Rapid Heat Processing of Fluid Foods bv Steam Iniection rl
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A. H. BROWN, M. E. LAZAR, T, WASSERMAN, G. S. SMITH, AND iM.W. COLE Western Regional Research Laboratory, Albany, Calif. T h i s work was undertaken to improve existing methods for the short-time, high-temperature, heat processing (pasteurization, enzyme inactivation, and volatile flavor stripping), and for concentration of fluid foods such as fruit and vegetable juices and.pur6es. A processing system has been developed, and tested on a pilot plant scale, in which fluid foods are heated to temperatures as high as 300’ F., concentrated, and cooled by vacuum evaporation in elapsed times of less than 1 second. With fruit juices and berry-sucrose purBe containing 30% solids, over-all heat transfer coefficients of 500 to 600
B.t.u. per hour per square foot per ’ F. are obtained in the evaporator. The evaporating section of the system shows high resistance to fouling of heat transfer surfaces. Flavor changes have been insignificant when several fruit juices and milk were heat-processed to attain desired results. Application of the system to commercial scale will contribute to the production of high-quality, full- and freshflavored foods and food concentrates. In addition, the equipment requires less material for construction and less floor space for installation than conventional equipment.
A
temperature heat treatments effect pasteurization, sterilization, and/or enzyme inactivation in many foods with less alteration of flavor than occurs in long-time, low-temperature heat processing. In consequence, a simple steam-injection heater was developed for use in controlled, continuous processing of fluid foods a t higher temperatures for shorter times than are practical in conventional processing equipment. Steam injection heating is not new. Numerous patents have been issued for both batch and continuous types of steam-injection heating equipment of varying complexity, including heaters with mechanically driven parts (8-10, 20-28). These patents relate largely to milk, although other fluid food products are included. Despite early developments, steam-injection heating has not been applied widely in the processing of fluid fiuit and vegetable products. Isolation of fruit essences has been studied for anumber of years. In 1931, Mackie (14 ) described the production of orange concentrate by a procedure which involved return of voiati!e coniponents. Reports on the recovery of apple essence have been published by Carpenter and Smith in 1934 ( 2 ) ,Poore in 1935 ( 1 9 ) , Mottern in 1936 (16), Milleville and Eskew in 1946 (16), Kaufman et al. (11), Walker et al. (24), and the authors ( 1 ) in 1951. In current essence-stripping practice, fruit volati’es are separated from the fresh material by partial distillation, and are concentrated after separation. Phillips et al. (18)have described an experimental unit for essence recovery by this procedure. Rapid heating and distillation are necessary with many fluits to minimize flavor changes during separation of fruit essences. Steam-injection heating holds promise, therefore, in the field of b fruit-essence recovery.
DIRECT steam-injection heater has proved useful in the high-temperature, short-time processing of fluid foods, including purees as well as liquids. Fluid foods can be heated to 300’ F. in 0.5 second or less a t practical processing rates. Pasteurization, sterilization, enzyme inactivation, and/or deodorization are among the results achieved with the injection heater on fruit juices, fruit and vegetable purees, and milk. Improvement in concentration or essence-recovery operations is obtained by use of the injection heater to superheat fluid entering a singletube, steam-jacketed vaporizer. A characteristic of the equipment is high resistance to fouling. The injection heater has no heat-transfer surfaces to foul. Lack of fouling in the vaporizer tube, even at high jacket temperatures, is attributed to the fact that the injection heater provides high fluid velocities over the heat-transfer surfaces. Over-all heat transfer coefficients in the vaporizer tube ( 1/2-inch IPS stainless steel pipe, steam-jacketed over 6 feet of its length) range from 510 to 600 B.t.u. per hour per square