The Effect of the Application of Edible Coatings on or before Ultraviolet Treatment on Postharvested Longan Fruits

Abstract

This study compared the effect of application of edible coating on or before ultraviolet treatment on postharvest longan fruits. The treated longan fruits were examined for weight loss, respiration rate, surface color changes, enzymatic activities (PPO, POD, and PAL), and total phenolic contents throughout the 7 storage days at ambient temperature. In addition, coat homogeneity was examined and cell structure of longan flesh at the end of storage was observed. The results showed that when UV was applied before coating (i.e., chitosan or carrageenan), it had relatively lower PPO and PAL activities and retained higher TPC in longan pericarp. However, the changes in enzymatic activities did not affect the surface lightness and browning index as they were more influenced by the type of coating, in which combination treatments with carrageenan showed higher surface lightness and lower browning index compared to treatment combinations containing chitosan. However, when UV treatment preceded coating, the combinations of UV plus chitosan coating produced lower PPO and PAL activities and retained better cell structure with less damage than the combinations of UV plus carrageenan coating. UV plus carrageenan coating showed relatively higher weight loss and respiration rate, with cell structure exhibiting bigger intercellular spaces at the end of storage. Therefore, application of UV treatment followed by chitosan coating was found to be the best treatment combination for controlling enzymatic activities and reducing senescence rate of longan fruits.

Multifunctional Role of Chitosan Edible Coatings on Antioxidant Systems in Fruit Crops: A Review

“…CS coating combined with UV-C irradiation was able to retain a higher level of TP content in longan fruit during 7 days at 28 °C [ 96 ]. Furthermore, Abdipour et al [ 97 ] also demonstrated that the application of both UV lights significantly prevent TP content changes, UV-C irradiated sweet cherry fruit showed a higher retention level of TP content than that observed in UV-B irradiated fruit.…”

“…Likewise, CS coated fresh cut lemon slices stored at different temperatures showed an increase in GPX activity at high temperature, suggesting that low temperature (0 °C) had an excellent inhibitory effect on the activity of GPX [ 54 ]. Contrarily, in longan fruit, the application of different UV-C and CS-based coating combinations had no significant effect on GPX activity on both pericarp and flesh during seven days of storage [ 96 ]. In guava fruit, composite coating containing CS/Nano-TiO 2 and CS and lemongrass essential oil inhibited GPX activity during storage with lower and higher values in coated fruit at 10 and 15 days of storage, respectively [ 51 , 77 ].…”

“…Fruit browning is mainly due an enzymatic oxidation of phenolics to quinones mediated by polyphenol oxidase (PPO) that reduce the consumer’s acceptability causing over 50% of loss in fruits [ 117 ]. Several studies have demonstrated that CS-based coatings has an inhibitory effect on PPO activity in different fruit crops such as strawberry [ 45 ], sweet cherry [ 57 ], cherimoya [ 41 ], loquat [ 37 , 51 ], longan [ 96 ], guava [ 58 , 77 ], grape [ 53 , 84 ], fig [ 75 ], apple [ 32 , 107 ], mango [ 50 , 102 ], pistachio [ 95 ], lemon [ 54 ], and pineapple [ 89 ]. These findings could be due to low O 2 availability, inside the fruit, necessary for initiate the browning reactions.…”

Effect of dip wash treatments with organic acids and acidic electrolyzed water combined with ultraviolet irradiation on quality of strawberry fruit during storage

“…Delaying of the ripening process and reduction of fruit softening by UVC application have also been reported (Baka et al 1999, Pan et al 2004Pombo et al 2009). Furthermore, some previous studies have shown that the combination of UVC with other preservative methods (edible coatings, heat treatment) have achieved good results in extending the postharvest life of fruits and vegetables and in maintaining their quality (Bal 2019;Pan et al 2004;Lin et al 2017).…”

Composite coatings based on konjac glucomannan and sodium alginate modified with allicin and in situ SiOx for ginger rhizomes preservation

“…POD, PPO, PAL activities were tested following the method of Venisse, Malnoy, Faize, Paulin, and Brisset (2002), Chen, Richard, Benhamou, and Timothy (2000), and Lin, Lasekan, Saari, and Khairunniza‐Bejo (2017), respectively. One unit of enzyme activity were defined as the quantity of the enzyme able to produce a 0.01 increase of the absorbance units per min.…”