Current Optical Evaluation of Freshness of ...

Recently, the growing awareness on health accelerates the demand for seafoods worldwide. Freshness of seafoods tends to be prior requirement. For the assessment on freshness of seafoods, so far, sensory, microbiological　and biochemical methods are used. However, these are not appropriate method for large quantities. In this case, optical methods have advantages of quickness and nondestruction. In this review, biochemical changes during storage are described as a theoretical basis of the freshness evaluation and several current topics on optical noninvasive methods are introduced. Fluorescence of NADH has been applied to scallop adductor muscle, which showed that transient increase in fluorescence intensity was followed by the decrease until 2days of observation . Based on absorption spectra of squid hemocyanin, the oxygen dissociation curve shifted to the left during storage,which suggested that the affinity of oxygen depends on freshness. As for the transparency of squid mantle, new technology with transmittance permitted to analyze the changes to turbid state. The results were almost consistent with that obtained from the sensory test. The range applied to these new methods is still narrow but many results obtained would be reported in the near future.