Group Title: Citrus Station mimeo report - Florida Citrus Experiment Station ; 55-7
Title: Effect of heat treatment on the survival of microorganisms in single-strength and concentrated juices from grove-run oranges
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 Material Information
Title: Effect of heat treatment on the survival of microorganisms in single-strength and concentrated juices from grove-run oranges
Series Title: Citrus Station mimeo report
Physical Description: 3, 6 leaves : ; 28 cm.
Language: English
Creator: Patrick, Roger
Hill, Elmer C
Citrus Experiment Station (Lake Alfred, Fla.)
Florida Citrus Commission
American Can Company
Publisher: Florida Citrus Experiment Station :
Florida Citrus Commission
Place of Publication: Lake Alfred FL
Publication Date: 1954
 Subjects
Subject: Orange juice -- Microbiology -- Florida   ( lcsh )
Concentrated fruit juices -- Preservation -- Florida   ( lcsh )
Microorganisms -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: Roger Patrick and E.C. Hill.
General Note: Caption title.
General Note: "October 12, 1954."
General Note: "American Can Company cooperating through establishment of grant-in-aid."
 Record Information
Bibliographic ID: UF00072369
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 74729256

Full Text
Citrus Station Mimeo Report 55-7
October 12, 1954


Effect of Heat Treatment on the Survival of Microorganisms in Single-Strength
and Concentrated Juices from Grove-Run Oranges1

Roger Patrick and E. C. Hill


There has been increased use of heat treatment to destroy the microorganisms
present in orange juices or in the semi-concentrates during the processing of
frozen concentrated orange juices. Some investigations have been made at this
Station and were reported on at previous Annual Processors Meetings. The destruc-
tion of two strains of spoilage organisms in orange juice was reported at the Third
Annual Processors Meeting, 1952. Lactobacillus plantarum and Leuconostoc mesen-
teroides inoculated into pasteurized juice, pH 3.7, were completely destroyed
when heated in 0.8 sec. to 1750F, and 1550F., respectively. During the 1952-53
citrus season this work was repeated on orange juices at pH 3.6, 3.8, and 4.0.
L. plantarum inoculated into juices and heated to 1650F. in 12 sec. was almost
completely destroyed at all pH levels. L. mesenteroides exposed to 1550F. in
12 sec. was destroyed except at pH 4.0, when heating in 12 sec. to 1650F. was
required. Also, it was pointed out that orange juice from grove-run fruit at
pH 3.8 and 4.0 with an unidentified mixed culture added, did not show complete
destruction of the microbiological contamination when heated to 1900F. in 12 sec.
Concentrates prepared from juice from the same lot of fruit, concentrated to
2-, 3-, and 4-folds, did not show complete destruction of organisms after heating
to 1850F. in 12 sec., but was considered commercially acceptable. Concentrates
at pH 3.8, did not show complete destruction of organisms in 3- and 4-fold juices
when heated in 12 sec. to 1850F., however, the numbers surviving in the concen-
trates were not considered significant. Similar results were found in 3- and
4-fold concentrates, pH 3.9, with acceptable results after exposures of 1650,
1750, and 1850F. for 12 sec. The character of the microbial contamination seemed
to have much to do with the numbers of organisms surviving the heat treatment.

After reviewing the observations that had been made, a different plan was
outlined for the 1953-54 season. Tests were made with single-strength, 2-, 3-,
and 4-fold juices from Hamlin, Pineapple and Valencia oranges during the season
when the quality of each variety was definitely on the decline and the contami-
nation of the interior was greater than that found in fruit of good quality. To
eight boxes of oranges picked from the tree, one box of drops was added, in an
effort to increase the contamination in the juice. Soft fruit was used, but
rotten fruit was discarded. The oranges were washed with a soap solution and
rinsed with unchlorinated water. The juice was extracted with Rotary presses at
the Citrus Experiment Station pilot plant and the heat treatment was effected with
the pasteurizer designed for pectinesterase inactivation studies. The temperatures
used were 1650, 1750, 1850, 1900, 2000, and 210OF. Single-strength juice was
heated in 0.8, 3, 6, and 12 sec., 2-, 3-, and 4-fold juices were heated in 3, 6,
and 12 sec. to the desired temperatures. Dextrose tryptone agar, pH 7.0, and
orange serum agar, pH 5.6, were used for plating,


1American Can Company cooperating through establishment of grant-in-aid.

