Chilled and frozen storage 215 chilled and stored at 4C. Sensory attributes were acceptable after 28 days and total plate counts less than 100 per gram. Studies by Tanchotikul et al (1989)have shown that the susceptibility to oxidation in precooked roasts during chilled storage increased as the end-point cooking temperature Increase Addition of 0. 25 or 0.5% polyphosphate to restructured, battered and breaded, cooked beef and pork nugget products protected them from off favours and lipid oxidation during chilled storage(Huffman et aL., 1987 Similar effects have been shown for garlic and onion juices (Jurdi- Haldeman et al., 1987). Garlic and onion juices were added to minced lamb which was then made into patties and cooked. After 0, 3 and 7 days of storage at 5C, TBA values were lower in patties from the two treatments than the control Although the market for preprepared sandwiches is expanding rapidly there are little published data on their chilled storage life. One study in the USA has looked at the storage life of commercially processed sandwiches including processed meats, roast beef and hamburgers packed in 50% CO 50% air mixture and stored at 4 C(McMullen and Stiles, 1989). Storage life ranges from 35 days for processed meat sandwiches, 28 to 35 days for roast beef and only 14 days for hamburgers. Both microbiological and taste panel tests were used to determine shelf-life. The sandwiches were heated to 50-55C in a microwave oven before tasting. In general the untrained taste panel found sandwiches acceptable after maximum microbial levels ere a Substantial differences in counts were found between replicates and between samples from the same replicates(Table 10.5). Coliform count never exceeded 2cfug. Further studies investigated laboratory packing in 30, 50 and 70%CO2 with either air or nitrogen. Excluding oxygen from the beefburger packs extended the shelf-life from 14 to 35 day Table 10.5 Growth of lactic acid bacteria in beefburgers stored in a modified gas 4°C Lactic acid bacteria(cfu g) ample 1 sample 2 <1×102 <1×102 <1×102 <1×102 <1×102 <1×102 54×103 1.4×102 2.7×10 1.0×102 9.2×105 4.5×107 1.0×1032 28×104 4.1×105 4.7×10° 1.4×10 12×107 14×105 2.0×10 3.0×10 <1×102 14×109 Source: McMullen Stiles. 1989.chilled and stored at 4 °C. Sensory attributes were acceptable after 28 days and total plate counts less than 100 per gram. Studies by Tanchotikul et al. (1989) have shown that the susceptibility to oxidation in precooked roasts during chilled storage increased as the end-point cooking temperature increased. Addition of 0.25 or 0.5% polyphosphate to restructured, battered and breaded, cooked beef and pork nugget products protected them from off- flavours and lipid oxidation during chilled storage (Huffman et al., 1987). Similar effects have been shown for garlic and onion juices (Jurdi￾Haldeman et al., 1987). Garlic and onion juices were added to minced lamb which was then made into patties and cooked. After 0, 3 and 7 days of storage at 5 °C, TBA values were lower in patties from the two treatments than the control. Although the market for preprepared sandwiches is expanding rapidly there are little published data on their chilled storage life. One study in the USA has looked at the storage life of commercially processed sandwiches including processed meats, roast beef and hamburgers packed in 50% CO2 : 50% air mixture and stored at 4 °C (McMullen and Stiles, 1989). Storage life ranges from 35 days for processed meat sandwiches, 28 to 35 days for roast beef and only 14 days for hamburgers. Both microbiological and taste panel tests were used to determine shelf-life. The sandwiches were heated to 50–55 °C in a microwave oven before tasting. In general the untrained taste panel found sandwiches acceptable after maximum microbial levels were achieved. Substantial differences in counts were found between replicates and between samples from the same replicates (Table 10.5). Coliform counts never exceeded 2 cfu g-1 . Further studies investigated laboratory packing in 30, 50 and 70% CO2 with either air or nitrogen. Excluding oxygen from the beefburger packs extended the shelf-life from 14 to 35 days. Chilled and frozen storage 215 Table 10.5 Growth of lactic acid bacteria in beefburgers stored in a modified gas atmosphere at 4 °C Week Lactic acid bacteria (cfu g-1 ) Replicate 1 Replicate 1 Replicate 2 Replicate 2 sample 1 sample 2 sample 1 sample 2 1 <1 ¥ 102 <1 ¥ 102 <1 ¥ 102 <1 ¥ 102 2 <1 ¥ 102 <1 ¥ 102 6.0 ¥ 102 5.4 ¥ 103 3 1.4 ¥ 102 2.7 ¥ 105 1.0 ¥ 102 9.2 ¥ 105 4 4.5 ¥ 107 1.0 ¥ 102 2.8 ¥ 104 4.1 ¥ 106 5 4.7 ¥ 106 1.4 ¥ 104 1.2 ¥ 107 1.4 ¥ 105 6 2.0 ¥ 106 3.0 ¥ 103 <1 ¥ 102 1.4 ¥ 106 Source: McMullen & Stiles, 1989