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Citrus Station Mimeo Report 60-5
September 16, 1959
Examination of Commercial Water Extracts of Orange Pulp Produced during
Processing of Late Season Fruit
R. W. Olsen, R. L. Huggart and F. W. Wenzel
The purpose of this report is to present and discuss the results from the
second part of an investigation which was undertaken to determine chiefly (a)
sore of the characteristics of commercial samples of water extracts of orange
pvi.p and (b) the relationship between these characteristics and the various pro-
co.iures which are used in orange concentrate plants for "pulp washing". Data
obtained from the first part of this study, which included the collection and
e:--mination of commercial samples of water extracts, orange pulps and orange
juices collected from nine plants when midseason oranges were being processed,
wa~ presented at the Fifth Annual Citrus Engineering Conference of the Florida
Section of the American Society of Mechanical Engineers on March 18, 1959 in
Laksland, Florida. A copy of this paper, which has been submitted for publi-
cation in the Transactions of the Fifth Annual Citrus Engineering Conference,
precedes this report, which contains and briefly discusses similar data obtained
from the examination of samples of water extracts, orange pulps and orange juices
collected from the same nine commercial plants when late season oranges were being
processed. It is suggested that the paper presented at the Engineering Conference
be read before considering the information in this report.
Experimental Procedures
Collection of Commercial Samples. During May, 1959, at which time some of
the late season pack of frozen orange concentrate was being processed, water ex-
tracts of orange pulp and samples of pulp, before and after extraction, were
collected from the same nine commercial plants which had previously furnished
samples during the midseason period. Samples of orange juices also were taken
in these plants immediately after the first juice-finishing operation. Also,
in three plants using centrifuges, samples were obtained of water extracts before
and after centrifugation. All samples were handled in the same manner as indi-
cated in the preceding report.
Processes and Equipment Used in Commercial Plants. In general, the same
processes and equipment were being used in the commercial plants as discussed in
the previous paper, except that in three plants some changes had been made. Cen-
trifuges were not being used in two plants and in one of these some changes had
been made in the recycling procedures; and in one plant the water extract was
being centrifuged, whereas previously the extract and juice were mixed and then
centrifuged before evaporation. The letter codes, which are used in Tables 2-7
showing the characteristics of the samples that were analyzed, together with a
brief description of the different pulp washing processes are given in Table 1.
The analytical procedures used for the determination of the characteristics
of the various products were the same as those listed in the preceding report.
Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
934 g 9/16/59 FWJ
Table 1. Processes used for water extraction of orange pulp in some commercial plants during 1958-59
citrus season
"""" o
Soluble so5 ds Bri
In pulp
Code used
in tables1
CF
CFC*
CFC*
CFRC*
Extraction process
Countercurrent flow through finishers
Countercurrent flow through finishers and
extract centrifuged
Countercurrent flow through finishers and
extract centrifuged
Countercurrent flow through finishers, extracts
recycled and final extract centrifuged
Countercurrent flow through finishers and
extract recycled
Countercurrent flow through rotating screen
Rotating screen and finisher used in double
juice finishing operation; water added after
rotating screen and extract recycled
Water added after first finisher in double
juice finishing operation
Not observed
Beor Ife
After
extraction
4.4
3.4
Before
extraction
10.4
11.0
11.2
11.0
10.4
10.8
10.8
11.0
Footnote2
Plant
No.
1
2
3
4
1 C = countercurrent flow of water and pulp; and C* = centrifuge used.
2 Sample not obtained
Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
934 9/16/59 FWW
3.6
3.6
5.2
7.4
5.8
CS
SFR
WNO
NO
In
water
extract
Footnote2
.6.1
6.2
7.2
8.0
7.3
7.0
6.2
7.4
L
Results and Discussion
Soluble Solids in Orange Pulp and Water Extracts. The Brix values of
orange pulp from each of the commercial plants, both before and after water ex-
traction, are presented in Table 1. A range from 3.40 to 8.20 Brix was found in
the pulps after extraction. Three of the four lower Brix values were found in the
discharged pulps from plants 2, 3 and 4 where processes consisted of a counter-
current flow through a series of finishers and the use of a centrifuge; also, in
plant 4 the extract was recycled. The highest Brix value was in the extracted
pulp from plant 8, where water was added after the first finisher in a double-
finishing operation.
As shown in Table 1, the Brix values of the water extracts ranged from 6.10
to 8.00. Less evaporation is required with an extract having a high Brix value
and a low Brix value in the extracted pulp is indicative of the recovery of more
soluble solids. This desirable combination was found in samples from plants 2,
3, 4 and 9.
