WATER POLLUTION CONTROL RESEARCH SERIES • 12060 FQE 12/70
Dry Caustic Peeling of Tree Fruit
for Liquid Waste Reductions
U.S. ENVIRONMENTAL PROTECTION AGENCY
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WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research. Series describes the
results and progress In the control and abatement of pollu**
tion of our Nationrs waters. They provide a central source
of information on the research, development, and demon-
stration activities of the Environmental Protection Agency
through inhouse research and grants and contracts with
Federal, State, and local agencies, research institutions,
and industrial organizations.
Inquiries pertaining to the Water Pollution Control Research
Reports should be directed to the Head, Publications Branch,
Research Information Division, R&M, Environmental Protection
Agency, Washington, B.C. 20460.
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Dry Caustic Peeling of Tree Fruit
for Liquid Waste Reduction
By
National Canners Association
Western Research Laboratory
Berkeley, California 94710
for the
ENVIRONMENTAL PROTECTION AGENCY
Project #12060 FQE
December 1970
For sale by the Superintendent ol Documents, U.S. Government Printing Office
Washington, D.C., 20402 - Price 60 cents
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EPA Review Notice
This report has been reviewed by the Environmental
Protection Agency and approved for publication. Approval
does not signify that the contents necessarily reflect
the views and policies of the Environmental Protection
Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendations for
use.
ii
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ABSTRACT
The peeling of apricots, peaches and pears was studied with a peel re-
moval unit consisting of a series of spindles holding rotating rubber
disks. The peel was removed by a wiping action of the flexible rubber
disks on fruit wetted with hot sodium hydroxide solutions. The quality
of fruit peeled with the experimental unit was comparable to fruit
peeled by conventional chemical peeling; peeling losses were about
the same for the experimental unit and the commercial units.
The most striking difference between the experimental unit and com-
mercial units was in fresh water requirements and waste water volume
and strength. The peeling of cling peach halves required one-fifteenth
of the fresh rinse water volume of a conventional commercial peeler.
The wastewater generated by the experimental peeling of peaches had
about one-third of the chemical oxygen demand and suspended solid
content of the wastewater from the commercial peeler.
The experimental peel removal unit accomplishes a diversion of poten-
tially water polluting organic material from the wastewater to a peel
sludge. The peel sludge has properties which allow it to be handled
readily and disposed of as a solid residual.
This report was submitted in fulfillment of Project Number 1Z060FQE
under the partial sponsorship of the Water Quality Office, Environ-
mental Protection Agency.
111
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CONTENTS
Section Page
1 Conclusions 1
11 Recommendations 3
111 Introduction 5
IV Design Phase 9
V Construction Phase 11
VI Operational and Evaluation Phase 21
Vll Discussion 31
Vlll Acknowledgements 35
IX References 37
X Patents and Publications 39
XI Appendices 41
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FIGURES
No. Page
1 Prototype Fruit Peel Removal Unit 8
2 Close-Up View of Prototype Peel Removal
Unit 8
3 Fabricated Neoprene Rubber Disks 10
4 Peel Removal Unit, General Concept 10
5 Peeler Tray 11
6 Standard Gear Arrangement Showing Idler
Support Bar 12
7 Peeler Spindle Bearing Supports and Knee
Action Component 12
8 Disk Cover 13
9 Disk Scraper Inserted in Spindle Housing 14
10 Spindle Configurations 1 Through 4 15
11 Spindle Configurations 5 Through 8 16
12 Spindle Configurations 9 and 10 17
13 Schematic Drawing of Experimental Peach
Peeling 22
14 Schematic Drawing of Commercial Pear
Peeling 26
15 Schematic Drawing of Commercial Peach
Peeling 29
Vll
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TABLES
No. Page
1 Sequence of Spindle Configurations Used 18
for the Shaft Positions of Peel Removal
Unit
2 Results of Peach Halve Peeling Using 23
Rotating Rubber Disk Peel Removal Unit
3 Rinse Water Volume and Wastewater 24
Characteristics for Peach Halve Peeling
4 Water Volume Requirements and Wastewater 25
Characteristics for Commercial Cling Peach
Peeler
5 Crossectional Size Distribution of Pears 27
6 Firmness Testing of Pears 27
7 Sodium Hydroxide and Sodium Carbonate 28
Content of Pears Peeling Sludge
8 Comparison of Wastewater Characteristics for 32
Commercial and Experimental Peeling of
Cling Peach Halves
9 Results of Whole Bartlett Pear Peeling Using
Rotating Rubber Disk Peel Removal Unit 33
10 Peeling Losses for Tree Fruit 33
IX
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SECTION I
CONCLUSIONS
1. Peel softened by hot solutions of sodium hydroxide can be re-
moved efficiently by a series of rotating rubber disks from
apricots, peaches and pears.
2. The quality of peeled fruit prepared with the experimental unit
compares favorably with that of fruit peeled by conventional
commercial equipment.
3. Peeling losses for apricots, peaches and pears peeled by the
experimental unit are the same or slightly lower than those
resulting from commercial peeling of these fruits.
4. The volume of fresh water needed and the volume of waste-
water generated during experimental peeling of peach halves
was one-fifteenth of that of conventional commercial peeling.
5. The chemical oxygen demand and suspended solids content of
wastewater generated during experimental peeling of peach
halves is one-third of that of wastewater generated during con-
ventional commercial peeling.
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SECTION II
RECOMMENDATIONS
1. A demonstration scale peel removal unit (at least 10 ton/hr
capacity) should be constructed and operated in a commercial
fruit cannery to confirm and extend the results obtained from
operation of the 2 ton/hr unit.
2. Quality of final products prepared using the new peeling proced-
ure should be carefully evaluated by experienced inspectors
from industry and/or government.
3. Data on the rinse water volume required and wastewater gener-
ated during the peeling of pears and apricots should be obtained
using appropriate spray rinsing rather than simple immersion.
-3-
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SECTION III
INTRODUCTION
The preparation of tree fruits for preservation by freezing, dehydration
or canning employs a complex technology and sophisticated equipment.
The equipment and technology used in peeling tree fruit was developed
over the years with high rates of production, adequate sanitation and
optimum product quality as the principal design criteria. Until quite
recently, only minor attention was paid to the effects of the peeling
technology on the quantities and strengths of liquid wastes generated
in the process as by-products.
Past and current research (and other water pullution abatement
efforts) have, for the most part, emphasized "end of the pipe"
handling and treatment of food processing wastewaters. Much time
and large sums of money have been spent in testing and adapting
methods of treatment and disposal for these liquid wastes. Rarely
have any of the treatment systems used proven completely satisfac-
tory. Variations in the nature and volume of food processing liquid
wastes and inconsistent ability of different treatment systems to
handle these variants have caused many problems.
In-plant surveys made by research teams from the National Canners
Association have shown that high percentages of the total dissolved
organic solids in the composite wastewater originate in unit operations
such as peeling and blanching of raw commodities.
The peeling of apples, apricots and peaches produces 0.47, 0. 16,
O
and 0. 42 Ibs of B. O. D. per case of finished product, respectively.
For peaches, the peeling operation, including the rinsing after peel
removal, comprises 40. 5 percent of the total Ib of B. O. D. discharged
in the composite liquid waste from a cannery.
Often individual waste streams representing no more than five percent
of the total wastewater volume may contain 50 to 70 percent of the
total discharge of dissolved solids. Generally, the concentrated
waste streams are diluted by converging streams of comparatively
clean waters.
-5-
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It has become increasingly apparent in recent years that it is more
efficient to abate water pollution by changing processing technology
rather than by expanding treatment facilities. There are many
potential ways in which foods can be prepared for preservation
which will drastically reduce the volume and strength of wastewater
generated. An engineering development of the past three years in
radical modification of conventional food processing technology to
reduce liquid waste volume and strength is the "dry caustic" peeling
of potatoes. This process resulted from work at the Engineering
and Development Division, Agricultural Research Service, United
States Department of Agriculture, Albany, California, » -* and
Magnuson Engineering, Inc., San Jose, California.
