The Regulation Of Layer-by-layer Self-assembled Edible Coating On Strawberry Metabolites

Strawberry is a kind of delicious fruit,but its short shelf life limits the economic benefits.Edible film coating has attracted wide attention because of its high safety and easy operation.In recent years,layer-by-layer self-assembly technology(LBL)has provided a new and more effective technology for postharvest storage.In present study,the polysaccharide-based edible coating constructed by the LBL approach was used on quality maintenance of strawberry fruit during storage,which is consist of 1.5%carboxymethyl chitosan and 1.5%chitosan.The change of physiological quality traits,metabolites,and gene expression in strawberry were determined.The objectives were to discover a new method and to provide the theoretical basis for shelf-life extension and quality maintenance of strawberry.The main conclusions are listed as following:(1)The strawberries coated with LBL coating film maintained brighter color,higher firmness,less weight loss and corruption index,higher total soluble solids but no significant difference in total acidity.The LBL coating maintained at higher level of total phenols and flavonoids content in strawberry,as well as maintained higher DPPH scavenging capacity and FRAP iron reduction capacity during storage.(2)The LBL coating effectively slowed down the increase of esters and furanones,promoted the biosynthesis of aldehydes and slowed down the decline of linalool and nerolidol.Meanwhile,the metabolomic study indicated that carboxymethyl chitosan/chitosan LBL coating mainly delayed the decline of terpenoids metabolites,and promoted the biosynthesis of phenylpropane and flavonoid metabolites.However,the carboxymethyl chitosan/chitosan LBL coating had little effect on primary metabolism in strawberry during storage.(3)It was indicated that carboxymethyl chitosan/chitosan LBL coating promoted the expression of genes involved in the phenylpropane and flavonoids biosynthesis,pyruvate decarboxylase(PDC),alcohol dehydrogenase(ADH),gibberellin 3-oxidase(GA3ox),gibberellin 20-oxidase(GA20ox),and nerolidol synthase 1(NES1)genes in strawberry during storage.The coating inhibited the expression of alcohol acyltransferase(AAT),quinone oxidoreductase(QR)and O-methyltransferase(OMT)genes during storage.It could be speculated that the LBL coating promoted the expression of genes related to secondary metabolism in strawberry,which increased the content of secondary metabolites with strong antimicrobial and antioxidant activities,such as polyphenols and flavonoids,as well as enhanced strawberry response to postharvest environmental stress stimuli.