Effect Of Thymol Microencapsulated Composite Cling Film Solution On Storage Quality Of Okra

Okra（Abelmoschus esculentus L.Moench）is an annual herb of the mallow family with high nutritional value.The fruit pods contain mucilage,which is composed of polysaccharides,soluble fiber,polyphenols and has medicinal properties such as liver protection,anti-fatigue,and blood cholesterol and blood sugar decrease.However,the skin of okra is thin,the stomata of okra are well developed and the respiratory intensity of okra is high after harvesting,so it is very susceptible to mechanical damage.Browning,rot and softening,water loss and wilting,lignification and other deterioration will occur after 3～5d at room temperature,so corresponding measures should be taken to preserve okra.Thymol microcapsules composite cling film solution（Thymol microcapsules/Konjac glucomannan/Low acyl,TKL）,is green and easy to prepare.In this study,okra was coated with TKL to investigate the effects of TKL on texture,color,nutrients,and volatile substances under low temperature conditions and further investigated the effects of antioxidant substances,antioxidant capacity,metabolism of reactive oxygen species,enzyme activity and phenolic substances on the browning of okra.The main findings of the study are as follows:（1）Okra was treated with TKL composite film solution at concentrations of 20,40,60,80,100 and 120 ppm thymol at the usual refrigeration temperature of 4±1°C and humidity of 90±5%to investigate the effect of the above TKL treatments on the basic storage parameters of okra and to screen the appropriate concentrations for okra storage.The results of the entropy-weighted analysis showed that the TKL composite film solution with thymol concentration of 40 ppm had the highest overall score and that this treatment was effective in maintaining hardness,sensory scores and reducing weight loss and spoilage of okra.At14d,this treatment group showed a 5.26%reduction in weight loss,a 26.67%reduction in spoilage and a 24.14%and 39.64%increase in hardness and sensory scores,respectively,compared to the control treatment group.（2）The effects of TKL40 on okra color,texture,nutrient composition and volatile components were investigated.TKL40 could delay the degradation of chlorophyll in okra during storage.At 14 d of storage,the TKL40 group had 17%higher chlorophyll content than the control group and effectively delayed the darkening and yellowing of okra fruit,with L*values 31%higher than the control group at the end of storage.It also reduced the degradation of cellulose and covalently bound pectin in the cell wall material and reduced the water soluble pectin content.At the end of storage,the cellulose and hemicellulose content of the treated group was 8.17%and 22.37%higher,respectively,than that of the control group..（3）TKL40 reduced the browning index of okra and had a regulatory effect on okra browning.On the one hand,it increased the antioxidant capacity of okra during storage,improved the scavenging ability of okra against DPPH and ABTS free radicals,activated Catalase（CAT）and Superoxide（SOD）activity,and promoted the accumulation of total phenolic and flavonoid substances as well as several phenolic substances such as quercetin3-O-gentianoside,p-coumaric acid,isoquercitrin and caffeic acid during storage.On the other hand,it reduced the damage to cell membranes during low temperature storage of okra,reduced the increase in Malondialdehyde（MDA）and H₂O₂during storage of okra,as well as delayed the increase in conductivity and O₂.^-production,and reduced the binding of phenolics to Polyphenol oxidase（PPO）.In addition,TKL40 inhibited the activity of PPO in okra during late storage.