Title: Water extraction of fruit solids from orange pulp
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00080904/00001
 Material Information
Title: Water extraction of fruit solids from orange pulp
Series Title: Water extraction of fruit solids from orange pulp
Physical Description: Book
Creator: Wenzel, F. W.
Publisher: Citrus Experiment Station :
 Record Information
Bibliographic ID: UF00080904
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 173274002

Full Text


Water Extraction of Fruit Solids from Orange Pulpl


F. W. Wenzel, R. L. Huggart, and R. W. Olsen
Florida Citrus Experiment Station, Lake Alfred



Most of the citrus processing plants in Florida producing frozen orange
concentrate are now using various types of equipment and processes, which are
usually referred to as "pulp washing", for the water extraction of fruit solids
from orange pulp. Such processes, which were added for the first time in some
Florida plants during the 1957-58 citrus season, have been adopted extensively
during the 1958-59 season because of two reasons, (a) the increase in yield of
soluble solids from fruit made possible by the water extraction of orange pulp
from juice finishers and (b) the possibility for improving the quality of frozen
orange concentrate by substitution of pulp washing procedures for a double juice
finishing operation. That an increase in yield results from water extraction of
pulp has been definitely established, but the question concerning the effect of
such a process on the quality of frozen orange concentrate is still being debated
by many persons in the industry.

Investigation of some of the problems arising from the use of various pro-
cesses for the water extraction of orange pulp was started at the Citrus
Experiment Station in April 1958. Data obtained from the examination of experi-
mental and commercial samples of water extracts of orange pulp and other informa-
tion resulting from studies made during the 1957-58 citrus season were discussed
at the Ninth Annual Citrus Processors' Meeting held at Lake Alfred on October 2,
1958. These and other results were subsequently published (5). During the
current citrus processing season, samples of orange juices, orange pulps and water
extracts were obtained from some commercial plants, as well as information con-
cerning the equipment and processes being used in these plants for the recovery of
fruit solids. The principal purpose of this paper is to present the data obtained
from the examination of these commercial samples so that some of the relationships
between the various characteristics of the water extracts and the procedures used
may be discussed. A secondary purpose is to describe also a small pilot plant
unit, which has been built and used at the Station, for obtaining water extracts
of orange pulp for experimental purposes and to present some data which have been
obtained using this pilot plant equipment.


EXPERIMENTAL PROCEDURES

Collection of Commercial Samples. Water extracts of orange pulp and
samples of pulp before and after extraction were collected from nine commer-
cial plants during the period January 28 to February 11 at which time some of
the midseason pack of frozen orange concentrate was being processed. Samples
of orange juices also were taken in these plants immediately after the first
juice finishing operation and in three plants using centrifuges it was possible



Presented at Citrus Engineering Conference, Florida Section of American
Society of Mechanical Engineers, March 18, 1959, Lakeland, Florida.

Florida Citrus Experiment Station
and Florida Citrus Commission
Lake Alfred, Florida
922 9/15/59 FWW









to obtain samples of water extracts before and after centrifugation. All samples
were filled into No. 1 plain tin cans, the cans closed and the products immedi-
ately frozen by immersion in a mixture of dry ice and isopropyl alcohol; the
samples were kept frozen during transportation to the Station and then stored
at -8 F. until examined,


Processes and Equipment Used in Commercial Plants. When the commercial
samples were obtained, information in considerable detail was furnished by all
companies, except one, concerning the equipment and process being used for water
extraction of orange pulp. Both paddle finishers with either brushes or paddles
and screw finishers were used in the various pulp extraction processes with the
number in a series ranging from three to six; rotating screens were employed in
two plants. Food Machinery In-Line juice extractors and Brown juice extractors
were utilized in five and four of the plants, respectively. A brief description
of the different processes then in use is given in Table 1, together with letter
codes which are also used in Tables 2 through 7 showing the characteristics of
the samples that were analyzed. Five plants (No. 1, 2, 3, 4 and 5) used a
countercurrent flow of pulp and water through a number of juice finishers
arranged in series; two of these plants (No. 4 and 5) also recycled the water
extract through the several finishers. A countercurrent flow of pulp and water
through a rotating screen was employed in one plant (No. 6). The extraction
process in another plant (No. 7) consisted of recycling the water extract through
a double finishing process using a rotating screen and a juice finisher. Water
was added between the first and second finishers of a double finishing operation
in another plant (No. 8). In four of the nine plants (No. 3, 4, 5 and 9) centri-
fuges of various types were used to reduce the amount of pulp in the water
extract prior to mixing with juice for evaporation and in another plant (No. 2)
the water extract and the juice were mixed and then centrifuged before
evaporation.


