332 Meat refrigeration Table 16.11 Examples of commercial cooling of meat slurries and soups in the Cooling method Cooling time Temperature To 20C Total Initial Final (h) In ambient at23°cin 0.6m vats In 0.6m vats with cold water jacket then ambient at21°C In 38 cm diameter pans in chill room at2to9°c In 35 cm deep bucket at 17.5 1 18 20°Cfor7 h then7°C Source: James, 1990c 1100kg batches of meat sauce could be cooled from 85 to 10C in less than 'used ing a vacuum cooling system. When a conventional blast air system was used the cooling time achieved was related to the product depth and even when the depth had been reduced to 70mm the cooling time was in excess of 6.5h 16.4 Process cooling Traditionally, ice has been added to meat mixtures during mixing and grind ng to maintain their temperature Liquid nitrogen(LN2) can also be used to maintain the temperature of meat during mixing thus increasing the extraction of soluble muscle proteins. LN2 or CO2 can also be used to chill restructured meat during mixing and cutting to -3C in approximately 10 to 15 min Jowls and bacon fat in 1400kg batches can be mixed and cooled from 7.3 to 0C within 12 min. The system uses a cycle of 50s LN2 and mixing then 15s mixing only to allow temperature equalisation Cryogenic systems are also available to maintain temperatures during tumbling. In cooked ham manufacture the use of liquid nitrogen was claimed to reduce meat dust during tumbling, substantially shorten the process time and improve hygiene 16.5 Cook-chill The term cook-chill usually refers to a catering system where food is pre pared, cooked and cooled in a central facility before being distributed to332 Meat refrigeration Table 16.11 Examples of commercial cooling of meat slurries and soups in the UK Cooling method Depth Cooling time Temperature of slurry (°C) To 20 °C Total Initial Final (cm) (h) (h) In ambient at 23 °C in 50 – 16 99 64 0.6 m3 vats In 0.6 m3 vats with 50 – 14 99 38 cold water jacket then ambient at 21 °C In 38 cm diameter pans 17 9.8 16 93 12 in chill room at 2 to 9 °C In 35 cm deep bucket at 30 17.5 18 55 18 20 °C for 7 h then 7 °C Source: James, 1990c. 1100 kg batches of meat sauce could be cooled from 85 to 10 °C in less than 30 min using a vacuum cooling system.When a conventional blast air system was used the cooling time achieved was related to the product depth and even when the depth had been reduced to 70 mm the cooling time was in excess of 6.5 h. 16.4 Process cooling Traditionally, ice has been added to meat mixtures during mixing and grind￾ing to maintain their temperature. Liquid nitrogen (LN2) can also be used to maintain the temperature of meat during mixing thus increasing the extraction of soluble muscle proteins. LN2 or CO2 can also be used to chill restructured meat during mixing and cutting to -3 °C in approximately 10 to 15 min. Jowls and bacon fat in 1400 kg batches can be mixed and cooled from 7.3 to 0 °C within 12 min. The system uses a cycle of 50 s LN2 and mixing then 15 s mixing only to allow temperature equalisation. Cryogenic systems are also available to maintain temperatures during tumbling. In cooked ham manufacture the use of liquid nitrogen was claimed to reduce meat dust during tumbling, substantially shorten the process time and improve hygiene. 16.5 Cook–chill The term ‘cook–chill’ usually refers to a catering system where food is pre￾pared, cooked and cooled in a central facility before being distributed to