foot per F. (based on inside area of tube) with water, apple juice, milk, and berry puree. The coefficient decreased only 1yo per hour during a 12-hour period of continuous operation on cloudy juice from Delicious apples. A pilot plant for processing fluid foods was developed a t this laboratory during the course of experimental work on fluid fruit and vegetable products. The pilot plant has proved to be unusually flexible and useful for processing operationssuch aspasteurization, sterilization, enzyme inactivation, deaeration, deodorization, essence recovery, and concentration. Two major objectives in the development of the processing system were the rapid heat processing of juices and purees under conditions such that the fresh flavor was altered as little as possible, and the isolation and concentration of “essences,” the characteristic volatile aroma components of fruit and vegetable materials, for subsequent return to the products. Ample evidence was found to show that short-time, high-
DESCRIPTION OF EQUIPMENT
A schematic diagram of the pilot plant installation is shown in Figure 1. The individual units comprise a feed tank, a geartype feed pump, a preheater, steam-injectim heater supplied with 2949
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INDUSTRIAL AND ENGINEERING CHEMISTRY
2950 I
COMBINATION EVAPORATOR
STEAM INJECTloN HEATER
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VAPOR
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STEAM JACKETED TUBULAR EVAPORATOR
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VAPOR LIQUID SEPARATOR
T P R E H EATER
Vol. 43, No. 12
PLATE COOLER
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LlQUlD RECEIVER
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BOT ?OMS TO WASTE
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RECEIVER
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Figure 1. Equipment Arrangement in Pilot Plant System for Processing Fluid Foods
clean steam, a steam-jacketed tubular vaporizer, a vapor-liquid separator, a plate cooler and/or a vacuum receiver for the liquid from the separator, and, for the vapors from the separator, a rectifying column, a metering pump to adjust the proportion of condensate taken as product, a condensate cooler, and a jacketed vacuum receiver for the condensate. Interchangeable sanitary piping permits connection of various components as required for specific processing operations. The rectifying column and metering pump are used only when the overhead product from the vapor separator is to be concentrated. The plate cooler, rectifying column, and metering pump are suitable for use only at atmospheric pressure, and are disconnected when the rest of the system is operated under vacuum. The need for clean, odorless steam is apparent, Suitable steam for these studies was obtained by using a small reboiler fed with untreated city water. A daily boiler bIowdown was adequate to avoid accumulation of odors or flavors in the reboiler. In some sections of the country, serious problems may exist in the production of clean steam. However, manufacturers of package boilers have informed the authors that clean, odorless steam may be generated directly if the feed water is properly treated and if proper feed pumps and other accessories are used on the boiler. Two features of the pilot plant installation are a steam-injection heater and a “combination evaporator.” The latter comprises a steam-jacketed tubular vaporizer which is fed with a mixture of fluid and vapor from the steam-injection heater. A typical model of the injection heater, suitable for processing a variety of fluid foods, is shown in disassembled form in Figure 2. As shown in the end view, the steam inlet, F , is tangential. From left to right, the components of the heater are the product inlet tube, A , the heater body with steam inlet, B , a thermocouple, C, which is located near the product outlet, the discharge orifice, D , and the product outlet tube, E. Gascets and flanges are not shown. The model in Figure 2 was constructed from a &inch length of */,-inch i.p.s. stainless steel pipe provided with conical-end fittings. The inside of the pipe was bored to 5 3 / e p inch to remove the inside weld, thus making the volume of the chamber 3.5 cubic inches.