The new process, now known as the USDA-Magnuson Infrared Anti-
Pollution Peeling Process, uses infrared energy at 1650°F to condi-
tion the surfaces of potatoes treated with strong sodium hydroxide
solutions. The peel can then be removed mechanically by soft
rubber scrubbing rolls rather than by water as is done in conventional
caustic peeling. A final spray rinse using low volumes of water
removes residual peel fragments and excess sodium hydroxide. The
effluent from the peeled potato rinsing may be combined with the
solid material generated to produce a thick, yet pumpable, sludge.
Direct comparison of the new process with conventional peeling has
demonstrated that the strength of the waste discharged has been
reduced by 40 percent. ' This result means that the capacity of
secondary treatment plants required to condition the effluent to a
satisfactory B. O. D. and suspended solids level** could be greatly
reduced with substantial overall savings in equipment and operating
costs. In situations where the potato processing effluent is treated
in a municipal system in combination with domestic sewage, the
resulting lower loadings allow for population growth in the area
served by the plant without requiring costly expansion.
The tonnage of potatoes processed each year is substantial and reduc-
tion of water pollution caused by this commodity received first atten-
tion by scientists and engineers. However, there are other food
commodities which are chemically peeled, and extension of the "dry
caustic" peeling process to these would provide the potential for
-6-
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significant water pollution abatement. For example, the weight
of tree fruit peeled by chemical methods was about 1, 000, 000 tons
in 1968. Each ton of apricots, peaches or pears processed, produced,
on the average, about 12 pounds of B. O. D. and 9 pounds of suspended
solids in the rinse water used in conventional chemical peeling. If
only a 40 percent reduction in strength of wastes from plants peeling
these fruits were achieved by "dry caustic" peeling, some 5,000,000
pounds of B. O. D. and 3,700,000 pounds of suspended solids would
be removed from the effluent waste streams each year.
This report describes results from a collaborative project between
the USDA and NCA to extend the water pollutional abatement potential
of "dry caustic" peeling of potatoes to apricot, peach, and pear peel-
ing.
The utility of the new peeling process for these three tree fruits was
shown to be promising in exploratory studies. '' The potential
for substantial reduction of liquid waste volume and strength by the
new method of peeling tree fruit was recognized by the EPA and funds
were made available to support an investigation.
-7-
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Figure 1
PROTOTYPE FRUIT PEEL REMOVAL UNIT
Figure 2
CLOSE UP VIEW OF PROTOTYPE PEEL REMOVAL UNIT
-8-
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SECTION IV
DESIGN PHASE
The original concept, using rubber disks in the removal of peel from
tree fruit treated with sodium hydroxide solution derived from the
USDA at Albany, California. They worked out a prototype model, as
shown in Figures 1 and 2. The unit consisted of an elevated series
of rotating rubber disks, driven by a chain and sprocket arrangement.
The rotating disks wipe the fruit clean of peel material as the product
is conveyed. A detailed description of this unit has been published.
The design of the scaled up peel removal section used in this project
was provided by the USDA at Albany, California. The design of the
fabricated neoprene rubber disks used in the unit for peach and pear
peeling is shown in Figure 3.
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Figure 3
FABRICATED NEOPRENE RUBBER DISKS
Figure 4
PEEL REMOVAL UNIT, GENERAL CONCEPT
-10-
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SECTION V
CONSTRUCTION PHASE
Construction of the peel removal unit, as shown in a general concepts
drawing in Figure 4, was accomplished by the USDA in Albany, Cali-
fornia. An employee of the NCA was assigned as a collaborator in
assisting USDA employees in the construction.
\
The shaft for each spindle of rubber disks, spacers, and stiffeners
was cut from 1/2 in. stainless steel rod. One-half, 1/4 and 1/8 in.
spacers were cut from clear plastic sheets; all spacers were 1-5/8
in. in diameter.
Nineteen slots for one five-foot section and 20 slots for the second
section were milled from 4 in. by 1/4 in. x 5 ft aluminum sheets to
accommodate the spindle shafts. A similar number of matched under-
size slots were milled from 1-3/4 in. by 1/2 in. by 5 ft nylon sheet.
One-eighth in. by 2 in. steel angles were cut, drilled and tapped to
form the support structure; this was assembled using 3/8 in. by
5/12 in. round head screws. The peel catching tray was fabricated
from sheet metal (See Figure 5. )
The idler gear support bar was constructed from 1 in. by 1/2 in. by
5 ft aluminum bar stock. Holes were drilled and tapped in the bar as
Figure 5
PEELER TRAY
-11-
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Figure 6.
STANDARD GEAR ARRANGEMENT
SHOWING IDLER SUPPORT BAR
shown in Figure 6. Spindles were held in position by a clamped 1/4
in. by 3/4 in. by 5 ft aluminum bar. Figure 7 shows the standard
gear arrangement of #18 sprocket gears with #8 sprocket idler gears.
A differential gear arrangement used alternate #16 and f 20 gears in
place of the #18 gears of the standard arrangement.
f
(D S&. CD
^T|
•-#*
Figure 7
PEELER SPINDLE BEARING SUPPORTS AND
KNEE ACTION COMPONENT
-12-
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The disk cover was fabricated from #20 gauge stainless steel sheet
as shown in Figure 8. A 1/8 in. clear plastic cover was loosely
fitted on each metal disk cover section; these were fitted with two
wooden knobs to facilitate removal.
Two spindle carriers similar to those fabricated from aluminum
were constructed from 3/4 in. exterior plywood.
WELP
Figure 8
DISK COVER
The starters and variable drive 3/4 H. P. motors were positioned as
shown in Figure 4. The starters were first attached to brackets and
then positioned to the welded rectangular frame support. The motor -
bases were connected to 3/4 in. exterior plywood and then clamped to
the steel frame support. V belts and pulley were connected and gal-
vanized steel belt guards constructed and attached to the units.
In the initial trial runs with peaches, a correction was needed to
prevent the peach halves from spinning in place along the sides of the
disk cover; 1/2 in. half-round wood stock was cemented to the cover
as indicated by the insert in Figure 8.
Another modification, the use of wiper bars in the second tray section,
Figure 9, was inserted to remove a large amount of tacky material
from pears before they came in contact with the fresh water.
-13-
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Figure 9
DISK SCRAPER INSERTED IN SPINDLE HOUSING
The custom fabricated neoprene rubber disks were not delivered
until after the apricot peeling had started. The disks used for the
apricot peeling experiments were fabricated and assembled by hand.
Four and 1/4 in. diameter by 1/32 in. thick disks were cut from a
roll of Shore A, durometer 50 *•"• food grade rubber sheet. One-
half in. diameter holes were punched out of both the rubber disks
and 2-3/4 in. diameter Mason jar lids used as stiffeners. The
spindles were assembled on the stainless shafts using the plastic
spacers.
Six different sequences of spindles were used for peeling experiments
on apricots, peaches and pears. Three of the sequences used 39 iden-
tical spindles and three of the sequences used a combination of sever-
al different spindle configurations. The ten different combinations
of rubber disks, spacers and stiffeners used for spindle configura-
tions have been assigned numbers and are shown diagramatieally in
Figures 10 through 12 as configurations 1 through 10.
The sequences of individual spindle configuration in the 39 slots
provided for the spindle shafts are designated by the letters A through
F. The spindle sequence A consisted of 39 identical spindle config-
urations designated by number 1. The spindle sequence F consisted
of 39 identical spindle configurations designated as number 2. The
spindle configuration D consisted of 39 identical spindle configurations
-14-
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Figure 10. SPINDLE CONFIGURATIONS 1 THROUGH 4
-15-
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1
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8
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Figure 11. SPINDLE CONFIGURATIONS 5 THROUGH 8
-16-
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'77'
10
Figure 12. SPINDLE CONFIGURATIONS 9 AND 10
-n-
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TABLE 1
SEQUENCE OF SPINDLE
CONFIGURATIONS USED FOR
THE SHAFT POSITIONS OF
PEEL REMOVAL UNIT
Shaft
Position
Number
Spindle
C onf igur ation *
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
6
7
8
5
6
5
8
7
6
5
6
7
8
5
6
5
8
7
6
5
6
7
8
5
6
5
8
7
6
5
SEQUENCE
C
Spindle
Configuration*
10
7
8
9
10
9
8
7
10
9
10
7
8
9
10
9
8
7
10
9
10
7
8
9
10
9
8
7
10
9
Spindle
Configuration*
3
3
3
4
3
3
3
4
3
3
3
4
3
3
3
4
3
3
3
4
3
3
3
4
3
3
3
4
3
3
-18-
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TABLE 1 (Cont'd. )
SEQUENCE
Shaft B C E
Position Spindle Spindle Spindle
Number Configuration * Configuration * Configuration *
31 6 10 3
32 7 7 4
33 8 8 3
34 6 10 3
35 5 9 3
36 6 10 4
37 8 8 3
38 7 7 3
39 6 10 3
*
See Figures 8 through 10
designated by number 4. The spindle sequences using a combination
of different spindle configurations to fill the 39 shaft slots were desig-
nated B, C, and E and are identified in Table I. The shaft position
numbers start with 1 at the feed end.
