DE-2530 (RP 192) -- Effect of Temperature Fluctuations on Energy Consumption and Quality Changes of Palletized Foods in Frozen Storage ✓ Most Recent

Pallet lots of frozen okra, peas, and strawberriBs were stored at: 1) -24°C constant (plus or minusl deg C), 2) at -24°C, but power shut-down overnight (-24° to -13°C), 3) -21°C (to -18°C) and 4) at -18°C (to -15°C). The temperature increases in these small rooms were estimated to be similar to the worst conditions that might exist in commercial freezer warehouses. Diurnal fluctuations were much smaller within the packages, particularly in the densely filled products located in the center of the lots. All three time-temperature indicators provided an approximate history of storage conditions. Compared to storage at a constart -24°C (-11°F), shutting down power at night yielded an 8% saving in energy consumption, which increased to 23% when temperature was brought down to -21°C (-6°F), and to near 30% when temperatures were reduced to -18°C (O°F) only. Weight losses increased from 0.28% in chamber (1) to 0.68% in chamber (4). Pouches lost much less weight than cartons, and internal packages less than those on the edge of the lots. Frost formation (in-package desiccation) increased from -24° to.18°C Hlo to OaF), and was more severe in the 'pouches than in the cartons. Clumping was reduced in all treatments with storage time. Sensory quality changes and ascorbic acid were reduced similarly, but the poorest treatment (4) lost at most half a grade score and up to 10% ascorbic acid. Total solids showed little relation to treatments. It was tentatively concluded, depending on energy cost and availability, that -20° to -18°C (overnight) might be the optimal storage condition for cartons, while pouches might be economically stored at -18° to -16°C (0° to 3°F) if for no longer than 6 months.