ASHRAE REFRIGERATION SI CH 40-2010 PROCESSED PRECOOKED AND PREPARED FOODS《处理预煮的准好的食物》.pdf

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1、40.1CHAPTER 40PROCESSED, PRECOOKED, AND PREPARED FOODSMain Dishes, Meals. 40.1Vegetables . 40.3Fruits. 40.5Potato Products. 40.5Other Prepared Foods 40.6Long-Term Storage . 40.7HERE are many categories of prepared foods. This chapterTcovers prepared meals, fruits, vegetables, and potato productsand

2、gives an overview of the HVAC storage for packaging materials and supplies;storage for ambient, refrigerated, and frozen ingredients; thawingand defrosting; refrigerated in-process storage; mixing, cutting,chopping, and assembly; sauce and/or gravy kitchens; cooking andcooling rice, pasta, and/or ot

3、her starches; unit operations for prepar-ing main dishes such as meat patties, ethnic foods, and poultryitems; dough manufacturing for pies and pizzas; assembly, filling,and packaging; cooling and freezing facilities; casing and palletiz-ing operations; finished goods storage for refrigerated and fr

4、ozenproducts; and shipping of outbound finished goods by truck or rail.In addition, these operations support equipment and utensil san-itation; personnel facilities; and areas for utilities such as refrigera-tion, steam, water, wastewater disposal, electric power, natural gas,air, and vacuum.Plants

5、and equipment for producing prepared foods should beconstructed and operated to provide for minimum bacteriologicalcontamination and easy cleanup and sanitation. Sound sanitarypractices should be followed at all stages of production. This is ofparticular concern in prepared food plants where the fin

6、ished prod-uct may not receive a kill step (in which harmful microorganismsare inactivated by high temperature, high pressure, electrical fields,etc.) before or after packaging. (See the section on Destruction ofOrganisms for more information.) All U.S. meat and poultry plants,and hence many prepare

7、d food plants, operate under USDA regula-tions. Finished and raw product paths are controlled to prevent crosscontamination, and sanitary standards are strictly followed.Preparation, Processing, Unit OperationsInitial steps in production of prepared foods involve preparation,processing, andunitmanuf

8、actureofitemsforassemblyandfillingonthe packaging line. These generally include scheduling ingredients;thawing or defrosting frozen ingredients, where applicable; manu-facturing sauces and gravies; cooking and cooling rice, pasta, and/orother starches; unit operations for manufacturing meat patties

9、andethnic foods, such as burritos; mixing vegetables and/or vegeta-bles and rice, pasta, or other starches; manufacturing dough; andcooling, storage, and transport operations before packaging.The preparation of this chapter is assigned to TC 10.9, RefrigerationApplication for Foods and Beverages.40.

10、2 2010 ASHRAE HandbookRefrigeration (SI)These processes require refrigeration for controlled temperingin refrigerated rooms; plate heat exchangers or swept-surface heatexchangers using chilled water or propylene glycol for preparationof sauces and gravies in processors; chilled water for cooling ric

11、e,pasta, and/or other starches; refrigerated preparation rooms formeat and poultry products; in-line coolers or freezers for meatpatties, burritos, etc.; ice for dough manufacture; and coolerrooms for in-process storage and inventory control.Refrigeration loads for each of these categories should be

12、 calcu-lated individually using the methods described in Chapter 24. Inaddition, loads should be tabulated by time of day and classified byevaporator temperature, chilled-water, ice, and propylene glycolrequirements. An assessment should be made whether an icebuilder is appropriate for chilled-water

13、 requirements to reducerefrigeration compressor capacity.Refrigerated rooms should be amply sized, be able to maintaintemperatures from 0 to 10Cas required for the specific application,have power-operated doors equipped with infiltration reductiondevices, and have evaporators that are easily sanitiz

14、ed. Evaporatorsfor rooms where personnel are working should be equipped withgentle airflow to minimize drafts. Rooms with temperature main-tained at 3C or below should have evaporators equipped for auto-matic coil defrost. Temperature controls for such rooms should betamperproof.Proper safeguards an

15、d good manufacturing practices duringpreparation and processing minimize bacteriological contaminationand growth. This involves using clean raw materials, clean waterandair,sanitaryhandlingofproductthroughout,propertemperaturecontrol, and thorough sanitizing of all product contact surfaces dur-ing c

