Impact of Isonicotinic Acid Blending in Chitosan/Polyvinyl Alcohol on Ripening-Dependent Changes of Green Stage Tomato

The effect of isonicotinic acid (INA) in a chitosan (CS)/polyvinyl alcohol (PVA) blend on ripening-dependent changes of preserved green tomatoes (Solanum lycopersicum L.) was examined at room temperature. The results showed that CS/PVA/INA 0.5 mM and CS/PVA/INA 1.0 mM formulations retarded firmness loss and delayed the pigmentation parameters i.e., lycopene (LYP), total carotenes (TCs), and titratable acidity (TA). The CS/PVA/INA 0.5 mM and CS/PVA/INA 1.0 mM formulations were able to delay the increase in malondialdehyde (MDA) and total polyphenol (TP) contents. Furthermore, the peroxidase (POD), polyphenoloxidase (PPO), and phenylalanine ammonia-lyase (PAL) activities of tomatoes coated with CS/PVA/INA 0.5 mM and CS/PVA/INA 1.0 mM formulations were lower than those in other treatments. Meanwhile, the CS/PVA blend had the highest TP content, as well as the highest PPO and PAL activities, at the late stage of maturation. The UV analysis showed that the CS/PVA/INA blend film is a promising UV-protective food packaging material. The pure CS, PVA, and INA formulations, as well as the CS/PVA, CS/PVA/INA 0.5 mM, and CS/PVA/INA 1.0 mM formulations, were characterized by infrared (FTIR). The three polymer formulations showed strong antifungal activity against Alternaria alternata and Botrytis cinerea.