Primary chilling of red meat 107 Table 6.3 Effect of side weight on evap loss(%)after cooling for 18 and 42h at 0C. 0.75ms and 95% relative humidity Chilling time Side weight(kg) 110130150 170 2.5 2.4 ource: Bailey and Cox. 1976 6.2. 1.2.6 Operational factors Investigations have been carried out in a commercial chiller that was designed to operate in either (1)a slow chilling mode to avoid cold short- ning or(2)a rapid chilling mode for a quick turnover and reduced weight loss. The work showed that operational factors are as important as techni- cal specifications with respect to total weight loss( Gigiel et al., 1989b).Over 50%of the variance in weight loss was accounted for by the difference in time that elapsed between death and hot weighing, whilst a further 11. 8% was related to the time that elapsed between hot weighing and loading the beef side into the chiller 6.2.1.3 Product loads If specified cooling schedules are to be attained, refrigeration machinery must be designed to meet the required heat extraction rate at all times during the chilling cycle Heat enters a beef chill room via open doors, via personnel, through the insulation, from lights and cooling fans, and from the cooling carcasses or sides. The product load is the major component of he total heat to be extracted from a fully loaded chill room(Collett and Gigiel, 1986) The rate of heat release from a single side varies with time. It is at a pea immediately after loading and then falls rapidly. The peak value is primarily a function of the environmental conditions during chilling and is not sub- stantially affected by side weights in the region of 120-140kg(Kerens, 1981) In commercial systems, the peak load imposed on the refrigeration plant is so a function of the rate at which hot sides are introduced into the chill room. Increasing air velocity, decreasing air temperature or shortening loading time increases the peak heat load. There is a four-fold difference in peak load between a chill room operating at 8 C, 0.5ms loaded over &h and the same room operating at 0C, 3ms-and loaded over 2h. The average product load can easily be calculated by dividing the total enthalpy change during chilling by the chilling time. The ratios of peak to later stages of chilling, when compressor off-loading might be required eo average(Table 6.4) and actual to average heat loads (Table 6.5)can be use both to determine compressor size and ascertain the heat loads during6.2.1.2.6 Operational factors Investigations have been carried out in a commercial chiller that was designed to operate in either (1) a slow chilling mode to avoid cold short￾ening or (2) a rapid chilling mode for a quick turnover and reduced weight loss. The work showed that operational factors are as important as techni￾cal specifications with respect to total weight loss (Gigiel et al., 1989b). Over 50% of the variance in weight loss was accounted for by the difference in time that elapsed between death and hot weighing, whilst a further 11.8% was related to the time that elapsed between hot weighing and loading the beef side into the chiller. 6.2.1.3 Product loads If specified cooling schedules are to be attained, refrigeration machinery must be designed to meet the required heat extraction rate at all times during the chilling cycle. Heat enters a beef chill room via open doors, via personnel, through the insulation, from lights and cooling fans, and from the cooling carcasses or sides. The product load is the major component of the total heat to be extracted from a fully loaded chill room (Collett and Gigiel, 1986). The rate of heat release from a single side varies with time. It is at a peak immediately after loading and then falls rapidly.The peak value is primarily a function of the environmental conditions during chilling and is not sub￾stantially affected by side weights in the region of 120–140 kg (Kerens, 1981). In commercial systems, the peak load imposed on the refrigeration plant is also a function of the rate at which hot sides are introduced into the chill room. Increasing air velocity, decreasing air temperature or shortening loading time increases the peak heat load. There is a four-fold difference in peak load between a chill room operating at 8°C, 0.5 ms-1 loaded over 8 h and the same room operating at 0 °C, 3 m s-1 and loaded over 2 h. The average product load can easily be calculated by dividing the total enthalpy change during chilling by the chilling time. The ratios of peak to average (Table 6.4) and actual to average heat loads (Table 6.5) can be used both to determine compressor size and ascertain the heat loads during the later stages of chilling, when compressor off-loading might be required. Primary chilling of red meat 107 Table 6.3 Effect of side weight on evaporative weight loss (%) after cooling for 18 and 42 h at 0 °C, 0.75 m s-1 and 95% relative humidity Chilling time Side weight (kg) (h) 50 110 130 150 170 18 2.7 2.0 1.9 1.8 1.7 42 3.6 2.5 2.4 2.2 2.1 Source: Bailey and Cox, 1976