BAKER AND BRUEMMER: ENZYMIC TREATMENT OF ORANGE JUICE
197
ENZYMIC TREATMENT OF ORANGE JUICE TO INCREASE
CLOUD AND YIELD, AND DECREASE SINKING PULP LEVEL
resistance of PE to heat inactivation forces the
Robert A. Baker and Joseph H. Bruemmer
USD A Citrus and Subtropical Products Laboratory
Winter Haven
microbial
quantities of a proteolytic enzyme in combination
with certain pectinases enhanced juice cloud. Juice
treated with pectinase and protease for 50 minutes
at 80°F followed by 165°F pasteurization had a
denser and more stable cloud than the 165° un
treated control. Overnight incubation of juice with
enzymes at 40 or 60 °F followed by 165° pasteur
ization produced a cloud density and stability which
exceeded that of untreated juice pasteurized at
200°. It was essential that the enzymes be added
pasteurization
than
after
treatment
pasteurization.
with
enzymes
Postcaused
varying degrees of cloud loss.
The addition
of
certain
Recognizing
the
possible
ad
ted a study of cloud stabilization without heat.
Brief treatment of fresh orange juice with ppm
rather
control.
vantages of lower temperature processing promp
Abstract
before
processor to raise the temperature of the juice to
a much higher level for cloud stability than for
pectinases
alone
to
juice prior to pasteurization rapidly reduced the
viscosity and volume of sinking pulp without dam
aging the cloud. Sinking pulp volumes were often
reduced 50% by treatment for 20 to 30 minutes.
The volume of coarse pulp in the juice was also
Initial work indicated that treating the juice
with a pectinase preparation would stabilize cloud
(1). This was accomplished by pectinase treatment
of centrifugally separated serum followed by resuspension of cloud. Centrifugal separation prior
to pectinase treatment was found to be unneces
sary, since stabilization could be achieved by adding
pectinases
directly
to
whole
juice
(2).
Under
optimal conditions density in the enzyme stabilized
juice was equivalent to that of fresh juice, but
not as high as that of heated juice.
We have now found that cloud density and
stability can be enhanced by adding small amounts
of a protease to the juice with the pectinase. Be
cause heat is necessary for pasteurization, we ex
amined the effect of heating on enzyme stabilized
juice.
We
also
examined
the
effect
of
enzyme
treatment on other juice characteristics such as
sinking pulp, viscosity, and coarse pulp levels. The
results of these studies are presented here.
greatly reduced by pectinase treatment.
Materials and Methods
Introduction
Fresh,
Stabilization of a dense natural juice cloud is
was
unpasteurized
obtained
from
Valencia
local
orange
processing
juice
plants
as
one of the primary objectives in the processing
needed for the cloud stability studies. Fifty, 100
of
been
and 200 ppm Klerzyme/100 ppm ficin were added
achieved by heating the juice to inactivate pectin-
to juice in water slurries, with a ratio of slurry
esterase
volume to juice volume of less than 1:1000. After
citrus
loss.
juices.
Traditionally,
this
has
(PE), the enzyme responsible for cloud
Heat stabilization of orange juice cloud is
incubating at 40, 60, or 80°, the juice was heated
advantageous because the juice must also be pas
to 165 or 200 °F and cooled immediately in a heat
teurized, and currently no alternative to heat is
exchanger with heating residence of less than 20
economical. Heating also increases the density of
sec. Heated juice was also treated by adding en
the cloud as well as stabilizing it (5).
zymes after pasteurization. Juice was stored at
Because of its acidic character, orange juice is
effectively
sterilized
at
temperatures
the boiling point of water. Bissett et al.
far
below
(3) have
40°F in sterile quart glass jars and portions were
removed
periodically
to
determine
the
stability
of the cloud.
shown that 160°F protected against spoilage, but
Cloud density was determined by centrifuging
recommended 170° to provide a margin of safety.
the juice for 10 min at 340 x g, and reading the
By contrast, they found 190 °F was the minimum
transmission of the supernatant with a Lumetron
temperature necessary for cloud stability.
Model
Thus,
401
cororimeter
(Photovolt
Corp.,
New
York, N. Y.) equipped with a 650 mu filter. Colori
"References to specific commercial products do not consti
tute endorsement. A laboratory of the Southeastern Marketing
and Nutrition Research Division."
meter tubes with a 20 mm light path were used.
Time-course studies of viscosity, sinking pulp,
FLORIDA STATE HORTICULTURAL SOCIETY, 1971
198
and coarse pulp loss were performed on fresh
hand reamed juice which had been strained to
remove only the seeds. Klerzyme at 200 ppm was
added as a water slurry with a slurry to juice
volume ratio of less than 1:1000. Incubation was
at 120°F. At 20 min intervals a 1 kg sample of
juice was removed, strained to remove the coarse
pulp and weighed. Straining was accomplished
with a conical food sieve with 1.6 mm openings
and a wooden pestle which was rotated in the cone
until the pulp stuck to it. The removed pulp was
also weighed, washed twice in 500 ml portions of
distilled water, and dried for 24 hrs at 200 °F.
