Primary chilling of red meat 101 6.2.1.1.1 Air temperature The results of the programme on beef chilling carried out at Langford clearly show the importance of air temperature on cooling time( Bailey and Cox, 1976). For ease of use the results of the investigations have been pre- sented as four plots of the logarithm of temperature against time covering wide range of side weights(100-220kg)and air velocities(0.5-3.0ms") Data for the slowest cooling area of the side, which was located by insert ing a probe into the centre of the thickest section of the leg, are Fig 6.1 and can therefore be used to determine the environmental condi tions required to attain a desired cooling time when a maximum final tem- perature has been specified Potential surface freezing problems can then be evaluated from the surface temperature plots(Figs. 6.2 and 6.3). These conjunction with the deep M. longissimus dorsi data(Fig. 6. 4) also identify toughening problems and the possible requirement for electrical stimulatio Cooling in air at a constant 4C, compared with 0'C, at 3ms wil crease the time to reach 7C in the deep leg of a 100kg side from 20.3 to 277h(a 36%increase). At 0.5ms, the time for a 220kg side to reach 7C will increase from 45.9 to 683h(a 49% increase). In systems designed to produce fully chilled sides, with average meat temperatures of 2-4C, the requirement for low air temperatures becomes even more important because of the small meat/air temperature difference at the end of the process. + Approximate average for British abattoirs 十哪四32232230 05105002 Time post-mortem ig. 6.1 Relationship between deep longissimus dorsi temperature and cooling time for beef sides(source: Bailey and Cox, 1976)6.2.1.1.1 Air temperature The results of the programme on beef chilling carried out at Langford clearly show the importance of air temperature on cooling time (Bailey and Cox, 1976). For ease of use the results of the investigations have been pre￾sented as four plots of the logarithm of temperature against time covering a wide range of side weights (100–220 kg) and air velocities (0.5–3.0 ms-1 ). Data for the slowest cooling area of the side, which was located by insert￾ing a probe into the centre of the thickest section of the leg, are shown in Fig. 6.1 and can therefore be used to determine the environmental condi￾tions required to attain a desired cooling time when a maximum final tem￾perature has been specified. Potential surface freezing problems can then be evaluated from the surface temperature plots (Figs. 6.2 and 6.3). These in conjunction with the deep M. longissimus dorsi data (Fig. 6.4) also identify toughening problems and the possible requirement for electrical stimulation. Cooling in air at a constant 4°C, compared with 0 °C, at 3m s-1 will increase the time to reach 7 °C in the deep leg of a 100kg side from 20.3 to 27.7 h (a 36% increase). At 0.5 ms-1 , the time for a 220 kg side to reach 7 °C will increase from 45.9 to 68.3 h (a 49% increase). In systems designed to produce fully chilled sides, with average meat temperatures of 2–4 °C, the requirement for low air temperatures becomes even more important because of the small meat/air temperature difference at the end of the process. Primary chilling of red meat 101 38·5 38·5 38·5 35 35 35 30 30 30 25 25 25 20 20 20 15 15 15 10 10 7 5 4 3 7 10 2 1 5 9 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 0·01 0·02 0·03 0·04 0·05 0·06 0·07 0·08 0·09 0·1 0·2 0·3 0·4 0·5 0·6 0·7 0·8 0·9 1·0 0·5 0·5 0·5 Y 1 1 3 2 2 1 0·5 3 21 3 Air speed (m s 3 2 –1) Time post-mortem (h) Deep long. dorsi temperature (°C) Chiller air temperature (°C) 840 Side weights 100 140 180 220 Approximate average for British abattoirs kg Fig. 6.1 Relationship between deep longissimus dorsi temperature and cooling time for beef sides (source: Bailey and Cox, 1976)