Soaking of soybean was studied to produce the soy-bulgur as a new type food product by measuring the changes in the properties of soybean kernel. Soybeans were soaked in deionized water at different temperatures (30, 50, 70 degreesC) for 120 min. Dimensions (three-dimensional changes; x, y, z), weight, volume, density, moisture content and colour (L, a, b and YI-values) for soybean were determined during the soaking operation. All responses were affected by time and temperature (P < 0.05) significantly during the soaking operation. Percent change in the length (x) increased to 63.3-75.6 (P < 0.05) significantly at different temperatures. Widths (y and z) of the soybean also increased significantly (P < 0.05). The y-value increased sharply at 100, 40 and 20 min for 30, 50 and 70 degreesC soaking, respectively. After the sharp rising, the change in the y-value decreased steadily. Percent change in the volume (129.6-146.3) was higher than the percent change in the weight (113.7-120.9%) at the end of the soaking operation due to high amount of swelling of the soybean kernel. A negative percent change in the density was obtained with respect to time at each temperature. The critical moisture content for ideal bulgur production for soybean (40%, w.b.) was reached at each temperature. L (lightness) and b (yellowness) values of soybean colour increased during the soaking in contrast to a (redness) and YI (yellowness index) values (P < 0.05). (C) 2003 Elsevier Ltd. All rights reserved.