Air impingement technology optimizes thawing of frozen foods.With the continual growth in the use of frozen foods, both in retail applications and in food service, there is a need to develop improved thawing techniques. Current methods, such as the use of still air, are often undesirably slow. Other techniques can be very expensive and cause uneven thawing, such as the use of microwaves. Air impingement impingement (impinj´m  nt),n the striking or application of excessive pressure to a tissue by food or a prosthesis. technology is one possible alternative that could improve the thawing of frozen foods. The objective of research at the University of California The University of California has a combined student body of more than 191,000 students, over 1,340,000 living alumni, and a combined systemwide and campus endowment of just over $7.3 billion (8th largest in the United States). was to obtain a better understanding of the heat and mass transfer that occurs when air impingement technology is applied to thaw frozen foods. It appears that the use of air impingement technology has the potential to significantly shorten thawing times for frozen foods. The results of this research could help improve the design of impingement thawing systems. Researchers thawed frozen products using a laboratory impingement system with a single impingement jet. Both a simulated meat product (Tylose ty·lose n. A balloonlike outgrowth of a parenchyma cell through a pit into the cavity of a plant vessel. Also called tylosis2. [French.] gel) and packages of frozen bratwurst were used as test materials. Heat transfer coefficients The heat transfer coefficient is used in calculating the convection heat transfer between a moving fluid and a solid in thermodynamics. The heat transfer coefficient is often calculated from the Nusselt number (a dimensionless number). were evaluated using inverse heat transfer analysis for a nylon disk at thawing temperatures. The scientists wrote a finite difference A finite difference is a mathematical expression of the form f(x + b) − f(x + a). If a finite difference is divided by b − a, one gets a difference quotient. model in Matlab v.6.0 to predict heat and mass transfer during impingement thawing. The thawing of the Tylose disk in a refrigerator using still air took more than 23 hours, while thawing under a single impingement jet took less than 5 hours. Thawing frozen packages of bratwurst took more than three times longer in still air than when using an impingement jet. The degree of improvement in thawing rates for the air impingement system was influenced by the thickness of the product. Heat transfer coefficients ranged from 60 W per [m.sup.2]K to 185 W per [m.sup.2]K and varied with position and time. Results from the finite difference model were in agreement with experimental data. Further information. R. Paul Singh, Department of Biological and Agricultural Engineering Agricultural engineers develop engineering science and technology in the context of agricultural production and processing and for the management of natural resources. The first curriculum in Agricultural Engineering was established at Iowa State University by J. B. , University of California, Davis The University of California, Davis, commonly known as UC Davis, is one of the ten campuses of the University of California, and was established as the University Farm in 1905. , 1 Shields Ave., 2030 Bainer Hall, Davis, CA 95616; phone: 530- 752-0811; fax: 530-752-2640; email: rpsingh@ucdavis.edu. |
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