FLORIDA STATE HORTICULTURAL SOCIETY, 1952
226
presented in Tables 1 and 2.
Degree Brix
was determined by refractometer at 28 DC. and
percent acid by titration with alkali, using the
standard method of the citrus industry.
Since previous work by Maurer et al. (5)
showed a significant relationship between the
naringin content of grapefruit and its maturity,
some hope was held for finding a similar re
lationship for Florida oranges and grapefruit.
Unfortunately, this observation was not borne
out by the grapefruit and orange varieties
studied. Neither Brix, percent acid nor ratio
could be correlated with the percent glucoside in the juice or its distribution in the fruit.
The percent hesperidin in the juice of oranges
was found to vary between 0.015 and 0.025
percent, while naringin in grapefruit juice va
ried from 0.016 to 0.036 percent for most of
the season.
Distribution of Glucosides. — It is shown
in Table 1 that almost 90 percent of the
naringin in Duncan grapefruit is concentrated
in the albedo, rag and pulp and this was also
true for the other varieties of grapefruit stud
ied. Also, it is shown in Table 2 that 75 to
80 percent of
the hesperidin
in Valencia
oranges was concentrated in the albedo, rag
and pulp. This also holds true for the other
orange varieties.
Thus, any attempt to ob
tain higher juice yields by increased pressure
or deeper burring by juice extractors would
tend to increase the glucoside content of the
juice (4).
In this work, the fruit extracted
to produce the largest juice yield contained
the highest concentration of glucoside in the
juice.
1.
The glucoside content of four varieties
of oranges and five varieties of grapefruit was
found to be rather constant once the fruit had
grown beyond an equatorial diameter of two
inches. Thereafter, as the fruit grew larger,
the glucoside content of all varieties studied
decreased
percentagewise with
respect to
weight of the fruit.
2.
No correlation could be found between
the change in glucoside content, distribution,
percent in juice and the maturity of the fruit.
The glucoside content of the orange juice
samples varied between 0.015 and 0.025 per
cent, while the grapefruit varieties ranged from
0.016 to 0.036 per cent.
3. The unusually high glucoside content
of small fruit on a dry-weight basis suggested
that it may have an important physiological
role in citrus fruit metabolism.
4.
From 75 to 80 per cent of the gluco
side found in the four varieties of orange was
concentrated in the albedo, rag and pulp,
while in the grapefruit varieties 90 per cent
was found in this same portion of the fruit.
LITERATURE CITED
1.
Armentano, L. The effect
blood pressure.
Feit. ges.
zin 102: 219. 1938.
2.
Davis,
W. B.
Determination
of flavanones
citrus fruits.
Anal. Chem. 19: 476-8. 1947.
in
3.
Hall, J. A.
Glucosides of the Navel orange.
Amer. Chem. Soc. 47: 1191-1195.
1925.
J.
4.
Hendrickson,
5.
Maurer, R. H., E. N. Burdick and C. W. Waibel.
Distribution
of
naringin
in
Texas
grapefruit.
Lower Rio Grande Valley Citrus and Vegetable
Inst. Fourth Annual Proceedings, Weslaco, Texas.
6.
Rusznyak, I., and A. Szent-Gyorgyi.
Flavanols as vitamins.
Nature 138:
7.
Szent-Gyorgyi, A. Methoden zur herstallung von
citrin. Ztsch. f Physiol. Chem. 255: 126-131. 1938.
Summary
An investigation of the glucoside content
of grapefruit and oranges led to the follow
ing conclusions:
of flavone dyes
on
Experimentelle Medi-
R., and J. W. Kesterson.
Orange
concentrate evaporator scale identified as hespe
ridin.
Citrus 14: No. 14, 26-7. 1952.
1950.
Vitamin P:
27. 1936.
VISCOSITY OF CITRUS MOLASSES
R. Hendrickson and J. W. Kesterson
Florida Citrus Experiment Station
Lake Alfred
Citrus molasses often acquires such a viscous
consistency that the familiar phrase "as slow
as cold molasses" can be illustrated beyond
all doubt.
In fact, the viscosity at room tem
perature sometimes increases to the point of
solidification and, during this storage change,
considerable insoluble
(2).
material
precipitates
Since high viscosity can lead to many
difficulties in the handling and utilization of
this product, a study was initiated to develop
a better understanding of viscosity in citrus
molasses.
HENDRICKSON AND KESTERSON:
To obtain representative material for the
study, samples of citrus molasses were proeured monthly throughout the 1950-51 season
from the evaporators of four processors. All
samples were adjusted initially to a Brix of
from 71° to 72°, and stored in one pint Mason
jars
in
a
constant-temperature
room
main
tained at 80 °F. Viscosities were determined at
80 °F. with a Brookfield Synchro-lectric viscometer (multi-speed model LVF). The of
ficial Lane-Eynon
volumetric method
was
used to determine total sugars.
