Study On Mechanism And Inhibition Of Fresh-cut Yam Yellowing

Fresh-cut yam is welcomed by consumers because of its high nutritional value and convenience.However,during the production,processing and storage of fresh-cut yam,the cold chain may be broken.When the temperature is higher than 15℃,the fresh-cut yam will turn yellow,which reduces the acceptance of consumers and its economic value.At present,the yellowing mechanism of fresh-cut yam is not clear,which limits the development of relevant inhibition technologies.Based on the previous studies,this research explored the mechanism and inhibition technology of fresh-cut yam yellowing.The major findings are as follows:Screening the key metabolic pathways in the yellowing process of fresh-cut yam by transcriptome binding proteome.The samples of yellow fresh-cut yam（stored at25℃for 36 h）and white fresh-cut yam（stored at 25℃for 0 h）were analyzed by transcriptome and proteome.The results showed that there were 6894 up-regulated and 6800 down-regulated DEGs and 1277 up-regulated and 677 down-regulated DEPs in yellow fresh-cut yam,compared to white fresh-cut yam.KEGG enrichment analysis showed that DEGs and DEPs were mainly enriched in glycolysis,PPP,TCA cycle,phenylpropanoid biosynthesis and curcuminoids biosynthesis pathways.Among them,glycolysis,PPP and TCA cycle constituted energy metabolism,while phenylpropanoid biosynthesis and curcuminoids biosynthesis constituted curcuminoids metabolism.Therefore,energy metabolism and curcuminoids metabolism played important roles in the yellowing process of fresh-cut yam.Study on the yellowing mechanism of fresh-cut yam based on energy metabolism and curcuminoids metabolism.In energy metabolism,during the yellowing process of fresh-cut yam,the transcriptional expression levels of related enzymes in glycolysis,PPP and TCA cycle pathways increased,the enzyme activities of H⁺ATPase and Ca²⁺ATPase increased,which induced the accumulation of ATP and energy charge and provided energy for yellow pigment formation.In curcuminoids metabolism,phenylpropanoid biosynthesis was the upstream and curcuminoids biosynthesis was the downstream,which constituted curcuminoids metabolism.The transcriptional expression levels and activities of PAL,C4H and 4CL in phenylpropanoid biosynthesis were up-regulated,which promoted the consumption of phenylalanine（starting substrate）and the synthesis of cinnamic acid,p-coumaric acid and feruloyl-Co A（intermediate products）,thus inducing the expression of phenylpropanoid biosynthesis pathway and providing more starting substrate for curcuminoids biosynthesis pathway.In the downstream curcuminoids biosynthesis pathway,CURS was up-regulated,which promoted the conversion of p-coumaroyl-Co A to bisdemethoxycurcumin,leading to the yellowing of fresh-cut yam.In addition,compared with the curcuminoids biosynthesis pathway in turmeric,DCS,CURS1,CURS2 and CURS3 were inhibited,resulting in the absence of curcumin or demethoxycurcumin,which revealed the yellowing mechanism and metabolic differences of curcuminoids in fresh-cut yam and turmeric.Inhibitory effects of ethanol treatment on fresh-cut yam yellowing and its mechanism.10%ethanol inhibited the yellowing of fresh-cut yam effectively during storage.In energy metabolism,10%ethanol down-regulated the transcriptional expression levels of related enzymes in glycolysis,PPP and TCA cycle pathways,reduced the enzyme activities of ATPases,and restricted the formation of ATP and energy charge,contributing to the inhibition of energy metabolism and the reduction of energy supply.In curcuminoids metabolism,10%ethanol effectively reduced transcriptional expression levels and the activities of PAL,C4H and 4CL,and limited the metabolic levels of related products,so as to inhibit the phenylpropanoid biosynthesis pathway.At the same time,10%ethanol significantly down-regulated the transcriptional expression level and activity of CURS,so as to block the biosynthesis of bisdemethoxycurcumin,which revealed the inhibition mechanism of 10%ethanol on the yellowing of fresh-cut yam.