Optimization of Sprouting and Infrared Radiation Combination Treatment for Production of Ready-to-Eat Sprouted Soybean

Antinutritional factors (ANFs) in the soybean limit its consumption in raw form. Although sprouting reduces ANFs to a certain extent, they are still beyond the safe limit of human consumption, limiting soybean consumption in sprouted form. The inactivation of soybean ANFs necessitates adequate heat treatment. Therefore, in the present study, post-sprouting infrared (IR) treatment was given to reduce ANFs, particularly trypsin inhibitors. The effects of IR power density (4250–4750 W/m²), exposure time (4–8 min), and stage of germination (5–11 mm length of sprouts) on color, firmness, and Trypsin Inhibitor Activity (TIA) were investigated. The response surface methodology was used to optimize the responses. The optimum conditions were 4497.5 W/m² IR power, 4 min exposure time, and 5.54 mm germination stage (average sprout length). The color difference, firmness, and TIA values obtained at optimal conditions were 2.43, 24.66 N, and 2.458 mg/g, respectively. Sprouting and IR combination treatment efficiently lowered the TIA to a safe level (~77% reduction from raw soybean) while retaining the quality of the sprouted grains. The study suggests that combination treatment can be effectively used to produce ready-to-eat soybean sprouts.