Using ice surrounding to improve radio frequency tempering uniformity of bulk pacific white shrimp (Litopenaeus vannamei)

Abstract

Localized heating is prone to occur in foods with irregular geometries subjected to radio frequency (RF) heating. Adding surrounding medium may effectively improve the heating uniformity of food with irregular shape like shrimps. A computer simulation model was constructed and verified by experiments to explore the RF tempering uniformity of bulk pacific white shrimps (Litopenaeus vannamei) surrounded by loosely stacked crushed ice (LSCI, porosity φ = 0.62), compacted crushed ice (CCI, φ = 0.44), and ice block (IB, φ = 0), respectively. Thermal and dielectric properties of shrimp cephalon, tail and caudal fan were obtained respectively, and assigned to the according portions of the geometrical model. Results showed that the caudal fan of shrimp was over-heated (48.8 °C) when the body temperature reaching around −2.0 °C without surrounding medium. Comparatively, only a 7.8 °C difference was found between the hot and cold spots in shrimps surrounded by CCI. Results indicated surrounding ice with reduced porosity significantly improved RF tempering uniformity of bulk frozen shrimps.