Colour changes in chilling, freezing and storage of meat 81 demand and acceptance of New Zealand lamb although the colour of the product in the frozen state is different from that when fresh. Frozen beef similarly differs from fresh and is often extremely unattractive when dis- played for sale in the frozen state. However, if it is allowed to partly thaw and bloom during display its attractiveness improves. Undoubtedly the price differential between frozen and fresh meat is an important factor in he acceptance of the frozen product by the consumer The appearance of frozen meat is markedly improved if retail sized por tions are first packed in film to exclude air between the meat surface and the film and then rapidly frozen. With this product, however, the price dif ferential between fresh and frozen would necessarily be small and the con- sumer would have to be persuaded by the trade that such frozen meat was in no way inferior to fresh 4.3 Conclusions 1 Consumers prefer bright-red fresh meats, brown or grey-coloured nd pink cured Myoglobin is the primary meat pigment and exists as bright-red oxymyoglobin(MbO2), purple-red deoxymyoglobin(Mb), or brown metmyoglobin(MetMb 3 Red colour (oxymyoglobin) is more stable at lower temperatures because the rate of oxidation of the pigment decreases At low tempera tures, the solubility of oxygen is greater and oxygen-consuming reac- tions are slowed down. There is a greater penetration of oxygen into the meat and the meat is redder than at high temperatures. 4 Conditioned meat is a brighter and more attractive red than uncondi- tioned meat but its colour stability becomes progressively poorer the longer it is conditioned 5 Commercial refrigerated display temperatures require close control if maximum shelf-life is to be obtained. Meat display temperatures of -1C would be ideal, but the higher temperatures commonly found limit shelf-life to 2 days or less. 6 Very fast freezing rates can potentially affect the colour of meat However, the range of rates available commercially are unlikely to have a significant effect on colour 7 Provided problems of freezer burn can be eliminated, the major appear ance problem that affects frozen meat arises from oxidation of oxymyo globin to metmyoglobin. Both temperature and illumination level affect he rate of discolouration during frozen storage, but light is by far the more serious factor 8 Surface condensation during thawing results in a milky appearance which disappears during chilled storage 9 Drying during thawing results in a darkening from which the meat does not recoverdemand and acceptance of New Zealand lamb although the colour of the product in the frozen state is different from that when fresh. Frozen beef similarly differs from fresh and is often extremely unattractive when dis￾played for sale in the frozen state. However, if it is allowed to partly thaw and bloom during display its attractiveness improves. Undoubtedly the price differential between frozen and fresh meat is an important factor in the acceptance of the frozen product by the consumer. The appearance of frozen meat is markedly improved if retail sized por￾tions are first packed in film to exclude air between the meat surface and the film and then rapidly frozen. With this product, however, the price dif￾ferential between fresh and frozen would necessarily be small and the con￾sumer would have to be persuaded by the trade that such frozen meat was in no way inferior to fresh. 4.3 Conclusions 1 Consumers prefer bright-red fresh meats, brown or grey-coloured cooked meats and pink cured meats. 2 Myoglobin is the primary meat pigment and exists as bright-red oxymyoglobin (MbO2), purple-red deoxymyoglobin (Mb), or brown metmyoglobin (MetMb). 3 Red colour (oxymyoglobin) is more stable at lower temperatures because the rate of oxidation of the pigment decreases. At low tempera￾tures, the solubility of oxygen is greater and oxygen-consuming reac￾tions are slowed down. There is a greater penetration of oxygen into the meat and the meat is redder than at high temperatures. 4 Conditioned meat is a brighter and more attractive red than uncondi￾tioned meat but its colour stability becomes progressively poorer the longer it is conditioned. 5 Commercial refrigerated display temperatures require close control if maximum shelf-life is to be obtained. Meat display temperatures of -1 °C would be ideal, but the higher temperatures commonly found limit shelf-life to 2 days or less. 6 Very fast freezing rates can potentially affect the colour of meat. However, the range of rates available commercially are unlikely to have a significant effect on colour. 7 Provided problems of freezer burn can be eliminated, the major appear￾ance problem that affects frozen meat arises from oxidation of oxymyo￾globin to metmyoglobin. Both temperature and illumination level affect the rate of discolouration during frozen storage, but light is by far the more serious factor. 8 Surface condensation during thawing results in a milky appearance which disappears during chilled storage. 9 Drying during thawing results in a darkening from which the meat does not recover. Colour changes in chilling, freezing and storage of meat 81