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SECTION VI
OPERATIONAL AND EVALUATION PHASE
Peeling of Peach Halves
The major effort in this study of peeling certain tree fruit was concen-
trated on evaluation of peel removal from peach halves. The bulk of
peaches harvested for processing are peeled before preservation.
The work on peach peeling was accomplished in a commercial cannery
in Richmond, California. This was done for several reasons. The
cannery location provided adequate supplies of peaches of commercial
grade, pitted with conventional equipment, and potentially returnable
to production. Experienced plant personnel were available to provide
estimates of the quality of peeled peach halves. Also, commercial
scale equipment was available for use in applying sodium hydroxide
solution.
The equipment used is shown schematically in Figure 13. The experi-
mental peeling of peach halves was conducted in the following manner.
Peach halves from the Filper pitting machines were placed in 5 gal.,
stainless steel pans and the peach weight was measured. The peach
halves were dumped into an elevator which delivered them to a cup
down shaker. The oriented peaches were conveyed through a com-
mercial sodium hydroxide solution applicator. The coated peach halves
were drained of excess sodium hydroxide solution and delivered by a
sheet metal trough to the peel removal unit. The peach halves moved
through the unit and dropped down a chute at the exit end into a surge
tank filled with water. The submerged peaches were removed from
the surge tank by an elevator with a 45 degree pitch into tared recei-
vers. One to three spray heads provided a rinsing of the peaches in
the elevator before delivery into the tared containers. The fresh water
introduced at the spray heads drained into the surge tank as make-up
water. The surge tank was fitted with an overflow pipe which emptied
into containers for volume measurement and wastewater sample col-
lection. The peeled peaches were examined for peeling quality by
visual inspection, weighed, and returned to the Filper pitter discharge
flume to be used in commercial production.
A large number of preliminary experiments of short duration were used
to determine good operating conditions. The results of these experi-
ments are tabulated in Table A-l in the Appendix. The major variables
-21-
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Cup Down
Shaker
— 1>--
Lye Applicator
•>-
Peelremoval Unit
o
Fresh Water
V <>
}4 .•i'
H_J^
Overflow Collection Point
Figure 13
SCHEMATIC DRAWING OF EXPERIMENTAL PEACH PEELING
-22-
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studied during the preliminary runs were: sodium hydroxide concen-
tration, sodium hydroxide bath temperature, residence time of peach
halves in sodium hydroxide applicator, draining time for coated
peach halves, peeling disk type and spacing, feed rate, peel removal
section slope and disk turning speed.
Table 2 summarizes the results of longer duration peeling experi-
ments with peach halves using the best operating conditions developed
during preliminary, short duration experiments. Peeling losses were
determined in 3 minute runs using conditions identical to those used
in the runs of approximately one hour duration.
TABLE 2
RESULTS OF PEACH HALVE PEELING USING
ROTATING RUBBER DISK PEEL REMOVAL UNIT
Run
No.
8-21-2*
8-21-1A
8-21-2**
8-21-2A
Feed
Rate
Ib/hr
4119
4286
4647
4996
NaOH
Strength,
Percent
1.5
1.5
Peel
Removal
Unit Slope,
in. /10 ft
15
9
Peeled
Fruit
Quality
Good
Fair
Peeling
Loss,
Percent
N. M. ***
5.1
N. M.
4.7
* Duration of run was 61 minutes
** Duration of run was 56. 3 minutes
*** N.M. = Not measured
Table 3 tabulates the water volume used in rinsing peeled peach halves
and analytical values measured on wastewater samples.
For comparative purposes, wastewater samples were collected from
the commercial peach half peeling unit (see Figure 15) and analyzed.
The results are tabulated in Table 4.
The wastewater overflow from the surge tank was collected in a 55 gal.
drain. A one gal. sample was removed from the drain at 15 min inter-
vals after mixing the contents of the drain. A composite sample was
prepared by mixing 0. 5 gal. portions of each of the 15 min grab
samples.
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TABLE 3
RINSE WATER VOLUME AND WASTEWATER
CHARACTERISTICS FOR PEACH HALVE PEELING
Rinse Water
Run Rate
No. gal. /hr gal. /ton
8-21-1 75 36
8-21-2 77 33
Wastewater Quality
Wastewater
Sample*
15 G
30 G
45 G
60 G
61 C
15 G
30 G
45 G
56 G
56 C
C.O. D.
ppm
30,000
60,000
63,300
97,400
75,700
30,000
53,900
69, 100
63,300
50, 200
,ss,
ppm
7,200
12,400
7,300
12,480
10,850
7,200
10, 150
12,600
18,400
9,750
PH
9-4
9.7
9.8
9.7
9.7
9.4
9.4
9.6
9.7
9.5
* Time in minutes, G=grab, C=composite.
Peeling of Whole Pears
The peeling of whole Bartlett pears was conducted at two locations.
A limited number of short duration peeling experiments with pears
was run in the commercial cannery with the sodium hydroxide appli-
cating equipment used for the peach halve peeling. It was too difficult
and potentially dangerous to personnel to obtain sodium hydroxide
treated pears from the commercial equipment in the cannery. The
commercial peeler has a pressurized section following the sodium
hydroxide application zone. The pears are conveyed through an air-
lock from the pressure section to a lowerator which delivers the
partially peeled pears to a flume. Removing pears from the lowerator
was judged by the Project Director to be hazardous due to the restricted
clearance between lowerator flights and sidewalls which could catch and
break hands and arms. Beyond this consideration of safety, the treated
pears at this point had lost considerable portions of their peel and were
not the best material for peeling experiments.
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TABLE 4
WATER VOLUME REQUIREMENTS AND WASTEWATER
CHARACTERISTICS FOR COMMERCIAL CLING PEACH PEELER
Fresh Water Wastewater
Wastewater Measurements
Input
gal. /ton
600
540
580
525
460
515
470
Ave."527"
Sampling
Point*
1
2
1
2
1
2
1
2
1
2
1
2
1
2
_
Volume,
gal. /ton
400
200
360
180
387 ,
193
350
175
307
153
347
168
313
157
527
C.O. D. ,
ppm
5,300
19, 600
5,600
16,700
5, 100
6,600
5,900
23,000
5, 100
30,000
5, 100
25, 100
4,900
31,700
13,550
SS,
ppm
1230
2430
1060
1280
780
1950
1150
3080
1320
5640
1540
5640
910
5240
2375
pH
11.3
10. 2
11.6
10.3
11. 1
10. 1
11. 1
10. 1
11.0
10.7
11.2
10.7
11.3
10.7
10. 8
* See Figure 15
Results obtained for pear peeling at the cannery are tabulated in Table A-2
in the Appendix. More extensive experimental peeling of pears was
conducted at the USDA Laboratory in Albany, California. A screw
drive sodium hydroxide applicator unit was used for these experiments
with which adequate residence times could be achieved. The results
of these peeling experiments are tabulated in Table A-3.
The rinsewater volume used in Run 10-28-1 of Table A-3 was 89 gaLper
ton and the wastewater had a C.O. D. of 10, 500 ppm, a SS content
of 2550 ppm and a pH of 10. 6, The rinse water for .the pear peeling
consisted of two tanks each containing 20 gal. of water. Analysis was
made on a composite sample of water from the two rinse tanks.
