1、31.1CHAPTER 31POULTRY PRODUCTSProcessing 31.1Chilling 31.1Decontamination of Carcasses 31.4Further Processing 31.4Freezing 31.5Packaging . 31.7Airflow Systems in Poultry Processing Plants . 31.8Plant Sanitation 31.9Tenderness Control. 31.10Distribution and Retail Holding Refrigeration 31.10Preservin
2、g Quality in Storage and Marketing . 31.10Thawing 31.11OULTRY, and broilers in particular, are the most widely grownPfarm animal on earth. Two major challenges face the poultryindustry: (1) keeping food safe from human pathogens carried bypoultry in small numbers that could multiply, sometimes to da
3、nger-ous levels, during processing, handling, and meal preparation; and(2) developing environmentally sound, economical waste manage-ment facilities. Innovative engineering and refrigeration are a part ofthe solutions for these issues.PROCESSINGProcessing is composed of three major segments: Dressin
4、g, where the birds are placed on moving line, killed, anddefeathered.Eviscerating, where the viscera are removed, the carcass ischilled, and the birds are inspected and graded.Further processing, where the largest portion of the carcassesare cut up, deboned, and processed into various products. Thep
5、roducts are packaged and stored chilled or frozen.A schematic processing flowsheet is described in Figure 1;equipment layout for the dressing area is given in Figure 2 and forthe eviscerating area in Figure 3. The space needed in the productionarea for the various activities is shown in Figure 4. A
6、modern, highlyautomated poultry processing plant processes 1 to 3 million birdsper week. In the 1970s, a standard U.S. plant was processing 1500birds per hour (2 shifts, 5 days), or close to 120, 000 birds per week.Barbut (2000) describes processing in detail.CHILLINGPoultry products in the United S
7、tates may be chilled to 26F orfrozen to lower than 26F. Means of refrigeration include ice,mechanically cooled water or air, dry ice (carbon dioxide sprays),and liquid nitrogen sprays. Continuous chilling and freezing sys-tems, with various means for conveying the product, are common.According to US
8、DA regulations (1990), poultry carcasses weighingless than 4 lb should be chilled to 40F or below in less than 4 h,carcasses of 4 to 8 lb in less than 6 h, and carcasses of more than 8 lbin less than 8 h. In air-chilling ready-to-cook poultry, the carcassesinternal temperature should reach 40F or le
9、ss within 16 hours(9CFR381.66).Slow air chilling was considered adequate for semiscalded, un-eviscerated poultry in the past. But with the transformation to evis-cerated, ready-to-cook, sometimes subscalded, poultry, air chillingwas replaced by chilling in tanks of slush ice. Immersion chilling ismo
10、re rapid than air chilling, prevents dehydration, and effects a netabsorption of water of 4 to 12%. Per U.S. regulations (9CFR441.10),water retention in raw carcasses and parts must be shown to be anunavoidable consequence of processing, to the specifications of theFood Safety and Inspection Service
11、 (FSIS). Additionally, water-retaining poultry must carry a label stating the maximum percentageof water retained. Objections to this weight gain from external wa-ter, a concern that water chillers can be recontamination points, andthe high cost of disposing of waste water in an environmentallysound
12、 manner have encouraged some operators to consider return-ing to air chillers.Continuous-immersion slush ice chillers, which are fed auto-matically from the end of the evisceration conveyer line, havereplaced slush ice tank chilling, a batch process. In general, tanksare only used to hold iced, chil
13、led carcasses before cutting up, or toage before freezing.The following types of continuous chillers are used:Continuous drag chillers. Suspended carcasses are pulledthrough troughs containing agitated cool water and ice slush.The preparation of this chapter is assigned to TC 10.9, Refrigeration App
14、li-cation for Foods and Beverages.Fig. 1 Processing Sequence of Fresh PoultryFig. 1 Processing Sequence of Fresh Poultry31.2 2010 ASHRAE HandbookRefrigerationSlush ice chillers. Carcasses are pushed by a continuous series ofpower-driven rakes.Concurrent tumble systems. Free-floating carcasses passth
15、rough horizontally rotating drums suspended in tanks of, suc-cessively, cool water and ice slush. Movement of the carcasses isregulated by the flow rate of recirculated water in each tank.Counterflow tumble chillers. Carcasses are carried throughtanks of cool water and ice slush by horizontally rota
16、ting drumswith helical flights on the inner surface of the drumsRocker vat systems. Carcasses are conveyed by the recirculatingwater flow and agitated by an oscillating, longitudinally orientedpaddle. Carcasses are removed automatically from the tanks bycontinuous elevators.These chillers can reduce
17、 the internal temperature of broilersfrom 90 to 40F in 20 to 40 min, at processing speeds of 5000 to10,000 birds/h (Figure 5). Chillers must meet food safety require-ments (see, e.g., 9CFR381.66) and the facilitys Hazard Analysis ofCritical Control Points (HACCP) plan (see Chapter 22).Adjuncts and r
