A Simple Colorimetric Volatile Nitrogen and Hydrogen Sulfide Indicator Based on Filter Paper and Saffron Petal Anthocyanins to Monitor Fish Spoilage in Intelligent Packaging.

An inexpensive, easy-to-use, simple, and non-toxic freshness indicator was developed based on anthocyanins from saffron petal waste material and filter paper to show the quality and shelf life of trout fillets. Previous studies considered the color changes of freshness indicators based on anthocyanins during fish spoilage due to pH changes following the production of volatile nitrogen. However, in this study, we showed that not only volatile nitrogen but also hydrogen sulfide (H₂S) gas produced during fish spoilage caused structural and color changes in anthocyanins. The indicator showed a wide range of naked-eye color changes from purple to light blue over a pH of 2–11 and from purple to yellow over different concentrations of H₂S gas compounds. The prepared indicator had good color stability and was not affected by various temperatures and times. pH, total volatile basic nitrogen, total viable count of trout fillets, and the color changes of the prepared indicators were simultaneously determined during 8 days of storage in the refrigerator. A significant correlation was observed between fish quality and visible color changes of the indicator. The sensitivity of saffron petal anthocyanins to volatile nitrogen and H₂S compounds showed that it could be used as a raw material for producing low-cost and efficient colorimetric indicators for spoilage detection of protein-rich foods. [ABSTRACT FROM AUTHOR]