Development of freshness indicator for quality of skate (Raja kenojei) during storage.

There is much interest in the fishery industry in developing freshness indicator which can reflect the storage history of products and their quality. Freshness is one of the main considerations for the fishery industry and consumption. In this study, a freshness indicator of fish products, especially skate (Raja kenojei), was developed. The release of amines especially ammonia from decomposing fish is concentrated in headspace and they can be detected by pH-sensitive sensor unit. The sensor unit was organized with polymer matrix solution, which contains bromothymol blue-phenol red as pHsensitive dye to monitor visible color changes from yellow to purple. We investigated the sensor unit formulation, which responds to the ammonia formation in fish products. The color change of the sensor unit was evaluated as well as the selection of the proper weight of fish products and packaging material. Results will be useful to establish a basis for development of a freshness indicator and to determine the suitability of freshness indicator formulations for intelligent food packaging applications.