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For comparison purposes, wastewater from a commercial pear peel-
ing unit (see Figure 14) was collected and analyzed. The pH was
10. 5, the C. O.D. was 5040 ppm. The rinse water volume was esti-
mated as about 200 gal. /ton of fresh pears.
Fresh Water
A"AA^\
Bin
Conveyer
Lye Dipper &
Steam Valve
Rotary
Washer
Overflow Collection Point
-j Flume
J--0-
Core Equipment
->-.
Sorting &
Trimming
Figure 14
SCHEMATIC DRAWING OF COMMERCIAL PEAR PEELING
Three facets of pear peeling were examined during the project. The
sizing and firmness of pears are important considerations in their
peeling performance by the methods used at the present time. Measure-
ments of size distribution of pears peeled successfully were made to
provide industry specialists with information which they could corre-
late with their experience using conventional peeling equipment. The
size distribution of a typical lot of pears is tabulated in Table 5.
Another important factor in pear peeling by conventional methods is
the firmness of the pears. Firmness is measured by reading the
force necessary to insert a rod into a pear to a standard depth, at
a point where the skin has been removed with a knife. The results of
the penetration testing of a lot of 33 pears typical of those used in the
experimental peeling are tabulated in Table 0.
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TABLE 5
CROSSECTIONAL SIZE DISTRIBUTION OF PEARS
Size, Percent Size, Percent
In. Present In. Present
in Lot in Lot
2 3/16 3 2 11/16 6
I 1/4 10 2 3/4 3
2 5/16 10 2 13/16 1
2 3/8 16 2 7/8 0
2 7/16 15 2 15/16 0
2 1/2 21 3 1_
2 9/16 4
2 5/8 8 Total 100
The results of the firmness testing indicated that the pears used were
in the normal range for successful commercial peeling.
TABLE 6
FIRMNESS TESTING OF PEARS
Penetration Number of Pears Distribution
Force, Ib Penetrated Percent
2-
3-
4-
5-
6-
7-
8-
9-
10-
2.9
3.9
4.9
5.9
6.9
7.9
8.9
9.9
10,9
Totals
4
4
6
6
5
3
3
1
1
33
12. 1
12. 1
18. 2
18.2
15.2
9.1
9.1
3.0
3.0
100. 0
The peel material which is wiped from the fruit as a sludge drops to the
bottom of the peel removal unit tray and can drain (or can be scraped)
counterflow to the peeled fruit. The peeling sludge can be handled
as a solid waste material. As disposal of solid waste in land
-27-
-------
more difficult in the future due to lack of appropriate sites, the peel
sludge has potential as a component of animal feed. A limited amount
of information on the composition of the peeling sludge was obtained
during the project. The weight of the sludge is approximately repre-
sented by the peeling loss. No direct measure of peeling sludge
weight was possible, due to the disposition of part of this material
on the walls of the equipment. It was impractical to determine the
weight of deposited peel sludge as well as to account for losses of
material discharged by centrifugal force from the peeling disks.
Values for the content of sodium hydroxide and sodium carbonate in
the pear peeling sludge are tabulated in Table 7.
TABLE 7
SODIUM HYDROXIDE AND SODIUM CARBONATE
CONTENT OF PEAR PEELING SLUDGE
Sampling
Date
9-29-1
9-29-2
9-30-1
9-30-2
10- 1-1
10- 1-2
10- 5-1
10- 6-1
10-13-1
10-13-2
10-14-4
10-14-5
10-28-1
Solids,
Percent
27.3
27.0
23.6
20.8
21. 6
18. 4
22. 4
22.2
28. 5
24.0
24.9
20. 2
23.5
NaOH
Wet Wt.
Percent
3.8
2. 1
2.0
0.6
1.7
0.3
1.7
1. 1
3.8
1.88
2.9
1.2
2.2
Na CO
Wet Wt.
Percent
2.6
2.4
1.8
1.4
1.6
0.9
1.3
1.4
2. 5
2.3
1.8
1. 2
2.3
Average 23.4 1.9 1.8
Peeling of Whole Apricots
A number of short term peeling experiments were completed at the
USDA Laboratory in Albany, California using Blenheim and Tilton
-28-
-------
apricots obtained from local canneries.
Due to the delay in delivery of vulcanized rubber peeling disks, time
allocated to construction of a spray rinsing section was diverted to
assembling peeling disks by hand. The rinsing of peeled apricots was
by simple submersion in fresh water contained in a tank. The waste-
water generated was considered as not representative of wastewater
from a spray rinsing unit. Therefore no wastewater samples from
apricot peeling experiments were collected.
The results obtained during the peeling of Blenheim apricots are tab-
ulated in Table A - 4 in the Appendix. The results obtained during the
peeling of Tilton apricots are tabulated in Table A - 5 in the Appendix.
Fresh Water
Halved
Fruit"
Cup Down
Shaker
/^7v^^\
Lye Peeler
j Rinse
i Section
i
Water Dip
0
Water
X^k/TA
Kotary
Washer
->-
Steam
Blancher
--£>
Sorting & Trimming
i
Figure 15
SCHEMATIC DRAWING OF COMMERCIAL PEACH PEELING
-29-
-------
SECTION VII
DISCUSSION
The operation of the peel removal equipment demonstrated on a sub-
stantial scale (one to two tons of raw fruit per hour) that peach halves
can be peeled efficiently by the low water volume peeling process.
The quality of the peeled fruit was as good or better than that of fruit
from commercial peeling units as judged by experienced industry
people.
The peeling losses measured for the experimental unit were slightly
lower than the peeling losses determined by measurement of commer-
cial peeling. The difference in peeling losses was not large enough
to provide an economic incentive based on higher product yield as is
the case for the new potato peeling process.
The major advantage for the new method for peach peeling results
from the lower water volume requirement and the reduction in the
strength of wastewater generated.
A detailed study of fresh water requirements for rinsing and charac-
terization of wastewater •was made for peach half peeling only for the
reason described in Section VI. The results of comparing commercial
peeling and experimental peeling of peaches showed that the new peel
removal method required only one-fifteenth of the fresh water used in
conventional commercial peeling. The wastewater produced in the
new peeling method was correspondingly reduced due to the use of
mechanical abrasion for peel removal rather than water pressure.
The strength of the wastewater from the experimental peeling of
peaches was higher per unit volume than the wastewater from conven-
tional chemical peeling. However, the much lower volume of waste-
water produced per ton of fruit by the use of mechanical peel removal
makes the Ib of C.O.D. (and of B. O*D., although this was not measured
directly) generated about one-third that of the conventional-chemical
peeling operation.
The numbers used to calculate values tabulated in Table 4 are derived
from Tables 2 and A-l. The average of the two wastewater volumes
and the average C.O.Q, andSSof the two composite samples were used
to calculate the values for the experimental peeler. The average
values from Table 2 were used to calculate values for commercial
-31-
-------
peeling. The contribution of the effluent from the blancher wastewater
shown in Figure 15 to volume, C.O. D, and SS was estimated as less than
0. 5 percent of the total and was not corrected for in the calculation.
A comparison of water usage, wastewater generation, and wastewater
characteristics in commercial and experimental peeling of peach
halves is tabulated in Table 8.
TABLE 8
COMPARISON OF
WASTEWATER CHARACTERISTICS FOR COMMERCIAL
AND EXPERIMENTAL PEELING OF CLING PEACH HALVES
WASTEWATER DISCHARGED
(PER TON PITTED PEACHES)
Peeler
Commercial
Experimental
vJLUAXlC |
gal.
527
34.5
'ib!
59.
18.
-'• »
5
1
V^l—/ J
lb.
10. 4
3.0
The results of the longer-duration pear peeling experiments are
summarized in Table 9.
Pre -Treatment of Unpeeled Pears^
Several treatments of unpeeled pears before the application of sodium
hydroxide solution were investigated to improve peeling efficiency and
to reduce peeling losses. The results of these experiments are
tabulated in Table A-3.
Dewaxing of whole pears by immersion in 2-propanol held at 165 F
reduced the peeling loss, but the quality of the peeled fruit was poorer
due to residual peel fragments. It was concluded that hot or cold
dewaxing of pears did not improve peeling sufficiently to justify the
extra operation which would be required.
