Mechanism Of Different Temperatures And Hydrogen Sulfide Treatment Inhibiting Browning Of Fresh-cut Chinese Water Chestnut

Chinese water chestnut(Eleocharis tuberosa)is rich in nutrients and crisp and delicious,but its skin is hard and difficult to peel off,which brings inconvenience to consumers.Fresh-cut Chinese water chestnut can greatly meet the needs of consumers.However,Chinese water chestnut is easy to change color after peeling,which affects the edible quality and reduces the shelf life and commercial value.At present,browning and yellowing are the main problems of discoloration of fresh-cut Chinese water chestnut.In recent years,studies have shown that low concentration of H₂S can play an active role in biological systems.In this paper,the effects of temperature and H₂S treatment on browning and yellowing of fresh-cut Chinese water chestnut were studied through antioxidant defense system,phenol metabolism pathway and phenylpropane metabolism pathway,and the mechanism of inhibiting discoloration was discussed.(1)Study on the mechanism of browning and yellowing of fresh-cut Chinese water chestnut by temperature treatment.The effects of different temperatures(4°C,10°C,20°C)on browning and yellowing of fresh-cut water chestnut during storage were studied.The results showed that fresh-cut water chestnut in 20°C treatment showed serious discoloration,and the L^*value of low temperature(4°C)treatment was significantly higher than that of other treatment groups(P<0.05),while the a^*and b^*values were significantly lower than those of other treatment groups(P<0.05),thus maintaining good sensory quality.At the same time,Low temperature(4°C)treatment can significantly inhibit the accumulation of superoxide anion(O₂^·-)and hydrogen peroxide(H₂O₂),slow down the scavenging ability of ABTS+·radical and DPPH radical,and reduce the antioxidant enzymes catalase(CAT),superoxide dismutase(SOD),ascorbate peroxidase(APX)and glutathione(GR).It inhibited the synthesis of total phenol,eriodictyol and naringin,and kept the activities of browning enzymes phenylalanine ammonia lyase(PAL),polyphenol oxidase(PPO)and peroxidase(POD),and the activities of chalcone isomerase(CHI),flavonoid 3'-hydroxylase(F3'H)and the expression of enzyme genes at a low level(P<0.05)(2)Study on the mechanism of browning and yellowing of fresh-cut Chinese water chestnut treated with H₂S.The effects of different concentrations of H₂S(0?10?l L^-1?15?l L^-1)on browning and yellowing of fresh-cut Chinese water chestnut during storage were studied.The results showed that,compared with the control group,H₂S treatment group kept significantly lower browning index(BI)value,inhibited the deepening of color of fresh-cut Chinese water chestnut during storage(P<0.05),inhibited the accumulation of active oxygen content,induced the improvement of free radical scavenging ability(ABTS+·,DPPH)and antioxidant enzyme activity(SOD,APX,GR,CAT)(P<0.05),accelerated the synthesis of total phenol,the activities of browning enzymes(PAL,PPO,POD)and phenylpropane metabolism-related enzymes(F3'H,CHI)and the production of eriodictyol and naringin were inhibited(P<0.05).In summary,low temperature(4°C)treatment low temperature treatment can inhibit various physiological and chemical reactions in fresh-cut Chinese water chestnut,inhibit the phenol metabolism rate in pulp tissue,maintain a good balance of active oxygen metabolism,and slow down the browning of samples.By inhibiting the metabolism of phenylpropane and reducing the synthesis of flavonoids,the yellowing of samples was delayed and the purpose of keeping fresh was achieved(P<0.05).15?l L^-1H₂S treatment can effectively eliminate the accumulation of active oxygen and inhibit the activity of browning enzyme by inducing higher antioxidant capacity and non-enzymatic antioxidant content of fresh-cut Chinese water chestnut,thus inhibiting the browning of samples.As with low-temperature treatment,15?l L^-1H₂S also effectively inhibited phenylpropane metabolism and reduced the synthesis of flavonoids(P<0.05),thus delaying the yellowing of fresh-cut Chinese water chestnut,keeping the good quality of samples and having obvious fresh-keeping effect.