A Method for the Immobilization of Xanthine Oxidase in CA-Alginate Membranes to Measure Hypoxanthine Concentration in Order to Assess Flesh Food Quality

The consumer\u27s acceptance of food quality is an important factor, especially in Third World Countries which import much of their food. Since flesh food (meat, fish) is shipped to those countries frozen or in cold storage, it is susceptible to temperature fluctuations during shipment, resulting in deterioration of the meat and unacceptable quality. Therefore an acceptable procedure to assess flesh food quality is necessary to protect the consumer and trader and to aid in the manufacture of high quality food products. Hypoxanthine concentration in flesh food has been a useful index for the assessment of freshness. Therefore, it was selected as the quality control indicator for the development of a rapid and effective method for quality analysis. An immobilized enzyme analysis system was developed, consisting of a continuous flow reactor, Clark electrode oxidase meter and an immobilized enzyme membrane of 2% Ca-alginate and 1.0 u/ml of xanthine oxidase. The membrane was incubated in 0.05M Tris-HC1 buffer, pH 8.4, containing 0.0028% glutaraldehyde. The optimum conditions for the operation of the immobilized enzymes system were pH 7.85, temperature 23°C, circulating buffer flow rate 0.4 ml/min, circulating buffer concentration 0.05M Tris-HC1, substrate (hypoxanthine) prepared in 0.01 M Tris-HC1 buffer. The storage stability of the immobilized membrane was more than three months. The system was evaluated by measuring the hypoxanthine accumulation in meat and fish during storage periods. Meats and fish tested showed that the hypoxanthine concentration increased with increasing refrigerated storage time. Also the system was compared with the colorimetric analysis, and the same pattern of hypoxanthine development was obtained with both analyses. Comparisons for beef and lamb during cold storage found that sensory evaluation especially as an edibility index, and hypoxanthine concentration, indicated that the majority of potential consumers would purchase and cook those given samples of meats, in which the hyponxanthine concentrations were low. When acceptability declined with increased storage time, the hypoxanthine concentration increased. This analysis procedure was simple, rapid, inexpensive and may prove to be an alternative or adjunct to the more time consuming and expensive colorimetric analysis, which may also encourage the extension of this work to other meat and fish and their products