Florida Citrus Experiment Station and
Florida Citrus Commission, Lake Alfred, Fla.
528-10/12/54-RP





-2-


Single-strength juices from Hamlin and Pineapple oranges, pH 3.7, showed good
destruction of organisms at 1650F. for 6 and 12 sec. with Hamlin orange juice
giving the better results, Tables 1 and 2. Dextrose tryptone agar and orange
serum agar inoculated with juice that had been heated in 6 sec. showed 60 organisms
per ml. and less than one per plate on orange serum agar, After 12 sece exposure,
the count was 40 and 0 per ml, on dextrose tryptone agar and orange serum agar,
respectively. Pineapple orange juice exposed for 6 sec. showed spreaders and
less than one colony per plate. Media inoculated with juice heated to temperature
in 12 sec. showed spreaders and one colony per plate.

Hamlin and Pineapple orange juices, pH 3.7, did not show complete destruction
of organisms at 2-, 3-, or 4-fold. In Hamlin 4-fold concentrate, there was a
definite decrease in numbers surviving at 1900F. with a 12 sec. exposure time
giving good results. In 2-fold and 3-fold juices there was a wide spread in the
counts obtained with dextrose tryptone agar and orange serum agar. It was diffi-
cult to point to an acceptable temperature and exposure time of heat treatment
(Table 3). A very similar situation is noted in Table 4 where the results of
heat treatment for 2-, 3-, and 4-fold Pineapple orange juices are listed. There
is a definite break in the numbers of organisms surviving at 190 to 200F,,
irrespective of the exposure times, and with such a difference in the results
from the two media inoculated with 2- and 3-fold juices that a preference as to
temperature and exposure times may not be determined satisfactorily.

Valencia single-strength juice at pH 4.0, showed a decrease in numbers of
microorganisms surviving after a heat treatment of 1900 and 200 F. with a pre-
ference at 2000F. at all exposure times (Table 5). The heat treatment of Valencia
orange concentrates did not give satisfactory reduction of microorganisms at any
of the temperatures or exposure times as indicated in Table 6. Four-fold con-
centrate gave the best results with heat treatment of 2100Fo for 12 sec. and that
may not be adequate from the standpoint of stability. The results in reduction
of microorganisms in the 2-fold and 3-fold concentrates were not good if con-
sidered from the processorst point of view. Not only were the counts on orange
serum agar high, but the total counts observed on dextrose tryptone agar were
higher.

It is uncertain what the high total counts would mean in terms of stability
in 2- and 3-fold concentrates prepared from these three varieties of oranges, if
placed under inadequate storage conditions. Without a doubt, the high population
that survived the heat treatment does suggest the poor quality of the fruit used
and a laboratory doing control checks on consumers goods would find cause for
complaint.

The best results from heat treatment of these products were obtained with
single-strength juices ranking first, 4-fold concentrate next, with 3-fold and
2-fold concentrates last in order. It is not clear that the pH of the juice or
concentrate had much effect on the survival of microorganisms during the heat
treatment. Of the orange juices, Valencia juice, pH 4.0, carried the highest
contamination probably because the fruit was very much overmature and harvested
after warm weather had returned, thus giving a better medium for growth under
very favorable conditions. Fewer organisms survived in single-strength Hamlin
orange juice after heat treatment than in the single-strength Pineapple orange


Florida Citrus Experiment Station and
Florida Citrus Commission, Lake Alfred, Fla
528a-10/12/54-RP







juice. The lowest numbers of organisms surviving in concentrated juices after
heat treatment were found in 4-fold Pineapple orange juice. This may have been
influenced by seasonal variation of the microcontamination, and &lso, the character
of the microcontamination seemed to have much to do with the numbers of organisms
surviving the heat treatment.














