Chemical and Physical Characteristics of Water Extracts of Orange Pulp. -
Data obtained by the examination of the water extracts of orange pulp from eight
commercial plants are reported in Tables 2-7 and when possible these analytical
values have been calculated to a 120 Brix basis for comparison purposes. Charac-
teristics of the orange juice samples are also listed and may be compared with
those of the water extracts.
Wide ranges of values were found for those characteristics of the water
extracts presented in Table 2. On a 120 Brix basis the pulp content ranged from
6.0 to 52.5% by volume; water-insoluble solids from 0.7 to 546.0 ag./100 g.;
pectinesterase activity from 3.5 to 93.8 units; and flavonoids, as hesperidin,
from 164.3 to 245.3 mg./100 ml. Values for water-insoluble solids, pectinesterase
activity and flavonoids, calculated on a 120 Brix basis, were greater in the ex-
tracts than in the orange juices from four, five and eight of the plants,
respectively.
Results shown in Table 3 indicate that the amounts of the different types
of pectin varied greatly in the different samples of the water extracts. The
quantity of water-soluble pectin was much greater in the extracts, on a 120 Brix
basis, than that in any of the orange juice samples. Ammonium oxalate-soluble
pectin and sodium hydroxide-soluble pectin in the extracts varied greatly from
2.5 to 97.0 mg./l00 g. and 0.0 to 129.7 mg./l00 g., respectively.
Relative viscosity and cloud data resulting from the examination of the
centrifuged water extracts or orange juices are given in Table 4. The sample of
extract from plant 5 had a high relative viscosity of 30.40 which was caused
chiefly by its large water-soluble pectin content of 154 mg./100 g. However, the
relative viscosities for the other water extracts ranged from 1.68 to 5.55 in
comparison with values from 1.45 to 2.23 for the orange juices. There was very
little difference in the cloud or turbidity in the water extracts, except for
two samples. The minimum light transmittance value of 32% for the extract from
plant 5 indicated the maximum turbidity, which resulted from the large quantity
of water-soluble pectin in it. The extract from plant 6 had very little cloud,
as shown by the maximum light transmittance value of 91$.
Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
934 h 9/16/59 FWW
Table 2. Characteristics of orange juices and water extracts of orange pulp
obtained from some commercial plants during the processing of the 1958-59 late
season pack of frozen orange concentrate
Plant Pulp Brix Pulpl Water-insoluble Pectinesterase Flavonoids
No. extraction value % solidsI activityl2 as hesperidin1
process by vol. mg./100g. mg./100 ml.
Water extracts of orange pulp
OFC*
CFC*
CFRC*
CFR
CS
SFR
WDF
NO
Minimum
Maximum
6.1
6.2
7.2
8.0
7.3
7.0
6.2
7.4
6.1
8.0
7.5
3.0
6.5
Note3
32.0
7.0
15.5
6.5
3.0
32.0
29.6
39.6
0.4
364.0
194.0
75.6
269.2
114.4
0.4
364.0
14.5
9.1
3.5
61.7
43.4
19.1
93.8
27.5
3.5
93.8
121.9
94.3
134.8
163.5
143.4
116.2
112.5
101.3
94.3
163.5
Water extracts of orange pulp4
CFC*
CFC"
CFRC*
CFR
CS
SFR
WDF
NO
Minimum
Maximum
15.0
6.0
11.0
Note3
52.5
12.0
30.0
10.5
6.0
52.5
Orange juices
12.5
11.0
13.5
12.5
13.0
11.5
12.5
9.5
10.7 9.5
12.4 13.5
1 Data obtained by A. H. Rouse, C.
floating pulp.
D. Atkins and E. L. Moore; does not include
2 (PE.u.)g. soluble solids X 1000.
3 No separation of pulp since liquid was uniform throughout af
4 Values calculated to 120 Brix basis for comparison purposes.
Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
934 a 9/16/59 AHR
12.0
12.0
12.0
12.0
12.0
12.0
12.0
12.0
12.0
12.0
58.2
76.6
0.7
546.0
318.9
129.6
520.9
185.6
0.7
546.0
14.5
9.1
3.5
61.7
43.4
19.1
93.8
27.5
3.5
93.8
11.7
12.4
11.5
11.7
12.1
11.0
12.0
10.7
239.8
182.5
224.7
245.3
235.7
199.2
217.7
164.3
164.3
245.3
61.3
68.8
68.8
52.9
61.3
55.8
65.8
52.9
52.9
68.8
Minimum
.Maximum
196.0
160.8
191.2
216.0
197.6
209.2
224.4
183.2
160.8
224.4
18.5
19.8
24.0
19.5
18.7
17.9
16.9
18.5
16.9
24.0
ter centrifugation.
