Abstract: In order to improve the quality of soybean milk, this study investigated the effect of soybean natural aging time on the quality of soybean milk in terms of soluble solid content, fat content, protein content, protein recovery, stability, precipitability and particle size distribution. Changes in the type and amount of volatile compounds were analyzed by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry. The results showed that compared with the control group (equilibrated for 10 h at 20 ℃ and 47% relative humidity), the contents of soluble solids, fat and protein in soybean milk made from soybeans with natural aging for 12 months decreased by 2.8%, 13.79% and 9.4%, respectively; the extraction rate of protein decreased by 1.73%; the stability decreased by 12.82%; the centrifugal sedimentation rate increased by 48.78%; the particle size distribution moved toward right and the average particle size increased from 229.6 to 312.9 nm; the content of main odorous substances increased by 7.24%, and the content non-odorous substances decreased by 0.93%. These results revealed that with the increase of soybean natural aging time, both physicochemical properties and flavor quality of soybean milk declined.

Key words: soybean, natural aging time, soybean milk, physicochemical properties, flavor compounds