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.
                              -1-

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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 1650F 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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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.
                                -19-

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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.
                                -23-

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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.
                                 -24-

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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.
                                 -25-

-------
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.
                                  -26-

-------
                           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-

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                           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 (165F)
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 CO. D. , ppm
Wastewater SS, ppm
2-Propanol (165F)
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 (165F)
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 62F 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
  yacrk 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

-------