Influence of soaking on the dimensions and colour of soybean for bulgur production

Abstract

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 °C) 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 °C 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).