Preparation of hydrolysates from bovine red blood cells and their debittering following plastein reaction

Protein hydrolysates from bovine red blood cells were prepared using commercially available Alcalase. The best nitrogen recovery (69.2%) was achieved at a degree of hydrolysis (DH) of 25%. However, the product so obtained had a strong bitter taste (4.3 on a 5-point scale). At DH 16%, the nitrogen recovery was 65.9% and the bitter taste of product decreased (to 3.5). The hydrolysate contained 81.8% crude protein (N × 6.25), 2.4% moisture and 15.8% sodium chloride and had excellent solubility characteristics in water in the pH range 2.6–9.5. The Hunter colour parameters of the hydrolysate showed that good release of haem compounds during the process had occurred. Incorporation of hydrolysates (up to 3%) in meat model systems enhanced their cooking yield by about 5%. The protein efficiency ratio value of the hydrolysate was 3.7 as compared with that of beef (2.8), pork (2.5) and cod (2.5) proteins. However, low contents of isoleucine and sulphur-containing amino acids gave an essential amino acid index of 67.3 for the product. The bitterness of hydrolysate was reduced considerably by plastein reaction with diethyl ester of glutamic acid. The resultant product had a crude protein (N × 6.25) content of 96.3% and contained 30.6% of glutamic acid. The total free amino acid content in the product decreased from 18.6 mg g−1 hydrolysate to 1.85 mg g−1 plastein.