Assessment of antibacterial and antioxidant properties of hydrolyzed soy protein

Soy protein, owing to its balanced profile of essential amino acids and its ability to generate bioactive peptides, represents a key resource in the development of innovative food and pharmaceutical products. Controlled hydrolysis of this protein can enhance a broad spectrum of functional properties and bioactivities, including antibacterial potency and free radical scavenging capability. In view of the growing challenge of microbial resistance to antibiotics and the recognized role of antioxidants in preventing chronic diseases, optimizing soybean hydrolysis methods has become a topic of notable importance. In this study, soybean protein was hydrolyzed using three distinct approaches: single‑enzyme hydrolysis, chemical acid hydrolysis, and a combined alkali–enzyme treatment. The resultant hydrolysates were evaluated for soluble nitrogen (SN/TN), degree of hydrolysis (DH), and bioactive properties. Quantitative analyses revealed that single‑enzyme hydrolysis yielded SN/TN of ۳۰% and DH in the range of ۱۲–۱۵%, indicating limited enzymatic accessibility due to the structural stability of the protein. Acid hydrolysis achieved an SN/TN of approximately ۳۴% with moderate structural disruption. In contrast, the combined alkali–enzyme method significantly increased enzymatic accessibility, producing SN/TN above ۷۰% and DH between ۳۸–۴۲%. Antibacterial assays (disk diffusion) demonstrated marked inhibition against Gram‑positive strains, notably Staphylococcus aureus and Bacillus cereus, with negligible effect on Gram‑negative strains such as Escherichia coli and Pseudomonas aeruginosa. Antioxidant activity, assessed via the DPPH assay, exhibited a linear increase with sample concentration, reaching ۵۸% free radical scavenging at ۱۰۰۰ ppm. Overall, these findings identify the combined alkali–enzyme approach as an effective strategy for producing high‑quality soybean protein hydrolysates with superior bioactive peptides and functional properties, offering significant potential for application in the food and pharmaceutical sectors.

کلیدواژه ها:

Bioactive Peptides ، Functional Properties ، Free radical scavenging ، Plant protein ، Soluble nitrogen