High-intensity ultrasound-assisted alkaline extraction of soy protein : optimization, modeling, physicochemical and functional properties
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Soybeans, classified within the legume family, have a historical legacy as a dietary staple across diverse cultures. Preferred due to their elevated protein content, versatility, and numerous health advantages, soybeans are a prominent source of plant-derived protein. They manifest in various forms, including whole beans, soybean oil, tofu, tempeh, soy milk, and a panoply of soy-based offerings. Relevant data underscores soybeans' protein composition, approximating around 40 percent. Currently, soybean protein extraction methods encompass a range of techniques such as freeze-thaw, ultra-high-pressure homogenization, alkali-soluble acid precipitation, microwave-assisted extraction, and subcritical water extraction. Nonetheless, these approaches frequently obtain suboptimal protein yields, undermine protein structural integrity, entail protracted processing time, incur elevated expenses and present formidable hurdles to industrial production. Based on these backgrounds, this research endeavors to establish a high-efficiency preparative protocol utilizing ultrasonic-assisted extraction for soy protein recovery. Meanwhile, it aims to systematically probe the protein's structural and functional properties, fostering a robust theoretical framework and empirical groundwork for the further advancement of soy protein resources. A synergistic approach integrating the Plackett-Burman design (PBD) and the Box- Behnken design (BBD) was employed to optimize the high-intensity ultrasound-assisted extraction (HUAE) process for soy protein. The PBD effectively pinpointed influential factors, while the BBD concurrently assessed interrelated responses: the yield of protein and the energy expenditure. Both aspects are pivotal in achieving optimal and resource- efficient protein extraction. From the PBD outcomes, four crucial parameters (liquid-to- solid ratio, temperature, ultrasonic amplitude, and extraction time) were meticulously considered for subsequent optimization endeavors. The response prediction was accurately tailored to the experimental conditions by employing a well-matched second-order polynomial model. The BBD findings unveiled the optimum conditions for HUAE of soy protein: a liquid-solid ratio concentration of 50:1 mL/g, a temperature of 50 degreesC, an ultrasonic amplitude of 48 percent, and an extraction time of 10 minutes. These optimized conditions yielded an actual extraction rate of 34.45 percent. Notably, compared to the conventional alkaline water extraction technique, the high-intensity ultrasound-assisted method substantially augmented the protein extraction rate (by approximately 33.69 percent) and remarkably shortened the protein extraction time from 60 minutes to 10 minutes. Furthermore, an exploration into the dissimilarity between the physicochemical and functional properties of soy protein garnered through the high-intensity ultrasound-assisted extraction method and the conventional extraction approach was undertaken. The findings indicated that soy protein extracted via ultrasonic treatment exhibited a more flexible molecular structure, accompanied by an augmentation in hydrophobic groups. This molecular adaptation translated to superior emulsion properties and increased antioxidant properties. Hence, when assessing the economic and environmental ramifications, it is deducible that ultrasonic-assisted alkaline extraction is an efficacious soy protein extraction method. This method not only yields protein with enhanced structural properties but also yields more potent antioxidant capacities, all achieved within 10 minutes and with diminished energy consumption (from the desirability response function). Nevertheless, it is noteworthy that the solubility of soy protein treated by ultrasound witnessed a considerable reduction in contrast to the control. This diminishing solubility may potentially confine the widespread utilization of the protein within the expansive realm of the food industry. The outcomes of this investigation furnish valuable insights into the judicious selection of optimal high-intensity ultrasound-assisted extraction parameters for soy protein, thereby paving the way for its broader integration and application within the food industry.
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M.S.