Application of tannic acid and Fe3+ crosslinking-enhanced chitosan films for wax apple (Syzygium samarangense) preservation

This study examines the effects of edible chitosan coatings reinforced with tannic acid (TA) and ferric iron (Fe 3+ ) double crosslinking on the quality of wax apples stored at room temperature. The effects of chitosan (CS) and CS/TA/Fe coatings on wax apple weight loss, decay index, respiration rate, titratable acidity, total phenolics, and other quality parameters were investigated. The weight loss and decay index of wax apples increased over time, with the CS coating delaying both compared to untreated fruits. On the final storage day, the CS/TA/Fe coating reduced weight loss by 34.35 % and maintained SSC at 9.17 ± 0.49. Additionally, the activities of catalase (CAT), ascorbate peroxidase (APX), polygalacturonase (PG), and pectin methyl esterase (PME) were evaluated. Compared to other groups, the CS/TA/Fe coating more effectively preserved the CAT and APX activities while delaying the increase in PG and PME activities. CS/TA/Fe coating preserved wax apple cell wall integrity and reduced respiration and oxidative damage (malondialdehyde levels), likely via a CS/TA/Fe supramolecular network limiting gas exchange, thus extending shelf life and maintaining quality.