Study And Application Of Eugenol Treatment On Fresh-Peeled Chinese Water Chestnut Preservation

Chinese water chestnut（Eleocharis tuberosa,CWC）has gained popularity due to its rich nutritional value and unique taste.As a kind of ready-to-eat aquatic vegetable,the fresh-peeled CWC is prone to mechanical damage during processing,resulting in a series of physiological and biochemical reactions,such as surface discoloration,quality deterioration,and microbial spoilage.Therefore,the preservation technology of fresh-peeled CWC and its underlying mechanism and application are important topics at this stage.Eugenol,as a natural plant preservative approved by the Food and Drug Administration,can not only inhibit the growth of microorganisms,but also delay the quality deterioration of fruit and vegetable.Although eugenol treatment has been reported to be used in the preservation of fresh-cut CWC,this study further investigated the mechanism of eugenol regulating its antioxidant system.In this study,the mechanism that eugenol could delay the quality deterioration of fresh-peeled CWC was demonstrated by analyzing the effects of eugenol immersion treatment on quality changes,phenolic metabolism,reactive oxygen species metabolism during the storage.Moreover,a corn gliadin nanofiber membrane with good film forming ability and degradability loaded with the natural active substance eugenol through electrospinning technology was prepared and then applied to the packaging of fresh-peeled CWC to investigate the preservation effect of eugenol-zein electrospun membrane.The main research results are as follows:（1）Eugenol treatment could delay the discoloration of fresh-peeled CWC,and the optimal concentration and the time of eugenol immersion treatment was 1 g/L and5 min.Eugenol treatment delayed the decrease of color difference L^*value and total soluble solid content in fresh-peeled CWC,inhibited the increase of color difference a^*,b^*value,browning degree,weight loss rate as well as respiratory intensity,and reduced the growth and reproduction of microorganisms.（2）Eugenol treatment inhibited the accumulation of total flavonoids and soluble quinones in fresh-peeled CWC,promoted the accumulation of phenolic substances,reduced the activities of phenylalanine ammonia-lyase,polyphenol oxidase,and peroxidase to inhibit the enzymatic browning reaction of phenols,thereby delaying the yellowing and browning of fresh-peeled CWC and maintaining its storage quality.（3）Eugenol treatment improved catalase,superoxide dismutase,ascorbic acid peroxidase,glutathione reductase,glutathione peroxidase,dehydroascorbic acid reductase and monodehydroascorbic acid reductase activities and DPPH free radicals scavenging ability,reduced the superoxide anion radicals（O₂·^-）and hydroxyl radicals（OH·^-）production rate,decreased the accumulation of hydrogen peroxide（H₂O₂）,malondialdehyde,and oxidized glutathione,and delayed the decrease of ascorbic acid and glutathione contents.In conclusion,eugenol treatment reduced the oxidative damage caused by ROS and improved antioxidant capacity by inducing higher antioxidant enzymes activities and antioxidant substances accumulation in fresh-peeled CWC.（4）The eugenol-zein electrospun membrane was prepared by electrospinning using corn gliadin as the substrate and eugenol as loaded natural active substance.The morphological characteristics of eugenol-zein electrospun membranes were analyzed by field emission scanning electron microscopy,and the physicochemical properties of eugenol-zein electrospun membranes were analyzed by fourier transform infrared spectroscopy and thermogravimetry.The inhibitory effects of eugenol-zein electrospun membranes on Staphylococcus aureus and Escherichia coli were demonstrated by antibacterial zone experiments.Furthermore,the application of eugenol-zein electrospun membrane to the packaging of fresh-peeled CWC delayed the deterioration of visual quality and the increase in the total bacterial count of fresh-peeled CWC,reduced the browning degree,weight loss rate,total flavonoids and soluble quinones content,and the loss of soluble solids,and promoted the increase in total phenolic content,thereby maintaining the storage quality of fresh-peeled CWC.