Bighead Carp Protein Control Of Enzymatic Hydrolysates From Antioxidant Research

Controlled-enzymatic modified proteins are currently used as a good source of bioactive protein ingredients, while the hydrolysates derived from bighead carp muscles protein may serve as antioxidants. The antioxidant ability was evaluated with regard to the scavenging effect on free radicals DPPH?, ?OH and O2?-. Through controlling processing parameters, it is possible to produce hydrolysates with a high antioxidant activity, which was mainly composed of peptides. Antioxidant abilities of hydrolysates were evaluated in chemical system, in linoleic acid oxidation system, in vitro and in vivo system. Hydrolysate C (PBCP) was proved to show anti-aging and antioxidant effect. For better application, some methods were used to reducing fishy flavor and to keep the bioactivity. Purification was conducted by membrane ultrafiltration and ion exchange chromatography and the mechanism of antioxidation was discussed.It revealed that the resulting hydrolysates could scavenge free radicals DPPH·,·OH and O2-? and showed different activities depending on the specificity of enzyme used and on processing conditions. It was proved that Alcalase produced antioxidant peptides most efficiently and hydrolysate showed the highest activity when compared to papain, Neutrase, Flavourzyme, Protamex and trypsin. Then, Artificial Neural Networks (ANN) was applied to build the hydrolysis model of bighead carp muscles protein with Alcalase and to optimize production conditions for hydrolysates (A, B and C) with the maximum scavenging ability on DPPH·,·OH and O2-, respectively.The physico-chemical character of the Hydrolysate A, B and C were evaluated and it revealed that three hydrolydates were mainly composed of peptides (>65%). The antioxidant ability of hydrolysates were evaluated in different system. In chemical system, EC50 of three hydrolysates was confirmed to be 2.509mg/ml,4.11 mg/ml及6.892 mg/ml on DPPH·,·OH and O2-, respectively. Hydrolysate showed the reducing ability and could inhibit lipoxygenase activity by 50% at the dosage of 50mg/ml. In simulated vitro system, the hemolysis of Red blood Cell (RBC), the swelling of mitochondria, the content of malonadehide (MDA) in liver and brain were decreased with hydrolysates adding. Meanwhile, the hydrolysates could decrease the production of conjugated dienes (CD) and MDA in linoleic acid oxidation system by spectrophotometer method and thiobarbituric acid reactive species (TBARS) assay. Hydrolysate C (PBHC) was most effective in all systems in a comprehensively point.The anti-aging effect of PBHC was observed through the life-span experiment of drosophila and was evaluated by antioxidant indexes of D-galactose (D-gal) induced senile mice. The addition of PBHC in feedstuff could increase the mean day and maximum day of drosophila. The contents of MDA, the activities of superoxide dimutase (SOD), glutathione peroxidase (GSH-Px), monoamine oxidase-B (MAO-B) in liver, brain and blood serum and the activities of Ca2+-Mg2+-ATPase and Na+-K+-ATPase in myocardial mitochondria in D-gal induced mice were determined. All index confirmed the anti-aging effect of PBHC. To well understand the immune regulation effect, the phagocytic functions of phagocytes were estimated by carbon clearance method and spleen, thymus index.Methods to remove fishy smell were conducted based on both reducing fishy flavor and keep bioactivity. Results showed that the fishy odour was removed effectively by yeast treatment. The bioactivity of hydrolysates was evaluated in different conditions such as different pH, different temperature. It was suggested that hydrolysate was heat-stable (>95%) and had better be sterilized in boiling water. Hydrolysate show stable antioxidant ability in both acid and mild condition and keep bioactivity (>75%) in simulated digesting condition. Spray-drying could be used to prouce powder due to its mild treatment.The hydrolysates were purified by membrane ultrafiltration and ion exchange chromatography. The fraction was used to protect RBC, which was attacked by·OH, and the microcosmic structure was observed by scanning electron microscopy (SEM). The chelating Fe2+ ability of all fractions of hydrolysates were evaluated and the mechanisms of antioxidant activity were discussed by exploring the relationship between antioxidant ability and chelating ability, molecular weight and amino acid composition.