Intelligent pH-sensitive indicator based on starch-cellulose and alizarin dye to track freshness of rainbow trout fillet

A novel pH-sensitive indicator was prepared by incorporation of alizarin in a starch-cellulose paper to monitor the freshness of rainbow trout fillet. Water solubility of the fabricated indicator reduced by incorporation of alizarin, while the percentage of swelling didn't change. FTIR certified that alizarin was properly incorporated which was revealed by the formation of intermolecular hydrogen bonding in the cellulose-starch matrix. SEM and ultraviolet-visible spectrum results also demonstrated that alizarin had good compatibility with the components of the indicator. The alizarin-starch-cellulose indicator (ASC) had greater color efficiency from yellow to purple at pH 2-11 and greater color stability after two months of storage at 4 °C. It can be concluded that the color changes of ASC, from orange to reddish brown, were entirely corresponded with TVB-N contents of fish, which presents a satisfactory capability of developed indicator to identify the initiation of spoilage in the refrigerated fish fillet.