Primary chilling of red meat 105 Table 6.2 Chilling time(in h) to 7C in the deep leg of 50-220 kg beef sides in air at.C,0.75ms"(source: Kerens and visser, 1978)or"C,1.0ms Conditions 100 0°C,075ms-1 176 274 0°C,1.0ms- 36.0 Source: Bailey and Cox, 1976. lean and heavy animals fat Comparisons can thus only be made over a limited weight range. In the Langford work(Bailey and Cox, 1976)using 140kg sides in air at C,0.5ms, cooling times of the fattest carcasses were as much as 20% above the average and the leanest 20% below. In South Africa(Kerens and Visser, 1978)cooling times at 0C,0.75ms" for fat and lean sides of 100kg were 24.5 and 190h, respectively, and for 125kg, 27 and 22h. res 6.2.1.2 Effect of environmental and carcass variables on weight loss Weight loss is governed by the same variables that affect cooling rate but with different relative importance. 6.2.1.2.1 Air temperature The effect of air temperature on evaporative weight loss during chilling dependent upon the criteria used to define the end of the chilling process (Fig. 6.5). When chilling for a set time(18h) weight loss increases as tem perature decreases. The opposite effect is found when chilling to a set temperature (10C in deep leg) with weight loss decreasing as the air temperature is lowered. However, the magnitude of the effect of air tem perature on weight loss is small, as a reduction in air temperature from 4 to 0C produces a change of <0. 1%(Fig. 6.5)under either criteria 6.2. 1.2.2 Air velocity The effect of air velocity is similar to that of air temperature. An increase from 0.5 to 3. 0ms-I made <0. 1% difference to losses when sides were chilled to a deep leg temperature of 10C. Increasing the air velocity from 0. 75 to 3ms raised weight losses by up to 0. 2% when measured over an 18 h chilling period(Fig. 6.5). In a longer chilling cycle, the effect would be even more severe. Hence there are considerable economic advantages to be gained in systems where the air velocity is reduced after the majority of the heat has been extracted from the carcasses( Gigiel and Peck, 1984) From this time on, the rate of cooling is then determined by thermal con- ductivity of the meat and not by the heat transfer coefficient at its surface In Australia, the Meat Research Corporation(1995)recommends the use of infrared thermometry to automate this process. If the room is alsolean and heavy animals fat. Comparisons can thus only be made over a limited weight range. In the Langford work (Bailey and Cox, 1976) using 140 kg sides in air at 0 °C, 0.5 m s-1 , cooling times of the fattest carcasses were as much as 20% above the average and the leanest 20% below. In South Africa (Kerens and Visser, 1978) cooling times at 0°C, 0.75 m s-1 for fat and lean sides of 100 kg were 24.5 and 19.0h, respectively, and for 125 kg, 27 and 22 h, respectively. 6.2.1.2 Effect of environmental and carcass variables on weight loss Weight loss is governed by the same variables that affect cooling rate but with different relative importance. 6.2.1.2.1 Air temperature The effect of air temperature on evaporative weight loss during chilling is dependent upon the criteria used to define the end of the chilling process (Fig. 6.5). When chilling for a set time (18h) weight loss increases as tem￾perature decreases. The opposite effect is found when chilling to a set temperature (10 °C in deep leg) with weight loss decreasing as the air temperature is lowered. However, the magnitude of the effect of air tem￾perature on weight loss is small, as a reduction in air temperature from 4 to 0 °C produces a change of <0.1% (Fig. 6.5) under either criteria. 6.2.1.2.2 Air velocity The effect of air velocity is similar to that of air temperature. An increase from 0.5 to 3.0 m s-1 made <0.1% difference to losses when sides were chilled to a deep leg temperature of 10 °C. Increasing the air velocity from 0.75 to 3m s-1 raised weight losses by up to 0.2% when measured over an 18 h chilling period (Fig. 6.5). In a longer chilling cycle, the effect would be even more severe. Hence, there are considerable economic advantages to be gained in systems where the air velocity is reduced after the majority of the heat has been extracted from the carcasses (Gigiel and Peck, 1984). From this time on, the rate of cooling is then determined by thermal con￾ductivity of the meat and not by the heat transfer coefficient at its surface. In Australia, the Meat Research Corporation (1995) recommends the use of infrared thermometry to automate this process. If the room is also Primary chilling of red meat 105 Table 6.2 Chilling time (in h) to 7 °C in the deep leg of 50–220 kg beef sides in air at 0 °C, 0.75 m s-1 (source: Kerens and Visser, 1978) or 0 °C, 1.0 m s-1 Conditions Side weight (kg) 50 75 100 140 180 220 0 °C, 0.75 m s-1 13.0 17.6 21.6 27.4 – – 0 °C, 1.0 m s-1 – – 25.6 30.9 36.0 42.1 Source: Bailey and Cox, 1976