Starch-cellulose and alizarin pH indicator to track freshness of rainbow trout fillet

Researchers at Urmia University in Iran developed a novel pH sensor to test the freshness on rainbow trout. The sensor was prepared by incorporation of alizarin in a starch-cellulose paper and had a good color change from yellow to purple at pH 2–11 and greater color stability after two months of storage at 4 °C. The research found that the color change was correlated to bacteria count in the fish. The study was published in the International Journal of Biological Macromolecules Vol. 132, Pages 157-165 @ https://www.sciencedirect.com/science/article/pii/S0141813019304635