16、leanup. Sauces, gravies, and cooked products must be cooledquickly to prevent conditions favorable for microbial growth. Referto Chapter 22 for further information on control of microorganisms,cleaning, and sanitation.Assembly, Filling, and PackagingThese activities include transporting components t

17、o packaginglines; preparing and depositing doughs for pies, ethnic dishes, andpizzas; filling or placing components into containers; placing con-tainers into packages; coding, closing, and checking the packages;and transporting packages to cooling and freezing equipment.Items that are pumpable, such

18、 as gravies and sauces, are usuallypumped to a hopper or tank adjacent to the packaging lines. Itemssuch as free-flowing individually quick frozen (IQF) vegetablesmay be transported to the lines in bulk boxes by lift truck directlyfrom cold storage. For example, mixes of vegetables, rice, pasta,and/

19、or other starches that have been prepared at the plant may bewheeled to the packaging lines in portable tanks or vats. Tempered,prefrozen meat or poultry rolls may be placed on special carts andwheeled to the packaging lines.A typical packaging line for meals consists of a timed conveyorsystem with

20、equipment for dispensing containers; a filler or fillersfor components that can be filled volumetrically; volumetric timeddispensers for sauces, gravies, and desserts; net weight filler sys-tems for components and mixes that cannot be placed volumetri-cally; slicing and dispensing apparatus for plac

21、ing componentssuch as tempered meat or poultry rolls and similarly configureditems; line space for personnel to place components that must beplaced manually; liquid dispensers for placing spices and flavor-ings; and a sealing mechanism for placing a sealed plastic sheetover the containers. This syst

22、em may be two or three compart-ments wide for high-volume production.The timed conveyor system is followed by a single filer to aligncontainers in single file before indexing into a cartoner. The contain-ersareautomatically inserted intocartons,afterwhichtheyarecodedand sealed. After leaving the car

23、toner, filled cartons are automati-cally checked for underweights and tramp metal, and then conveyedto cooling or freezing equipment. Other types of packaging linesmay include some or all of the mentioned apparatus; they are usuallyspecific for the prepared food items being filled and packaged.Comme

24、nts regarding product and equipment safeguards, goodmanufacturing practices, and actions to minimize microbial growthapply to packaging activities as well.It is good practice to air-condition filling and packaging areas,particularly when these areas are subject to ambient temperaturesand humidities

25、that can affect product quality and significantly in-crease potential bacteriological exposure. Also, workers are moreproductive in air-conditioned areas. Packaging-area air condition-ing is usually supplied through air-handling units that also provideventilation, heat, and positive pressure to the

26、area. Some applica-tions use separate refrigeration systems; others use chilled water orpropylene glycol from systems installed for product chilling. Gen-erally, no other significant refrigeration is required for filling andpackaging areas.Cooling, Freezing, CasingCartons from packaging are cooled o

27、r frozen in different ways,depending on package sizes and shapes, speed of production, cool-ing or freezing time, inlet temperatures, plant configuration, avail-able refrigeration systems, and labor costs relative to productionrequirements. Refer to Chapter 29 for additional information.In small pla

28、nts, stationary air-blast or push-through trolley freez-ers are used when flexibility is required for a variety of products. Inthese cases, fully mechanized in-line freezers are not economicallyjustified. In larger plants with high production rates, mechanizedfreezers (e.g., automatic plate, belt, s

29、piral belt) are used extensively.These freezers significantly reduce labor costs and provide for in-line freezing.The prepared foods business has many line extension additionsand changes. Each product change results in component differencesthat may change the freezing load and/or time because of inl

30、et tem-peratures, latent heat of freezing, and/or package size (particularlydepth). Each product should be checked to ensure that productionrates for the line extension or different products match the currentfreezing capacity.Over time, experience and advances in packing line technologytend to make

31、packaging lines more efficient and capable of higherproduction rates. These advances often are implemented with exist-ing cooling or freezing capacity, which is relatively constant. Thismay result in freezerexit temperaturesabove 18C if reservefreez-ing capacity is not available or cannot be physica

32、lly added becauseof space limitations. For new or expanded plants, allow space and/or reserve freezer capacity. Increases in packaging line speed andefficiency of 25 to 50% are reasonable to expect. Each instanceshould be individually evaluated.Casing the cartoned product follows freezing with in-li

33、ne pro-duction of meals and main dishes. Manual casing is used in smallplants and/or with low production rates. High-speed productionlines use semiautomatic and automatic casing methods to increaseproductivity and lower labor costs. Inspection at this point is neces-sary to ensure that freezing has

