Dielectric properties of cottage cheese and surface treatment using microwaves

This research determines the dielectric properties of cottage cheese and explores the application of microwave treatment to reduce surface spoilage microorganisms, extending the shelf-life of cottage cheese in sealed plastic containers. Dielectric properties of cottage cheese of 0, 2 and 4% fat content were measured at temperatures between 5 and 65 degrees C. The penetration depths of microwaves of 2450 and 915 MHz were estimated to be between 1.2 and 3.2 cm. Microwaves were then used to treat the surface of the cheese in containers shielded on the sides and the bottom. Temperature distribution followed an exponential decay along the depth, as described by a model derived front Lambert's law. Microbiological, sensory and pH analyses of samples after treatment and 1-4 weeks after storage at 3 degrees C showed that microwave surface treatment could contribute to extending the shelf-life of cottage cheese, but further studies are necessary to identify optimum conditions that would maintain appearance and texture. (C) 1998 Elsevier Science Limited. All rights reserved..