The heater shown will process fluids at rates up to 100 or more gallons an hour and to temperatures up to 300” F. or more. The Auid retention time in the heater may be made at least as short as 0.4 second. In experimental work, retention time in the heater has been adjusted by inserting a ballast of proper size to reduce the volume of the heating chamber. Ballasts occupying two thirds of the volume of the chamber have not interfered with operation of the heater. When used as the sole source of heat, the injection heater is not suitable for concentrating feed materials to an appreciable degree, for reasons explained later in this paper. The combination evaporator was devised, therefore, to increase the flexibility of the processing system in regard to concentration of feed materials. A steam-jacketed tubular evaporator was installed, incorporating the steam-injection heater as a preheater or superheater. The jacketed tube consists of a section of ‘/2-inch i.p.s. stainless-steel pipe, steam-jacketed over 6 feet of its length. In operation of the combination evaporator, temperatures are adjusted so that the fluid leaves the injection heater with sufficient heat content to form a vapor-liquid mixture containing from 1 to 3% by weight of vapor at the entrance of the steam-jacketed tube. Because of the relatively large volume of the vapor-liquid mixture, the veiocity of the fluid is high at the entrance of the jacketed section, and increases rapidly as further vaporization occurs. A11 heat-transfer surfaces are swept by a mixture of vapor and liquid moving a t high velocity, with the result that heat-transfer rates are good and remain at practical operating levels for considerable periods of time. The operating principle of the combination evaporator was described by Peebles and Manning in 1937 ( 1 7 ) . IXHERENT CHARACTERISTICS OF STEAM-INJECTION HEATING
When appreciable concentration of product is an objective, steam-injection heating has limited applicability because of physical relationships governing the heating process. Steam is consumed in proportion to the amount of heat required to raise the temperature of the feed to the desired level; all steam consumed appears in the feed as condensate, thus tending to dilute the product.
INDUSTRIAL AND ENGINEERING CHEMISTRY
December 1951
The dilution may be offset in part by evaporative cooling of the fluid leaving the steam injection heater. Evaporative cooling occurs if the vapor separator is maintained a t a pressure below the vapor pressure of the fluid a t the temperature prevailing in the injection heater. The amount of water evaporated is proportional to the amount of heat which must be removed to cool the fluid to its vapor-liquid equilibrium temperature in the separator. The net amountof product dilution during steam-injection heating followed by evaporative cooling depends, therefore, primarily on the temperature of the feed and the equilibrium temperature (or pressure) in the separator. If the two temperatures are equal, the product is slightly more concentrated than the feed. If the feed temperature is higher or lower than the equilibrium temperature in the separator, the product is correspondingly more or less concentrated than the feed. In practice, fluids processed by steam injection are diluted unless the feed is preheated, or unless the vapor separator is operated under vacuum. This limitation led to the development of thc combination evaporator. The latter has the advantages of the steam-injection heater and minimizes limitations inherent in steam-injection heating. Product concentration may be controlled during processing in the combination evaporator with little regard to feed temperature or to the pressure maintained in the vapor-liquid separator.
295 1
stability of the heater has been obtained during heating of various fluids, including fruit and vegetable juices, fruit and vegetable pur6es, and milk for periods ranging from 0.4 to 1.5 second. In all cases, the thermocouple junction located a t the outlet orifice of the heater indicated temperatures varying f 2 or 3' F. at a rate much lower than the response rate of the indicating potentiometer. Confirming evidence of the complete condensation of steam was obtained by flashing dilute aqueous alcohol from the injection heater into the vapor separator, and collecting and analyzing the overhead and bottom products for alcohol content. Five tests were made with aqueous solutions containing from 2.3 to 3.7% by weight of ethanol, including