Pilot Plant Process and Equipment. The assembly of a small pilot plant
unit for the water extraction of pulp was recently completed at the Citrus
Experiment Station. This unit consists of pulp feeding equipment and a series
of four small Chisholm-Ryder Sepro-sieve screw finishers equipped with 0.020
inch screens. Countercurrent flow was used with pulp being fed into the first
finisher and discharged from the fourth finisher; water was added to the fourth
finisher and the extracts were then pumped successively back into each of the
other three finishers with the final extract being discharged from the first
finisher.


Analytical Procedures. After removal of the samples from storage at
-8 F. and thawing, the Brix value of 18 samples of orange pulp was determined;
12 samples of water extract and 9 of orange juice were examined for 20 chemical,
physical, microbiological or organoleptic characteristics. All Brix values
were determined using a refractometer. Conventional methods were used for the
determination of total acid, ascorbic acid, pH and pulp content. Analytical
methods used for the quantitative determination of pectinesterase activity and



Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida


922a 9/15/59 FWW






Table 1. Processes used for water extraction of orange pulp in some commercial plants during 1958-59
citrus season.
Soluble solids 0 Brix
In pulp_ In
Plant Code used Before After water
number in tables1 Extraction process extraction extraction extract

1 CF Countercurrent flow through finishers 12.2 6.4 4.0
2 CF Countercurrent flow through finishers; 9.6 3.42 7.5
however, extract and juice mixed and then
centrifuged before evaporation

3 CFC* Countercurrent flow through finishers and 10.6 2.4 4.9
extract centrifuged
4 CFRC* Countercurrent flow through finishers, 12.0 5.2 7.7
extracts recycled and final extract centrifuged
5 CFEC* Same as plant number 4 10.2 3.6 7.5
6 CS Countercurrent flow through rotating screen 11.0 7.6 8.6
7 SF Rotating screen and finisher used in double 9.4 5.0 6.5
juice finishing operation; water added after
rotating screen and extract recycled
8 WDF Water added after first finisher in double 10.4 3.2 7.9
juice finishing operation
9 NOC* Not observed, but extract centrifuged 10.8 4.0 7.7

1 C = countercurrent flow of water and pulp; and C* = centrifuge used.
2 Soluble solids in pulp after centrifugation of mixture of extract and juice.



Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida
922b 9/15/59 FWJ






-3-


and other pectic substances have been published (6); also those for water-
insoluble solids (7), flavonoids (2), cloud or turbidity (1, 4) and diacetyl
values (3). The relative viscosities of the centrifuged extracts and orange
juices were determined at 260 C. using an Ostwald pipette. The water extracts
and orange juices were plated on orange serum, dextrose and potato dextrose
agars to obtain the microorganism counts. The flavor and color of these pro-
ducts were checked by the authors.


RESULTS AND DISCUSSION

Soluble Solids in Orange Pulp and Water Extracts. Presented in Table 1
are the Brix values of orange pulp from nine commercial plants, both before and
after water extraction by the indicated processes. The soluble solids in the
pulp after extraction ranged from 2.4 to 8.2 Brix; these values show the rela-
tive efficiencies of the various extraction processes for the recovery of soluble
solids from the pulp. Two of the lower Brix values were found in the discharged
pulp from plants 2 and 3 where processes consisted of a countercurrent flow
through a series of finishers; the third lower value was in pulp from plant 5
where in addition to this process recycling of the extract was used. Centri-
fuges were also employed in these three plants. The highest Brix value in pulp
after extraction was in the sample from plant 8 where the extraction process
consisted of adding water between the first and second finishers of a double
juice finishing operation.

The Brix values of the water extracts, as shown in Table 1, ranged from
4.0 to 8.6* Brix; however, six of the nine samples were in the range of 6.50 to
7.9* Brix indicating the desirability of obtaining as much soluble solids as
possible in the water extracts, so as to eliminate the necessity of evaporation
of excessive amounts of water. Processes used in plants 2, 5 and 9 resulted in
the desirable combination of a high Brix value in the extract and a low Brix
value in the extracted pulp.


Chemical and Physical Characteristics of Water Extracts of Orange Pulp. -
Results reported in Tables 2 to 7, inclusively, show various characteristics of
water extracts of orange pulp, and wherever possible, analytical values have
been calculated to a 12* Brix basis for comparison purposes; minimum and maximum
values are also indicated. Data obtained from the examination of the orange juice
samples are also listed and comparison of these values with those of the water
extracts, calculated to 12 Brix basis, shows the relative amounts of substances,
such as ascorbic acid, insoluble solids, pectin and others, in these products.
If the quantity of any substance is shown to be greater in the 12 Brix extract
than that in a 120 Brix orange juice, then the amount of this substance in orange
concentrate made from juice and extract will be slightly greater than that in
concentrate made only from the juice.



Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida
922c 9/15/59 FWW










Large differences in pulp content, water-insoluble solids, pectinesterase
activity and flavonoids in the water extracts are indicated by the data in Table
2. In samples from seven of the plants water-insoluble solids, calculated to a
120 Brix basis, were considerably greater than that in the orange juices; the
pectinesterase activity was higher in extracts than in juices from five plants;
and all of the extracts had a much greater flavonoid content than that in the
juices.

Some of the large differences in pulp content, water-insoluble solids and
pectinesterase activity in the water extracts were the result of the use of
centrifuges in some plants to reduce the pulp content in the extracts before
mixing it with juice for evaporation; however, other factors were also respons-
ible for some of these differences. Extremely large amounts of water-insoluble
solids, together with high pectinesterase activities, were found in extracts from
plants 5, 6, 7 and 0. Some of the variations noted in the extraction processes,
other than centrifugation, in these plants included recycling of extract, double
finishing and use of rotating screens. Differences in the flavonoid content of
the extracts did not seem to be related to any specific process. It is interest-
ing to note that in five of the extracts the amount of flavonoids was practically
the same, irrespective of differences in both extraction processes and quantity
of water-insoluble solids; perhaps this is an indication that the solubility
limit for these substances in the water extracts had been reached.

Results reported in Table 3 show that larger quantities of water-soluble
pectin were in the water extracts thaL in the juices; the values in the extracts
on a 120 Brix basis ranged from G6.0 ti 234.0 mg./l00 g., whereas the range in
the juices was from 25.3 to 52.0 mg./lCO g. Differences in both ammonium oxalate-
soluble and sodium hydroxide-soluble pectin in the extracts are also evident and
in six samples these pectic substances were greater in the extracts than in the
juices. The higher values for water-soluble pectin were in the extracts from
plants 4, 5, 6, and 7 where variations, other than centrifugation, in the extrac-
tion processes included the recycling of extract and the use of rotating screens.
Recycling of extract provides a longer time of contact between pulp and extract
resulting in the removal of larger amounts of water-soluble substances. Differ-
ences in ammonium oxalate-soluble and sodium hydroxide-soluble pectins in the
extracts did not appear to be related to any specific extraction process other
than centrifugation.

Relative viscosity and cloud or turbidity data obtained from the examination
of the centrifuged water extracts or orange juices are presented in Table 4. The
relative viscosity in the extracts ranged from 2.16 to 23.90 as compared to a
range of 1.73 to 2.62 in the juices. The large amounts of water-soluble pectin
and water-insoluble solids in the extracts from plants 4, 5, 6 and 7 are the
principal cause of the extremely high viscosities of these samples. The viscous-
ness of these extracts was readily detectable when they were evaluated for flavor.



Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida
922d 9/15/59 FWW





Table 2. Characteristics of orange juices and water extracts of orange pulp
obtained from some commercial plants during the processing of the 1953-59 midseason
pack of frozen orange concentrate,
Plant Pulp Brix Pulpl Water-insoluble Pectinesterase Flavonoids
number extraction value solids1 activity1'2 as hesperidin1
process % by vol. mg./100 g. mR./100 ml.

Water extracts of orange pulp


CF
CF
CFC*
CFRC*
CFRC*
CS
SFR
WDF
NOC*


4.0
7.5
4.9
7.7
7.5
8.6
6.5
7.9
7.7
4.0
8.6


Orange juices
14.0 148.0
14.0 156.0
13.5 140.8
23.0 192.0
18.5 141.6
13.0 155.6
20.5 220.8
11.0 97.6
15.0 72.0


72.0
220.3


27.3
17.6
7.3
4.9
49.5
73.6
26.6
33.2
17.3
4.9
73.6
pulp4


6.0
22.5
3.5
Footnote3
it
it
13.0
17.5
9.0
3.5
22.5
Water extracts
18.5
37.0
8.5
Footnote3


24.5
27.0
14.5
8.5
37.0


76.3
101.3
75.0
139.1
121.9
121.9
121.9
124.8
121.9
75.0
139.1


58.0
140.0
17.2
0.4
209.2
270.4
163.8
210.0
73.2
0.4
270.4
of orange
174.0
225.2
42.1
0.6
334.7
377.3
311.5
319.0
114.1
0.6
377.3


Data obtained by A. H. Rouse, C. D. Atkins and E. L. Moore.
2 (PE.u.)g. soluble solids X 1000,
3 No separation of pulp since liquid was uniform throughout after centrifugation.


