50 Meat refrigerati possibility that cold shortening may occur at the surface, even if it does not occur in the bulk of the meat. Whether or not cold shortening occurs on the surface will often depend on the amount of fat cover over the carcass. This leads to the question of whether shortening can be eliminated whilst retaining high cooling rates? This can be done in two ways: (1)by prevent- ing the underlying cold contraction or(2) by restraining the muscle suffi ciently to prevent the deleterious shortening. The second solution has been veloped with considerable success and has generally involved adopting novel methods of hanging the carcass, such as from the hip(Taylor, 1996) The alternative avenue, of prevention, has found favour with the wide spread application of electrical stimulation(ES)of the carcass immediately after death. This procedure greatly accelerates post-mortem metabolism by stimulating the muscles to contract and relax at a very fast rate, which quickly depletes glycogen and ATP and thus accelerates rigor. Es of the carcass after slaughter can allow rapid chilling without much of the toughening effect of cold shortening. Taylor (1987) and Taylor (1996) provide details of optimum ES treatments. Es has also been shown to be effective in reducing cold shortening in deer meat( Chrystall and Devine 1983; Drew et al-,1988) Although chilling or freezing pre-rigor produces tough meat caused by old shortening or thaw rigor it still has good functional properties(Xiong and Blanchard, 1993 ). It is therefore feasible to manufacture good quality comminuted meat products from hot boned pre-rigor refrigerated beef. Abu-Bakar et al.(1989) found no differences in eating quality between Wieners manufactured from either hot boned beef chilled rapidly using CO2 or brine, or conventionally chilled cold boned beef. As arule of thumb, cooling to temperatures not below 10"C in 10h for beef and lamb(Offer et al, 1988)and in 5h for pork(Honikel, 1986)can avoid cold shortening 3.2 Development of conditioning(ageing) The terms'conditioning,, ageing,, ripening,, maturing'and"the resolution of rigor have all been applied to the practice of storing meat for periods beyond the normal time taken for cooling and setting, to improve its tenderness after cooking. Conditioning imposes a severe limitation on processing conditions because it is a slow process. The deficiencies in the commercial conditioning of meat were clearly lustrated by replies to a questionnaire to sections of the trade in the UK in 1977/8(Dransfield, 1986). At the time a period of storage for wholesale meat was often not specified by retailers. When specified the duration of ad much to do with distribution and turnover of meat and could often be shortened by commercial pressures. At retail, beef was kept for 1-4 days and most beef was sold 3-6 days after slaughter(Palmer, 1978)possibility that cold shortening may occur at the surface, even if it does not occur in the bulk of the meat. Whether or not cold shortening occurs on the surface will often depend on the amount of fat cover over the carcass. This leads to the question of whether shortening can be eliminated whilst retaining high cooling rates? This can be done in two ways: (1) by prevent￾ing the underlying cold contraction or (2) by restraining the muscle suffi- ciently to prevent the deleterious shortening. The second solution has been developed with considerable success and has generally involved adopting novel methods of hanging the carcass, such as from the hip (Taylor, 1996). The alternative avenue, of prevention, has found favour with the wide￾spread application of electrical stimulation (ES) of the carcass immediately after death. This procedure greatly accelerates post-mortem metabolism by stimulating the muscles to contract and relax at a very fast rate, which quickly depletes glycogen and ATP and thus accelerates rigor. ES of the carcass after slaughter can allow rapid chilling without much of the toughening effect of cold shortening. Taylor (1987) and Taylor (1996) provide details of optimum ES treatments. ES has also been shown to be effective in reducing cold shortening in deer meat (Chrystall and Devine, 1983; Drew et al., 1988). Although chilling or freezing pre-rigor produces tough meat caused by cold shortening or thaw rigor it still has good functional properties (Xiong and Blanchard, 1993). It is therefore feasible to manufacture good quality comminuted meat products from hot boned pre-rigor refrigerated beef. Abu-Bakar et al. (1989) found no differences in eating quality between Wieners manufactured from either hot boned beef chilled rapidly using CO2 or brine, or conventionally chilled cold boned beef. As a ‘rule of thumb’, cooling to temperatures not below 10 °C in 10h for beef and lamb (Offer et al., 1988) and in 5 h for pork (Honikel, 1986) can avoid cold shortening. 3.2 Development of conditioning (ageing) The terms ‘conditioning’, ‘ageing’, ‘ripening’, ‘maturing’ and ‘the resolution of rigor’ have all been applied to the practice of storing meat for periods beyond the normal time taken for cooling and setting, to improve its tenderness after cooking. Conditioning imposes a severe limitation on processing conditions because it is a slow process. The deficiencies in the commercial conditioning of meat were clearly illustrated by replies to a questionnaire to sections of the trade in the UK in 1977/8 (Dransfield, 1986). At the time a period of storage for wholesale meat was often not specified by retailers. When specified the duration of storage had much to do with distribution and turnover of meat and could often be shortened by commercial pressures. At retail, beef was kept for 1–4 days and most beef was sold 3–6 days after slaughter (Palmer, 1978). 50 Meat refrigeration