The initial viscosity of each molasses sam
ple, as shown in Table 1, was determined
immediately after adjusting the Brix to 71° 72° and the temperature to 80 °F. Samples
from plants C and D, which partially clarify
their citrus press liquor, were more uniform
and of lower viscosity than molasses from
plants A and B. None of these exhibited the
low viscosities (300 to 375 cps. at 80 °F.)
typical of fully clarified citrus molasses of the
same Brix (1). The centipoise is a viscosity
unit that scientifically described how thick
or thin a liquid is. It is more readily under
standable by thinking of 0-500 centipoises as
indicating a viscosity somewhere between wa
ter and table syrup, while honey would read
about 5,000 centipoises. Between 5,000 and
50,000 centipoises molasses pours with increas
ing difficulty and pyramids when it falls be^lorida Agricultural
ries, No. 38.
Experiment
Station
TABLE
Journal
1. —
Se
fore leveling out.
11-18-50
12-21-50
1-19-51
2-20-51
4-12-51
5-17-51
6-27-51
Somewhere between 50,000
and 100,000 centipoises molasses is so thick
that a pint Mason jar of it can be inverted
without losing the contents and for all prac
tical purposes it is a solid. Color can be used
to a limited extent as an indication of initial
viscosity.
In general, the lighter the color,
the more insolubles present and the higher
the viscosity.
The samples under study were analyzed for
total sugars to establish any relationship that
might exist between sugar content and vis
cosity.
It seemed possible that a molasses
of low sugar content would reflect a higher
viscosity, since loss of sugars through fermen
tation of the press liquor would require great
er concentration to reach the same Brix. This
greater concentration would increase the in
solubles content which is a contributing fac
tor to high viscosities. No significant relation
ship between total sugar content, shown in
Table 2, and the initial viscosity was found
due to the overshadowing effect of other vari
ables.
An interesting note is that less than
30 per cent of the samples studied would pass
the state minimum requirements of 45 per
cent total sugars if concentrated only to the
minimum Brix (71°) required by the state
standards.
Improper peel and press liquor
storage is indicated by the low sugar con
tent.
A typical plot showing how the viscosity
of citrus molasses changes while in storage
Initial viscosity
of
freshly
produced
citrus molasses procured from four plants
throughout the 1950-51 season.
(71°72° Brix, 80°F.)
Viscosity
Date Processed
227
MOLASSES VISCOSITY
Plant A
4140
2000
2000
2300
4200
47,500
19,500
Plant
in
Centipoises
B
Plant C
Plant D
8500
16,000
4800
1500
1960
2840
2000
1900
2500
2500
750
3100
10,600
2900
1700
2300
11,600
8,000
1800
1200
1550
TABLE 2. — Total sugar content of citrus molasses
samples procured for viscosity study.
Percent
Dale Processed
11-18-50
12-21-50
1-19-51
2-20-51
4-12-51
5-17-51
6-27-51
Plant A
44.4
45.6
48.0
47.4
44.2
44.0
43.0
Total
Plant
42.7
35.8
37.0
40.4
45.8
44.2
43.7
B
Sugars
as
Invert
Plant C
Plant D
35.8
36.9
46.4
43.8
38.5
41.8
34.6
35.9
46.4
45.5
44.1
37.5
44.8
34.7
FLORIDA STATE HORTICULTURAL SOCIETY, 1952
228
is given in Fig. 1.
The particular samples
depicted were obtained early in the 1950-51
season and since other later samples produced
similar curves they were omitted for the sake
of brevity. The viscosity of most samples was
found to increase linearly in relation to the
time of storage. The increase in viscosity fur
ther was found attributable to the formation
of a gelatinous structure easily broken by stir
ring or heating. Although viscosity measure
ments made at the beginning of this study
indicated a non-changing viscosity on account
of excessive stirring, subsequent readings es
tablished -the
linearly increasing
viscosity.
However, the insolubles of the molasses tend
ed to settle, thus causing the top portion
of the sample to exhibit too low a viscosity.
This occurred only in samples of sufficiently
low viscosity to allow settling of insolubles.
Formation and evolution of gas
which in
creased the volume of the sample and broke
the fragile built-up structure also caused false
ly low viscosity readings.
When the molasses samples were stirred
violently to disperse the gelatinous structure
30
formed during 160 days of storage, the ac
cumulated viscosity increase practically dis
appeared.
Further static storage, however,
brought about viscosity increases at corre
spondingly similar rates. The citrus molasses
processor can therefore lower the viscosity of
his molasses considerably by merely pumping
it from his storage tank. On the other hand,
if it is stored for any considerable period by
the purchaser there is always the possibility
that a highly viscous condition will return.
