36E-59 |
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S. YUAN and S. K. C. Chang. Cereal & Food Sciences, North Dakota State Univ., 322 Industrial Agriculture & Communications Ctr., Fargo, ND 58105 Soymilk consumption is increasing due to health benefits. Beany off-flavor is a major factor limiting the acceptance of soymilk. The off-flavor is mainly derived from enzymatic oxidation or auto-oxidation of linoleic and linolenic acids. Therefore, lipid composition and lipoxygenases in soybean would affect the oxidation of fatty acids in soymilk during processing. Recently, two low-linolenic acid soybean varieties, IA 3017 and IA 2064, were developed. Comparing the off-flavor profiles produced by the new varieties with that produced by a traditional soybean (Proto) and a lipoxigenase-null variety in soymilk processing would provide understanding as to their suitability for soymilk processing. Our objective was to determine off-flavor compounds in soymilk produced from four soybean varieties and to determine how off-flavor compounds was affected by heating time. Soybean (the 4 varieties mentioned above) was processed into soymilk, which was heated to boiling and held for up to 20 min. Solid phase micro-extraction method was used to extract the volatile compounds in the soymilk. Off-flavor compounds, including hexanal, hexanol, 2-nonenal, 1-octen-3-ol, 2, 4-decadienal, and dimethyl trisulfide were quantitated using gas chromatography with an internal standard. Eighteen commercial soymilk products were also analyzed for comparison with the lab-processed samples. Results showed that variety is significant (p<0.05) in producing off-flavor with the lipoxygease-null variety having the lowest off-flavor profile, followed by the low-linolenic acid varieties. Proto had the highest quantities of off-flavor compounds. Heating time decreased hexanal, hexanol, 1-octen-3-ol, and 2-nonenal significantly (p<0.05). The extent of decrease in off-flavor production by heating soymilk differed among varieties. Dimethyl trisulfide was not present in freshly prepared soymilk, but was detected in rehydrated soymilk prepared from commercial powder products. The results suggest that the two low-linolenic varieties are suitable for soymilk production with respect to off-flavor formation. Proto soymilk requires longer heating to reduce the off-flavor compounds.
Session 36E, Fruit & Vegetable Products: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |