A new colorimetric measurement of fish freshness using nucleoside oxidase.

Abstract

A simple and rapid colorimetric method for the measurement of the freshness of fish meat was developed using a nucleoside oxidase-catalyzed oxidative coupling reaction. Fish freshness can be expressed by the Kx value according to the following equation1K x(%) = 100(HxR+Hx)/(IMP +HxR+Hx). To measure the Kx value, hypoxanthine (Hx) and inosine-5'-monophosphate (IMP) were converted to inosine (HxR) by nucleoside phosphorylase and alkaline phosphatase, respectively, and then HxR was oxidized by nucleoside oxidase in the presence of Af-ethyl-7V-(2-hydroxy-3-sulfopropyl)-3,5dimethoxyaniline sodium salt (DAOS)and 4-aminoantipyrine. The amount of colored substance formed was proportional to the amountsof these compounds.Oneassay was completedwithin 10minand good comparative results were obtained between the A , value from the proposed method and from the HPLCmethod. A method for measuring HxR, Hx, and IMP ratios was also developed.

A New Approach for the Determination of Fish Freshness by Electrochemical Impedance Spectroscopy

“…Also, the bacteriological method together with the chemical detection of pH, total volatile acids, total volatile bases (Hollingworth and others 1991;Suwetja and others 1989;Alur and others 1991), and methylamine compounds (Lehninger 1982; Wong and others 1988;Ohashi and others 1991b) do not indicate early loss of freshness caused by autolytic deterioration but indicate rather the outcome from bacterial spoilage. K value (Ehira and Uchiyama 1969;Isono 1990;Ohashi and others 1991a), from the autolytic decomposition of adenosine triphosphate (ATP), is considered to be a trustworthy indicator of fish freshness and is adopted by the Japanese seafood industry (Saito and others 1959;Watanabe and Karube 1986;Boyle and others 1991). K value is the ratio (HxR + Hx)/(ATP + ADP + AMP + IMP + HxR + Hx), where HxR is inosine, Hx is hypoxanthine, IMP is inosine 5'-monophosphate, AMP is adenosine 5'-phosphate, and ADP is adenosine diphosphate.…”

“…It has been shown that K values increase with spoilage (Watanabe and others 1987;Luong and others 1991). Although K value is reliable for many fish species, it is not suitable for indicating freshness of salmon, halibut, yellowtail, and numerous other tropical fishes (Isono 1990;Boyle and others 1991;Greene and others 1990). In these cases K 1 value (K 1 = (HxR + Hx)/(IMP + HxR + Hx)) is used instead.…”

Rapid Near-Infrared Spectroscopic Method for the Determination of Free Fatty Acid in Fish and Its Application in Fish Quality Assessment

“…In 1988, Wong et al reported a rapid method for TMA in fish using a test strip. In 1991, Ohashi et al used a semiconductive trimethylamine gas sensor to detect trimethylamine to assess fish quality; Krzymien et al (1990) used trimethylamine headspace analysis to determine fish freshness; Isono (1990) investigated a new colorimetric measurement of fish freshness using nucleoside oxidase; Greene et al (1990) used patterns of nucleotide catabolism as freshness indicators in flatfish from the Gulf of Alaska. These methods however, require a lot of sample preparation and involve many chemical manipulations.…”