WATER POLLUTION CONTROL RESEARCH SERIES • 12060 FQE 12/70 Dry Caustic Peeling of Tree Fruit for Liquid Waste Reductions U.S. ENVIRONMENTAL PROTECTION AGENCY ------- 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. ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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- ------- 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- ------- 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- ------- 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- ------- 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- ------- Figure 1 PROTOTYPE FRUIT PEEL REMOVAL UNIT Figure 2 CLOSE UP VIEW OF PROTOTYPE PEEL REMOVAL UNIT -8- ------- 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. ------- Figure 3 FABRICATED NEOPRENE RUBBER DISKS Figure 4 PEEL REMOVAL UNIT, GENERAL CONCEPT -10- ------- 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- ------- 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- ------- 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- ------- 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- ------- (I » 1*1 KAI O Q 0 ~" "" | */%• ? g \ I ! f " rr-~ •1 M k A f | | i v ^ i ? k y* V Figure 10. SPINDLE CONFIGURATIONS 1 THROUGH 4 -15- ------- 1 ? I ( < p i > < », t !> — c ^ ii • c ? S M " — : .. __„-»* __ „ '« ) 5 o o w [I " II --- 8 :;zf Figure 11. SPINDLE CONFIGURATIONS 5 THROUGH 8 -16- ------- '77' 10 Figure 12. SPINDLE CONFIGURATIONS 9 AND 10 -n- ------- 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- ------- 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- ------- 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- ------- 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- ------- 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- ------- 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- ------- 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- ------- 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 ------- |