Values calculated to 120 Brix basis for comparison purposes.


Florida Citrus Experiment Station
and Florida Citrus Commission
Lake Alfred, Florida
922e 9/15/59 FWW


Minimum
Maximum


27.3
17.6
7.3
4.9
49.5
73.6
26.6
33.2
17.8
4.9
73.6

15.3
19.0
20.0
31.9
21.1
20.2
38.6
14.3
19.5
14.3
38.6


Minimum
Maximum


CF
CF
CFC*
CFRC*
CFRC*
CS
SFR
WDF
NOC*


Minimum
Maximum


236.6
165.2
189.3
220.6
198.7
172.6
230.2
192.9
193.4
165.2
236.6


103.1
73.3
94.3
129.1
79.4
63.1
82.5
70.6
75.0
S63.1
129.1


12.0
12.0
12.0
12.0
12.0
12.0
12.0
12.0
12.0
12.0
12.0


11.8
11.9
11.2
13.6
13.0
12.1
12.1
11.2
12.5
11.2
13.6


11.0
23.0


I







Table 3. Characteristics of orange juices and water extracts of orange pulp
obtained from some commercial plants during the processing of the 1958-59
midseason pack of frozen orange concentrate.
Pectin as anhyCroalacturonic acidi- mg./100g.
Plant Pulp Brix Water Ammonium Sodium
number extraction value soluble o::alate hydroxide Total
process solrble soluble


Water extracts of
4.0 40.0
7.5 66.7
4.9 41.3
7.7 146.7
7.5 146.7
8.6 126.7
6.5 100.0
7.9 56.7
7.7 73.3


4.0
8.6


41.3
146.7


Water extracts of
12.0 144.0
12.0 106.7
12.0 101.0
12.0 220.6
12.0 234.0
12.0 176.4
12.0 1G4.6
12.0 86.0
12.0 114.1


12.0
12.0


11.8
11.9
11.2
13.6
13.0
12.1
12.1
11.2
12.5
11.2
13.6


Minimum
Maximum


orange pj.o
12.7
27.3
2.0
0.0
21.3
27.3
20.7
27.3
16.7
0.0
27.3


orange pulp2
38.0
43.7
4.9
0.0
34.1
38.0
38.2
41.5
25.9


86.0
234.0
Orange juices
26.7
29.3
40.7
46.7
44.7
34.7
52.0
25.3
30.0
25.3
52.0


23.3
21.0
20.7
29.3
29.8
32.7
14.0
18.7
26.0
14.0
32.7


Data obtained by A. H. Rouse, C. D. Atkins and E. L. Moore.

Values calculated to 120 Brix basis for comparison purposes.


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida
922f 9/15/59 FWW


CF
CF
CFC*
CFRC*
CFRC*
CS
SFR
WDF
NOC*


Minimum
Maximum


CF
CF
CFC*
CFRC*
CFRC*
CS
SFR
WDF
NOC*


Minimum
Maximum


16.0
31.3
4.0
0.0
42.0
53.3
34.7
50.0
23.3
0.0
53.3


48.0
50.1
9.8
0.0
67.2
74.3
64.0
75.9
36.2
0.0
75.9

41.3
36.0
35.3
40.0
34.0
32.7
48.7
36.7
38.7
32.7
48.7


76.7
125.3
47.3
146.7
210.0
207.3
155.4
134.0
113.3
47.3
210.0


230.0
200.5
115.7
223.6
335.3
288.7
286.8
203.4
176.2
115.7
335.3

91.3
-86.3
96.7
116.0
108.5
100.1
114.7
80.7
94.7
80.7
116.0


0.0
43.7


I


" i


- --









Table 4. Characteristics cf orange Juices and water extracts of orange pulp
obtained from some commercial plants during the processing of the 1950-59 midseason
pack of frozen orange concentrate.

Plant Pulp Brix Relative Cloud or Water-soluble Water-insoluble
number extraction value viscosityl turbidity2,3 pectin2 solidsz
process mg./100 g. mg./100 g.