In the final pear peeling experiments it was found that placing l/4in.
stainless steel bars across the peeling tray parallel to the spindles
-32-
-------
TABLE 9
RESULTS OF WHOLE BARTLETT PEAR PEELING
USING ROTATING RUBBER DISK PEEL REMOVAL UNIT
Run
No.
10- 2
10-16
10-28
-
-1*
-4**
_!***
Feed
Rate,
Ib/hr
170
2050
1786
NaOH
Strength
Percent
15.2
17.3
17.0
Peeled
Fruit
Quality
Good to
Poor
Good
Good
Peeling
Loss,
Percent
11.3
20.4
15.8
*13. 0 minute run
**12. 3 minute run
###30. 1 minute run
wiped a substantial portion of softened flesh from the pear surfaces
(see Figure 9). This modification of the peeler unit had considerable
promise in diverting organic material coating peeled tree fruit from
the wastewater to the solid residue fraction.
Peeling Losses
Peeling losses were determined for the experimental peel removal
unit and a commercial unit for each of the three fruits studied. The
data collected during the peeling loss determinations is tabulated as
a range of values in Table 10,
TABLE 10
PEELING LOSSES FOR TREE FRUIT
Peeling Loss, Percent
Commodity
Apricots
Peaches
Pears
Experimental
3.7
5.3
11
- 8.3
- 7.5
- 20
Commercial
6.4 -
5.5 -
12 -
9.3
8.0
15
-33-
-------
Cost Estimate
The next logical step in demonstrating the utility of "dry caustic"
peeling of tree fruit would be a five-fold scale up to a unit with a
capacity of 10 tons of fruit per hour* The estimated capital cost of
the peel removal section of a ten ton per hour capacity unit is
$16,000.
-34-
-------
SECTION VIII
ACKNOWLEDGEMENTS
The collaboration in this project by Robert P. Graham, Mark R. Hart,
Gerald S. Williams, and others of the Engineering and Development
Laboratory, Western Utilization Research and Development Division,
Agriculture Research Service, United States Department of Agriculture,
was instrumental in developing the results reported.
The cooperation, interest and assistance of many individuals associa-
ted with the canning industry is gratefully acknowledged: we especially
thank E. L. Mitchell, W. L. Doucett, Ernest Johnson, R. Lovelace,
S. Platou, S. M. Anderson, R. Ketcher and L. K. Taber.
We appreciate the advice offered by Kenneth A. Dostal of WQO of EPA
during this project, and especially for help in preparation of the final
report.
The following project team from NCA made contributions to the collec-
tion of the data tabulated in this report:
Harry J. Maagdenberg Karen Kemper
Nabil L. Yacoub Carol Barnes
Valuable contributions to the reporting of the results of the project
were made by:
Edwin S. Doyle Stuart Judd William Murray
Walter A. Mercer Jack W. Rails
Grant Director Project Director
-35-
-------
SECTION IX
REFERENCES
1. Mercer, W.A.; Rose, W.W.; and Doyle, E.S.; Physical and
chemical characterization of the fresh water intake, separate
in-plant waste streams and composite waste flows originating
in a cannery processing peaches and tomatoes, Res. Report
No. D-1612. prepared for the State of California Water Quality
Control Board (March, 1965).
2. Anon., Preliminary data, National Canners Association,
Food Canning Wastes
3. Spicher, P.O.: Agardy, F. J. ; and Orlob, G. T. ; Proc. 22nd
Ind. Waste Conference, 1967, Part I, p. 44, Purdue University,
Lafayette, Indiana.
4. Graham, R. P. ; Huxsoll, C. C. ; Hart, M. R. ; Weaver, M. L. ; and
Morgan, A.I. Jr. ; Prevent Potato Peel Pollution, Food
Engineering, June, 1969.
5. Graham, R. P. ; Huxsoll, C.C.jHart, M.R. ; Weaver, M. L. ;
and Morgan, A.I., Jr. ; "Dry" Caustic Peeling of Potatoes,
Food Technology 23 (2), 61-66, (1969).
6. Smith, T. , Proceedings, National Symposium on Food Processing
Wastes, Portland, Oregon, April, 1970, pages 359-361.
7. Graham, P. P. , Ibid, pages 355-358.
8. Dostal, K.A., Secondary Treatment of Potato Processing Wastes,
Final Report, Report No. FR-7, U.S. Department of the Interior,
FWPCA, Pacific Northwest Water Laboratory, Corvallis, Oregon
97330, July, 1969.
9. Hart, M.R. ; Graham, R. P. ; Huxsoll, C. C. ; and Williams, G.S. ;
An Experimental Dry Caustic Peeler for Cling Peaches and Other
Fruit, 30th Annual Meeting, Institute of Food Technologists, San
Francisco, California, May 25, 1970, Paper No. 59.
-37-
-------
10. Hart, M.R. ; Graham, R. P. ; Huxsoll, C. C. ; and Williams,
G. S. ; An Experimental Dry Caustic Peeler for Cling Peaches
and other Fruit. J. Food Sci. 35 (6), 839-41 (1970).
11. Anon. ASTM Standard Methods, Part 9. page 1303. Tentative
Method for Indentation of Rubber by Means of a Durometer, 1958.
-38-
-------
SECTION X
PATENTS AND PUBLICATIONS
The USDA has applied for a Public Service Patent in the United States
of America for the process of removing fruit peel by the action of
rotating rubber disks.
The first public presentation of the results of the research done under
Grant 12060FQE was at the Second National Symposium on Food Waste
Treatment Research, Denver, Colorado, March 23-25, 1971.
-39-
-------
SECTION XI
APPENDICES
Table
No. Page
A - 1 Results of Rotating Disk Peel Removal From
Mixed Size Dixon Variety Cling Peach Halves 42
A - 2 Results of Rotating Disk Peel Removal from
Sized Whole Bartlett Pears 46
A - 3 Results of Rotating Disk Peel Removal from
Mixed Size Whole Bartlett Pears 47
A - 4 Results of Short Duration Peeling Experiments
on Mixed Size Blenheim Apricots 50
A - 5 Results of Short Duration Peeling Experiments
on Mixed Size Tilton Apricots 51
-41-
-------
TABLE A-l
RESULTS OF ROTATING DISK PEEL REMOVAL FROM
MIXED SIZE DIXON VARIETY CLING PEACH HALVES
Run No. *
8-10-1 8-10-2 8-11-1 8-11-2 8-11-3 8-12-1
NaOH Cone. , %
Disk Rotating Speed, RPM
Peeler Slope, in. /10ft
Feed, Ib
Feed Time, Sec
Feed Rate, Ib /hrs
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Spindle Sequence
Gears Used
Peeled Fruit Quality
Rinse Water, gal.
Rinse Water, gal. /ton
Wastewater pH
Waste-water C.O.D. , ppm
Wastewater SS, ppm
1.3
373
14
232.5
135
6200
220. 1
219.0
5.8
B
S
Fair
19.5
168
7.0
4814
830
1.4
373
14
221.2
225
3550
208.9
206.8
6.51
B
S
Fair
19.1
173
7.8
5222
1120
1.2
373
14
221. 1
N.A.
4422
N.A.
209.9
N.A.
B
S
Fair
29.2
264
N.R.
N.R.
N.R.
1.3
373
14
227.7
180
4460
212. 8
211. 4
5.03
B
S
Fair
N.R.
N.R.
N.R.
N.R.
N.R.
1.3
N.A.
N.A.
269.3
180
5380
N.A.
252.8
6.1
B
S
Fair
N.R.
N.R.
N.R.
N.R.
N.R.
1. 4**
N.A.
N.A.
226.9
180
4540
N.A.
N.A.
2.4
B
N.R.
N.A.
N.R.
N.R.
N.R.
N.R.
* NaOH Dip Time was 10 sec
** NaOH Treatment Only
at 200 F for all runs.
-42-
-------
TABLE A-l (Cont'd. )
Run No.
