Ultrasound-Assisted Alkaline Treatment Effect on Antioxidant and ACE-Inhibitory Potential of Walnut for Sustainable Industrialization

Purpose: Bioactive peptides from food industry by-products can contribute to good health and well-being (SDG 3) and ensure sustainable industrialization. We investigated the influence of ultrasound-assisted alkali action on the bioactive potencies of the walnut by-product peptide fractions (WMPFs). Design/Methodology/Approach: The walnut meal protein was extracted via ultrasonic-assisted alkaline treatment and then hydrolyzed with trypsin. Peptide fractions were obtained via an ultrafiltration process using specific molecular weight cut-off membranes. The amino acid, antioxidant and ACE-inhibitory activities were assayed using standardized protocols. Findings: A fairly balanced amino acid profile was observed. Glu, Arg, and Asp were the dominant amino acids measuring 23.5–25.7, 14.2–14.9 and 9.9–11.5 g/100g protein respectively. Generally, peptides with molecular weight 1 (1–3) kDa peptide fraction inhibiting 50% ACE (IC50) at 0.2 mg/mL. The antioxidant and ACE repressive actions were generally higher in the ultrasonicated samples compared to the control samples. Research Limitation: The study involved the use of a specific type of counter-current ultrasound pretreatment machine. The antioxidant and antihypertensive potencies of the peptide fractions were not compared with existing artificial antihypertensive drugs. Practical Implications: This study demonstrates that walnut meal protein could be fashioned as a commercial value-added functional food ingredient as evidenced by the antioxidant and antihypertensive activities of the peptide fractions. These bioactive peptides could be useful in the pharmaceutical as well as food processing industries. The ultrasonic pretreatment could help extract vital components from food industry by-products like groundnut and soybean meals. Social Implication: Besides generating additional literature on the subject area, the study highlights information that will help policy formulation to promote the use of natural food resources to enhance good health and well-being as set out in sustainable development goal three. Originality/Value: Previous works provided insufficient information on the ultrasound-assisted alkaline pretreatment and subsequent trypsin enzymolysis to improve walnut meal peptide antioxidant and antihypertensive activities. This study fills that gap and provides the basis for further study into the area.