- ___ __ ~._ --
Table 3. Characteristics of orange juices and water extracts of orange pulp
obtained from some commercial plants during the processing of the 1958-59 late
season pack of frozen orange concentrate
Pectin as anhydrogalacturonio acid1 mg./100 g.
Plant Pulp Brix Water Ammonium Sodium
No. extraction value 'soluble oxalate hydroxide Total
process soluble soluble
Water extracts of orange pulp
CFC*
CFC*
CFRC*
CFR
CS
SFR
WDF
NO
Minimum
Maximum
6.1
6.2
7.2
8.0
7.3
7.0
6.2
7.4
6.1
8.0
74.0
40.0
92.0
154.0
63.0
60.0
67.0
40.0
40.0
154.0
5.0
5.0
1.5
50.0
59.0
15.0
47.0
15.0
1.5
59.0
6.5
6.0
0.0
78.0
37.0
19.0
67.0
25.0
0.0
78.0
Water extracts of orange pulp2
CFC*
CFC*
CFRC*
CPFR
CS
SFR
WDF
NO
Minimum
Maximum
12.0
12.0
12.0
12.0
12.0
12.0
12.0
12.0
12.0
12.0
145.6
77.4
153.4
231.0
103.6
102.8
129.6
64.9
64.9
231.0
9.8
9.7
2.5
75.0
97.0
25.7
90.9
24.3
2.5
97.0
12.8
11.6
0.0
117.0
60.8
32.6
129.7
40.6
0.0
129.7
Orange juices
11.7
12.4
11.5
11.7
12.1
11.0
12.0
10.7
10.7
12.4
24.0
24.7
29.3
26.7
22.7
24.0
22.7
20.0
20.0
29.3
20.7
19.3
24.7
16.0
18.0
16.7
18.0
13.0
13.0
24.7
35.3
27.3
34.0
32.7
34.7
30.7
29.3
28.0
27.3
35.3
85.5
51.0
93.5
282.0
159.0
94.0
181.0
80.0
51.0
282.0
168.2
98.7
155.9
423.0
261.4
161.1
350.2
129.8
98.7
423.0
80.0
71.3
88.0
75.4
75.4
71.4
70.0
61.0
61.0
88.0
SData obtained by A. H. Rouse, C. D. Atkins and E. L. Moore.
2 Values calculated to 120 Brix basis for comparison purposes.
Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
934 b 9/16/59 CDA
Minimum
Maximum
I I I ... ..... .... ... .....
Table 4. Characteristics of orange juices and water extracts of orange pulp
obtained from some commercial plants during the processing of the 1958-59 late
season pack of frozen orange concentrate
Plant Pulp Brix Relative Cloud or Water-soluble Water-insoluble
No. extraction value viscosity- turbidity2,3 pectin2 solids2
process mg./lOOg. mg./100g.
Water extracts of orange pulp
2 CFC* 6.1 4.97 52.0 74.0 29.6
3 CFC* 6.2 2.18 52.0 40.0 39.6
4 CFRC* 7.2 5.55 45.0 92.0 0.4
5 CFR 8.0 30.40 32.0 154.0 364.0
6 CS 7.3 1.68 91.0 63.0 194.0
7 SFR 7.0 4.00 51.0 60.0 75.6
8 WDF 6.2 3.34 53.0 67.0 269.2
9 NO 7.4 2.00 54.0 40.0 114.4
Minimum 6.1 1.68 32.0 40.0 0.4
Maximum 8.0 30.40 91.0 154.0 364.0
Orange juices
2 11.7 1.56 53.0 24.0 196.0
3 12.4 1.60 44.0 24.7 160.8
4 11.5 1.81 47.0 29.3 191.2
5 11.7 2.23 53.0 26.7 216.0
6 12.1 2.14 53.0 22.7 197.6
7 11.0 1.60 53.0 24.0 209.2
8 12.0 1.64 48.0 22.7 224.4
9 10.7 1.45 52.0 20.0 183.2
Minimum 10.7 1.45 44.0 20.0 160.8
Maximum 12.4 2.23 53.0 29.3 224.4
Data obtained
E. L. Moore.
by G. H. Ezell; and 2 by A. H. Rouse, C. D. Atkins and
Figures are percentage light transmittance of centrifuged extracts using
Lumetron 402-E with 730 filter and 14 ml. cell.
Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
934 c 9/16/59 ELM
-3-
It is seen from the data in Table 5 that the acid content of the water ex-
tracts was always less than that in the orange juice from the same plant; this
caused, in general, higher Brix-to-acid ratios and slightly higher pH values in
the water extracts than those in the juices. The amounts of ascorbic acid both in
the extracts, on a basis of 120 Brix, and in the juices were in the same range of
35 to 46 mg./lOO ml.
Effect of Centrifugation and Other Plant Procedures. The effect of the
use of a centrifuge for removal of pulp on the characteristics of water extracts
of orange pulp is shown by data given in Table 6. Plants 2, 3 and 4 were using
centrifuges, which in each plant resulted in a large decrease in the pulp, water-
insoluble solids, pectinesterase activity, and in both the oxalate-soluble and
sodium hydroxide-soluble pectins. The quantity of water-soluble pectin and the
relative viscosity were slightly greater in the extract after centrifugation in
the sample from plant 4; also, there was a slight increase in turbidity and the
flavonoid content was slightly lowered. The use of a centrifuge had little effect
on any of the other characteristics listed in Table 6.
In plants 5, 6, 7 and 8 where centrifuges were not being used, the water
extracts, in general, contained the larger amounts of water-insoluble solids,
pectinesterase activity, and both oxalate-soluble and sodium hydroxide-soluble
pectins. The extraction processes in these plants involved the use of rotating
screens, double finishing and recycling of the extracts. The highest value for
water-soluble pectin was found in the extract from plant 5, which was one of the
plants employing recycling.
Microbiological Characteristics of Water Extracts of Orange Pulp. The
diacetyl values and the plate counts on three media for the water extracts are
reported in Table 7. The low diacetyl values and low microorganism counts found
in these samples indicate that good sanitary practices were being followed in all
of the plants in connection with both the equipment and procedures that were used
for pulp washing. Also, none of the extracts had any objectionable off-flavor,
which would usually be detectable if undesirable microorganism growth had
occurred.
Very little orange aroma or flavor was detectable in any of the water ex-
tracts. Some astringency, but little bitterness, was found in all of the samples,
as well as a definite peel aroma. All of the extracts had a milky appearance and
a slight greenish yellow color.
As pointed out in the previous report, water extracts of orange pulp were ob-
tained in that investigation which were not considered to be satisfactory for use
in the production of frozen orange concentrate for various reasons. However, the
data discussed in this report concerning extracts, obtained when late season
oranges were being processed, do not provide any firm basis for serious objections
to the use of such aqueous extracts in the production of frozen orange concentrate.
It is believed that the extracts examined, although only eight in number, were
produced by typical commercial procedures in use at that time.
Acknowledgments
Thanks are extended to the commercial companies from whom samples of orange
juices, orange pulps and water extracts of pulp were obtained, as well as inform-
ation about the pulp extraction processes that were used.
The authors appreciated the assistance of G. D. Atkins, R. W. Barren, G. H.
Ezell, E. C. Hill, E. L. Moore, Roger Patrick and A. H. Rouse who obtained a
major portion of the analytical and microbiological data presented in this paper.
Florida Citrus Experiment Station and Florida Citrus Commission,
Lake Alfred, Florida. 93L i 9/16/AQ wbl
Table 5. Characteristics of orange juices and water extracts of orange
pulp obtained from some commercial plants during the processing of the
1958-59 late season pack of frozen orange concentrate
Plant Pulp Brix Acid as Brix/acid Ascorbic
No. extraction value citricl ratio pH1 acid1
process % mg./lOO ml.
Water extracts of orange pulp
CFC*
CFC*
CFRC*
CFR
GS
SFR
WDF
NO
Minimum
Maximum
6.1
6.2
7.2
8.0
7.3
7.0
6.2
7.4
6.1
8.0
0.32
0.38
0.45
0.47
0.39
0.38
0.37
0.41
0.32
0.47
19.0
16.3
16.0
17.0
18.7
18.4
16.8
18.0
16.0
19.0
4.0
3.6
3.9
3.8
4.0
3.9
3.9
3.6
3.6
4.0
Water extracts of orange pulp2
CFC*
CFC*
CFRC*
CFR
CS
SFR
WDF
NO
Minimum
Maximum
12.0
12.0
12.0
12.0
12.0
12.0
12,0
12.0
12.0
12.0
0.63
0.74
0.75
0.71
0.64
0.65
0.71
0.67
0.63
0.75
19.0
16.3
16.0
17.0
18.7
18.4
16.8
18.0
16.0
19.0
Orange juices
11.7
12.4
11.5
11.7
12.1
11.0
12.0
10.7
10.7
12.4
Minimum
Maximum
0.79
0.90
0.88
0.89
0.82
0.75
0.84
0.69
0.69
0.90
14.8
13.8
13.1
13.1
14.8
14.7
14.3
15.5
13.1
15.5
SData obtained by R. L. Huggart and R. W. Barron.
