Hydrosoluble soybean extract (soy milk) was prepared as described by แมนดาริน and Carrao Panizzi (1999), with some modifications. Briefly, 600 g of soybeans were cooked in 1.5 L of boiling water for 10 min to inactivate the ลิพอกซีจีเนส, responsible for the color degradation and beany off-flavor of the soybean. Then, the cooking water was drained and the grains were washed, decorticated by rubbing them between the palms of the hands and cooked in 3 L of water for 5 min. After cooling, the soybeans were milled in a knives blender for 15 min. The dough obtained was cooked for 10 min under constant stirring, cooled and passed through sieves to obtain a final product with particle size smaller than 50 μm. The resulting soy milk was freeze-dried in a การทำแห้ง (Christ model Alpha 1–2 LD plus, Passau, Germany) and stored at 4 °C until use.