7-27-1 7-27-2 7-27-3 7-29-1 7-29-2 7-29-3
NaOH Cone. , %
Disk Rotating Speed, RPM
Peeler Slope, in. /10 ft
Feed, Ib
Feed Time, Sec
Feed Rate, Ib /hrs
Peeled Weight, Ibs
Washed Weight, Ib
Total Peel Loss, %
Spindle Sequence
Gears Used
Peeled Fruit Quality
Rinse Water, gaL
Rinse Water, gal. /ton
Wastewater pH
Wastewater C.O..D. , ppm
Wastewater SS, ppm
Run No.
NaOH Cone. , %
Disk Rotating Speed, RPM
Peeler Slope, in. /10 ft
Feed, Ib
Feed Time, Sec
Feed Rate, Ib /hrs
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Spindle Sequence
Gears Used
Peeled Fruit Quality
Rinse Water, gal.
* O
Rinse Water, gal. /ton
f ^^
Wastewater pH
x
Wastewater C. O. D. , ppm
Wastewater SS, ppm
2.7
373
16
89.2
90
3600
74.8
75.6
16. 1
D
S
Fair
N.R.
N.R.
N.R.
N.R.
N.R.
7-29-A
2.3
373
16
89.6
60
5380
84.7
83.9
6.5
D
S
Fair
20.7
461
2.4
373
16
89.8
90
3600
81.4
79.4
11.3
D
S
Fair
N.R.
N.R.
N.R.
N.R.
N.R.
7-29-5
4.8
143.3
150
3440
141.0
D
#*
2.5
373
16
89.6 ,
90
3600
80.6
79.8
10.9
D
S
Fair
N.R.
N.R.
N.R.
N.R.
N.R.
7-29-6
3.7
138.6
150
3330
138.6
D
***
Fair
2.8
373
16
146.5
150
3600
137.6
135.9
7.3
D
S
Fair
23.7
323
N.R.
N.R.
N.R.
7-29-7
4.0
373
16
145.0
150
3480
134.4
132.3
8.7
B
S
Fair
23.7
328
3.8
373
16
152.5
150
3600
142.7
139. 9
8.2
D
S
Fair
23.7
312
N.R.
N.R.
N.R.
8-7-1
2.3
373
16
232.9
270
3100
214.2
214.2
8.0
B
S
Fair
20.3
174
7.0
4,360
560
4.4
373
16
148.0
150
3600
137.0
135.2
8.5
D
S
Fair
23.7
320
N.R.
N.R.
N.R.
8-7-2
1.5
373
16
222.0
270
3100
205.5
7.4
B
S
Fair
20.3
183
6.4
7,930
1390
** NaOH Treatment only
*** Through reel washer
-43-
-------
Run No.
TABLE A-l (Cont'd. )
8-12-2 8-12-3 8-12-4 8-13-1 8-13-2 8-14-1
NaOH Cone. , %
Disk Rotating Speed, RPM
Peeler Slope, in. /10 ft
Feed, Ib
Feed Time, Sec
Feed Rate, Ib/hr
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Spindle Sequence
Gears Used
Peeled Fruit Quality
Rinse Water, gal.
Rinse Water, gal. /ton
Wastewater pH
Wastewater C.O. D. , ppm
Wastewater SS, ppm
Run No.
NaOH Cone. , %
Disk Rotating Speed, rpm
Peeler Slope, in. /10 ft
Feed, Ib
Feed Time, Sec
Feed Rate, Ib /hr
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Spindle Sequence
Gears Used
Peeled Fruit Quality
Rinse Water, gal.
Rinse Water, gal. /ton
Wastewater pH
Wastewater C.O. D., ppm
Wastewater SS, ppm
1.6
266
11
230.7
180
4620
221.9
219.3
4.9
B
S
Good
N.R.
N.R.
N.R.
N.R.
N.R.
8-14-2
1.7
373
6
217.3
90
8770
208. 1
204.8
6.0
B
S
Good
19.6
181
8.2
5222
1070
1.4
266
11
211.8
180
4240
203.6
201. 1
5.1
B
S
Fair-
Poor
N.R.
N.R.
N.R.
N.R.
N.R.
8-14-3
1.6
373
0
211.3
90
8450
203.9
200. 4
5.2
B
S
Good
19.6
186
7.5
4696
970
1.4
373
11
208.7
180
4180
197.5
298.2
5.4
B
S
Fair-
Poor
N.R.
N.R.
N.R.
N.R.
N.R.
8-18-1
1.6
373
15
229.7
180
4594
217.0
215.2
6.3
A
S
Good
20.9
182
7.7
4817
860
1.7
373
11
218.5
135
5800
207.2
206.9
5.3
B
S
Good
19.1
175
N.R.
N.R.
N.R.
8-18-2
1.7
373
15
219.4
135
5851
207. 5
205.3
6.4
A
S
Good
20. 4
186
7.9
6072
1150
1.8
373
6
224.0
135
5970
207.6
208.5
7.32
B
S
Good
19.1
171
N.R
N.R.
N.R.
8-19-1
1.4
373
15
227. 2
180
4544
215.4
215.7
5.2
A
S
Good
21.1
186
5.0
3413
840
1.7
373
6
219.1
135
5950
207.0
204.2
6.80
B
S
Good
19.1
175
7.1
4088
640
8-19-2
1.4
373
15
228.8
180
4576
218. 6
216.4
5.4
A
S
Good
21.1
185
4.9
6168
1630
-44-
-------
TABLE A-l (Cont'd. )
Run No.
8-19-3 8-20-3 8-21-1 8-21-1A 8-21-2 8-21-2A
NaOH Cone., %
Disk Rotating Speed, rpm
Peeler Slope, in. /10 ft
Feed, Ib
Feed Time, Sec
Feed Rate, Ib /hr
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Spindle Sequence
Gears Used
Peeled Fruit Quality
Rinse Water, gal.
Rinse Water, gal. /ton
Wastewater pH
Waste-water C.O.D, , ppm
Wastewater SS, ppm
Run No.
NaOH Cone. , %
Disk Rotating Speed, rpm
Peeler Slope, in. /10 ft
Feed, Ib
Feed Time, Sec
Feed Rate, Ib/hr
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Spindle Sequence
Gears Used
Peeled Fruit Quality
Rinse Water, gal.
Rinse Water, gal. /ton
Wastewater pH
x
Wastewater C.O. D. , ppm
Wastewater SS, ppm
1.4
373
15
225. 4
180
4508
212.3
212.8
5.8
B
S
Good
21. 1
187
5.5
5099
1220
8-31-6
1.5
373/322
15
212. 1
180
4240
203.0
177.0
6.7
C
S
Good
N.R.
N.R.
N.R.
N.R.
N.R.
1.4
373
15
215.7
180
4314
206.7
205.3
4.8
B
S
Good
N.R.
N.R.
N.R.
N.R.
N.R.
8-31-7
1.5
373/800
15
229.8
180
4590
218.3
217.3
5.4
C
S
Good
N.R.
N.R.
N.R.
N.R.
N.R.
1.5
373
15
241.8
3660
4119
N.R.
3974
N.R.
B
S
Good
75.7
35.6
9.7
75,700
10,850
9-1-1
2.5
369
15
5282
3600
5282
N.R.
4822
N.R.
C
S
Good
77.1
29.2
6.6
29,606
7140
1.5
373
15
214.3
180
4286
205.3
203.3
5. 1
B
S
Good
N.R.
N.R.
N.R.
N.R.
N.R.
9-1-1A
2.5
369
15
258.8
180
5170
243.3
236. 4
6.6
C
S
Good
N.R.
N.R.
N.R.
N.R.
N.R.
1.3
373
9
243. 6
3380
4647
N.R.
4154.8
N.R.
B
S
Fair
72. 2
33
9.5
50,200
9,750
9-2-1
2.0
369
15
5333
3600
5333
N.R.
4960. 1
N.R.
C
S
Good
68.3
25.6
6.0
6990
1640
1.3
373
9
219.8
180
4396
211.5
209.4
4.7
B
S
Fair
N.R.
N.R.
N.R.
N.R.
N.R.
9-2-1A
2.0
369
15
259.3
180
5180
242.4
241. 1,
7.0
C
S
Good
N.R.
N.R.
N.R.
N.R.
N.R.
