ABSTRACT
Contents 37.1 Introduction ..................................................................................................................735 37.2 Examination of the Opacity of the Eye Lens ................................................................ 736 37.3 Measurement of the Electrical Resistance ......................................................................737 37.4 Determination of the Hematocrit Value and Examination of Erythrocytes .................. 738 37.5 Enzymatic Methods ......................................................................................................739 37.6 Spectroscopic Analysis ...................................................................................................742 37.7 Conclusions ...................................................................................................................747 References ................................................................................................................................748
37.1 Introduction Product authenticity is an emerging area of concern within the food industry. Given the perishable nature of sh, extension of its shelf life is a requirement of normal trading. However, frozen sh usually have a much lower market price than fresh sh; therefore the substitution of frozenthawed for fresh sh is a signi cant authenticity issue. According to the Food and Agricultural Organization (FAO) and the Japan Agriculture Standard (JAS) regulations, labeling should state that the sh has been frozen and must not be refrozen as usual, and frozen-thawed sh must be labeled as previously frozen [1,2]. ese have become regulatory requirements in most countries nowadays. It is generally accepted that fresh sh (or llets/portions) and frozen-thawed sh are types of products which should be di erentiated [8]. Fresh sh is, indeed, understood as being sh freshly caught or which has been chilled and stored for a short period at normal refrigeration
temperature prior to purchase or use. For storage over longer periods freezing is normally utilized. However, while frozen storage is e ective in protecting against microbiological deterioration of sh meat, its physicochemical and organoleptic properties su er [16]. e consumer perception of such sh is inferior to that of the fresh material and this is re ected in the price which it realizes. In practice, a considerable number of frozen sh are thawed in sh shops, stored on ice, and sold as unfrozen sh without being labeled as such. For the bene t of the consumer and prevention of unfair competition in the trade of shery products, correct labeling of frozen-thawed sh or llets is desirable.
