146 Meat refrigeration EO°Ni9寸E° Fig. 7.3. Freezing time of 15 cm thick boxed blocks(source: James et aL, 1979). Table 7. Ay zing time from4to-7° thermal centre of 50, 75 and 100kg beef quarters 50k 100k Hindquarter Forequarter Source: James et al.. 1987 investigations had used air Temperature in air systems ranged from -ll to 40C and weight loss from 0.3 to 1. 19%. In their own investigations beef quarters ranging in weight from 40 to 140kg were frozen in air at -32C Im s On average, hindquarters below 50kg and forequarters below 75kg could be frozen in a 24 h operation (Table 7.7). There was no statistical dif ference in bacterial counts before and after freezing. 7.5.3 Mutton carcasses Mutton production is seasonal and continuity of supply for processing can be achieved by frozen storage and subsequent thawing and boning(Creed and James, 1984) Data from the investigations of Creed and James were used to verify a predictive program for freezing of mutton carcasses. The predictions indi- cated that any condition more severe than -20C, 0.5ms, would achieve a 24 h freezing operation for unwrapped carcasses(Table 7. 8). To guaran tee an overnight(15-16h) freezing cycle for wrapped carcasses, conditions more severe than -30C, 4ms, would be required. 7.54 ofal Although edible offal comprises 3-4% of the cold weight of a carcass there little published data on its refrigeration(Creed and James, 1983 ). Theinvestigations had used air. Temperature in air systems ranged from -11 to -40 °C and weight loss from 0.3 to 1.19%. In their own investigations beef quarters ranging in weight from 40 to 140kg were frozen in air at -32 °C, 1.5 m s-1 . On average, hindquarters below 50 kg and forequarters below 75 kg could be frozen in a 24 h operation (Table 7.7). There was no statistical dif￾ference in bacterial counts before and after freezing. 7.5.3 Mutton carcasses Mutton production is seasonal and continuity of supply for processing can be achieved by frozen storage and subsequent thawing and boning (Creed and James, 1984). Data from the investigations of Creed and James were used to verify a predictive program for freezing of mutton carcasses. The predictions indi￾cated that any condition more severe than -20 °C, 0.5 m s-1 , would achieve a 24 h freezing operation for unwrapped carcasses (Table 7.8). To guaran￾tee an overnight (15–16h) freezing cycle for wrapped carcasses, conditions more severe than -30 °C, 4 m s-1 , would be required. 7.5.4 Offal Although edible offal comprises 3–4% of the cold weight of a carcass there is little published data on its refrigeration (Creed and James, 1983). The 146 Meat refrigeration 0 20 40 60 80 100 120 38 25 55 38 112 75 –30 –20 –10 Time from 4 to –7 °C (h) Air temperature (°C) 0.5 m/s 5.0 m/s Fig. 7.3. Freezing time of 15 cm thick boxed blocks (source: James et al., 1979). Table 7.7 Average freezing time from 4 to -7 °C at thermal centre of 50, 75 and 100 kg beef quarters Weight 50 kg 75 kg 100 kg Hindquarter 22 29 33 Forequarter 13 20 25 Source: James et al., 1987