Effect of Ultrasound and Sodium Bicarbonate Treatment on the Soaking Characteristics of Mung Beans

In order to improve the texture characteristics and soaking efficiency of mung bean, this paper investigated the effect of ultrasound and sodium bicarbonate treatments on the water absorption kinetics, water distribution, water migration, hardness, seed coat structure, total phenol and phytic acid content of mung bean. The effects of ultrasound on the water absorption characteristics, hardness and nutrient content of mung bean depended on the changes in the seed coat of mung bean. Ultrasound treatment with an intensity of 400 W made mung bean epidermis form microporous channels, thus promoting water absorption, increasing the bound and free water contents, reducing hardness and significantly decreasing the total phenol and phytic acid contents (P<0.05). Sodium bicarbonate (1.5%) affected the soaking characteristics of mung bean probably by changing the pH of the soaking solution. The addition of sodium bicarbonate increased the pH of the soaking solution, and hence decreased the water absorption rate, reduced the content of total phenol, inhibited the reduction of phytic acid, altered the contents of bound and free water, but showed no significant effect on the hardness of mung bean. In summary, the optimum soaking time of the control group and the 1.5% sodium bicarbonate group were 7 h, whereas that of the ultrasound group (400 W) was 4 h by using hardness as index. This paper explored the mechanism underlying the effect of ultrasound and sodium bicarbonate treatment on the soaking characteristics of mung bean, which can provide theoretical guidance for the application of a new pretreatment technology in the development of miscellaneous food products.