Optimisation of antioxidant, antimicrobial and metal-chelating properties of bioactive peptides from blood wastes by enzymatic hydrolysis

Context Production of bioactive peptides from slaughterhouse wastes through use of enzymatic hydrolysis adds economic value and reduces environmental hazard from its direct disposal to landfill. Aim The present study was conducted to evaluate antioxidant, antimicrobial and metal-chelating activity of sheep, goat and rabbit plasma hydrolysate from blood. Methods Plasma protein of sheep, goat and rabbit blood was hydrolysed by using trypsin enzyme at optimum conditions of 37°C, pH 8.0 and 1:100 enzyme to substrate ratio, with different hydrolysis time. In vitro digestibility of digested and undigested plasma protein hydrolysates was analysed by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. The antioxidant activity of plasma protein and its hydrolysates was assayed by ABTS+ and DPPH radical-scavenging activities and ferric reducing antioxidant power (FRAP). Antimicrobial activities of undigested and digested samples were evaluated by the well diffusion method. The chelating activity of Fe2+ was determined by the formation of Fe2+–ferrozine complex. Key results The degree of hydrolysis increased up to 8 h for sheep hydrolysate, and up to 6 h for goat and rabbit hydrolysate. Plasma hydrolysate from rabbit exhibited higher ABTS+ and DPPH radical-scavenging activities along with increased FRAP activity. Strong bacterial inhibition was observed against E. coli, and moderate activity against B. cereus, S. enterica and S. aureus at 6 and 8 h by plasma hydrolysate of all species. Metal-chelating activity increased linearly and was highest for rabbit plasma hydrolysate. Conclusion Plasma hydrolysate from trypsin digestion of sheep, goat and rabbit blood wastes exhibited antioxidant activities; the most potent activity was found for rabbit plasma hydrolysate. Furthermore, the efficient iron-chelating activity of plasma hydrolysates and inhibition of pathogenic microorganisms indicate the bioactive potential of plasma hydrolysate obtained from sheep, goat and rabbit blood. Implications The functional properties of plasma hydrolysate of the different species suggest a promising source of nutraceuticals for food industries looking to convert abattoir wastes.