16 Secondary chilling of meat and meat products Meat is chilled immediately after slaughter. Most of the subsequent opera- tions in the cold chain are designed to maintain the temperature of the meat Cooking is a very common operation in the production of many meat products and operators appreciate the importance of rapidly cooling the cooked product. However, any handling such as cutting, mixing or tumbling will add heat to the meat and increase its temperature. A secondary cooling operation is always required with chilled meat and meat products to reduce their temperature to approaching 0C and maintain their storage life The aim of any cooking process for meat/meat produce is to ensure the destruction of vegetative stages of any pathogenic microorganisms. However, there is always the possibility that the cooking process will not kill some microorganisms that produce spores or that the food can become recontaminated. Therefore, microbiologists recommend that the tempera ture of the meat should be rapidly reduced, especially from approximately 60 and 5C, to prevent multiplication of existing or contaminating bacte ria. Rapid cooling is also desirable with cooked products to maintain quality by eliminating the overcooking that occurs during slow cooling There are specific cooling recommendations for cook-chill and cook-freeze catering systems. However, even with thin products these are difficult to achieve without surface freezing. Cooling large hams and other cooked meat joints is inherently a much slower process and studies have shown that companies often have very poor cooling systems. The methods available to cool meat joints, pies and other cooked prod ucts have been described in detail by James(1990a). A review of the use of vacuum cooling in the food industry has been published by McDonald and Sun(2000)
16 Secondary chilling of meat and meat products Meat is chilled immediately after slaughter. Most of the subsequent operations in the cold chain are designed to maintain the temperature of the meat. Cooking is a very common operation in the production of many meat products and operators appreciate the importance of rapidly cooling the cooked product. However, any handling such as cutting, mixing or tumbling will add heat to the meat and increase its temperature. A secondary cooling operation is always required with chilled meat and meat products to reduce their temperature to approaching 0 °C and maintain their storage life. The aim of any cooking process for meat/meat produce is to ensure the destruction of vegetative stages of any pathogenic microorganisms. However, there is always the possibility that the cooking process will not kill some microorganisms that produce spores or that the food can become recontaminated. Therefore, microbiologists recommend that the temperature of the meat should be rapidly reduced, especially from approximately 60 and 5 °C, to prevent multiplication of existing or contaminating bacteria. Rapid cooling is also desirable with cooked products to maintain quality by eliminating the overcooking that occurs during slow cooling. There are specific cooling recommendations for cook–chill and cook–freeze catering systems. However, even with thin products these are difficult to achieve without surface freezing. Cooling large hams and other cooked meat joints is inherently a much slower process and studies have shown that companies often have very poor cooling systems. The methods available to cool meat joints, pies and other cooked products have been described in detail by James (1990a). A review of the use of vacuum cooling in the food industry has been published by McDonald and Sun (2000)
322 Meat refrigeration The majority of plants rely on air blast cooling systems for the chilling of pre-cooked meat products. In batch systems the products, packs or tray of cooked material are placed directly on racks in the chiller or on trolleys that can be wheeled into the chiller when fully loaded. Continuous systems range from trolleys pulled through tunnels to conveyorised spiral or tunnel Some meals and products are chilled using cryogenic tunnels, however, care must be taken to avoid surface freezing. Imperviously packed prod- ucts can be chilled by immersion in cooled water or other suitable liquid. With some cooked products such as large hams in moulds and sausages, chlorinated water sprays can be used in the initial stages of cooling Increas ingly, pie fillings are pressure-cooked and vacuum cooled. With many prod ucts an initial cooling stage using ambient air can often substantially reduce the cooling load in the cooling system 16.1 Cooked meat 16.1.1 Legislation In the UK the Food Safety (Temperature Control) Regulations(1995 apply to any food that "is likely to support pathogenic micro-organisms