operation of the separator at 2.0 and and 14.7 pounds per square inch absolute in different tests. Fractionation obtained was 87, 91, 92, 94, and 100% of the theoretical separation as calculated from the Rayleigh equation for batch distillation. Rapid condensation of steam in the injection heater is undoubtedly aided by the spin induced in the fluid by tangential entry of the steam. Spin is visible in the fluid discharged from the heater into the separator, even after the fluid has expanded through a 0.070-inch orifice, passed through a 4-inch length of '/*-inch i.p.s. pipe, and again expanded into the separator. Steam-injection heaters of the type shown in Figure 2 are highly stable in operation. During as much as 12 hours of conCHARACTERISTICS OF T H E STEAM-INJECTION HEATER tinuous operation of the injection heater, using manual control, the temperature attained by the fluid in the heater remained conDuring the development of the steam-injection heater, parstant within 3' or 4" F. without attention from the operator other ticularly for fluid retention times of less than a second, doubt than to correct drift. Operating stability is not inherent but is existed as to whether complete condensation of steam was obeasily obtained by proper design and operation of the heater. tained in the chamber. Several tests indicated that condensaPreferably, the discharge orifice is of proper size to maintain the tion is substantially complete. An injection heater, similar in pressure in the chamber a t 20 pounds per square inch or more construction to that shown in Figure 2, was made from a 12-inch above the vapor pressure of the fluid at the processing temperalength of B/g-inch i.p.s. stainless steel pipe, with thermocouple ture. The size of orifice depends, of course, on the processing tests junctions located 25/(, 7, and 111/2 inches downstream from rate as well as the processing temperature. Steam is supplied to the steam inlet. A similar heater was made from a 12-inchlength the heater a t pressures ranging from 10 to 15 pounds per square of 3/4-inch i.p.s. stainless steel pipe with thermocouple test juncinch above the pressure maintained in the chamber of the heater. tions located 21/2, 51/2, 81/2,and 11 inches downstream from the If feed and steam supply pressures can be kept reasonably consteam inlet. The copper-constantan couples were fabricated stant, orifices are not needed a t the steam and feed inlets of the from 30-gage wire, and were connected to an eleetronic indicating injection heater. potentiometer. The bare test junctions were immersed in the The type heater described herein has another desirable fluid stream. During heating of water from 65" F. to the range feature. Many of the patented injection heaters have steam250" to 290" F. in either of the elongated test heaters, all thermoheated walls or pipes in contact with the fluid in process; couple readings agreed within f 2 " F. Fluctuations in temperathus, material inevitably burns on the hot surfaces. In the ture were about 1 2 ' F. in magnitude and occurred a t a relatively present model, the slow rate. No temsteam inlet is cooled perature g r a d i e n t by t h e incoming was observed along fluid, and turbulence the axis of the heaters in the fluid caused or from the center by tangential entry line to the walls of of the steam minit h e c h a m b e r s . In mizes p o c k e t s o r t h e a/B-inch i.p.s. dead spaces where model of the heater, solids may deposit. the time required for A d h e r i n g deposits the water to pass have been found in from the steam inlet the chamber of the to the first thermopresent injection couple junction was heater with only about 0.15 second, one of the commodiwithout making ties tested. When allov,~ance for the milk is processed, volume occupied by even a t t e m p e r a the cavity formed in ture8 a s low a s the water by the in245' F., milkstone coming steam. Adis deposited on all ditional evidence of Figure 2. Steam Injection Heater for Fluid Foods interior surfaces of complete condensadischarge orifice; heater body; C thermocouple; D A product inlet tube; B the heater. tion of steam and and E product outlet tube) tangential steam inlet shown in F and B P
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INDUSTRIAL AND ENGINEERING CHEMISTRY
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Vol. 43, No. 12
TABLE I. HEAT TRAXSFER COEFFICIENTS DURING EVAPORATION IS COMBINATIOX EVAPORATOR