Florida Citrus Experiment Station and
Florida Citrus Commission, Lake Alfred, Fla.
528b-10/12/54-RP






TABLE 1
Effect of heat treatment on the destruction of microorganisms in
Hamlin orange juice from grove-run fruit, pH 3.71


Temp. Exposure Numbers per ml. of juice
OF. time Dextrose tryptone Orange serum
sec. agar, pH 7.0 agar, pH 5.6
None None 22,000 12,300
210 0.8 0 0
3.0 20 0
6.0 0 0
12.0 0 0
.200 0.8 60 0
3.0 0 0
6.0 30 0
12.0 20 0
190 0.8 40 0
3.0 40 0
6.0 50 0
12.0 0 0
185 0.8 40 0
3.0 30 0
6.0 150 0
12.0 30 0
175 0.8 20 0
3.0 40 0
6.0 30 0
12.0 40 0
165 0.8 70 0
3.0 220 0
6.0 60 0
12.0 40 0
1


One box of dropped fruit
Florida Citrus Experiment Station and
Florida Citrus Commission, Lake Alfred, F3
528c-10/12/54-RP


was added to 8 boxes of picked fruit.






TABLE 2
Effect of heat treatment on the destruction of microorganisms in
Pineapple orange juice from grove-run fruit, pH 3.72


Temp. Exposure Numbers per ml. of juice
OF. time Dextrose tryptone Orange serum
sec. ager, pH 7.0 agar, pH 5.6

None None 32,000 24,000
210 0.8 470 20
3.0 570 0
6.0 Spreaders 0
12.0 6 ppl 0
200 0.8 380 0
3.0 480 0
6.0 700 0
12.0 420 0
190 0.8 400 0
3.0 610 0
6.0 780 0
12.0 410 0
185 0.8 470 0
3.0 640 0
6.0 830 0
12.0 880 0
175 0.8 500 0
3.0 Spreaders 0
6.0 Spreaders 0
12.0 1,120 0
165 0.8 960 0
3.0 640 0
6.0 Spreaders 0
12.0 Spreaders 0
20ne box of dropped fruit was added to 8 boxes of picked fruit.
Florida Citrus Experiment Station and
Florida Citrus Commission, Lake Alfred, Fla.
528d-10/12/54-RP






TABIE 3
Effect of heat treatment on the destruction of microorganisms in two, three, and four-fold
concentrates prepared from grove-run Hamlin oranges, pH 3.73

Numbers per ml. of reconstituted juice
Temp. Exposure Two-fold Three-fold Four-fold
OF. time Dextrose Orange Dextrose Orange Dextrose Orange
sec. tryptone agar serum agar tryptone agar serum agar tryptone agar serum agar
pH 7.0 pH 5.6 pH 7.0 pH 5.6 pH 7.0 pH 5.6
None None 15,000 5,000 10,000 10,000 5,000 15,000
210 3.0 300 20 115 25 60 20
6.0 280 20 60 40 100 0
12.0 100 0 180 30 70 0
200 3.0 560 0 180 90 110 50
6.0 410 20 90 20 90 20
12.0 380 20 200 30 80 20
190 3.0 610 20 230 25 115 30
6.0 350 20 140 20 70 0
12.0 300 130 180 20 60 0
185 3.0 500 20 280 20 120 20
6.0 550 0 250 40 50 40
12.0 350 150 90 60 120 0
175 3.0 670 90 290 70 120 20
6.0 570 90 250 25 180 50
12.0 420 110 250 100 150 20
165 3.0 870 40 570 40 500 50
6.0 130 50 330 70 150 20
12.0 320 90 150 70 180 80
3One box of dropped fruit was added to 8 boxes of picked fruit.
Florida Citrus Experiment Station and
Florida Citrus Commission, Lake Alfred, Fla.
528e-10/12/54-RP