18、eplacements for continuous-immersion chillingshould be used, if available, because immersion chilling is believedto be a major cause of bacterial contamination. Water spray chilling,air blast chilling, carbon dioxide snow, or liquid nitrogen spray arealternatives, but with the following limitations:
19、Liquid water has a much higher heat transfer coefficient than anygas at the same temperature of cooling medium, so water immer-sion chilling is more rapid and efficient than gas chilling. Water spray chilling, without recirculation, requires much greateramounts of water than immersion chilling. Prod
20、uct appearance should be equivalent for water immersion orspray chilling, but inferior for air blast, carbon dioxide, or nitro-gen chilling, because of surface dehydration.Air chilling without packaging could cause a 1 to 2% loss of mois-ture, whereas water immersion chilling allows from 4 to 15%moi
21、sture uptake, and water spray chilling up to 4% moistureuptake. Salt-brine chilling is the fastest chilling medium, but haslittle use in fresh poultry chilling.Coolant temperature and degree of contact between coolant andproduct are most important in transferring heat from the carcass sur-face to th
22、e cooling water. The heat transfer coefficient between thecarcass and the water can be as high as 630 Btu/hft2F. Mechan-ical agitation, injection of air, or both can improve the heat transferrate (Veerkamp 1995). Veerkamp and Hofmans (1974) expressedheat removed from poultry carcasses by the followi
23、ng empiricalrelationship.(1)whereh = apparent heat transfer coefficient, Btu/hft2Fm = mass of the carcass, lb = cooling time, sQi= maximum heat removal, BtuFigure 5 shows time-temperature curves in a commercial counter-flow chiller and compares calculated and measured values.With adequately washed c
24、arcasses and adequate chiller overflowin counterflow to the carcasses, the bacterial count on carcassesshould be reduced by continuous water-immersion chilling. How-ever, incidence of a particular low-level contaminant, such as Sal-monella, may increase during continuous water-immersion chilling;thi
25、s can be controlled by chlorinating the chill water. However, forchlorine to be effective, the waters pH should be 7.0.Spray chilling without recirculation has reduced bacterial surfacecounts 85 to 90% (Peric et al. 1971). Microbe transfer by spray chill-ing is unlikely. Chilling with air, carbon di
26、oxide, or nitrogen presentsno obvious microbiological hazards, although good sanitary practicesFig. 2 Equipment Layout for Live Bird Receiving, Slaughtering, and Defeathering AreasFig. 2 Typical Equipment Layout for Live Bird Receiving, Slaughtering, and Defeathering AreasQQi- 0 . 0 0 9 h 0.73+loglo
27、g=0.194 h 0.187log m 0.564 h 2.219log+logPoultry Products 31.3are essential. If the surface of the carcass freezes as a part of the chill-ing process, the bacterial load may be reduced as much as 90%.Air or gas chilling is commonly used in Europe. In air-blastand evaporative chilling, heat is conduc
28、ted partly by the air-to-carcass contact and partly by evaporation of moisture from thecarcass surface. The amount of water removed by evaporationdepends on the carcass temperature, but even at 14F it is about1%. The apparent heat transfer coefficient ranges from 16 to63 Btu/hft2F. Major disadvantag
29、es of air chilling are slowcooling, dripping from one bird to another in multitiered chill-ers, and weight loss during chilling. A diagram of a one-tieredevaporative air chiller is given in Figure 6. To reduce contamina-tion, it is very important that birds do not touch or drip on eachother if multi
30、ple layers are used. Cryogenic gases are generally used in long insulated tunnelsthrough which the product is conveyed on an endless belt. Somefreezing of the outer layer (crust freezing) usually occurs, and thetemperature is allowed to equilibrate to the final, intended chilltemperature. Some plant
31、s use a combination of continuous waterimmersion chilling to reach 35 to 40F and a cryogenic gas tunnelto reach 28F. The water-chilled poultry, either whole or cut up, isgenerally packaged before gas chilling to prevent dehydration.Fig. 3 Equipment Layout for Eviscerating, Chilling, and Packaging Ar
32、easFig. 3 Typical Equipment Layout for Eviscerating, Chilling, and Packaging Areas31.4 2010 ASHRAE HandbookRefrigerationIce requirements per bird for continuous immersion chillingdepend on entering carcass temperatures and weight, entering watertemperature, and exit water and carcass temperature. Fo
33、r a counter-flow system, 60F entering water and 65F exit water, 0.25 lb of iceper pound of carcass is a reasonable estimate. This may be com-pared to a requirement of 0.5 to 1 lb of ice per pound of poultry forstatic ice slush chilling in tanks. For continuous counterflow water-immersion chillers, i
