Influence of refrigeration on evaporative weight loss from meat 89 Table 5.1 Percentage weight loss from thick samples of lean mutton cooled fror de in air at 1-2C. for a set time. at different air Air velocity(ms") Cooling time(h) 1.64 1.60 3.25 0.56 1.67 3.03 Table 5.2 Percentage weight loss from 15 x 15 2cm at 1-2C, to a set maximum temperature at differen air thick samples of lean mutton cooled from one side velocities Air velocity(ms Final temperature(°C 0.56 1.20 Source: Lovett et al 1976 decrease(Pm-Pa), so the overall effect is not obvious. The results of experi- ments carried out on samples(15 x 15 x 2cm thick) removed from freshly killed sheep(Lovett et aL, 1976), show that the effect depends upon the definition of the completion of chilling, either within a set time(Table 5.1) or to a given maximum temperature(Table 5.2) Independent experiments using beef sides confirmed these findings. When chilling time was defined as that required to a set temperature (10C in the deep leg), increasing air velocity from 0.5 to 1.0ms- reduced reight loss by 0. 15%(Cooper, 1970). When chilling for a set time(20h), ncreasing the air velocity from 0.75 to 3ms increased weight loss from 2.75to3.3%( Hodgson,1970) Minimal weight loss during chilling is therefore attained by using the lowest temperature and highest humidity that are practically feasible, and the minimum air velocity needed to meet the temperature/time require- ments In single stage chilling the lowest temperature that can be used is 1C to avoid freezing at the surface of the meat Toughening resulting from rapid chilling (cold shortening, )limits the use of such methods with lamb and beef. To avoid cold shortening a number of systems have been ntroduced that involve an initial holding period at a high temperature, con sequently increasing weight loss.decrease (Pm - Pa), so the overall effect is not obvious.The results of experi￾ments carried out on samples (15 ¥ 15 ¥ 2 cm thick) removed from freshly killed sheep (Lovett et al., 1976), show that the effect depends upon the definition of the completion of chilling, either within a set time (Table 5.1), or to a given maximum temperature (Table 5.2). Independent experiments using beef sides confirmed these findings. When chilling time was defined as that required to a set temperature (10 °C in the deep leg), increasing air velocity from 0.5 to 1.0m s-1 reduced weight loss by 0.15% (Cooper, 1970). When chilling for a set time (20 h), increasing the air velocity from 0.75 to 3 m s-1 increased weight loss from 2.75 to 3.3% (Hodgson, 1970). Minimal weight loss during chilling is therefore attained by using the lowest temperature and highest humidity that are practically feasible, and the minimum air velocity needed to meet the temperature/time require￾ments. In single stage chilling the lowest temperature that can be used is -1 °C to avoid freezing at the surface of the meat. Toughening resulting from rapid chilling (‘cold shortening’) limits the use of such methods with lamb and beef. To avoid cold shortening a number of systems have been introduced that involve an initial holding period at a high temperature, con￾sequently increasing weight loss. Influence of refrigeration on evaporative weight loss from meat 89 Table 5.1 Percentage weight loss from 15 ¥ 15 ¥ 2 cm thick samples of lean mutton cooled from one side in air at 1–2 °C, for a set time, at different air velocities Air velocity (m s-1 ) Cooling time (h) 4 22 3.7 1.64 4.11 1.4 1.60 3.25 0.56 1.67 3.03 Source: Lovett et al., 1976. Table 5.2 Percentage weight loss from 15 ¥ 15 ¥ 2 cm thick samples of lean mutton cooled from one side in air at 1–2 °C, to a set maximum temperature, at different air velocities Air velocity (m s-1 ) Final temperature ( °C) 13 7 4 3.7 0.95 1.14 1.27 1.4 1.09 1.32 1.48 0.56 1.20 1.49 1.69 Source: Lovett et al., 1976