Effect of chitosan with different molecular weights on the antifungal activity against Colletotrichum gloeosporioides and activation of the non‐enzymatic antioxidant system on infected papaya

Abstract

Chitosan (Ch) is a biopolymer with excellent antimicrobial and antioxidant properties, capable of maintaining the organoleptic quality of fruits. These properties have been related to its molecular weight. However, the effect of different molecular weights on the non-enzymatic antioxidant system and postharvest quality of anthracnose-infected papaya is still unknown. Therefore, this study evaluated the effect of different Ch molecular weights (13, 25, and 55kDa) on anthracnose development, antioxidant capacity, and postharvest quality of papaya. The Ch-55, Ch-25, and 13kDa inhibited the development of Colletotrichum gloeosporioides. In comparison with thiabendazole, Ch with different molecular weights showed fungicidal effects. Ch-55kDa reduced anthracnose incidence and severity and maintained postharvest quality parameters of papaya. In addition, Ch-55 and Ch-13kDa favored synthesis of ascorbic acid, total phenolics, and antioxidant capacity. Therefore, Ch-55kDa is an alternative to the protection against C. gloeosporioides and a stimulant of the non-enzymatic antioxidant system in papaya fruits during its postharvest storage. PRACTICAL APPLICATION: Ch with different molecular weights have different effects over anthracnose control and postharvest quality in papaya. In addition, they have different stimulation levels on the non-enzymatic antioxidant system of papaya fruits, in a higher level than the chemical fungicide TBZ, by regulating the growth of the fungus and the degradative processes that are generated in fungal infection. In this sense, we believe that our findings could be of interest for producers and farmers to take advantage of this biopolymer to control anthracnose, preserve the postharvest quality, and stimulate the non-enzymatic antioxidant system of papaya fruit.