Off-flavor of soymilk is a barrier to the acceptance of consumers. The objectionable soy odor can be reduced
through inhibition of their formation or through removal after being formed. In this study, soymilk was prepared by three
grinding methods (ambient, cold, and hot grinding) from two varieties (yellow Prosoy and a black soybean) before undergoing
three heating processes: stove cooking, one-phase UHT (ultrahigh temperature), and two-phase UHT process using a
Microthermics direct injection processor, which was equipped with a vacuuming step to remove injected water and volatiles.
Eight typical soy odor compounds, generated from lipid oxidation, were extracted by a solid-phase microextraction method and
analyzed by gas chromatography. The results showed that hot grinding and cold grinding significantly reduced off-flavor as
compared with ambient grinding, and hot grinding achieved the best result. The UHT methods, especially the two-phase UHT
method, were effective to reduce soy odor. Different odor compounds showed distinct concentration patterns because of
different formation mechanisms. The two varieties behaved differently in odor formation during the soymilk-making process.
Most odor compounds could be reduced to below the detection limit through a combination of hot grinding and two-phase
UHT processing. However, hot grinding gave lower solid and protein recoveries in soymilk
Off-flavor of soymilk is a barrier to the acceptance of consumers. The objectionable soy odor can be reducedthrough inhibition of their formation or through removal after being formed. In this study, soymilk was prepared by threegrinding methods (ambient, cold, and hot grinding) from two varieties (yellow Prosoy and a black soybean) before undergoingthree heating processes: stove cooking, one-phase UHT (ultrahigh temperature), and two-phase UHT process using aMicrothermics direct injection processor, which was equipped with a vacuuming step to remove injected water and volatiles.Eight typical soy odor compounds, generated from lipid oxidation, were extracted by a solid-phase microextraction method andanalyzed by gas chromatography. The results showed that hot grinding and cold grinding significantly reduced off-flavor ascompared with ambient grinding, and hot grinding achieved the best result. The UHT methods, especially the two-phase UHTmethod, were effective to reduce soy odor. Different odor compounds showed distinct concentration patterns because ofdifferent formation mechanisms. The two varieties behaved differently in odor formation during the soymilk-making process.Most odor compounds could be reduced to below the detection limit through a combination of hot grinding and two-phaseUHT processing. However, hot grinding gave lower solid and protein recoveries in soymilk
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