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A. V. KULKARNI¹, C. O. Rovedo, and R. P. Singh. (1) Department of Biological and Agricultural Engineering, University of California at Davis, One Shields Ave, Davis, CA 95616

Air impingement has been successfully used for different kind of processes like drying of paper and wood, and baking and toasting of foods. By impinging air, the convective heat transfer coefficient is maximized, diminishing the time needed to complete the process.

An air impingement device was used to thaw cylindrical samples (18 mm thickness and 22 mm diameter) of meat and dairy products. Two different air velocities (5 and 45 m/s) were used to conduct the experiments at 25°C. The results were compared with thawing data obtained in stationary air.

Samples were placed at two different distances, 5 and 10 mm, from a 20-mm-diameter impingement jet. The temperature increase was recorded by placing a thermocouple at the center of each sample. The moisture loss during thawing was less than 1% in all cases. Air velocities were determined using a Pitot tube.

There were five-fold and three-fold reductions in thawing time for dairy and meat products, respectively, when air impingement was used, compared with stationary air. The thawing time notably decreased when the distance between the sample and the impingement jet decreased. The final quality of the product was satisfactory in all cases.

The results showed the potential for a substantial decrease in the thawing time using air impingement. The maximum air velocity permitted will be determined mainly by the textural characteristics of a given product.