Water extracts of orange pulp
1 CF 4.0 2.58 73 48.0 58.0
2 CF 7.5 4.39 72 66.7 140.8
3 CFC* 4.9 2.16 63 41.3 17.2
4 CFRC* 7.7 13.78 37 146.7 0.4
5 CFRC* 7.5 23.90 35 146.7 209.2
6 CS 8.6 23.00 35 126.7 270.4
7 SPR 6.5 18.33 40 100.0 168.8
8 WDF 7.9 2.98 58 56.7 210.0
9 NOC* 7.7 3.99 41 73.3 73.2
Minimum 4.0 2.16 35 41.3 0.4
Maximum 8.6 23.90 73 146.7 270.4

,Orangr juices
1 11.8 1.73 45 26.7 148.0
2 11.9 1.88 54 29.3 156.0
3 11.2 2.07 42 40.7 140.8
4 13.6 2.62 47 46.7 192.0
5 13.0 2.12 47 44.7 141.6
6 12.1 1.81 48 34.7 155.6
7 12.1 2.52 45 52.0 220.8
8 11.2 1.94 57 25.3 97.6
9 12.5 2.05 45 30.0 72.0
Minimum 11.2 1.73 42 25.3 72.0
Maximum 13.6 2.61 57 52.0 220.8


1Data obtained by G. H. Ezell; and 2 by A. H. Rouse, C. D. Atkins and E. L.
Moore.

3 Figures are percentage light transmittance of centrifuged extracts using
Lumetron 402-E with 730 filtat and 14 ml. cell.


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida
922g 9/15/59 FWI











Comparison of data in Table 5 for water extracts with that for the orange
juices, indicates that the percentage of acid was generally smaller in the ex-
tracts than in the juices, which caused both a higher Brix-to-acid ratio and a
slight increase in pH in the extracts. Only slight differences in ascorbic acid
were found between the juices and the extracts on a 12' Brix basis. Variations
in the extraction processes in the different plants, as described in Table 1, are
believed to have little effect upon the characteristics of the water extracts
listed in Table 5, since these are chiefly dependent upon the maturity and variety
of the fruit that is processed. The lower Brix values found in some of the
extracts may have resulted from the use of a greater water-to-pulp ratio in the
extraction process.


Effect of Use of Centrifuge on Characteristics of Water Extracts of Orange
Pulp. Five plants were using centrifuges, as mentioned in Table 1, to remove
pulp from water extracts, but samples of extract before and after centrifugation
were obtained only from three of these plants. Examination of the data in Table
6 shows the effect of centrifugation on some of the characteristics of water
extracts of orange pulp.

Results obtained from the examination of the water extracts from plants 3
and 9 will be discussed first, because it is believed for reasons to be mentioned
later that these data are more realistic than those shown for the samples from
plant 4. Centrifugation of the extracts from plants 3 and 9 had little effect
upon the Brix value, acid, pH, ascorbic acid, cloud or turbidity and water-
soluble pectin; however, a small reduction occurred in the flavonoids, relative
viscosity and total pectin. A large decrease in the pulp content, water-insoluble
solids, pectinesterase activity and in the oxalate-soluble and sodium hydroxide-
soluble pectins was brought about by centrifugation. An objectionable off-flavor
was detectable in the extract from plant 9 after centrifugation and since no off-
flavor was evident in the extract before centrifugation, this indicates that a
centrifuge may be a source of contamination, especially since the extract with
the off-flavor also had a high microorganism count and high diacetyl value, as
shown in Table 7.

Some of the characteristics of the extracts obtained before and after cen-
trifugation from plant 4 were different than those in samples from plants 3 and 9.
These samples of extract were collected in plant 4 after the extract before cen-
trifugation had been held in tanks for recycling for some time because processing
had been stopped for cleaning of equipment; therefore, these samples should not be
considered exactly representative of this process. Data in Table 6 show that this
extract contained 34.5% pulp, 238.8 mg./l0 g. of water-insoluble solids and a
pectinesterase activity of 70.0 units,all of these values being very high and
providing conditions conducive to clarification. The 91.3 mg./100 g. of oxalate-
soluble pectin was greater than the 86.7 mg./100 g. of water-soluble pectin found
in this extract, indicating that demethylation of water-soluble pectin by pectin-
esterase had occurred and resulted in partial clarification of the extract. Also



Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida
922h 9/15/59 FWW






Table 5. Characteristics of orange uices and water extracts of orange pulp
obtained from some commercial plants during the processing of the 1958-59 mid-
season pack of frozen orange concentrate.
Plant Pulp Brix Acid as Brix/acid Ascorbic
number extraction value1 citric1 ratio pH1 acid1
process 7Z m./l0 ml.
Water extracts of orange pulp


