Bioactive peptide production by hydrolysis of porcine blood proteins in a continuous enzymatic membrane reactor

BACKGROUND: During slaughter a hog produces approximately 3 L of blood. However, only a small proportion of porcine blood is currently used in food, feed or fertiliser, most of it being treated as waste and discarded. In this study the possibility of hydrolysing porcine blood proteins by enzyme in a membrane reactor for the production of bioactive peptides was investigated. Red blood corpuscles, blood plasma and defibrinated blood plasma were hydrolysed by various proteases, and the hydrolysates were evaluated for bioactive properties.RESULTS: The hydrolysate produced by hydrolysing red blood corpuscles with a mixture of trypsin, chymotrypsin and thermolysin had the highest angiotensin I-converting enzyme (ACE)-inhibitory activity (IC₅₀ = 0.58 mg mL⁻¹) and scavenging effect on α,α-diphenyl-β-picrylhydrazyl (DPPH) (65%) after 6 and 10 h of hydrolysis respectively. When the hydrolysis was carried out in an enzymatic membrane reactor with an enzyme/substrate ratio of 1:5 and a residence time of 100 min, the process reached steady state in 2 h. The ACE-inhibitory activity of the product during the steady state process was 86% and its scavenging effect on DPPH was 54%. The membrane process also decolourised the enzyme-hydrolysed product, thus improving the appearance of the product.CONCLUSION: This study demonstrated that hydrolysates of porcine blood possess antihypertensive and antioxidant activities. Using red blood corpuscles as the substrate, the hydrolysis could be carried out in a membrane reactor with a mixture of proteases to produce bioactive peptides continuously. Therefore processing of porcine blood in an enzymatic membrane reactor is a potential method for producing a health-promoting product.