The effect of fluctuating vs. constant frozen storage temperature regimes on some quality paramets of selected food products

Samples of frozen rash salmon, smoked mackerel, stewed pork pieces, ice cream, pizza (with a mozzarella cheese topping), hollandaise sauce, strawberries, and blanched broccoli were mildly temperature abused by subjecting them to temperature fluctuations below the freezing point. This involved three temperature fluctuation cycles of -30 degreesC to -10 degreesC to -30 degreesC on consecutive weeks followed by storage at a constant -30 degreesC for 8 mo. The samples were compared with duplicate sets held for 8 mo at a constant -60 degreesC (superfreezing) or -30 degreesC (control) and testing (objective and sensory) was conducted after 0, 1, 2, 4 and 8 mo. The temperature regimes had a larger effect on peroxide (PV) and free fatty acid (FFA) values than on any of the other parameters tested over the product range. The pattern in the data was the same for each fat-containing product in that superfreezing (-60 degreesC) gave the lowest PVs and FFAs, the control (-30 degreesC) was intermediate, while the fluctuating regime gape the highest values. PVs and FFAs also increased with length of time in frozen storage. While smoked mackerel had relatively high PVs curd FFAs, rancidity was not a major problem in any of the fat-containing products as indicated by sensory tests. The temperature regimes had a minimal effect on texture, colour, water-holding capacity and drip loss on thawing for most of the products. However, superfreezing resulted in a better retention of vitamin C in strawberries. (C) 2002 Elsevier Science Ltd. All rights reserved.