CF
CF
CFC*
CFRC*
CFRC*
CS
SFR
WDF
NOC*
Minimum
Maximum


4.0
7.5
4.9
7.7
7.5
8.6
6.5
7.9
7.7
4.0
8.6


0.36
0.48
0.32
0.48
0.56
0.56
0.40
0.54
0.47
0.32
0.56


11.1
15.6
15.3
16.0
13.4
15.4
16.3
14.6
16.4
11.1
16.4


3.6
4.1
4.0
4.0
3.9
3.9
4.0
4.0
3.9
3.6
4.1


Water extracts of orange pulp2


CF
CF
CFC*
CFRC*
CFRC*
CS
SFR
WDF
NOC*


Minimum
Maximum


12.0
12.0
12.0
12.0
12.0
12.0
12.0
12.0
12.0
12.0
12.0


1.08
0.77
0.78
0.75
0.90
0.73
0.74
0.82
0.73
0.73
1.08


11.1
15.6
15.3
16.0
13.4
15.4
16.3
14.6
16.4
11.1
16.4


Orange juices


11.8
11.9
11.2
13.6
13.0
12.1
12.1
11.2
12.5
11.2
13.6


Minimum
Maximum


1.00
0.84
0.91
1.02
1.13
0.96
1.02
0.92
0.83
0.33
1.13


11.8
14.2
12.3
13.3
11.5
12.6
11.9
12.2
15.1
11.5
15.1


3.7
3.9
3.8
3.8
3.8
3.8
3.8
3.8
3.9
3.7
3.9


Data obtained by R. L. Huggart and R. W. Barron.


Values calculated to 120 Brix basis for comparison purposes.


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida
9221 9/15/59 FWW


I









Table 6. Effect of the use of a centrifuge for removal
water extracts of orange pulp.


of pulp on the characteristics of


Plant No. 3 Plant No. 9 Plant No. 4
CFC* NICC* CFRC*
Values before nd after centrifuation
~-~----~~I---~.--~ -.- --- ~iUZ


Before After


Before After


Before After


Brix value
Acid as citric1
Brix/acid ratio1
pH1
Ascorbic acidl-mg./100 ml.

Pulp-% by vol.2
Water-insoluble solids2-mg./100g.
Pectinesterase activity2
Flavonoids as hesperidin2-mg./100 ml.
Objectionable off-flavor

Cloud or turbidity2
Relative viscosity3
Water-soluble pectin2 mg./100 g.
Oxalate-soluble pectin2 "
Sodium hydroxide-soluble pectin2-"
Total pectin2 mg./lOO g.


5.2
0.35
14.9
3.9
24

5.5
50.0
13.7
81.2
No

63
2.23
41.3
5.0
12.0
58.3


4.9
0.32
15.3
4.0
23

3.5
17.2
7.3
75.0
No

63
2.16
41.3
2.0
4.0
47.3


7.8
0.47
16.6
3.9
35

13.0
130.4
21.
136.2
No

42
4.26
72.0
21.3
32.0
125.3


7.7
0.47
16.4
3.9
34

9.0
73.2
17.3
121.9
Yes

41
3.99
73.3
16.7
23.3
113.3


9.0
0.57
15.3
3.9
41

34.5
238.8
70.0
160.6
Yes

69
3.25
86.7
91.3
56.7
234.7


7.7
0.43
16.0
4.0
37


Footnote4
0.4
4.9
139.1
Yes

37
13.78
146.7
0.0
0.0
146.7


Data obtained by R. L. Huggart and R. W. Barron;
and-3 by G. H. Ezell.


2 by A. H. Rouse, C. D. Atkins and E. L. Moore;


4No separation of pulp since liquid was uniform throughout after centrifugation.


Florida Citrus Experiment Station
and Florida Citrus Commission
Lake Alfred, Florida
922j 9/15/59 FWW






-6-


the presence of an objectionable off-flavor in this extract, as a result of the
growth of microorganisms, showed that either the rate of the extraction process
was not fast enough or that good sanitary practices were not being used. Because
of these reasons, it is believed that the data obtained from the examination of
the extracts from plant 4 are not too realistic and should not be used as the
basis for conclusions concerning the use of centrifuges. However, it is interest-
ing to note from the data in Table 6 that centrifugation of this extract removed
almost all of the water-insoluble solids and pectinesterase activity and completely
removed all of the oxalate-soluble and sodium hydroxide-soluble pectins; however,
a large increase in the water-soluble pectin occurred which resulted in the
extract after centrifugation having a good cloud and a high relative viscosity.


Microbiological Characteristics of Water Extracts of Orange Pulp. That
microorganisms will grow in water extracts of orange pulp during the extraction
process is evident from the high microorganism counts on orange serum agar and
high diacetyl values found in extracts from plants 4 and 9 as shown by data in
Table 7. Counts of 200,000 or more were also obtained when four of the water
extracts were plated on dextrose agar. It should be recalled that the pH of all
of the water extracts, except one, was in the range of 3.9 to 4.1, as shown by
data in Table 5, and that this condition is conducive to microorganism growth.
These results indicate the necessity for applying good sanitary practices to any
pulp extraction process and also to complete the extraction as rapidly as possible
so that the occurrence of microbiological problems may be avoided.


