The Role Of Lipoxygenase (LOX) In The Formation Of Aroma Of Fresh Waxy Corn

This paper aimed at detecting volatile components,aromas,key enzymes activity from LOX pathway and LOX isozymes from two waxy corn cultivars,namely 'Jingtianzihuanuo No.2' and 'Suyunuo No.11',were harvested at four time points.By difference comparison,correlation analysis and LOX activity regulation to explore aroma characteristics of fresh waxy corns,relationship between key aroma active ingredients and LOX isozymes composition and activity,providing theoretical basis for flavor control of fresh waxy corns.The results were listed as following:1.Fresh waxy corns mainly detected 11 kinds of volatile components,including acetaldehyde,ethanol,pentanal,pentanol,hexanal,hexanol,heptanal,heptanol,3-octene-2-one,(E)-2-octene aldehyde and 1-octen-3-ol,with hexanal and hexanal being the most dominant compounds(53.35%?-85.85%),the contents of C6 aldehydes and alcohols were decreased obviously after blanching(2.26%?17.57%).Quantitative odor intensity analysis results showed grassy and green bean flavor were clearly perceived and unacceptable,while blanched samples were acceptable.Correlation analysis showed grassy and green bean flavor were significantly positively related to the contents of hexanal and hexanol.Quantitative estimation indicated that the contents of hexanal and hexanol were 0.20?127.89 mg/L,while blanched samples were 0.01?26.98 mg/L.2.LOX,HPL and ADH activity of two waxy corns at different harvest time exist significant differences.LOX activity was increased with the harvest time extended(0.40?3.69 U/gFW),HPL and ADH activity were 0.10?0.42 U/gFW and 0.25?0.80 U/gFW,showed no similar trends to LOX activity.Aliphatic chain aldehydes,alcohols and ketones volatile components represented by C6 alcohol and aldehyde and grassy and green bean flavor were reduced from fresh waxy corn juice treated with pH 9.0 buffer compared with pH 7.0.The results were consistent with pH 9.0 could inhibit LOX activity.The formation of C6 alcohol and aldehyde and other volatile components from waxy corns was related to LOX pathway,especially LOX activity.3.Four genes expression of waxy corns were detected by real-time fluorescence quantitative PCR,ZmLOX1,ZmLOX2 and ZmLOX10 expression of 'Jingtianzihuanuo No.2' at F2 harvest time were 38.66,116.99 and 92.26 times of 'Suyunuo No.11',while ZmLOX3 expression of 'Jingtianzihuanuo No.2,at F4 harvest time was 5.54 times of 'Suyunuo No.11'.Volatile components of fresh waxy corns were consistent with gene expression,high levels of gene expression were also high in the volatile components from LOX pathway.To track LOX activity,water-soluble protein of waxy corns were purified by salting out and centrifuging,LOX molecular weight of 'Jingtianzihuanuo No.2' was 91.40?96.07 kDa,while 'Suyunuo No.11' was 100.58?102.92 kDa.