A Wechat miniprogram (‘Fresh color’) based on smart phone to indicate the freshness of Atlantic salmon (Salmo salar L.) and oysters on site by detection of the color changes of curcumin films

In this study, a color recognition system based on Wechat microprogram and curcumin films was developed for the first time to quickly detect the freshness of raw Atlantic salmon and oysters on site. The color of curcumin films, which varies with the freshness of Atlantic salmon and oysters, was measured with a handheld colorimeter. High performance liquid chromatography was used to determine the K value of Atlantic salmon and oysters each day and Conway dish was used to determine the TVB-N of Atlantic salmon and oysters each day. The color difference values were significantly positively correlated with the K values (R2 = 0.9450, P = 0.0012) and volatile ammonia (R2 = 0.998). Through the combination of color difference and freshness, the miniprogram was developed. Freshness was measured for Atlantic salmon stored at 4 °C for 7 days and for oysters stored at 4 °C for 6 days. The results of the miniprogram (‘Fresh Color’) based on color difference were also in good agreement with those of K value and TVB-N，that was, Atlantic salmon and oysters all began to become stale after being stored for 5–6 days. This indicates that the Wechat miniprogram provides a promising technology for rapid detection (less than 5 s) of freshness of raw Atlantic salmon and oysters on site.