-45-
-------
Run No. *
TABLE A-2
RESULTS OF ROTATING DISK
PEEL REMOVAL FROM SIZED WHOLE
BARTLETT PEARS
9-16-2 9-16-3 9-16-4 9-17-2 9-17-3
NaOH Cone., %
Peeler Slope, in. /10 ft
Feed, Ib
Feed Time, Sec
Feed Rate, Ib /hr
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Disk Spacing, in.
Gears Used
Rinse Water, gal.
Fruit Size
21. 1
15
39.7
153
1022
33.0
i
32. 6
7.1
1
S
5
21. 1
15
39.8
93
1795
31. 1
31.6
8.7
1
S
4
21. 12
15
36.9
83
2660
31.0
30.1
6.8
1
S
4
21.9
20
38.4
92
2513
30. 3
29.3
9.1
1
S
5
21.9
20
37.3
83
2685
27.0
25. 1
12.2
1
S
3
The disk rotating speed was 369 RPM, spindle sequence was E, and
o
the sodium hydroxide bath temperatures 178 F for all runs.
-46-
-------
Run No.
TABLE A-3
RESULTS OF ROTATING DISK PEEL REMOVAL FROM
MIXED SIZE WHOLE BARTLETT PEARS
9-30-2 9-30-3 10-1-1 10-1-2 10-1-3 10-1-4
NaOH Cone., %
o
NaOH Temp. F
Disk Rotating Speed, rpm
Feed, Ib
Feed Time, Sec
Feed Rate, Ib/hr
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Peeled Fruit Quality
Rinse Water, gal.
Rinse Water, gal jtan
Wastewater pH
Waste-water C.O.D. , ppm
Wastewater SS, ppm
o
2-Propanol (175 F)
Dip Time, Min
NaOH Dip Time, Sec
Run No.
NaOH Cone. , %
NaOH Temp. , F
Disk Rotating Speed, rpm
Feed, Ib
Feed Time, Sec
Feed Rate, Ib/hr
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Peeled Fruit Quality
Rinse Water, Gal.
Rinse Water, gal. /ton
Wastewater pH
Wastewater C, O. D. , ppm
Wastewater SS, ppm
2-Propanol (165°F)
Dip Time, Min
NaOH Dip Time, Min
16.7
165
369
77.1
120
2313
66.9
65.0
15.7
Good
16.0
415
9.0
6360
1500
0
145
10-5-6
16.2
165
369
77.0
145
2053
64.4
62.2
19.5
Good
16.0
416
9.0
6000
980
0
155
16.7
165
369
77.2
120
2316
62.9
61.25
20.7
Good
16.0
415
9.0
4960
1050
0
170
10-6-1
16.8
165
369
79.8
125
2335
66.3
64.4
19.3
Good
16.0
402
9.0
5476
1210
0
124
15.8
165
369
74.5
120
2235
56.2
54. 65
26.6
Good
16.0
430
7.0
6031
810
0
175
10-6-2
16.8
165
369
78.55
155
2417
69.3
66.95
14.8
Good
16.0
407
9-2
5555
1170
0
152
15.8
165
369
91.6
150
2198
71.6
69.45
24.2
Good
16.0
350
8.3
5436
1120
0
137
10-6-3
16.5
165
369
78.5
120
2355
68.4
65.8
16.2
Good
16.0
407
9.3
7063
1500
0
152
15.8
165
369
118.6
180
2372
111.2
107.6
9.3
Poor
16.0
270
9.6
10714
2600
0
127
10-6-4
16.5
165
369
78.35
128
2260
66.5
64.6
17.5
Good
16.0
409
8.9
5000
1150
0
152
15.8
165
369
73.0
120
2190
64.8
63.8
12. 6
Good
16.0
438
N.R.
N.R.
N.R.
0
145
10-6-5
16.5
165
369
76. 15
120
2284
63.1
61.4
19.4
Good
16.0
420
8. 6
4920
990
0
152
-47-
-------
TABLE A-3 (Cont'd.)
Run No.
10-6-6 10-12-1 10-12-2 10-12-3 10-12-4 10-12-5
NaOH Cone. , %
NaOH Temp. °F
Disk Rotating Speed, rpm
Feed, Ib
Feed Time, Sec
Feed Rate, Ib/hr
Peeled Weight, Ib
Washed Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Peeled Fruit Quality
Rinse Water, gal.
Rinse Water, gal. /ton
Wastewater pH
Wastewater C«O. D. , ppm
Wastewater SS, ppm
2-Propanol (165°F)
Dip Time, Min
NaOH Dip Time, Sec
Run No.
NaOH Cone. , %
NaOH Temp. °F
Disk Rotating Speed, rpm
Feed, Ib
Feed Time, Sec
Feed Rate, Ib/hr
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Peeled Fruit Quality
Rinse Water, gal.
Rinse Water, gal. /ton
Wastewater pH
Wastewater C.O.D. , ppm
Wastewater SS, ppm
2-Propanol (165°F)
Dip Time, Min
NaOH Dip Time, Sec
16.5
165
369
61.4
152
2231
60. 1
58.8
58.8
17.6
Good
16.0
450
8.5
3770
670
0
152
10-13-1
17.0
165
369
74. 15
145
1977
65.65
64.5
12.8
Good
16.0
432
10.0
2260
820
0
145
18.8
165
369
75.4
120
2262
68.95
67.45
67.45
10.5
Fair
16.0
431
10.42
3515
1070
1
135
10-13-2
16.8
165
369
74.4
120
2232
67.0
65.85
11.5
Good
16.0
431
10. 1
3385
880
1
80
18.8
165
369
75.85
120
2275
67.5
65.8
65.8
13.2
Fair
16.0
423
10.35
3180
840
0
160
10-13-3
16.8
165
369
74.3
120
2224
70.55
68.45
7.9
Poor
16.0
431
10.4
3720
1P70
**
80-130
18.2
165
369
77.2
120
2316
67.1
65.9
65.9
14.6
Good
16.0
415
10.02
2840
990
1
80
10-14-4
16.8
165
369
74.35
130
2124
.61.35
60.4
18.8
Good
16.0
431
9.55
2720
580
***
140
18.2
165
369
77.35
137
2142
66.9
65.3
65.3
15.6
Good
16.0
415
10. 1
2800
1200
0
140
10-14-5
16.8
165
369
75.6
170
1800
65.7
64.6
14.7
Good
16.0
423
9.75
2720
520
0
140
18.3
165
369
76.4
85
3667
67.95
66. 15
66. 15
13.4
Good
16.0
420
10.3
3100
1070
1
85
10-14-6
16.8
165
369
75.0
150
2368
66.3
65.25
13.0
Fair
16.0
426
9.80
2800
640
1
80
** Unpeeled pears dipped in 2-propanol at 62°F for 3 min and in second bath
for 5.3 min.
*** Unpeeled pears blanched in hot water for one minute.
-48-
-------
TABLE A-3
Run No.
10-15-1 10-15-2 10-15-4 10-16-4 10-28-1
NaOH Cone. , %
NaOH Temp. °F
Disk Rotating Speed, rpm
Feed Ib /
Feed Time, Sec
Feed Rate, Ib/hr
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Peeled Fruit Quality
Rinse Water, gal.
Rinse Water, gal. /ton
Wastewater pH
Waste-water C.O.D. , ppm
Wastewater SS, ppm
NaOH Dip Time, Sec
17.1
165
369
37.25
N.R.
N.R.
37. 1
N.R.
N.A.
N.R.
16.0
860
9.4
5480
1140
145
17.1
165
369
73.25
130
2187
61.60
61.50
16.04
Good
N.R.
N.R.
N.R.
N.R.
N.R.
145
17.2
165
369
76.05
147
2444
64. 10
63.4
16.6
Good
N.R.
N.R.
N.R.
N.R.
N.R.
140
17.3
165
369
211.3
738
2050
N.R.
168.9
20.4
Good
N.R.
N.R.
N.R.
N.R.
N.R.
115
17.0
165
369
895.5
1805
1786
N.R.
753.6
15.8
Good
40.0
89
10.58
10,530
2550
N.R.