Solids in Feed Material, Feed Material Water Waterd Delicious apple ,juice Winesap app!e?uice Pulpy apple juice Berry-Sucrose puree
7c
0 0 12.3 12.4 14.1 33
Over-all Heat Transfer Data Over-all' Over-all heat Av. liquid temp. transfer temp. in difference, coefficient, evaporator steam to B.t.u./hr./ tube, F. fluid, O F. sq. f t . / O F.a 220 104 60 5 161 148 550 222 515 105 225 535 102 560 219 68 220 86 510
Indiridual Film He-nsfer Individual Temperature Diffe enoes, O F , b Tube Steam 'Across wall to t o tube tube wall wall fluid 14
20
11 11 8 9
E 44 45 31 36
38 60 49 46
29
41
Data (Calculated) Individual Heat Transfer Coefficients' B.t.u./Hr./Sq. Ft.1' F. Steam Tube Liquid side walle side 3300 3000
3500
3600 3600 3600
1040 1040 1040 1040 1040 1040
1630 1340 1100 1180 1330 1070
Based on inside ares of tube. To nearest O F. Value given is thermal conductivitv of stainless steel divided by wall thickness of '/%-inch pipe. d Test made with vapor separator a; 1.25 inches Hg abs. pressure, all other teats made with separator a t atmospheric pressure. Q
b
c
CHARACTERISTICS OF THE COMBINATION EVAPORATOR
Noteworthy characteristicsof the combination evaporator, properly operated, are resistance to fouling of the heat-transfer surfaces and good heat-transfer rates, even with materials considered difficult to process. Foods processed in the combination evaporator include juices (grape, tomato, orange, five varieties of apple, and pulpy apple juice, the commercial product made by grinding apples through a very fine screen), milk, and purees (apricot, pea, peach, pear, and berry, the latter a blend of raspberries, youngberries, and sucrose). The combination evaporator and steam injection heater are operated as continuous processing units. The system is started and stabilized with water as feed (usually ~1ithin several minutes), the food material is processed, and the system is again fed with water, all without interruption of operation. Thus, the food material is handled only during nearly steady-state operation; contact between the food material and hot dry surfaces in the equipment is avoided. At the end of each run on a new material, the system was disassembled and inspected. Tenacious deposits have been found in the evaporator tube only when the operating procedure differed from that outlined in the preceding paragraph. With proper operation of the system, deposits found in the evaporator tube have been slight in amount and have been easily removed from the tube by brushing or swabbing. Over-all heat transfer coefficients obtained in the jacketed section of the combination evaporator ranged from 510 to 600 B.t.u. per hour per square foot per O F., based on the inside area of the tube, using water, three types of unclarified apple juice, and a berry-sucrose purBe as feed materials. ( S o correction was made for heat losses in calculating the over-all coefficients.) The data are summarized in Table I. A similar result, not shown in the table, was obtained during concentration of raw milk, when 56% by weight of the feed was vaporized in a single pass through the Combination evaporator. Also shown in Table I are estimates of the individual coefficients comprising the over-all coefficient. The estimates were made by using the Nusselt equation as presented by Mchdams ( I f ? )t o approximate the steam-side coefficient and solving for the individual temperature drops (steam to outside of tube, across tube, and inside of tube to boiling fluid) by trial and error. The liquid-side heat transfer coefficients so obtained range from 10'70 B.t.u. per hour per square foot per ' F. for berry puree to 1630 for water. The latter value is well within the range of values obtained by McAdams et al. (13) for the boiling of water inside horizontal, steam-jacketed tubes. Data in Table I show that the pipe wall of the combination evaporator constitutes a substantial proportion of the total resistance to heat transfer. Replacement of the pipe (0.109-inch nominal wall thickness) with tubing (perhaps 16-gage, 0,062-inch nominal wall thickness) would effect a material increase in the over-all heat transfer coefficient. Fouling tendency in the combination evaporator was carefully
