Novel application of an optical inspection system to determine the freshness of Scomber japonicus (mackerel) stored at a low temperature

This study evaluated the use of an optical inspection system (OIS) to determine the freshness of mackerel ( Scomber japonicus ). The correlations between the light reflection intensity (LRI) of mackerel eyes (determined using an OIS) and the volatile basic nitrogen content (VBN) and K-value were analyzed. After unloading at the harbor, the mackerel were stored at 4 °C for 9 days and the VBN, K-value, and LRI were determined at 3-day intervals. During storage, the LRI, VBN, and K-value all increased. Furthermore, the LRI was correlated with the K-value and VBN. Therefore, although the LRI cannot be applied as an absolute standard for evaluating freshness, the LRI using an OIS is a suitable nondestructive method for evaluating freshness for quality and risk management in the processing industry when handling large numbers of fish.