Study On The Mechanism Of Stress Browning In Multi Temperature Zone Of Potato Gradient Slices

The growing popularity of fresh-cut fruits and vegetables and the problem of browning are limiting the industrialization of many fruits and vegetables,such as potatoes.However,the mechanisms associated with browning are not known.In this paper,the potato YS505,a variety prone to browning,was selected for the study.Different storage temperatures of 4 ℃and 12 ℃ and different cutting densities of slices and strips were set for multiple treatments.The fresh-cut products were analyzed for color and appearance changes and browning enzymes and phenols,and the results of metabolomics and transcriptomics techniques were used to screen for differential browning metabolites,differentially expressed key genes and related metabolic pathways.And the relevant results were verified using real-time quantitative RT-q PCR technology.The specific results are as follows:(1)A study of physiological and enzymatic changes in appearance at different storage temperatures and cutting densities revealed that differences in browning of fresh-cut potatoes were related to the levels of phenylpropane metabolism and reactive oxygen species(ROS)metabolism.Sliced products stored at 12 °C showed higher levels of browning,higher activity of polyphenol oxidase(PPO),peroxidase(POD),phenylalamine ammonia-lyase(PAL),cinnamate-4-hydroxylase(C4H)and 4-coumarate-Co A ligase(4CL),and higher accumulation of phenolic compounds and ROS compared to the 4 °C chilled group.A similar pattern was observed in the sliced group compared to the sliced group under refrigeration at4 °C.(2)Metabolomic analysis of samples at different storage periods(2 d and 6 d)indicated that 9-Oxo ODE,12-OPDA,Isoscoparin-2’’-(6-(E)-ferulylglucoside),Sphingosine,LAspartic acid and glutathione were the differential browning substances in fresh-cut potatoes.Analysis of differentially expressed genes and related metabolic pathways after NADPH oxidase inhibitor-diphenyl chloride salt treatment using transcriptomics techniques revealed that ERF106,MYB1R1 and MYB48 transcription factors and genes such as POD42,POD47,POD52,Catalase(CAT)and triphosphopyridine nucleotide(NADPH)were down-regulated in expression,mainly involved in phenylpropane metabolism and lipid metabolism pathways.It is hypothesized that fresh-cut potato browning involves lipid,amino acid,glutathione and phenylpropane metabolism,and is closely related to ROS synthesis and catabolism.(3)To further confirm the involvement of the phenylalanine metabolic pathway in regulating the browning process in fresh-cut potatoes,RT-q PCR analysis revealed that the genes encoding key enzymes of the phenylalanine metabolic pathway,PPO,POD,PAL,C4 H,4CL,hydroxycinnamoyl Co A quinate hydrocycinnamoyl transferase(HQT),hydroxycinnamoyltransferase(HCT)and catechol-O-methyltransferase(COMT 1)all show some differential variation,suggesting that fresh-cut potato browning may not only be associated with phenolase regionalization alone,but may also be an actively induced process requiring the de novo synthesis of phenylalanine metabolism.In summary,the differences in browning of fresh-cut potatoes are not exclusively related to the phenyl propane metabolic pathway,but are caused by the combined and coordinated action of several metabolic pathways,including ROS metabolism,lipid metabolism and amino acid metabolism.The results of the study provide new ideas and a more comprehensive molecular and metabolic basis for the study of enzymatic browning mechanisms in fresh-cut potatoes,as well as a theoretical basis for the development of browning control technologies for fresh-cut fruits and vegetables.