Intangible but not intractable: the prediction of fish ‘quality’ variables using dielectric spectroscopy

Abstract

In many fields the concept and measurement of quality is of prime importance. The fish industry is no exception to this and many sensory approaches have been devised to quantify this rather intangible property. The EU 5th framework project 'SEQUID' has concentrated on the measurement of the dielectric properties of fish tissue as a function of time both in frozen and chilled storage. The many deteriorative biochemical and microbiological processes that take place during the gradual spoilage of such materials have a subtle influence on the dielectric properties across the spectrum but notably in the microwave frequency region. In this region the complex interactions of water, solutes and structure-forming proteins are systematically changed by death and decay. Chilling or freezing may slow these processes but such preservation techniques do not halt them entirely. The SEQUID project has shown that it is possible, using a combination of time domain reflectometry and multivariate analysis, to predict certain quality-related variables, both sensory and biochemical, with comparable accuracy to existing methods. These results are presented in this paper.