Colorimetric freshness indicators in aquatic products based on natural pigments: A review

Aquatic products are highly favored by consumers due to their rich content of essential trace elements, such as high-quality animal protein and Docosahexaenoic Acid (DHA), which can effectively enhance immunity and disease resistance. However, the storage factors during circulation, such as temperature and humidity, make aquatic products prone to deterioration. At present, Colorimetric freshness indicators (CFIs) has been widely used in aquatic products, which can provide the quality information on food by monitoring the changes in the internal packaging environment. CFIs mainly uses natural pH-sensitive pigments (such as anthocyanin, curcumin, and alizarin) to exhibit different colors varying pH conditions. This enables consumers to judge the freshness of packaged aquatic products accurately. The discoloration principle of natural pH-sensitive pigments is particularly important in their application for freshness monitoring of aquatic products. Furthermore, this review focuses on extraction methods for natural pH-sensitive pigments and provides insights into future research for CFIs in freshness monitoring of aquatic products. Overall, this review provides a valuable reference for subsequent researchers to design CFIs more rationally and advance their development in freshness monitoring within the field of aquatic products.