obsewed during stripping of essence from 11,000 gallons of apple juice, in the equipment shown in Figuie 1, as a step in making full-flavored frozen apple juice concentiate (24). Juice was pressed from the apples, strained through cheesecloth, and fed to the combination evaporator where 19 to 2070 by weight of the juice was vaporized to separate essence. The juice was pleheated t o about 80' F. before entering the injection heater, heated to 240' to 250" F. in the injection heater, flashed to about 230" F. a t the evaporator inlet, and discharged from the evaporator into the separator, which was maintained at atmospheric pressure. The steam jacket of the combination evaporator was operated during each run at a nearly constant pressure in the range of 'TO to 80 pounds per square inch. Sustained heat-transfer data from operation of the combination evaporator on apple juice foi more than 250 hours are presented in Table 11. During 240 hours of operation, runs 1 to 37 inclusive, the apparatus was disassembled, inqiected, and cleaned only six times, at the intervals indicated in the table. No other cleaning was employed except for operation of the system on \+aterfor 15 to 20 minutes a t the end of each run during which time the water was heated to about 270" F. in the injection heater. Conclusions regarding the operation of the combination evaporator, drawn from the data of Table 11, are as follows: 1. With juice from red Delicious, \\ inesap, Gravenstein, and Rome Beauty apples, the over-all heat transfer coefficient decreased, on the average, only 0.9% per hour during periods of operation ranging from 4.3 to 11.8 hours. The rate of fouling ranged from 0 to 1.9% decrease in over-all heat transfer coefficient per hour of operation. 2. With juice from Jonathan apples, the over-all heat transfer coefficient decreased, on the average, 3.5% per hour during periods of operation ranging from 5.9 to 8.6 hours. (No attempt TTas made to minimize fouling by changes in operating conditions.) 3. The over-all heat-transfer coefficient decreased only 5 to 15% during operating periods, on apple juice, of 50 to 60 hours without cleaning other than operation on water a t intervals of 4 to 8 hours. 4. The system tends to be self-cleaning, even after partial fouling, as shown by restoration of the over-all heat transfer coefficient following runs 8 and 9 on juice iiom Jonathan apples. The results outlined are in contrast to reports received at this laboratory, indicating that conventional types of tubular pasteurizers and vaporizers may require complete and thorough cleaning at intervals of 2 t o 6 hours duiing operation on apple juice. a
Another difficulty sometimes encountel cd in conventional types of tubular vaporizers is slugging-that is, the alternate discharge of liquid and vapor from the vaporizer. Slugging has not been encountered in the combination evaporator, presumably because the system is fed positively, and a significant pressure gradient exists in all portions of the jacketed tube. During the operation on apple juice, the pressure drop through the jacketed tube was 4 to 5 pounds per square inch during vaporization of 20% by weight of the juice fed at the rate of about 350 pounds an hour.
December 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
2953
General View of Pilot Plant Equipment
BIOCHEMICAL AND MICROBIOLOGICAL OBSERVATIONS
A number of biochemical and microbiological tests have been made to determine the effectiveness of the system for accomplishing desired results in the products handled. Although thorough studies have not been attempted on microorganism destruction, enzyme inactivation, or flavor preservation, the results thus far obtained are favorable. For many products, insignificant &mor change occurs during processing a t temperatures of about 250' F. for less than a second. Raw milk was heated to 245' F. in the injection heater and cooled evaporatively to 80' F . in 0.7 second without development of more cooked flavor than is caused by conventional pasteurization a t 160' F, for 15 seconds. Raw milk was concentrated from 11.4 to 26.0% solids in a single pass through the 6-foot combination evaporator without development of a perceptible cooked flavor. The injection heater was operated at 244' F., and the vapor separator was maintained under vacuum during the concentration. Much of the undesirable feed flavor-that is, the flavor in the milk arising from the type of feed consumed by the cow-present in the raw milk was removed during both processing operations. Several varieties of apple juice were processed a t temperatures of about 245" F. to isolate essence; qualified taste panels were unable to detect cooked flavors in the reconstituted products from the operation. The enzyme phosphatase in raw milk was found to be inactivated by heating the milk to 185" F. and cooling evaporatively to 95" F. in a total time of 0.4 second. Oxidative enzymes in fruit and vegetable juices and purees were inactivated by routine stripping operations involving heat treatments at 220' to 250" F. for less than a second. Effective pasteurization occurred during steam-injection heating of the tested fluid foods. Orange juice ,was processed for 1.8 seconds at 167' F., and for 0.8 second a t 193' Fa. in two tests;
