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430 CHAPTER 39 1962 Guide And Data Book cooled by the boiling refrigerant (low side). The juice cycle is the same as in Fig. 1 except that the water vapor is directly and intimately mixed and condensed in cold water. The con densate is drawn from the hot welL The pressure is maintained by a relatively email steam ejector or mechanical vacuum pump. Note that the essential difference lies in interposing water as a heat transfer medium between the hot refrigerant and the juice, and between the vapor and the cold refrigerant. Advantages of this system are: 1. Centrally located standard Unitary refrigeration equipment can be ased. Controls and instrumentation can be standard. 2. Refrigerant hires are short, and hold-up is low. 3. Evaporators need not be designed to hold refrigerant. 4. No danger of refrigerant contaminating the juice. 5. Very little steam or water are required. Steam is needed only to maintain pressure, and water only to remove heat of compression. Disadvantages of this system are: 1. Because of the use of water as an intermediate beat transfer medium, the bot refrigerant gas must be hotter and the cold re frigerant must be colder than in Pig. 1. The suction to discharge temperature spread on the refrigeration unit is greater, and therefore, the energy input to the compressor per pound of water evaporated is greater than for Fig. 1. 2. Equipment for handling water streams is required for this process which is not required m Fig. 1. Vapor Recompression and Thermo-Compression Fig. 3 shows a schematic system for concentration in which the vapor from the juice, instead of being condensed, is com pressed to a higher temperature and pressure and used to evaporate more juice. The vapor is compressed by a booster steam ejector. This can also be accomplished by a mechanical compressor, but to date none are being used for fruit juice concentration in this country. The evaporator is heated with steam and the condensate is pumped out to drain. The juice cycle is similar to Figs. 1 and 2 except that the vapor is recompressed and eventually leaves the system as condensate. The work of compression is supplied by the high pressure steam fed to the booster ejector. Advantages of this system are: 1. The capital investment for steam ejectors ia low compared to that for refrigeration systems. 2. No low temperature condenser is required. 3. No intermediate water circulation system is required. Disadvantages of this system are: 1. More steam is required rhan for either Fig. 1 or 2 and its use u relatively inefficient. 2. More cooling water b needed than for either Fig. 1 or 2. Plate Evaporator A plate evaporator, essentially a modified plate type heat exchanger, has recently been introduced to the concentrating processors with installations in Florida for oranges and in California for lemons. This unit combines the functions of heat treating and concentrating, single or multiple effect, with or without vapor recompression. It operates at a considerably higher temperature for a much shorter time than conventional equipment, with claimed improvements in product flavor.. The Krin- thick stainless steel plates with )4-in. thick gaskets, operate in groups of 4 to provide a single-pass, climb ing and falling film evaporator. Through 'suitable ported and sealed cut-outs, juice flows up between plates 1 and 2 and down between plates 3 and 4, with steam between plates 2 and 3, and 4 and 1 of each group. From the large discharge manifold the mixture of concentrate plus vapor passes to a horizontal cyclone separator. Using this equipment, orange juice has been concentrated from 10 percent solids to 72 per cent solids; although at the higher, more viscous, concentra tions, some of the concentrate must be recirculated to insure a wetted wall. The following operational and performance data were ob tained on an early production installation of plate evaporators for frozen orange concentrate: a. Double effect (40 plates each) with vapor recompressioa. b. 1800 gph feed, 245 gpb productat 60deg Brix (1300 lb perhr water removed). c. Preheat feed to 200 F for 234 to 3 sec. d. Contact time with heat exchange surface b 10 see. e. First effect: 165 F, 19 in. vacuum. f. Second effect with 30 percent recycle: 120 F, 27 in. vaseum. t Flash cooler: 80 F, 29 in. vacuum. Total throughput time of 30-75 sec. Compared to the conventional concentration methods, the plate evaporator requires approximately )4 ol the capital, 34 of the building height (9 ft), 34 of the steam, ) of the water and 34 of the cleanup time (1 hr). ORANGE JUICE The production of frozen concentrated orange juice follows tite general processing procedure detailed previously. After the citrus juice and oil . are extracted, as separate streams from the pulp by one of several conventional meth ods, the peel oil content of the juice is measured. If it is found to exceed the value set by standards, adjustments are made in the extraction process by blending or diversion. To a certain extent, oranges are blended before the juice is ex tracted. Brix and acid values for extracted juice are deter mined at frequent intervals (hourly) as a check and control of the fresh fruit blending; Immediately after concentrating, the juice is cooled to 20 to 32 F. The general rule at present is to concentrate to more than 42 deg Brix and then blend the concentrate with fresh juice, essence, or both to the standard Brix range of 41.5 to 43.5 deg Brix. It is conventional to blend sweet late season juice with tart, sour early season juice of the same crop of oranges through the bulk storage of the concentrate, thus extending the processing season (early is usually before July 1st in California). Proper blending is done on toe basis of the data noted in the section Selection, Grading, and Storage. Frequently simultaneously harvested fruit will represent the earlier stages of one crop and the later stages of another. ffOien Fruit Juice Concentrates 431 ^gge are blended by mixing oranges before juice extraction, on toe basis of grading and storing data. [jnited States standards lor frozen concentrated orange jujee have been established, effective 25 July 1949. In brief, gtey require that the best grade of concentrate when reconsti- nrw>tM>nf fresh oraneeiuice. DOSsesses a very good color; is practically free from delects; possesses a good flavor." A poy V00^ color is a bright yellow to yellow-orange color typical of fresh orange juice. Defat* refer to particles of membrane, core, skin, seeds and portions thereof, recoverable