or the formation of toxins'and that must be kept at or below 8C. Regulation 11 does not define a cooling time or rate, only that the food should be cooled as quickly as possible following the final heating stage The guidance document to the above regulations produced by the Department of Health is even less specific Under heading Vill, cooling of food, paragraph 47 it states: The cooling period for any food would not be regarded as unacceptable merely because other equipment, not present at he business, could have cooled the food more quickly. The time taken to chieve cooling must be consistent with food safety. Cooling will often be a step which is critical to food safety The Meat Products(Hygiene) Regulations(1994)contain special condi tions for meat-based prepared meals. They require that the meat product and the prepared meal shall be refrigerated to an internal temperature of +10C or less within a period of not more than 2h after the end of cooking However, they then go on to state that produce may be exempt from the 2h period where a longer period is justified for reasons connected with the production technology employed. The wording is similar in the EC Meat recurve In the USa the essential rules of the US Regulations(318. 179 CFR CH Il, 1.1.96 edition) on safe cooling of cooked meats are Chilling shall begin within 90 min after the cooking cycle is completed All products should be chilled from 488C to 12. 7C in no more than
The majority of plants rely on air blast cooling systems for the chilling of pre-cooked meat products. In batch systems the products, packs or trays of cooked material are placed directly on racks in the chiller or on trolleys that can be wheeled into the chiller when fully loaded. Continuous systems range from trolleys pulled through tunnels to conveyorised spiral or tunnel air blast chillers. Some meals and products are chilled using cryogenic tunnels, however, care must be taken to avoid surface freezing. Imperviously packed products can be chilled by immersion in cooled water or other suitable liquid. With some cooked products such as large hams in moulds and sausages, chlorinated water sprays can be used in the initial stages of cooling. Increasingly, pie fillings are pressure-cooked and vacuum cooled. With many products an initial cooling stage using ambient air can often substantially reduce the cooling load in the cooling system. 16.1 Cooked meat 16.1.1 Legislation In the UK the Food Safety (Temperature Control) Regulations (1995) apply to any food that ‘is likely to support pathogenic micro-organisms or the formation of toxins’ and that must be kept at or below 8 °C. Regulation 11 does not define a cooling time or rate, only that the food should be cooled as quickly as possible following the final heating stage. The guidance document to the above regulations produced by the Department of Health is even less specific. Under heading VIII, cooling of food, paragraph 47 it states: ‘The cooling period for any food would not be regarded as unacceptable merely because other equipment, not present at the business, could have cooled the food more quickly. The time taken to achieve cooling must be consistent with food safety. Cooling will often be a step which is critical to food safety’. The Meat Products (Hygiene) Regulations (1994) contain special conditions for meat-based prepared meals. They require that the meat product and the prepared meal shall be refrigerated to an internal temperature of +10 °C or less within a period of not more than 2 h after the end of cooking. However, they then go on to state that produce may be exempt from the 2 h period where a longer period is justified for reasons connected with the production technology employed. The wording is similar in the EC Meat Products Directive. In the USA the essential rules of the US Regulations (318.17 9 CFR CH III, 1.1.96 edition) on safe cooling of cooked meats are: • Chilling shall begin within 90 min after the cooking cycle is completed. • All products should be chilled from 48.8 °C to 12.7 °C in no more than 6 h. 322 Meat refrigeration
