canada. 1.
Flora, L. F. 1976. Juice quality from whole muscadine grapes held in frozen storage. American Journal of Enology and Viticulture. 27(2):84.
Flora, L. F. 1977. Processing and quality characteristics of muscadine grapes. Journal of Food Science. 42(4) : 935.
Harris, H. 1971. Annual Progress Report, Auburn Expt. Sta., Auburn, Ala.
Hedberg, P. R. 1977. Long term storage of table grapes. Australian Journal of Experimental Agriculture. 17:866.
Ishii, S., and T. Yokotsuka. 1972. Clarification of fruit juice by pectin transeliminase. Journal of Agriculture and Food Chemistry. 20(4):787.
Joslyn, M. A., S. Mist, E. Lambert. 1952. The clarification of apple juice by fungal pectin enzyme preparations. Food Technology. 6:133.
Lopez, A. 1969. Canning of juices and fruit drinks. In A Complete Course in Canning. The Canning Trade, Baltimore, Maryland. 324.
45
46
Magness, J. R. 1976. Research in fruit growing by the USDA. In History of Fruit Growing and Handling in the United States of America and Canada. Regatta City Press Ltd., Kelowna, British Columbia, Canada. 182.
McEachern, G. R. 1978. Vines: grapes and muscadines. In Growing Fruits, Berries and Nuts in the South. Gulf Publishing Co., Houston, Texas. 50.
Nelson, K. E., and J. P. Gentry. 1966. Two-stage generation of sulfur dioxide within closed containers to control decay of table grapes. American Journal of Enology and Viticulture. 17:290.
Nelson, K. E., and J. P. Gentry. 1968. Packaging grapes in unvented containers. Blue Anchor. 45(2) :33.
Nelson, K. E., and M. Ahmedullak. 1970. Effect on Cardinal grapes of position of sulfur dioxide generators and retention of gas and water vapor in unvented containers American Journal of Enology and Viticulture. 21:70.
Neubeck, C. E. 1959. Pectin enzymes in fruit juice technology. Journal AOAC. 42:374.
Pederson, C. S. 1971. Grape juice. In Fruit and Vegetable Juice Processing Technology. AVI Publishing Co., Inc., Westport, Conn. 234.
Pomeranz, Y., and C. E. Meloan. 1978. Theory of spectroscopy. In Food Analysis; Theory and Practice. AVI Publishing Co., Inc., Westport, Conn. 39.
Prescott, S. C , and B. E. Proctor. 1937. Juices. In Food Technology. McGraw-Hill Book Co. New York. 548.
Ryall, A. L., and J. M. Harvey. 1959. The cold storage of venifera table grapes. USDA Handbook No. 15 9.
Sastry, L. V. L., and R. G. Tischer. 1952. Stability of the anthrocyanin pigments in Concord grape juice. Food Technology. 6:264.
Shoemaker, J. S. 1978. Grapes. In Small Fruit Culture. AVI Publishing Co., Inc., Westport, Conn. 75.
Siewart, S. W., W. E. DuPree, and J. G. Woodroof. 1951. Home methods of preserving grapes. Georgia Agri. Exp. Sta. Mimeo Series 37.
47
Sistrunk, W. A., and J. N. Cash. 1974. Processing factors affecting quality and storage stability of Concord grape juice. Journal of Food Science. 39:1120.
Smit, C. J. B., H. L. Cancel, T. 0. M. Nakayama. 1971. Refrigerated storage of muscadine grapes. American Journal of Enology and Viticulture. 22:227.
Smock, R. M., and A. M. Neubert. 1950. Apples and Apple Products, Interscience Publishers, Inc. New York. 296.
Thrash, N. 1968. Canning for your family. University of Georgia Extension Service Bulletin. 602.
Tischer, R. G. 1951. A high temperature process for the extraction of grape juice. Food Technology. 5:160.
Tressler, D. K., and M. A. Joslyn. 1971. The preparation of grape juice. In Fruit and Vegetable Juice Processing Technology. AVI Publishing Co., Inc. Westport, Conn. 2 47.
Tressler, D. K. 1971. Historical and economic aspects of the juice industry. In Fruit and Vegetable Juice Processing Technology. AVI Publishing Co., Inc. Westport, Conn. 1.
Tufail, M., and M. B. Bhatti. 1973. Extraction and clarification of grape juice. Agriculture Pakistan. 24(2): 175.
Winkler, A. J., and H. E. Jacob. 1925. The utilization of sulfur dioxide in the marketing of grapes. Hilgardia. 1:107.
Woodroof, J. G. 1975. Other methods of fruit processing. In Commercial Fruit Processing. AVI Publishing Co., Inc. Westport, Conn. 447.
Woodroof, J. G., S. R. Cecil, and W. E. DuPree. 1956. Processing muscadine grapes. Georgia Experiment Station Bulletin. N.S. 17.