Autolysis of shrimp head by gradual temperature and nutritional quality of the resulting hydrolysate

Autolysis method was investigated for protein recovery from shrimp head (SH) of white shrimp (Penaeus vannamei). Autolysis of SH by several temperature conditions (40 °C, 50 °C, 60 °C and gradual temperature) at its initial pH showed protein recovery of 43.6%, 73.6%, 50.3% and 87.4%, respectively. Autolysis of SH by gradual temperature (temperature was risen 5 °C every half an hour, from 40 °C to 70 °C) served best for the preparation of autolysis hydrolysate (AH) with the maximum degree of hydrolysis (DH) 48.6% and the maximum protein recovery 87.4%. Subsequently, the chemical components of SH and its AH obtained by gradual temperature were investigated and comparably evaluated. Protein contents of SH and AH by gradual temperature method amounted to 60.6% and 88.8% (dry basis), respectively. Both SH and AH had high contents of tasting or functional amino acids. The contents of essential amino acids (EAA) of SH and AH were 340.26 and 405.30 mg/g protein, respectively. The amino acids scores of SH and AH were 73 and 96, respectively. The EAA of AH covered 96–100% of the FAO/WHO ideal protein. The high performance size exclusion chromatography of AH showed that with the increasing of DH values, there occurred a larger amount of smaller polypeptides with molecular weight <5000 Da. The nutritional value of SH could be greatly enhanced by gradual temperature autolysis.