no surviving organisms were found on plates inoculated with 1-m.1. portions of the processed material. Raw milk containing 25,000 organisms per ml. was processed a t 185' F. for 0.4 second; no surviving organisms were found in samples plated at a I: 100 dilution. Viable coli organisms were present in the raw milk but were not found in the processed milk. During stripping of essence, heat processing of apple juice a t 245' F. for 1.1 seconds gave a sterile product. In another test, freshly pressed apple juice was inoculated with active and sporulating cells of Schzzosaccharomyces octos porus, a heat-resistant yeast, in the amount of 20,000 per ml. The juice was raised to 244' F. in the steam-injection heater and cooled evaporatively to 84' F. in 0.7 second. No surviving organisms were found during incubation of three samples of the processed juice on an apple juice-yeast extract agar. FUTURE
The food producers of this country are becoming increasingly conscious of the value of food concentrates. Substantial savings effected in both container and shipping costs are reflected in the retail price of the product. Concentrated fruit juices and milk are finding ready acceptance in the retail market; concentrated fruit purees are packed for remanufacture into baby foods. The trend is to be encouraged. The type of equipment described in this paper appears promising in the manufacture of concentrated fluid foods, particularly those that are heat-sensitive. Considerable engineering data will be required, however, to scale the equipment to commercial she. A new combination evaporator, designed specifically to provide engineering data, is under construction a t the Western Regional Research Laboratory. The new evaporator will have about ten times the heat transfer surface of the unit described in this paper and will be in operation on food products during the
INDUSTRIAL AND ENGINEERING CHEMISTRY
2954
Vol. 43, No. 12
tained at practical levels for many hours of operation. Over-all HEATTRAKSFER RATESIN COMBINATION heat transfer coefficients in the steam-jacketed tube of the comTABLE 11. SUSTAINED EVAPORATOR FEDWITH APPLEJUICE bination evaporator ranged from 510 to 600 B.t.u. per hour per Change in square foot per ’ F. with water, apple juice, and berry pur6e. Over-all Heat Heat Operating Time, Transfer Coefficient Transfer The pilot plant system will heat fruit and vegetable juices to Hours B.t.u./Hr./Sq. Ft./’ F. Coefficient temperatures as high as 300’ F. and cool them to 80’ F. or less during Cumulative First Last Run Per hour hour Each Run between in a total time of less than a second, with controlled amounts of of run disassembly NO. run of run %/Hour concentration. Operations successfully conducted in the pilot Red Delicious plant, with insignificant flavor change in a number of food prod-1.2 630 590 1 5.4 590 -0.6 2 5.4 570 ucts, include pasteurization, sterilization, enzyme inactivation, 570 0 570 3 5.8 570 550 -0.6 4 6.0 deaeration, deodorization, essence stripping, and concentration. 5 6 7
fi:2 5.9 5.2
22.6
..
5‘80 590 GOO
570 540 570
-0.3 -1.4 -1.0
Jonathan 8 9
5.9 5.9
570 520
440 400
-3.9 -3.9
Winesap 10 11 12 13
7.8 8.3 8.0 6.8
590 550 550 500
550 540 530 550
-0.9 -0.2 -0.5 4-1.5
6iO
630
-0.7
710 630
600
610
600 610 610 600
590 560 590 580 580
-1 9 -0.6 -1.0 -0.9 -0.4 -1.1 -0.7
14
4: 3
60.0
630
50.1
..
..
..
0
Carpenter, D. C., and Smith, E. C., IXD. ENQ.CHEM.,26, 449
-2.7 -3.3
Crighton, \V. T. (to Produceis Creamery Co.), U. S. Patent
640 650
640 640
-0.2
Jonathan 24 25
8.4 8.6
520 460
4CO 330
8.1
i:0
39.8
6.8
-1.8 -1.1
560 560 580
550 510 510
-0.4 -1.3 -1.6
Red Delicious 32 33
6.6 6.4
510 490
470 450
-1.2 -1.3
610
570
-1.0
(Nov. 12, 1935).
20, 1938).
6: 6
45.3
..
Winesap 35
5.5
600
610
$0.3
Red Delicious 36
4.6
600
570
-1.1
Winesap 37
5.4
600
..
540
..
-1.8
610
540
-1.0
A
2,334,317 (Nov. 16, 1943).
Grindrod, G., U. S. Patent 2,170,195 (Aug. 22, 1939). Hammer, B. W.,Horneman, H. C., and Parker, RI. E. (to Sealtest System Laboratoiies), U. 9. Patent 2,130,643 (Sept.
-0.8
4kb
4.9 7.0 7.6
Gravenstein
(1934).
..
440
550 550
Winesap 29 30 31
34
(1951).