34、f plant water temperature is considerably above65F, it may be economical to use a heat exchanger between incom-ing plant water and exiting (overflow) chill water.Ice production for chilling is usually a complete in-plant opera-tion, with large piping and pumps to convey small crystalline ice orice s
35、lush to the point of use. To reduce ice consumption, someimmersion chillers are double-walled and depend on circulatingrefrigerant to chill the water in the chiller. The chiller has an ammo-nia or refrigerant lubricant between the outer and inner jacket, withthe inner jacket serving as the heat tran
36、sfer medium. Agitation or adefrost cycle must be provided during periods of slack production toprevent the chiller from freezing up.Chilling and holding to about 28F, the point of incipient freez-ing, gives the product a much longer shelf life compared with aproduct held at ice-pack temperatures (St
37、adelman 1970).DECONTAMINATION OF CARCASSESContamination of poultry meat by foodborne pathogens duringprocessing can be potentially dangerous if microbes multiply to crit-ical numbers and/or produce poisonous toxins (Zeidler 1996, 1997).The Hazard Analysis of Critical Control Points (HACCP) system(se
38、e Chapter 22 and the section on HACCP Systems in PoultryProcessing) was specifically developed for each food to eliminate orkeep pathogen levels very low so food-related illnesses cannot breakout. Appropriate refrigeration and strict temperature controlthroughout the food channel is vital to suppres
39、s microbial growth inhigh-moisture perishable foods and meats in particular. Decontamination steps are now being added just before chilling.Numerous methods have been developed (Bolder 1997; Mulder1995), including lactic acid (1%), hydrogen peroxide (0.5%), andtrisodium phosphate (TSP) sprays. Ozone
40、 (O3) is a strong oxi-dizer and can be used to decontaminate chiller and scalding water;however, it is very corrosive. Gamma irradiation of poultry is approved in many countries,including the United States; products are available for sale in a fewoutlets. The publics fear of this technique limits sa
41、les. However,the threat of food poisoning is reducing objections to irradiatedfoods because irradiation is very effective, and can kill 95.5% ofnon-spore-forming pathogens (Stone 1995). A dose of 250 krad isthe most suitable for poultry.Steam under vacuum effectively kills 99% of the surface bacte-r
42、ia on beef and pork carcasses and is used commercially. In this con-tinuous system, the carcass is carried on a rail to a chamber. Avacuum is pulled and steam at 290F is applied for 25 ms. Uponbreaking the vacuum, the carcass surface is cooled to prevent thesurface from cooking. USDA engineers devel
43、oped steam equipmentfor poultry in 1996.FURTHER PROCESSINGMost chickens and turkeys, for both chilled and frozen distri-bution, are cut up in the processing plant. More than 90% of thebroilers in the United States are sold as cut-up products produced atFig. 4 Space-Relationship-Flow Diagram for Poul
44、try Process-ing PlantFig. 4 Space-Relationship-Flow Diagram for Poultry Processing Plant(Square feet of floor space needed)Fig. 5 Broiler and Coolant Temperatures inCountercurrent Immersion ChillerFig. 5 Broiler and Coolant Temperatures in Countercurrent Immersion ChillerFig. 6 One-Tier Evaporative
45、Air ChillerFig. 6 One-Tier Evaporative Air ChillerPoultry Products 31.5the processing plant. The cutting procedure is almost fully auto-matic.Backs and necks are often mechanically deboned, giving a com-minuted slurry that is frozen in rectangular flat cartons containingabout 60 lb. Turkey breasts,
46、legs, and drumsticks are available asseparate film-packaged parts, and turkey thigh meat is marketed asa ground product resembling hamburger. Partial cooking and bread-ing and battering of broiler parts is done in poultry processingplants.Unit OperationsThe following types of equipment used for furt
47、her processing ofpoultry products are also used in red meat facilities.Size Reduction and Mixing Machines. Several types of size-reduction and mixing equipment are available.In grinding, meat is conveyed by an auger and forced through agrinding plate.Flaking is done by cutting blades locked at a spe
48、cific angle on arotating drum. Flaking does not extensively break muscle cells, asin grinding, and moisture loss and dripping are limited. Producttexture resembles muscle texture.Chopping is generally conducted with silent cutter equipment.Meat is placed in a rotating bowl with ice, which is used to
49、 keepthe temperature low, and vertical rotating blades chop the movingmeat. The length of chopping time determines the particle size.The end product is used in hot dogs and sausages.Mixing, tumbling, and injecting machines produce a uniformproduct out of various meats and nonmeat ingredients such as salt,sugar, dairy or egg proteins, spices, and flavorings. Together withsalt, mixing also helps extract myosin, which acts likes a glue inholding the product together. Injection machines insert an accurate and repeatable volume ofliquid that conta