34、been satisfactory and that the cartonsare properly sealed and not disfigured. It is also important to ensurethat cartons do not defrost during conveyor hangups or line stop-pages.Product palletizing follows product casing. Manual palletizing isused for small plants and/or low production rates, and a

35、utomaticpalletizers are used for higher production rates. Most palletizing isdone adjacent to or near cold-storage facilities, and the pallets aretransported to the cold-storage rooms with a lift truck. Some manualpalletizing occurs inside cold-storage rooms, particularly for slowproduction lines, t

36、o prevent product warm-up, but it is more costlybecause labor rates are higher for workers in cold-storage rooms.Someplantsareequippedwithair-blastfreezingcellstoaugmentin-line freezing capacity. These are used primarily for cased prod-ucts when existing in-line freezers are overloaded and to reduce

37、Processed, Precooked, and Prepared Foods 40.3temperatures of products that have been frozen through the latentzone but have not been sufficiently pulled down for placement incold storage. These products are usually loosely stacked on palletswith enough air space around the sides of the cases to achi

38、eve rapidpulldown to 18C or lower.Finished Goods Storage and ShippingLarger prepared foods operations usually have enough cold stor-age space to store the necessary refrigerated and frozen ingredientsand at least 72 h of finished goods production. This volume of spaceallows proper inventory control,

39、 adequate scheduling of ingredientsfor production, and sufficient control of finished goods to ensure thatthe product is 18C or lower before shipment and that it meets thecriteria established for product quality and bacteriological counts.Refrigeration loads for these production warehouses are calcu

40、-lated as suggested in Chapters 23 and 24. Special attention, how-ever, should be given to product pulldown loads and infiltration.Liberal allowances should be made for product pulldown, becausefreezing problems do occur, and some plants or sections of plantsare under negative pressure at times beca

41、use more air is exhaustedthan supplied through ventilation, almost always caused by theneed to remove an undesirable component (e.g., steam, heat, dust)without commensurate mechanical air supply to offset the exhaust.This can result in infiltration by direct inflow, which is a seriousrefrigeration l

42、oad (see Chapter 24) that should be corrected. Thisproblem is not only costly in energy use, but it also makes it diffi-cult to maintain proper storage temperatures.Refrigerated trucks and/or rail cars are generally used for ship-ping. Shipping areas are usually refrigerated to 2 to 7C, and thetruck

43、 loading doors are equipped with cushion-closure seals toreduceinfiltrationofoutsideair.SeeChapter23foradditionalinfor-mation on refrigerated docks. Where refrigerated docks are not pro-vided, take special care to ensure that the frozen product is rapidlyhandled to prevent undue warming.Refrigeratio

44、n LoadsRefrigeration loads cover a wide range of evaporator tempera-tures and different types of equipment. Most plants cover thesewith two or three basic saturated suction temperatures. Where twosuction temperatures are provided, they are usually at 37 to 43Cfor freezing and cold storage and 12 to

45、7C for cooling loads.Where provided, a third suction temperature is usually from 29 to23Cfor frozen product storage rooms and other medium- to low-temperature loads. The third suction temperature is advantageouswith relatively large frozen product storage loads to reduce energycosts.Refrigeration lo

46、ads should be tabulated by time of day, season,evaporator temperature, and equipment type or function. Thisrecord should be made periodically for existing operations; it isessential for new or expanded plants. These tabulations reveal theloading diversity and provide guidance for existing operations

47、 andfor equipment sizing for added capacity or new plants.In addition, loads should be tabulated for off-shift production,weekends, and holidays to provide proper equipment sizing and foreconomic operation for these relatively small loads. See Chapter 24for information on load calculation procedures

48、.Refrigeration SystemsMost refrigeration systems for prepared foods use ammonia asthe refrigerant. Two-stage compression systems are dominant, be-cause compression ratios are high when freezing is involved andenergy savings warrant the added expense and complexity. Evapo-rative condensers are extens

49、ively used for condensing the refriger-ant. Evaporators are designed for full-flooded or liquid overfeedoperation, depending on the equipment or application. Direct-expansion evaporators are not used extensively.New plant designs limit employees exposure to large quantitiesof ammonia. This can be accomplished by locating evaporators, suchas propylene glycol chillers, water chillers, and ice builders, in ornear machine rooms and away from production employees. Freezerscan be located in isolated clusters near machine rooms so that thelow-pressure receivers are also in or near