The washed, dried pulp was vacuum dried at
200 °F for 24 hrs before weighing.
Sinking pulp was measured on the strained
juice (4). Supernatants from the sinking pulp
readings were decanted and saved for viscosity
measurements. The precipitates were washed twice
by resuspending in distilled water and recentrifuging at 10,000 x g for 10 min. This washed "sink
DAYS
60
Figure 1.—Density and stability of cloud in enzyme treated
orange juice. Juice was incubated for 50 min at 80°F with
50, 100 or 200 ppm Klerzyme in combination with 100 ppm
ficin,
followed
by
165°
pasteurization.
Neither was there any loss of cloud during the
ing pulp" was then dried in the same manner as
first three weeks as occurred in the 50 min treat
the coarse pulp.
ment. Instead the cloud level was unchanged for
Viscosity of the supernatant from the sinking
pulp test was measured with a Brookfield viscometer
(Brookfield Engineering Laboratories,
Inc., Stoughton, Mass.) equipped with a UL adap
ter. After straining, the weight, sinking pulp, and
viscosity measurements were made within 20 min.
Klerzyme 200
powder was
supplied courtesy
of Wallerstein Co., Morton Grove, 111., and ficin
was purchased from Sigma Chemical Co., St.
36 days, after which there was a slight increase
in turbidity. Both 40 and 60° treatments yielded
juices with cloud stability greatly exceeding the
165° control, and slightly better than the 200°
control.
These results show that orange juice can be
stabilized quickly at 80° or within 24 hrs at 40°
or 60° and be pasteurized at a lower temperature
than is conventionally required. However, there
was a possibility that the added enzymes might
Louis, Mo.
Results and Discussion
The effect of pasteurization on stability of short
time enzyme treated juice is shown in Figure 1.
Prepasteurization treatment for 50 min at 80 °F
with either 50, 100 or 200 ppm Klerzyme in com
bination with 100 ppm ficin provided an enhance
ment of the initial cloud level. The 165° control
was stable for approximately 50 days at 40°F,
after which there was a gradual loss of cloud.
While the 50 and 100 ppm Klerzyme/100 ppm
ficin combinations tended to clarify somewhat dur
ing the experimental period, the 200 ppm Kler
zyme/100 ppm ficin treated juice was very stable.
There was a modest cloud loss during the first 20
days, after which the cloud level did not change.
When 200 ppm Klerzyme/100 ppm ficin was
added to juice and stored overnight at 40 or 60°F
before pasteurizing, there was no initial increase
in cloud density over the 165° control (Figure 2).
affect the flavor of the juice, either directly or as
initiators of some enzymic off-flavor production.
A panel of 12 trained testers were asked to dif30
60°
20
40
DAYS
60
Figure 2.—Density and stability of cloud in enzyme treated
orange juice. Juice was incubated for 24 hours at 40 or 60°F
with 200 ppm Klerzyme and 100 ppm ficin, followed by 165 °
pasteurization.
BAKER AND BRUEMMER: ENZYMIC TREATMENT OF ORANGE JUICE
199
Table 1.
Effect of treating orange Juice
with 200 ppm Klerzyme at 120°F on sinking pulp
80-
levels and viscosity.
200° ENZ
Time
(min)
Per 100 ml juice
Dry:Kms
Wetrml
16
0
Figure 3.—Density and stability of cloud in enzyme treated
orange juice. Juice was treated with 200 ppm Klerzyme and
100 ppm ficin after pasteurizing at 165 or 200 °F.
ferentiate in a triangular test between 200°F
heated juice and juice heated to 165° F which
had been treated for 24 hrs at 40 °F with 200 ppm
Klerzyme and 100 ppm ficin. There were only six
correct responses out of 24 for the 12 week juice
and nine out of 24 for the 16 week juice. These
fell short of the 13 correct responses necessary
for significance at the 5% level, indicating the
panel could not distinguish between the enzyme
treated juice and the control juice.
It was assumed that this combination of en
zymes would be equally effective if added after
pasteurization rather than before. Figure 3 shows
that when juice was pasteurized first, the subse
quent addition of enzymes clarified the juice. While
this effect was partially reversed by later develop
ment of cloud, neither enzyme treated sample
0.337
D.M.
W/V*
2.11
Viscosity
cps
7.68
20
8.5
1*0
8.0
0.213
2.50
3.18
60
8.0
0.202
2.52
3.18
-
-
3.68
was as cloudy as the controls at 40 days. Enzyme
treatment caused more damage to the juice pas
teurized at 200° than at 165°.
Treatment with Klerzyme alone was less effec
tive than when the pectinase was used with ficin
(Figure 4). None of the levels tested enhanced
the initial cloud level above that produced by
heating alone. Only 200 ppm stabilized the cloud
at a density exceeding that of the control at 70
days.
