EFFECT OF AMBIENT-SOAKING TIME ON SOYBEAN CHARACTERISTICS FOR TRADITIONAL SOYMILK EXTRACTION

The effect of ambient temperature soaking time on soybean (Glycine max) was studied for cold extraction of soymilk. Changes of hydration rate, grinding time, crude protein, and solid recovery were parameters considered for seeds soaked for 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 h. Soybean hydration at ambient temperature showed a good fit (r = 0.9982) with Peleg’s model. Whole soybean seeds imbibed about 90% of water absorbable to reach equilibrium in the first six hours of hydration. The moisture content increased from 12% to maximum of 147% for a soaking time of 10 h. The water absorption reached to a maximum of 121% of the original weight of the soybeans after soaking for 10 h. The grinding time of the soybeans gradually decreased with soaking time for the first six hours, 214 s, and then increased gradually with each subsequent hour of soaking to reach 296 s after 39600 s of soaking. Both crude protein and total soluble solids generally increased gradually with soaking time from 0.91 to 1.48% and 0.867 to 1.67% Brix respectively for the soaking time studied. This study concludes that during preparations for traditional soymilk extraction, soybeans should be soaked for at least 7 h or at most 9 h.