oil and others. YcV good flavor refers to that typical of fine distinct fresh orange juice extracted from fresh mature sweet oranges. Fur ther standards are set for toe ratio of Brix value to the weight percent of acid (as anhydrous citric acid). The range of stand ard Brix4o-acid ratios of Florida oranges is not less than 12 to 1 and not more than 18 to l.The ratio for California oranges is not less than 10 to 1 nor more than 16 to 1. The Brix value of toe concentrate has been standardised at not less than 41.5 deg and not greater than 43.5 deg. GRAPEFRUIT JUICE In toe production of frozen concentrated grapefruit juice, essentially the same equipment is used--fruit washers, finishers, falling film evaporators--as in the production of frozen concentrated orange juice. Some adjustments at the extractors are necessary to accommodate grapefruit, the larger fruit. While either seedless or seeded grapefruit may be used, seeded varieties, such as the Duncan, are generally preferred because they tend to yield a product of better flavor. Zero storage of the product is recommended. As in the manufac ture of the orange product, concentration is carried beyond that of the finished product (to 55 Brix or higher) and fresh cat-back juice is added until the desired strength is obtained. This cut-back juice restores much of the volatile aroma that was lost during the concentration. When reconstituted from properly prepared concentrate, the product is of excellent flavor and resembles the fresh juice closely. Both Bweetened and unsweetened frozen concentrated grapefruit juices have been produced--the sweetened product ia greater quantities. Both types are covered by U.S. De partment of Agriculture Grades. With the unsweetened product, toe final Brix may vary from 38-42. The sweetened concentrate, exclusive of sweetening ingredient, must total at least 36 Brix, and the finished concentrate may vary from 38-48 Brix. Hie sweetening ingredient is added according to the Brix-acid ratio in the fresh juice and that desired in the finished product. Current opinion favors a Brix-acid ratio of about 12 to ] in sweetened concentrates. It is intended that ail the types mentioned be reconstituted by adding three parts of water to one of concentrate. Frozen concentrated grapefruit juices are covered by military specifications. BLENDED GRAPEFRUIT AND ORANGE JUICE Properly prepared frozen concentrated blended grapefruit juice and orange juice is of excellent quality and resembles the beshly prepared product. Although it is less popular than frozen concentrated orange juice, it finds a place in any line of frozen food products. The same procedures are used in producing this blend as are used in preparing the straight products. During blending, cuthack of both juices is added to restore fresh flavor and aroma. Blended productsof both sweetened and unsweetened types are covered by USDA Standards for Grades and military specifications. The USDA Grade standards recommend not less than 50 percent orange juice in the mixture and as much as 75 percent orange juice when it is light in color. The military specifications call for from 60-75 percent orange juice. With the unsweetened product, the USDA Grades call for 40-44 Brix in the final concentrate. With the sweetened product, the Brix value must be 38, exclusive of the sweetening ingredi ent, and from 40-48 in the finished product. Brix-to-aeid ratios may vary from 8:1 to 18:1 with the unsweetened product and from 9:1 to 13: i if sweetening ingredients are added. TANGERINE JUICE Differences in the nature of the tangerine require modifica tion in the methods of handling during picking, hauling and storage at the plant. While the grapefruit and orange are generally roundand quite firm and will withstand considerable rough handling, toe tangerine is somewhat flat, irregular in shape, and has a loose, tender skin which is easily broken. If the skin is broken and the fruit bruised, bacteria and yeasts readily attack the fruit and undesirable enzyme actions occur. For these reasons they cannot be handled in orange bins but must be handled in boxes or loose in trucks to a depth of not over two feet The Dancy tangerine is the common variety. The processes and equipment used in manufacturing the concentrated tangerine juice are, however, practically the same as with oranges. Since the fruit is smaller, the yield of juice from a given number of extractors is smaller and about double the amount of extracting equipment is required to furnish juice to keep the evaporators operating at full ca pacity. Usually the freshly extracted juice is centrifuged in a continuous machine to remove a large portion of the sus pended pulp and reduce the tendency for off-flavors to form. USDA Standards for grades have not been established for frozen concentrated tangerine juice. Usually, the value for Brix-to-acid ratio, concentration and peel oil content follow closely those prescribed for the orange product. Some con sider that the 41.5 Brix is a little too strong for a 4-fold tan gerine product and believe that about 39 Brix results in a better reconstituted juice. PINEAPPLE JUICE Pineapple juice is prepared from small fruit and the parts of larger pineapples that are not suitable for packing as pieces of fruit. The main sources are the cores, the layer of flesh between toe shell and cylinder that is cut for toe prepa ration of pineapple slices, mid juice which drains from the crushed pineapple. The juice material amounts to about 34 of toe weight of the fresh fruit. It is inspected in order to remove pieces of shell and spoiled flesh. The juice is extracted by passing through disintegrators and screw presses. It is then centrifuged to remove heavy foreign material and exces sive insoluble solids. Processing of juice up to this point is the same for the production of either single strength or concen trate. '' Pineapple concentrate is produced from single strength juice in equipment similar to that used for the production of orange mid other fruit juice concentrates. The first step in toe concentrating operation b to strip out the volatile flavoring materials. These are separated as about a 100-fold product and added back to toe firm.1 concentrate. The concentration takes place in multiple effect evaporators, with the final effect at about 70 F. Pineapple concentrate is produced either as a 3-to-l product which has a Brix of about 46.5, or as a 4344o-l product with a Box of about 61 F. Hie 3-to-l concentrate is produced in both a sterile and a frozen form; however, even the sterile product