29E-9 |
Performance evaluation of household refrigerators during the thawing and freezing of selected meat products |
B. A. ANDERSON1, S. Sun1, F. Erdogdu2, and R. P. Singh1. (1) Dept. of Biological & Agricultural Engineering, Univ. of California, Davis, 1 Shields Ave., 2030 Bainer Hall, Davis, CA 95616-5294, (2) Food Engineering Dept., Mersin Univ., Ciftlikkoy-Mersin, 33342, Turkey Recently, new refrigerators have entered the market with “quick thaw” and “quick freeze” capabilities. Thawing meat products at room temperature is not recommended because a microbial “danger zone” temperature range exists between 5 and 60°C. However, thawing in a conventional refrigerator can be undesirably slow. For freezing, it is best to freeze foods quickly to maintain good quality and reduce the formation of large ice crystals. The time required for freezing and thawing different meat products was determined for five different models of household refrigerators. Air temperatures and heat transfer coefficients in freezing and thawing compartments were also measured. In the thawing study, three meat products at two different weight levels were thawed from -18°C to -2°C. Two refrigerators had “quick thaw” compartments, while one had a multipurpose compartment set to its highest temperature setting. Products in the other two refrigerators, which did not have special compartments, were thawed in the fresh food section. In the freezing study, three refrigerators had “quick freeze” capabilities, while the other two were set to their coldest freezer setting. Heat transfer coefficients were measured using aluminum blocks with similar shape and dimensions to those of the meat products. It was found that some refrigerator models froze and thawed foods significantly faster than others (p<0.05). The refrigerators with the fastest freezing and thawing times were found to be those with the highest heat transfer coefficients and largest temperature gradients. This generally occurred in refrigerators with “quick thaw” and “quick freeze” capabilities. Heat transfer coefficients ranged from 7 to 14 W/m2K during freezing and from 4 to 8 W/m2K during thawing. The quick thawing and freezing functions generally improve the heat transfer rates, but the amount of improvement varied. With these results, manufacturers can better design refrigerators with quick thawing and freezing functions.
Session 29E, Food Engineering: Transport processes and kinetics
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