60 Meat refrigeration Table 4.4 Relationship between evaporative weight loss and appearance of sliced beef topside after 6h display Change in appearance (gcm) to001 Red, attractive and still wet: may lose some brightness 0150.025 Surface becoming drier, still attractive but darker 0.0250.035 Distinct obvious darkening, becoming dry and leathery Dry, blackening 0.050.10 Source: Swain and James, 1986. Hood(1971)who showed that the rate of metmyoglobin formation on the surface of these muscles was different The increase in the rate of dis colouration with an increase in temperature is explained by the lowering of the solubility of oxygen in the meat(Urbin and Wilson, 1958)and the faster formation of metmyoglobin( George and Stratmann, 1952)nearer the surface Changes in appearance are normally the criteria which limit display of ration pped products, rather than microbiological considerations. Deterio- unwra in the appearance of unwrapped meats has been related to the degree of dehydration (Table 4. 4)which makes the product unattractive to consumers 4.2.8. 2 Frozen The major problem in retail marketing of frozen meat is its appearance. The freezing process causes changes in the structure and colour of the muscle, nd the deterioration in appearance during frozen storage and display ulti- mately leads to rejection of the product by the consumer. Storage tempera ture, light intensity on the display area and method of packaging all affect the rate of deterioration. The appearance of fresh meat is a primary factor n acceptability at retail level and the same criteria of attractiveness will apply to frozen meat, retailed either frozen or after thawing. The poor colour of the frozen product and the drip associated with it when it thaws, have in the past both contributed to consumer resistance. The problem of light-catalysed pigment oxidation remains the largest single problem in the display of frozen meat. It can be overcome by opaque ackaging in cartons, but the trade and consumer have to develop a very high level of mutual trust for it to be accepted. Where it has been tried in the past (Trieb, 1971) sales of meat packed in cartons were less than those n transparent film. Frozen imported carcass meat has been an item of commerce in the United Kingdom for almost a century and its retail marketing is an estab- lished part of the meat trade. Consumer satisfaction is evident by theHood (1971) who showed that the rate of metmyoglobin formation on the surface of these muscles was different. The increase in the rate of dis￾colouration with an increase in temperature is explained by the lowering of the solubility of oxygen in the meat (Urbin and Wilson, 1958) and the faster formation of metmyoglobin (George and Stratmann, 1952) nearer the surface. Changes in appearance are normally the criteria which limit display of unwrapped products, rather than microbiological considerations. Deterio￾ration in the appearance of unwrapped meats has been related to the degree of dehydration (Table 4.4) which makes the product unattractive to consumers. 4.2.8.2 Frozen The major problem in retail marketing of frozen meat is its appearance.The freezing process causes changes in the structure and colour of the muscle, and the deterioration in appearance during frozen storage and display ulti￾mately leads to rejection of the product by the consumer. Storage tempera￾ture, light intensity on the display area and method of packaging all affect the rate of deterioration. The appearance of fresh meat is a primary factor in acceptability at retail level and the same criteria of attractiveness will apply to frozen meat, retailed either frozen or after thawing. The poor colour of the frozen product and the drip associated with it when it thaws, have in the past both contributed to consumer resistance. The problem of light-catalysed pigment oxidation remains the largest single problem in the display of frozen meat. It can be overcome by opaque packaging in cartons, but the trade and consumer have to develop a very high level of mutual trust for it to be accepted. Where it has been tried in the past (Trieb, 1971) sales of meat packed in cartons were less than those in transparent film. Frozen imported carcass meat has been an item of commerce in the United Kingdom for almost a century and its retail marketing is an estab￾lished part of the meat trade. Consumer satisfaction is evident by the 80 Meat refrigeration Table 4.4 Relationship between evaporative weight loss and appearance of sliced beef topside after 6 h display Evaporative loss Change in appearance (g cm-2 ) up to 0.01 Red, attractive and still wet; may lose some brightness 0.015–0.025 Surface becoming drier, still attractive but darker 0.025–0.035 Distinct obvious darkening, becoming dry and leathery 0.05 Dry, blackening 0.05–0.10 Black Source: Swain and James, 1986