Color and Flavor of Water Extracts of Orange Pulp. The water extracts had
a yellow or greenish-yellow color together with a milky appearance and the inten-
sity of the color was much less than that in the orange juices. Extracts which
had been recycled during the extraction process were poorer in appearance and
color. The flavor of six of the water extracts was considered to be satisfactory
since no objectionable off-flavors were detectable. A slight amount of astringency
was present in six extracts and a moderate amount in the other three samples;
slight bitterness was found in only one extract. A peel aroma of moderate inten-
sity was evident in all of the extracts. A slight orange flavor was detectable
in six samples, only two of which had a slight orange aroma. Objectionable off-
flavors were evident, as indicated in Table 7, in three of the water extracts.
The off-flavors in the extracts from plants 4 and 9 resulted from the growth of
microorganisms, whereas the poor flavor of the sample from plant 1 was possibly
caused by the use of Temple oranges of inferior quality, which were being used
for the production of bulk concentrate.


Use of Water Extracts of Orange Pulp in Production of Orange Concentrate. -
It is evident from the data presented in Tables 2 to 7, inclusively, that the
extraction of orange pulp by the various processes being used in commercial plants
is resulting in water extracts of both acceptable and unacceptable quality because
of wide variations in their characteristics. In a previous publication (5) it was
pointed out that when a relatively small volume of extract is mixed with a large
volume of evaporator feed juice, the effect of large amounts of undesirable


Florida Citrus Experiment Station
and Florida Citrus Commission
Lake Alfred, Florida
922k 9/15/59 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 mid-
season pack of frozen orange concentrate.
Plant Pulp Diacetyl Microorganism counts2 X 1000 Objection-
number extraction value Orange serum Dextrose Potato able
process p.p.m. agar agar dextrose agar off-flavor
pH 5.5 pH 7.0 pH 3.4

Water extracts of orange pulp
1 CF 1.0 34.0 310.0 9.5 Yes4
2 CF 3.1 72.0 95.0 40.0 No
3 CFC* 1.7 0.0 200.0 Footnote3 No
4 CFRC* 9.7 480.0 430.0 3.0 Yes5
5 CFRC* 3.3 54.0 90.0 7.0 No
6 CS 1.5 20.0 80.0 6.0 No
7 SFR 1.4 13.3 15.2 2.5 No
8 WDF 1.1 11.0 45.0 4.0 No
9 NOC* 10.2 569.0 232.0 81.0 Yes5
Minimum 1.0 0.0 15.2 2.5 -
Maximum 10.2 569.0 430.2 81.0 -

Orange juices
1 1.7 6.0 11.0 15.0 No
2 3.2 72.0 95.0 40.0 No
3 3.2 32.0 114.0 15.0 No
4 2.2 12.0 23.0 5.0 No
5 2.4 24.0 24.5 15.4 No
6 2.4 16.0 406.0 5.0 No
7 2.1 128.0 120.0 96.0 No
8 1.3 Footnote3 24.0 Footnote3 No
9 3.8 241.0 178.0 62.0 No
Minimum 1.3 6.0 11.0 5.0 -
Maximum 3.8 241.0 406.0 96.0 -


1 Data obtained by E. C. Hill; and 2 by Roger Patrick and E. C. Hill.

3Plate counts too low to be of significance.

4 Objectionable off-flavor in water extract was possibly caused by use of
Temple oranges of inferior quality; concentrate was being packed in bulk.

Objectionable off-flavor in water extract was caused by growth of micro-
organisms as indicated by the high diacetyl value and high microorganism
counts.


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida
922m 9/15/59 FWW







-7-


substances in a water extract will be minimized because of their dilution. How-
ever, this circumstance should not be used as a reason for condoning the produc-
tion of water extracts of poor quality. Apparently, equipment and procedures are
available with which fruit solids can be satisfactorily recovered from orange pulp,
since some of the water extracts examined were products with such characteristics
that no reason was evident from data available at this time for not using them in
the production of orange concentrate. However, if the extraction process is not
carried out rapidly and under sanitary conditions, unsatisfactory extracts of poor
quality will result.


Use of Pilot Plant Unit for Water Extraction of Orange Pulp. Data shown in
Tables 8, 9 and 10 were obtained using a small pilot plant unit, which has been
previously described. Juice from a Food Machinery In-Line extractor was passed
through a screw finisher and the discharged pulp fed to the pulp extraction unit.
Results given in Table 8 show that the Brix value of orange pulp was reduced from
11.7* Brix to 3.10 Brix by using a countercurrent flow of pulp and water through
four finishers. The extract increased from 1.6 Brix to 7.20 Brix in passing
through the unit. The time required for the pulp to pass through the unit was
approximately three minutes, indicating the rapidity with which soluble solids
may be extracted from the orange pulp.