Secondary chilling of meat and meat products 323 able 16.1 Recommended good practice and maximum cooling times for uncured meat Cooling time(h) Good practice Maximi To50°C From50°to12°C From12°to5°C 1618 Total time to5°C Source: Gaze et al.. 1998 able 16.2 Recommended good practice and maximum cooling times for cured meat Cooling time(h) Good practice Maximi To50°C From50°to12°C From12°to5°C 1.75 Total time to5°C 10.00 12.50 Source: Gaze et al.. 1998 Chilling shall continue and the product should not be packed for ship ment until it has reached 4. 4C These US Federal Regulations have been widely adopted outside areas under the control of the USDA, including by European retailers. Further recommendations have been made by Gaze et aL., 1998. Their main recom ' For a typical uncured cooked meat product, made from good quality raw material under hygienic conditions and with sound process controls, it is suggested that the following limitations (Table 16.1) for cooling time from completion of the cooking process should apply For products which are cured(defined as minimum 2.5% salt on water phase and 100 ppm nitrite in-going), these times may be extended (Table 16.2). As an approximation it is suggested this be by 25%. 16.1.2 Practical In many industrial cooking operations whole hams and large meat joints are often cooked and cooled in an intact form and then supplied to restau- rants or retail shops where they are sliced before sale. Surveys(Cook, 1985: James, 1990b and c; Gaze et al., 1998) have shown that industry uses a variety of methods for cooling whole hams(Table 16.3, Table 16.4 and Table 16.5) In these processes the earlier data showed that cooling times were as long
• Chilling shall continue and the product should not be packed for shipment until it has reached 4.4 °C. These US Federal Regulations have been widely adopted outside areas under the control of the USDA, including by European retailers. Further recommendations have been made by Gaze et al., 1998. Their main recommendations are that: • ‘For a typical uncured cooked meat product, made from good quality raw material under hygienic conditions and with sound process controls, it is suggested that the following limitations (Table 16.1) for cooling time from completion of the cooking process should apply.’ • ‘For products which are cured (defined as minimum 2.5% salt on water phase and 100 ppm nitrite in-going), these times may be extended (Table 16.2). As an approximation it is suggested this be by 25%.’ 16.1.2 Practical In many industrial cooking operations whole hams and large meat joints are often cooked and cooled in an intact form and then supplied to restaurants or retail shops where they are sliced before sale. Surveys (Cook, 1985; James, 1990b and c; Gaze et al., 1998) have shown that industry uses a variety of methods for cooling whole hams (Table 16.3, Table 16.4 and Table 16.5). In these processes the earlier data showed that cooling times were as long Secondary chilling of meat and meat products 323 Table 16.1 Recommended good practice and maximum cooling times for uncured meat Cooling time (h) Good practice Maximum To 50 °C 1 2.5 From 50 °C to 12 °C 6 6 From 12 °C to 5 °C 1 1.5 Total time to 5 °C 8 10 Source: Gaze et al., 1998. Table 16.2 Recommended good practice and maximum cooling times for cured meat Cooling time (h) Good practice Maximum To 50 °C 1.25 3.25 From 50 °C to 12 °C 7.5 7.5 From 12 °C to 5 °C 1.25 1.75 Total time to 5 °C 10.00 12.50 Source: Gaze et al., 1998
324 Meat refrigeration Table 16.3 Examples of commercial ham cooling in the UK Cooling method 动品 Total Final rature° In metal mould in chill oom17to6°C,0.2ms In bag in chill room -3°Cto-10°0.3ms In bag water shower then chill room at-1°then 3°Cto5°C In bag in ambient 13.5 15°Cto7°C Source: James, 1990c later study cooling times were still as long as 16h but final temperatur.e as 21h, and final temperatures high: 15-20C(Table 16.3, Table 16.4). In the were no higher than 8C (Table 16.6) A similar picture is seen in data on the cooling of cooked pork with final mperatures as high as 12C and cooling times of up to 20h(Table 16.4) Corresponding figures for the cooling of cooked beef were 15C and 22h (Table 16.4). Data obtained from numerous sources within the UK cater- ing industry by Mottishaw(1986)indicate that the cooling procedures for bulk-cooked meats could also vary considerably(Table 16.6). For example, some meat products are said to be cooled to 1C in 2h, whereas at the other extreme, products may take 72h to cool to 4 C. Commonly, a 4.5kg product ill take 12h to cool below 5C and larger products could take longer. In ddition, there is often a delay before chilling begins, this may vary from 10 min up to 6h 16.1.3 Experimental studies The most relevant cooling data for cooling of cooked meat from laboratory investigations are shown in Table 16.7. A simple process for estimating the immersion cooling time of beef roasts has been produced by Nolan (1986). Generally, the results show that immersion cooling is almost twice as fast as air cooling at the same temperature. Vacuum cooling was an order of magnitude faster than immersion cooling but the weight loss was substantially (over twice) higher. Using a less severe vacuum treatment or a combination of the different methods is likely to provide an optim solution The James and Bailey(1982) study showed that in ham cooling, a 0. 75h initial cooling period in ambient air reduced the initial load on the refrig- eration by a factor of almost 2. If the ham was placed straight into air at