In addition to juice cloud, other physical char
acteristics of the juice will be affected by pectinase-protease
treatment. Properties of the juice
partially or wholly dependent upon pectin and
therefore susceptible to pectin degradation include
sinking pulp, viscosity, and the quantity of coarse
pulp removed in finishing. Table 1 shows that the
sinking pulp level dropped rapidly in juice con
taining 200 ppm Klerzyme at 120 °F. The volume
occupied by the sinking pulp was reduced almost
50% in the first 20 min of treatment. This re
duction was due both to a decrease in the quantity
of pulp, as evidenced by the drop in the dry
weights, and to an increase in the pulp density,
as shown by the increase in % dry matter. Vis
cosity of the juice also declined rapidly.
When Klerzyme was added to unfinished juice
containing coarse pulp, the amount of pulp removed
by a 1.6 mm screen decreased steadily. In Table 2
the dry weight and dry weight as % of wet weight
Table 2. Effect of treating orange Juice vith 200 ppm
Klerzyme at 120°P on coarse pulp levels and quantity of
expressed juice.
Figure 4.-Density and stability of cloud in enzyme treated
orange juice. Juice was incubated for 50 min at 80°F with
50, 100 or 200 ppm Klerzyme, followed by 165° pasteuriza
tion.
0
lk.2
k.2
5.66
910
20
52.3
2.9
5.5U
926
1*0
U7.6
2.6
5.U6
9*3
60
39.5
2.3
5.82
950
200
FLORIDA STATE HORTICULTURAL SOCIETY, 1971
(% D.M.) indicate that this decline was due en
tirely to a reduction in the quantity of pulp and
not to an increase in density. The quantity of
strained juice which could be expressed from this
pulpy juice increased accordingly. Treatment with
a pectinase alone was thus able to rapidly reduce
the sinking pulp volume, viscosity, and coarse pulp,
thereby increasing the amount of strained juice
expressed from the raw juice. Whether these side
effects of enzymic cloud stabilization would be
desirable or undesirable would depend on the juice
165° had a denser and more stable cloud than
untreated juice. This procedure also decreased
the viscosity, sinking pulp, and coarse pulp levels
product being considered.
1. Baker, R. A., and J. H. Bruemmer. 1969. Cloud sta
bility in the absence of various orange juice soluble compon
ents. Proc. Fla. State Hort. Soc. 82:215-220.
2. Baker, R. A., and J. H. Bruemmer. 1971. Effect of
pectinase treatment on orange juice cloud stability. In press.
In summary, a method is described by which
orange juice cloud may be stabilized at lower
temperatures than conventionally employed for
heat stabilization. This method involves the in
cubation of the juice with small quantities of both
a pectinase and a protease prior to pasteurization.
Juice treated in this manner and pasteurized at
of fresh juice.
Acknowledgements
We would like to thank Messrs. Charles J.
Wagner, Jr., William H. Miller and Miss Linda K.
Connell for technical assistance.
LITERATURE CITED
3.
Bissett, O. W., M. K. Veldhuis, and N. B. Rushing.
1953. Effect of heat treatment temperature on the storage life
of Valencia orange concentrates. Food Technol. 7:258-260.
4. Florida Dept. of Citrus, Lakeland, Fla. Regulation
105-1.19. December 1, 1970.
5. Loeffler, H. J. 1941. Maintenance of cloud
juice. Inst. Food Technol. Proc. 1941:29-36.
in citrus
SOME NEW ANALYTICAL INDICATORS OF PROCESSED
ORANGE JUICE QUALITY*
John A. Attaway and Robert D. Carter
Florida Department of Citrus
Lake Alfred
Abstract
Twelve fruit samples including 'Hamlin',
'Pineapple' and 'Valencia' oranges were extracted
with commercial equipment using both a harsh,
destructive squeeze and a soft squeeze. Thirtythree chemical constituents and physical charac
teristics were determined for each of the 24 juice
samples. Averages and ranges for each of the
analyses and flavor panel evaluations of all juices
are reported. Significant correlation coefficients
(r = .765 to r = .939) for flavor score and
various constituent values are presented. Two
flavor score prediction equations were found using
multiple regression analysis. Both produce statistic
ally significant correlations (r = .979 and r =
.984) between observed subjective flavor values
and the formula calculated, predicted flavor scores.
Florida Agricultural Experiment Stations Journal Series
°*Cooperative research of the State of Florida, Department
of Citrus and Agricultural Research and Education Center.
Five new possible indicators of quality of pro
cessed orange juice were found, namely limonin,
protein, calcium, alcohol insoluble solids and cloud.
Introduction
The citrus processing industry has long relied
on a limited number of analyses to indicate the
quality of a processed orange juice. Brix, acid,
ratio, oil, color and organoleptic analyses have
generally served to delineate product quality.
Through the years the industry has developed a
range of values within which orange juice with
satisfactory quality is supposed to fall. Frequently,
however, it is demonstrated that products with
"satisfactory"
values
for the analytical factors
will show poor organoleptic reception. This indi
cates the presence in orange juice of other con
stituents which contribute to or detract from pro
duct quality. The purpose of this paper is to report
possible new analytical indicators of product quali
ty which should be of interest to processors of
citrus products. A 'Juice Definition Project' begun
in the 1970-71 season has furnished data for this
report. The project is to be continued for succes
sive seasons.