Since the viscosity of citrus molasses can in
crease rapidly while in storage, the processor
must use pumps and motors of higher capacity
and horsepower to pump molasses from a stor
age tank.
This necessity is aggravated by
the settling of suspended insolubles which
significantly adds to the viscosity of molasses
near the storage tank outlet and is further
amplified by reason of pipe friction increasing
in proportion with viscosity.
When the molasses samples were diluted to
65° Brix and held in 80 °F. storage, the ma
jority of samples acted much like the 71° -72°
Plant A
Pldnt B
Plant C
Plant D
Citrus Molasses
7l-72°Brix
Procured n/18/50
.4
V)
Samples
,/Vigorously
Vi
r
Stirred Samples
before reading
Viscosity
Stirre
o
o
o
J0-
,€)
i
i Insolubles
Settling
Out
o
u
I
20
40
60
80
100
120
Days of 80°F Storage
140
Fig. 1. — Rate of viscosity change of citrus molasses samples while in storage.
160
180
200
HENDRICKSON AND KESTERSON:
Conclusions
Brix samples but maintained a correspondingly
lower viscosity.
Although previous
laboratory
experiments
established that more insolubles precipitated
from high pH press liquors with the possible
consequence of a higher viscosity, no corre
lation was found between pH and viscosity.
An attempt to relate the quality and quantity
of pectin in citrus molasses to viscosity was
also to no avail. The procedure for determin
ing pectin measured the quantity of alkali re
quired to de-esterify a known weight of al
cohol precipitate from 150 grams of molasses.
No attempt was made to relate viscosity to
percent pectin since the data of Iranzo and
Veldhuis (3) showed it to be futile.
When the rate of viscosity increase in centipoises per day was determined and tabulated
as shown in Table 3, no relation was found
between this factor and sugar content, pH,
insoluble solids, quality and quantity of pec
tin. The rate was calculated to represent the
average change during the first month of stor
age. No seasonal trends were noted either
in the initial viscosity or rate of viscosity in
crease.
Initial viscosity, however, is prob
ably a rough index of the rate of future vis
cosity change and therefore an aid in antici
pating high viscosity troubles.
Sub-surface gas formation was clearly visi
ble in approximately 50 per cent of the sam
ples, while swelling from more profuse gas
formations occurred only in 25 percent of the
samples.
Three samples were found to be
very noticeably unstable, so much so that even
mild stirring released such quantities of gas
from solution that the molasses foamed up
and overflowed from the container in a mat
ter of minutes.
This phenomenon is much
like charged soda water which also foams
and boils with only mild agitation. The high
viscosity of molasses as compared to water
prevents the quick escape of the released
carbon dioxide and thereby causes swelling.
TABLE 3.
1. Partial clarification of press liquor in
the manufacture of citrus molasses has the
beneficial effect of providing a lower and
more uniform viscosity in the final molasses.
2. Total sugar content, pH, quality and
quantity of pectin in citrus molasses were
not significantly related to the initial viscosity
or to the rate of viscosity increase while in
storage.
3. The viscosity of most molasses samples
appeared to increase linearly with time and
was considerably influenced by agitation, set
tling of insoluble solids and sub-surface gas
formation.
4. The viscosity increase of citrus molasses
during storage was in a large part due to the
formation of a gelatinous structure.
When
the gelatinous structure was broken, it would
immediately start to reform.
5. The viscosity of most molasses samples
continued to increase even after 160 days of
storage.
This increase in viscosity can be
practically eliminated by thorough agitation
or heat.
6.
Molasses samples of 65° Brix exhibited
changes similar to 71°-72° Brix samples, but
at a lower level.
7. No seasonal trends were noted either in
initial viscosity or the rate of viscosity in
crease.
8. A viscosity increase of more than 500
centipoises per day is cause for serious con
cern since the molasses will probably solidify
within three months.
LITERATURE CITED
1.
Hendrickson, R. Florida citrus molasses — Clari
fication of citrus press liquor.
Fla. Agr. Exp.
Sta. Tech. Bui. 469: 5-24. 1950.
2.
Hendrickson, R., and J. W. Kesterson.
Storage
changes in citrus molasses.
Proc. F'la. Hort. Soc.
63: 154-162. 1950.
3.
Iranzo, J. R., and M. K. Veldhuis.
The composi
tion of Florida citrus molasses.
Proc. Fla. Hort.
Soc.
11-18-50
12-21-50
1-19-51
2-20-51
4-12-51
5-17-51
6-27-51
61:
205-211.
1948.
Rate of viscosity increase for citrus
molasses samples in undisturbed storage.
Centipoise
Date Processed
229
MOLASSES VISCOSITY
Plant A
220
580
240
450
430
1300
2200
Plant B
310
200
730
190
490
370
700
Increase
per
Day
Plant C
Plant D
70
120
130
120
130
80
60
70
250
130
70
70
220
90