Physicochemical quality maintenance and bioactive compounds enhancement of Thai guava fruit cv. ‘Kim Ju’ by using combinative hot water and methyl jasmonate immersion

Postharvest life of Thai guava fruits is limited due to skin damage and physicochemical changes during cold storage. Both methyl jasmonate (MeJA) and heat treatments are potential approaches maintaining postharvest quality of fruits. Thus, the aim of this work was to investigate the effects of hot water and MeJA immersion on physicochemical quality of ‘Kim Ju’ guava fruit during storage at 12 ± 1 °C for 18 d. The fruit were immersed in hot water at 40 °C for 30 min (H), 0.1 mM MeJA for 10 min (0.1 mM MeJA) or H followed by 0.1 mM MeJA (H + 0.1 mM MeJA) and untreated fruit were used as control. The determined parameters were visual appearance, colour, texture, pectin substances, antioxidant activities, bioactive compounds and antioxidant enzymes activities. The results showed that H + 0.1 mM MeJA treatment maintained visual appearance and colour as compared to 0.1 mM MeJA, H or control treatment, consequently. The treatment of H + 0.1 mM MeJA retarded softening according to the inhibition of soluble pectin increase and insoluble pectin decrease. The treatment enhanced the both antioxidant and free radical scavenging activities as compared to control. These were accompanied with the increments of bioactive compounds such as ascorbic acid, total phenols, flavonoids and peroxidase activity and the retardation of catalase activity decrease. In conclusion, the H + 0.1 mM MeJA treatment could maintain postharvest qualities involving visual appearance and texture and enhanced nutritional value of guava fruit during cold storage.