-49-
-------
TABLE A-4
RESULTS OF SHORT DURATION
PEELING EXPERIMENTS ON MIXED
SIZE BLENHEIM APRICOTS
Run No. *
NaOH Cone. , %
NaOH Temp. °F
Disk Rotating Speed, rpm
Peeler Slope, in. /10 ft
Feed, Ib
Feed Time, Sec
Feed Rate, Ib/hr
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Gears Used
Peeled Fruit Quality
Rinse Water, gal.
Rinse Water, gal. /ton
NaOH Dip Time, Sec
6-18-6
25-30
210
266
-4
60
240
900
53.9
42.7
28.8
S •»+*»+
*Vf
N.R.
5.0
167
33
6-19-1
25-30
150
266
0
30
90
1200
27.6
25.0
16.7
S
N.R.
5.0
333
70
6-19-2
25-30
140
373
0
30
35
3080
29.3
27.5
8.3
S
N.R.
5.0
333
70
6-19-4
25-30
160
373
4
30
90
1200
26.3
25.3
15.6
D
N.R.
5.0
333
70
6-19-5
25-30
150
373
4
30
90
1200
27.3
26. 1
13.0
D***
N.R.
5.0
333
70
* Spindle sequence was A in all runs.
**S Standard
***D Differential
N.R. Not recorded
-50-
-------
TABLE A-5
RESULTS OF SHORT DURATION PEELING EXPERIMENTS ON
MIXED SIZE TILTON APRICOTS
Run No. *
6-22-2 6-22-3 6-23-1 6-23-2 6-23-3 6-26-1
NaOH Cone. , %
NaOH Temp. °F
Peeler Slope, in. /10 ft
Feed, Ib
Feed Time, Sec
Feed Rate, Ib/hr
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Disk Spacing, in.
Gears Used
Peeled Fruit Quality
Rinse Water, gal.
Rinse Water, gal. / ton
NaOH Dip Time, Sec
Run No.
NaOH Cone. , %
NaOH Temp. °F
Peeler Slope, in. /10 ft
Feed, Ib
Feed Time, Sec
Feed Rate, Ib/hr
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Disk Spacing, in.
Gears Used
Peeled Fruit Quality
Rinse Water, gal.
Rinse Water, gal. /ton
NaOH Dip Time, Sec
25-30
210
8
30
120
900
26.3
26.2
12.6
3/4
D **
Good
5.0
333
30
6-26-2
25-30
210
16
45
90
1800
41.7
40. 1
7.3
1/2
S
Good
5
222
35
25-30
210
8
30
120
900
26.7
26.2
12.6
3/4
D
Good
5.0
333
30
6-26-3
25-30
210
16
45
75
1920
41.2
40.0
8.4
1/2
1/2D
Good
5
238
32
25-30
210
15
45
120
1350
40.8
40.5
10.0
3/4
D
Good
5.0
222
22
6-26-4
25-30
210
16
45
65
2500
41.7
39.4
7.1
1/2
D
Good
5
222
30
25-30
210
15
60
60
3600
57.1
53.8
10.3
3/4
D
Good
5.0
167
22
6-30-1
12.4
210
16
60
115
1875
53.1
53.0
11.5
1/2
D
Good
a
166
30
25-30
210
15
30
40
2700
28.4
26.7
11.0
3/4
S***
Good
5.0
333
22
6-30-2
11.5
210
16
60
120
1800
54.1
53. 2
9. 8
1/2
D
Fair
5
167
30
25-30
210
8
45
40
2330
41.3
40.7
9.5
1/2
S
Good
5.0
222
30
7-1-1
10.8
140
16
60
120
1800
56.6
N.R.
N.R.
1/2
D
Fair
5
167
66
-51-
-------
TABLE A-5 (Cont'd. )
Run No.
1-1-2 7-1-3 7-1-4 7-1-5 7-7-1
7-7-2
NaOH Cone. , %
NaOH Temp. °F
Peeler Slope, in. /10 ft
Feed, Ib
Feed Time, Sec
Feed Rate, Ib /hr
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Disk Configuration
Disk Spacing, in.
Gears Used
Peeled Fruit Quality
Rinse Water, gal.
Rinse Water, gal. /ton
NaOH Dip Time, Sec
Run No.
NaOH Cone. , %
NaOH Temp. F
Peeler Slope, in. /10 ft
Feed, Ib
Feed Time, Sec
Feed Rate, Ib./ hr
Peeled Weight, Ib
Washed Weight, Ib
Total Peel Loss, %
Disk Configuration
Disk Spacing, in.
Gears Used
Peeled Fruit Quality
Rinse Water, gal.
Rinse Water, gal. /ton
NaOH Dip Time, Sec
* The disk rotating
sequence was A
**S Standard
***D Differential
N.R. Not recorded
11.1
140
16
60
120
1800
54.5
54.3
9.5
0
1/2
D
Fair
5
167
72
7-9-1
9.8
210
16
60
68
3200
55.9
N.R.
6.8
0
3/4
D
Good
5
166
24
speed was
10.8
210
16
60
120
1800
55.2
N.R
8. 0
0
1/2
D
Fair
5
167
27
7-9-2
10.0
210
16
60
68
3200
56. 2
57.0
6.3
0
3/4
D
Good
5
166
27
373 RPM
-52
10-11
210
16
60
120
1700
55.0
N.R.
8.3
0
1/2
D
Fair
5
167
27
3-9-3
9.8
210
16
60
68
3200
57.8
56.5
5.9
0
3/4
D
Good
5
166
27
11.5
210
16
60
120
1800
55.5
53.8
10. 3
0
1/2
D
Fair
5
167
27
7-9-4
10. 8
210
16
60
68
3200
57. 6
55.0
7.5
0
3/4
D
Good
5
166
27
for all runs and
-
11.0
210
16
60
68
3200
55.3
N.R,
8.0
0
3/4
D
Good
5
166
24
7-10-1
10. 0
210
16
60
68
3200
55.3
55.0
8.3
0
3/4
D
Good
5
166
27
the spindle
11.2
210
16
60
68
3200
55.9
N.R.
6.8
0
3/4
D
Good
5
166
24
7-10-2
10.0
210
16
60
68
3200
55.0
54.1
9.8
0
3/4
D
Good
5
166
27
-------
1
5
XivrsMon Number
•} ! Subjec/ Fu-ld & Group
^ j
05D
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
^T «* 4-« « 1 /** A • . • T^ ^ ^ x"« ^ * f •
Western Research Laboratory
Title
DRY CAUSTIC PEELING OF TREE FRUIT FOR LIQUID
WASTE REDUCTIONS
10
22
Authors)
Mercer, Walter^A.
Rails, Jack W.
Maagdenberg, Harry J.
16
Project Designation
EPA, WQO Project No. 12060 FQE
21
Note
Descriptors (Starred First)
*Peel Removal, Tree Fruit, Food Processing, Canning, Freezing,
Dehydration, Peaches, Pears, Apricots
25
Identifiers (Starred First)
*Peel Removal, Liquid Waste Reductions
27
Abstract
The peeling of apricots, peaches and pears was studied with a peel removal unit
consisting of a series of spindles holding rotating rubber disks. The peel was re-
moved by a wiping action of the flexible rubber disks on fruit wetted with hot sodium
hydroxide solutions. The quality of fruit peeled with the experimental unit was com-
parable to fruit peeled by conventional chemical peeling; peeling losses were about
the same for the experimental unit and the commercial units.
The most striking difference between the experimental unit and the commercial
units was in fresh water requirements and waste water volume and strength. The
peeling of cling peach halves required one-fifteenth of the fresh rinse water volume
of a conventional commercial peeler. The wastewater generated by the experimental
peeling of peaches had about one-third of the chemical oxygen demand and suspended
solid content of the wastewater from the commercial peeler.
The experimental peel removal unit accomplishes a diversion of potentially water
polluting organic material from the wastewater to a peel sludge. The peel sludge
has properties which allqw jf *"° h^ T-ia-nrHpH rparlily anrl disposer! nf as cnli/j
ya°crk W. Rails
Institution
National Canners Association
«VR 10? (REV JULY 1969)
WRSIC
SEND TO: WATER R ESOUR C ES SC I EN T I Fl C INFORMATION CENTER-
US DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C. 20240
SPO: 1969-389-339
------- |