TABIE 4
Effect of heat treatment on the destruction of microorganisms in two, three, and four-fold
concentrates prepared from grove-run Pineapple orange juice, pH 3.74

Numbers per ml. of reconstituted juice
Temp. Exposure Two-fold Three-fold Four-fold
oF. time Dextrose Orange Dextrose Orange Dextrose Orange
see. tryptone agar serum agar tryptone agar serum agar tryptone agar serum agar
pH 7.0 pH 5.6 pH 7.0 pH 5.6 pH 7.0 pH 5.6
None None 12,000 11,000 12,000 7,000 6,800 8,000
210 3.0 490 200 100 40 90 40
6.0 370 120 140 50 40 0
12.0 320 160 110 0 40 0
200 3.0 700 560 250 40 80 30
6.0 160 210 150 50 70 0
12.0 460 150 280 50 70 0
190 3.0 630 160 220 30 100 0
6.0 490 270 20 60 90 0
12.0 670 230 90 70 110 0
185 3.0 310 150 230 30 60 0
6.0 600 240 280 50 110 0
12.0 Spreaders 260 310 80 100 0
175 3.0 600 200 150 30 220 0
6.0 670 200 290 50 100 0
12.0 720 200 310 90 150 0
165 3.0 2,100 150 230 90 290 0
6.0 940 180 400 40 140 0
12.0 Spreaders 110 300 80 100 0
~ne box of dropped fruit was added to 8 boxes of picked fruit.


Florida Citrus Experiment Station and
Florida Citrus Commission, Lake Alfred, Fla.
528f-10/12/54-RP









TABLE 5
Effect of heat treatment on the destruction of microorganisms
in Valencia orange juice from grove-run fruit, pH 4.05

Exposure Numbers per ml. of juice
Temp. time Dextrose tryptone Orange serum
OF. sec. agar, pH 7.0 agar, pH 5.6

None None 182,000 251,000
210 0.8 130 0
3.0 280 0
6.0 0 0
12.0 0 0
200 0.8 140 0
3.0 0 0
6.0 0 0
12.0 0 0
190 0.8 0 0
3.0 0 0
6.0 170 0
12.0 130 0
185 0.8 190 0
3.0 Spreaders 0
6.0 180 0
12.0 110 0
175 0.8 0 0
3.0 150 0
6.0 160 0
12.0 500 0
165 0.8 150 0
3.0 270 0
6.0 130 0
12.0 130 0
5 One box of dropped fruit was added to 8 boxes of
picked fruit.


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TABLE 6
Effect of heat treatment on the destruction of microorganisms in two, three, and four-fold
concentrates prepared from grove-run Valencia oranges, pH 4.06

Numbers per ml. of reconstituted juice
Temp. Exposure Two-fold Three-fold Four-fold
OF. time Dextrose Orange Dextrose Orange Dextrose Orange
sec. tryptone agar serum agar tryptone agar serum agar tryptone agar serum agar
pH 7.0 pH 5.6 pH 7.0 pH 5.6 pH 7.0 pH 5.6
None None 152,000 203,000 140,000 252,000 161,000 231,000
210 3.0 560 330 300 95 145 95
6.0 460 280 165 150 105 75
12.0 400 280 120 95 80 80
200 3.0 650 400 270 205 220 120
6.0 740 370 260 220 140 95
12.0 550 330 255 124 120 110
190 3.0 640 570 515 285 285 155
6.0 880 360 350 220 140 85
12.0 570 400 245 130 150 65
185 3.0 650 400 345 210 170 160
6.0 650 470 350 220 150 100
12.0 700 400 380 225 150 110
175 3.0 640 390 530 210 280 160
6.0 730 310 410 200 200 85
12.0 590 460 380 220 235 85
165 3.0 620 540 1,300 1,125 2,180 2,350
6.0 730 360 1,045 220 610 80
12.0 940 520 500 210 285 120
6One box of dropped fruit was added to 8 boxes of picked fruit.
Florida Citrus Experiment Station and
Florida Citrus Commission, Lake Alfred, Fla.
5281t -10/12/54-RP




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