as 21 h, and final temperatures high: 15–20 °C (Table 16.3,Table 16.4). In the later study cooling times were still as long as 16 h but final temperatures were no higher than 8 °C (Table 16.6). A similar picture is seen in data on the cooling of cooked pork with final temperatures as high as 12 °C and cooling times of up to 20 h (Table 16.4). Corresponding figures for the cooling of cooked beef were 15 °C and 22 h (Table 16.4). Data obtained from numerous sources within the UK catering industry by Mottishaw (1986) indicate that the cooling procedures for bulk-cooked meats could also vary considerably (Table 16.6). For example, some meat products are said to be cooled to 1 °C in 2 h, whereas at the other extreme, products may take 72 h to cool to 4 °C. Commonly, a 4.5 kg product will take 12 h to cool below 5 °C and larger products could take longer. In addition, there is often a delay before chilling begins, this may vary from 10 min up to 6 h. 16.1.3 Experimental studies The most relevant cooling data for cooling of cooked meat from laboratory investigations are shown in Table 16.7. A simple process for estimating the immersion cooling time of beef roasts has been produced by Nolan (1986). Generally, the results show that immersion cooling is almost twice as fast as air cooling at the same temperature.Vacuum cooling was an order of magnitude faster than immersion cooling but the weight loss was substantially (over twice) higher. Using a less severe vacuum treatment or a combination of the different methods is likely to provide an optimum solution. The James and Bailey (1982) study showed that in ham cooling, a 0.75 h initial cooling period in ambient air reduced the initial load on the refrigeration by a factor of almost 2. If the ham was placed straight into air at 324 Meat refrigeration Table 16.3 Examples of commercial ham cooling in the UK Cooling method Weight Height Cooling Total Final (kg) of joint time to (h) temperature (°C) (cm) 20 °C (h) In metal mould in chill 6.4 19 12 1.4 15 room 17 °C to 6 °C, 0.2 ms-1 In bag in chill room 7.3 18 9.3 21 2 -3 °C to -10 °C, 0.3 ms-1 In bag water shower then 6.8 18 6.6 14 5 chill room at -1 °C then 3 °C to 5 °C In bag in ambient 6.8 20 – 13.5 24 15 °C to 7 °C Source: James, 1990c
Table 16.4 Previously unpublished survey data on cooling of cooked meat in industry and shops Meat Wt Diam mm Method rap Initial Time(h) 10C Final temp/time g Cto50°C Ham 6.35 Chill roon176°C0.2ms Metal mould 15/14 3.8 726 Chill room -3/-1oC03ms- Sealed bag 3.8 4 Chill room 17-6. 0.2 ms- Sealed bag 0.0 Shop air 15-7C<0.2ms Sealed ba -055 4.7 9/21 4/13.5 1/13.5 4.7 22/13.5 Shower 20min. chill 3/5C 4h Sealed bas ∽8 9.3 5/14 Bacon 4.54 114 Factory air, 20-12C 4/12.5 114 2.6 15/13.5 114 16/13.5 Pork 6.80 Shower 20min, chill-1C 4h, chill 3/5C Bag 5/1 5/12 p30-20°C7h,chil86°C 20476-101 Kitchen22°c2h,chil2/5°C Uncovered 4/7.5 2.0476-101 4/9.0 Beef5.9016 Kitchen23°C1.5h,chil3-5° Netted 9/15 Chil200° Netted 2.6 11.0 Shop30-20°c7h, chill 186°C Punctured 15/2 101 Blast chill -5/-3C 1.2 ms Uncovered 713.9 3.86 127 Blast chill 4/5C 2 ms Netted 3.40 127 Domestic fridge 2/7C static Netted 3.40 Chil1/2°C0.3ms Netted 3.63 Blast freeze" ms- Netted 1.6 4. 9/48
Secondary chilling of meat and meat products 325 Table 16.4 Previously unpublished survey data on cooling of cooked meat in industry and shops Meat Wt Diam mm Method Wrap Initial Time (h) 10 °C Final temp/time kg temp °C to 50 °C Ham 6.35 191 Chill room 17–6 °C 0.2 ms-1 Metal mould 71 3.6 – 15/14 70 3.8 – 15/14 7.26 178 Chill room -3/-1 °C 0.3 ms-1 Sealed bag 69 3.8 12.7 2/21 68 3.4 12.5 2/21 Chill room 17–6 °C 0.2 ms-1 Sealed bag – 4.8 20.0 9/21 – 4.7 20.0 9/21 6.80 203 Shop air 15–7 °C <0.2 ms-1 Sealed bag 69 3.7 – 24/13.5 75 4.2 – 21/13.5 75 4.7 – 23/13.5 75 4.3 – 22/13.5 6.80 178 Shower 20 min, chill 3/5 °C 4 h Sealed bag 72 2.6 9.3 5/14 Bacon 4.54 114 Factory air, 20–12 °C Bag 76 1.9 – 14/12.5 4.08 114 71 2.6 – 15/13.5 4.08 114 76 2.7 – 16/13.5 Pork 6.80 203 Shower 20 min, chill -1 °C 4 h, chill 3/5 °C Bag 77 2.2 6.8 5/12 6.35 203 79 2.2 7.2 5/12 5.44 165 Shop 30–20 °C 7 h, chill 18–6 °C Bag 82 4.5 19.5 12/20 2.04 76–101 Kitchen 22 °C 2 h, chill 2/5 °C Uncovered 100 2.0 5.9 4/7.5 2.04 76–101 100 1.9 5.5 4/9.0 Beef 5.90 165 Kitchen 23 °C 1.5 h, chill 13–5 °C Netted 93 2.4 13.0 9/15 6.80 152 Chill 20–0 °C Netted 70 2.6 11.0 0/16 5.90 165 Shop 30–20 °C 7 h, chill 18–6 °C Punctured 75 4.4 22.0 15/22 bag – 101 Blast chill -5/-3 °C 1.2 ms-1 Uncovered 90 – 3.4 7/3.9 3.86 127 Blast chill 4/5 °C 2 ms-1 Netted 73 1.7 5.3 5/7 3.40 127 Domestic fridge 2/7 °C static Netted 72 2.2 7.5 9/7 3.40 127 Chill 1/2 °C 0.3 ms-1 Netted 71 1.9 6.8 9/7 3.63 127 Blast freeze -30 °C 1 ms-1 Netted 73 1.6 4.6 9/4.8