The effect of the water-to-pulp ratio used on the recovery of soluble solids
is shown by the data in Table 9. As the ratio of water-to-pulp was increased
from 0.50 to 2.00, the percentage of soluble solids recovered increased from 51
to 81%. In commercial operations it is desirable to keep the water-to-pulp ratio
as low as possible so as to avoid the evaporation of excessive amounts of water.
Countercurrent flow of pulp and extract through processing equipment and recycling
of extract are used to increase the soluble solids in the extract so that the
water-to-pulp ratio may be maintained as low as possible.

It is seen from the data in Table 10 that the percentage of soluble solids
recovered was increased as a larger number of finishers were used in the extrac-
tion process.

The pilot plant extraction unit has also been utilized to prepare water
extracts of orange pulp, which were added to orange juices used for making experi-
mental packs of frozen orange concentrate to determine what effect the extracts
will have on the quality of this product after storage.


SUMMARY
The characteristics of water extracts of orange pulp collected from nine
commercial plants producing frozen orange concentrate have been determined and
these characteristics compared with those of orange juices obtained from the same
plants.


Florida Citrun Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida
922n 9/15/59 FWW





Table 8. Soluble solids in water extracts
during countercurrent extraction of orange pulp
using four finishers and a 1:1 water-to-pulp
ratio.

Feed pulp to 1st finisher 11.7 Brix
Extract from 1st finisher a 7.20 Brix
2nd 5.60 "
3rd 3.1 "
4th = 1.60 "
Discharged pulp from 4th finisher = 3.1 Brix
1
Average values of several samples taken during
continuous extraction.




Table 9. Effect of water-to-pulp ratio on
recovery of soluble solids during countercurrent
extraction of orange pulp using four finishers.

Water/pulp Soluble solids Number
ratio recovered-7 of runs

0.50 51 1
0.75 68* 3
1.00 72* 4
1.25 78* 3
2.00 81 1

Average values of data from number of runs
indicated.


Table 10. Effect of number of finishers used
on recovery of soluble solids during countercurrent
extraction of orange pulp using a 1:1 water-to-pulp
ratio.

Number of Soluble solids
finishers recovered-%
2 62
3 75
4 83


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida
922o.-9/15/59 FWt












Large differences were found in many characteristics of the samples collected
from the different plants. The effect of the various processes, which are briefly
described, used in the commercial plants on the characteristics of the water
extracts of orange pulp are discussed.

A description is given of a small pilot plant unit built and used for the
recovery of fruit solids from orange pulp and some experimental data obtained
with this unit are presented.


ACKNOWLEDGEMENTS

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 informa-
tion about the pulp extraction processes that were used.

The authors appreciated the assistance of C. D. Atkins, R. W. Barron, 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.

Suggestions and assistance of C. D. Atkins during the construction of the
small pilot plant unit for the extraction of orange pulp are hereby acknowledged.



























Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida
922p 9/15/59 FWW








-9-


LITERATURE CITED


1. Atkins, C. D., A. H. Rouse and E. L.
cloud retention in frozen concentrated orange
colorimeters. Proc. Florida State Hort. Soc.


Moore. 1955. Determination of
and grapefruit juices with various
68: 124-127.


2. Hendrickson, R. and J. W. Kesterson. 1954. Hesperidin, the principal
glucoside of oranges. Occurrence, properties and possible utilization. Florida
Agr. Exp. Sta. Tech. Bul. 545.

3. Hill, E. C. and F. W. Wenzel. 1957. The diacetyl test as an aid for
quality control of citrus products. I. Detection of bacterial growth in orange
juice during concentration. Food Technol. 11: 240-243.

4. Huggart, R. L., E. L. Moore and F. W. Wenzel. 1951. The measurement
of clarification in concentrated citrus juices. Proc. Florida State Hort. Soc.
64: 185-188.

5. Olsen, R. W., F. W. Wenzel and R, L. Huggart. 1958. Recovery of fruit
solids from orange pulp. Proc. Florida State Hort. Soc. 71: 266-274. Also,
Citrus Magazine 21: (4) 8-10, 16-18.

6. Rouse, A. H. and C. D. Atkins. 1955. Pectinesterase and pectin in
commercial citrus juices as determined by methods used at the Citrus Experiment
Station. Florida Agr. Exp. Sta. Tech. Bul. 570.

7. Rouse, A. H. and C. D, Atkins. 1955. Methods for estimation of
insoluble solids in citrus juices and concentrates. Proc. Florida State Hort.
Soc. 68: 117-121.


















Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida
922q 9/15/59 FWW




University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs