Abstract: To broaden its utilization, the defatted soybean meal was milled by balll mill. The particle size distribution and aggregation of soybean powder after different times (lasting 6, 7, 8, 9,10 h) milling were analyzed. Then the particle sizes of the powder were measured by photon correlation spectroscopy (PCS), and their aggregation was observed by microscopy. The results showed that milling from 6h to 8h, little difference was found in the size distributions of soybean powder,and all their peak lie on about 530 nm. After 10 h milling, the minimal particle size of soybean powder reaches around 100 nm. Most aggregation particles of soybean powder are below 3 μm, and the aggregations of soybean powder with different sizes seem quite similar. The aggregation property of the powder changes obviously, when the particle size of soybean powder decreases to about 100 nm.

Key words: defatted soybean meal, ball mill, aggregation, particle size