2.4. Hardness measurement
The hardness of the soaked soybeans was measured by a penetration test using a TA-XT2i Texture Analyser (Stable Micro Systems, Surrey, UK) equipped with an HDP/MTP multiple pea rig. In this test, 18 soaked soybeans were simultaneously tested by applying a force in the direction perpendicular to the hilum. The settings used were as follows: pre-test speed (2 mm s1 ), test speed (2 mm s1 ), penetration distance (3.5 mm), and force (0.05 N). The maximum force (N) necessary to penetrate the soaked soybeans (with tegument) was determined as an indicator of hardness.