High‐power sonication‐assisted extraction of soy protein from defatted soy meals: Influence of important process parameters

Abstract This study investigated the influence of important process parameters in high‐power sonication (HPS)‐assisted alkali extraction of protein from defatted soybean flakes and flour for higher yields. HPS power densities from 90 to 720 J/mL, substrate: water ratios at 1:8, 1:10, and 1:12 (wt/vol), and extraction durations of 15‐ and 30‐min were evaluated for their impact on protein recovery from meals. Extraction was carried out at 60°C and pH 8.5, and the protein content of the supernatant was determined with bicinchoninic acid assay (BCA) assay. Flakes showed the highest protein recovery of 77.5% at 720 J/mL and 15 min extraction with an unsonicated control of 63.0%. Being smaller in particle size, flour was less susceptible to HPS treatments and showed the highest protein recovery of 80.3% at 360 J/mL and 30 min extraction with an unsonicated control of 74.3%. HPS recovered a comparable amount of protein from flakes compared to recovery from sonicated or unsonicated flours. In addition, HPS treatments resulted in shorter incubation durations and generated higher yields without further extraction at 60°C. Thus, it decreased the yield difference between incubation durations and decreased cumulative protein release rate. HPS reduced the volume‐weighted mean diameter (D [4,3] ) of flakes by more than fourfold; however, it did not significantly reduce the flour size further. It can thus be summarized that HPS pretreatment breaks the cellular structure of soybean meals, mostly flakes, and can significantly increase the protein recovery from them, even when extraction times are shortened. Practical Applications Application of high‐power sonication (HPS) technology was shown to increase protein extraction yields by 10‐15% beyond conventional alkali extraction from soymeal by reducing the particle size of the meal. Conventional alkali extraction utilizes soy flour and requires 30 min incubation at 60ºC, whereas HPS pretreatment increased protein extraction yield in less incubation duration andless amount of water in the substrate based on the types of substrate. Therefore, HPS could improve protein yield and reduce the cost of production by reducing incubation duration, saving energy, and utilizing flakes instead of flourduring conventional industry scale processing.