Freezing a Fillet-o-Fish

Abstract

The frozen food industry is a billion dollar industry that demands efficient manufacturing of consumer products. Through modeling the freezing within a fish fillet, the process of storing and distributing this product is better understood. The purpose of this experiment is to determine the time to freeze a fillet of tilapia (Oreochromis aureus) of known shape and properties. Then through utilizing the fillet temperature, the shelf life or freshness is determined through a consumer based freshness test that provides a nominal shelf life for common species, including tilapia. Another objective is to determine the bacteria concentration of Pseudomonas aeruginosa, common bacteria found on fish and other seafoods, during and after freezing. Using Gambit and FIDAP, a three dimensional slab of 10cm x 5cm x 2 cm was modeled in a -4?C freezer where each side was exposed to convection except for the bottom which was simulated as resting on a surface (a shelf in the freezer). This fillet model froze in ~ 45 minutes and the shelf life was determined to be 22 days, according to the industry freshness chart by Dr. Joe Regenstein. The initial concentration of the Pseudomonas aeruginosa was 1x105 CFU (colony forming units). After freezing, this concentration decreased to 9.8x10-4 or 0.2%.