Comparison And Analysis On The Volatility Components And Intermediate Products In Soymilk Prepared From Different Lipoxygenase-free Soybean Varieties

Lipoxygenase(Lox)exists in soybean seeds.Lox induces enzymatic oxidation and produces some off-flavor compounds seriously affecting the quality of soybean products in the processing.In this study,physicochemical properties such as Lox type,enzyme activity,protein and fatty acid of different samples were detected.Meanwhile,static-headspace gas chromatography(SHS-GC)was used to analyze twelve representative off-flavor compounds of soymilk.The catalytic functions and products of different Lox isozymes were studied to find out its effect on flavor component of soybean products.This study established the theoretical base for the control offflavor in soybean products.The results showed that:(1)The optimized static headspace gas chromatography(SHS-GC)was used to determine 12 kinds of off-flavor compounds in soymilk.The optimized conditions for SHS-GC were,3 mL,60 min,and 70? of quantity,time and temperature respectively.(2)Compared with normal varieties,the off-flavor contents of hexanal,2-pentyl furan,1-octene-3-one,trans-2-octenal and trans,trans-2,4-nonadienalin soymilk prepared by lipoxygenase-free soybeans were lower and significantly different(p<0.05).(3)The type of Lox affected the flavor components and ripened soybean seeds contain 3 major lipoxygenases.Lox2 was the main factor affecting flavor,which showed a very significant positive correlation(p<0.01)with hexanal,trans-2-hexenal,2-pentyl furan,1-pentanol,1-octene-3-one,trans-2-octenal and trans,trans-2,4-nonadienal,and a significant positive correlation(p<0.05)with benzaldehyde and trans,trans-2,4-decadienal.(4)The Lox type is the main reason for the difference of flavor compounds in soymilk prepared by different lipoxygenase-free soybeans.However,the difference of flavor components in soymilk prepared by same type of lipoxygenase-free soybeans is mainly due to fatty acids,especially poly unsaturated fatty acids(PUFA).Therefore,selection of lipoxygenase-free soybeans to prepare soymilk can significantly improve the flavor quality of soymilk.This result provides theoretical support for the selection of lipoxygenase-free soybean varieties and the production of no-beany soybean products industry.Also provides basic research on the pathways and mechanisms of producing specific flavor with different Lox.