2 Values calculated to 120 Brix for comparison purposes.
Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
934 d 9/16/59 RLH
3.8
3.4
3.7
3.8
3.8
3.8
3.8
3.5
3.4
3.8
Table 6, Effect of the use of a centrifuge for removal of pulp on the characteristics of water
extracts of orange pulp
Plant No. 2
CFC*
Plant No. 3
CFC*
Plant No. 4
CFRC*
Plant No. 2
CFC*
Characteristic
Brix value'
Acid as citric1 %
Brix/acid ratio1
pH1
Ascorbic acid1 mg./100 ml.
Pulp % by vol.2
Water-insoluble solids2 mg./100g.
Pectinesterase activity2
Flavonoids as hesperidin2 mg./lOOml.
Objectionable off-flavor
Cloud or turbidity2
Relative viscosity3
Water-soluble pectin2 mg./100g.
Oxalate-soluble pectin2 i
Sodium hydroxide-soluble pectin2-"
Total pectin2 mg./lO0g.
Values for extracts before and after centrifugation
Before After Before
6.2 6.1 6.2
0.34 0.32 0.38
18.2 19.1 16.3
3.9 4.0 3.6
22 21 20
11.5
182.4
52.9
124.8
No
55
3.92
78.0
22.0
43.0
143.0
7.5
29.6
14.5
121.9
No
52
4.97
74.0
5.0
6.5
85.5
6.0
110.4
24.6
94.3
No
59
2.10
40.0
13.0
21.0
74.0
After
6.2-
0.39
16.3
3.6
21
3.0
39.6
9.1
94.3
No
52
2.18
40.0
5.0
6.0
51.0
Before
7.0
0.45
15.6
3.9
22
13.0
304.4
102.8
150.6
'No
57
3.62
85.0
53.0
78.0
216.0
After
7.2
0.45
16.0
3.9
22
6.5
0.4
3.5
134.8
No
45
5.55
92.0
1.5
0.0
93.5
Juice and extract
to evaporator
11.0
0.72
15.3
3.8
37
9.5
148.4
17.1
85.8
No
43
2.22
42.0
14.0
28.0
84.0
1 Data obtained by R. L. Huggart and R. W.
G. H. Ezell.
Barron; 2 by A. H. Rouse, C. D. Atkins and E. L. Moore; and 3 by
Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
934 e 9/16/59 FWW
Table 7. Characteristics of orange juices and water extracts of orange pulp
obtained from some commercial plants during the processing of the 1958-59 late
season pack of frozen orange concentrate
Pulp Diacetyl Microorganism counts X 1000
Plant extraction value Orange serum Dextrose Potato Objectionable
No. process p.p.m. agar agar dextrose agar off-flavor
pH 5.5 pH 7.0 pH 3.4
Water extracts of orange pulp
2 CFC* 2.3 97.0 84.0 12.0 No
3 CFC* 2.1 23.0O 21.03 0.0 No
4 CFRC* 2.4 28.03 35.03 12.03 No
5 CFR 1.9 54.0 28.0 6.0 No
6 CS 2.6 51.0 37.0 56.0 No
7 SFR 2.4 47.0 40.0 69.0 No
8 WDF 2.1 35.0 60.0 10.0 No
9 NO 2.2 10.0 10.0 5.0 No
Minimum 1.9 10.0 10.0 0.0 -
Maximum 2.6 97.0 84.0 69.0 -
Orange juices
2 6.1 512.0 504.0 34.0 No
3 2.8 12.0 17.0 0.0 No
4 3.4 31.0 33.0 0.0 No
5 2.5 18.0 18.0 0.0 No
6 3.6 55.0 37.0 80.0 No
7 3.6 110.0 86.0 105.0 No
8 3.2 9.0 40.0 0.0 No
9 3.1 17.0 17.0 10.0 No
Minimum 2.5 9.0 17.0 0.0 -
Maximum 6.1 512.0 504.0 105.0 -
1 Data obtained by E. C. Hill; and 2 by Roger Patrick and E. C. Hill.
Data obtained using water extracts prior to centrifuging.
Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
934 f 9/16/59 RP
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