Grindrod, G. (to Grindrod Process Corp.), U. S. Patent Reissue 19,193 (June 5, 1934). Grindrod,G. (to Giindrod Process Corp.),U. S. Patent 2,020,309
470
510
LITERATURE CITED
..
7.3 7.4
27 28
The authors wish to acknowledge the cooperation of E. H. Barger, Borden’s Dairy Delivery Co., San Francisco, Calif., in tests made with milk; the assistance of R. C. Rice, George Keller, and Everett Wolford of the Fruit and Yegetable Chemistry Laboratory, Pasadena, Calif., in various tests on orange juice and bacteriological tests on other products; and the contributions of various members of the staff of this laboratory, particularly M.J. Powers, for a portion of the bacteriological studies, and C. C. Nimmo for organoleptic evaluation of processed samples.
Brown, A. H., Lazar, hl. E., Wasserman, T., and Ramage, W.D., Food Packer, 32, KO.1, 20 (1951) and 32, No. 2, 34
Rome Beauty 22 23
Red Delicious 26
ACKNOWLEDGMENTS
11.8
22.1
11.8
..
..
..
..
Hammer, B. W., Horneman, H. C., Quam, S. N., Lockwood, F. F., Beery, H. F., arid Parker, h1. E. (to Sealtest System Laboratoiies), U. S. Patent 2,130,644 (Sept. 20, 1938). Hawk, L. R. (to Golden State Co., Ltd.), U. S. Patent 2,492,635 (Dec. 27, 1949). Horneman, H. C. (to National Dairy Products Corp.), U. S. Patent 2,130,645 (Sept. 20, 1938). Kaufman, V. F., Ximmo, C. C., and WaIker, L. H., Canner, 112. No. 1, 19 (1951).
hlcridams, 1%‘. H., “Heat Transmission,” 2nd ed., p. 269, F e w York, McGraw-Hill Book Co. (1942). hIcAdams, W. H., Woods, TT‘. K., and Bryan, R. L., Trans. Am. SOC.Mech. Engrs., 63, 545 (1941).
late fall of 1951. Results of the work will be published periodically. The first commercial installation of equipment based on the work reported here was made in November 1951. The unit, an apple essence stripping and recovery system with a capacity of 500 gallons of apple juice an hour, was designed and constructed by Oscar Krenz, Inc., Berkeley, Calif., for Silveria and O’Connell, Sebastopol, Calif. SUMMARY
A versatile and useful pilot plant system for the heat processing of fluid foods has been described. The system features two experimental units-a steam injection heater and a combination evaporator. The latter is a single-pass evaporator in which the fluid is heated above the boiling point in the injection heater and is flashed into a steam-jacketed tube. The combination evaporator is characterized by good heat transfer rates which are main-
Mackie, A. M., Food Ind., 3, 528 (1931). hIilleville, H. P., and Eekew, R. K., Western Canner and Packer, 38, KO. 11, 51 (1946). hlottern, H. H., Proc. b8nd Ann. Meeting Washington State Hort. Assoc., p. 114 (1936).
Peebles, D. D., and Manning, P. D. V. (to D. D. Peebles), U. S. Patent 2,090,985 (Aug. 24, 1937). Phillips, G. W. M., Eskew, R. K., Claffey, J. B., Davis, R. A,, and Homiller, R. P., IXD, ENG.CHEM.,43, 1672 (1951). Poore, H. D., Fruit Prod. J., 14, 170, 201 (1935). Rogers, C. E., U. S. Patent 2,115,470 (April 26, 1938). Ibid. 2,122,954 (July 5, 1938). Rogers, C. E. (to C E. Rogers Co.), U. S. Patent 2,238,373 (April 15, 1941). Sodelgreen, A. L. (to Heibert D. Pease) U. S. Patent 2,086,338 (Julj 6 , 1937).
Walker, L. H., Nimmo, C. C., and Patterson, D. C., Food Tech., 5, No. 4, 148 (1951). RECEIVEDApiil 16, 1951. Western Regional Research Laboratory is one of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.
