Research On The Antioxidant Activities Of Hydrolysates From Duck Meat

Antioxidants play an important role both in food system by retarding oxidation-induced deterioration and in human health by protecting the body from various diseases caused by excessive free radicals.Nowadays,the antioxidant peptides derived from animal protein hydrolysates have attracted more and more attention,because these peptides are considered safe,highly efficient and nutritional.In our study,antioxidant peptides were prepared from duck meat protein through controlled enzymatic technology.The antioxidant activities of hydrolysate were evaluated by chemical models in vitro.Then the effects of the processing conditions and a simulated gastrointestinal digestion on the antioxidant activities of hydrolysate were studied.At last,antioxidant peptides were purified by using consecutive chromatographic methods and the amino acid sequences of the peptides were identified by Nano-LC-ESI-LTQ-Obitrap MS/MS.The detail contents and conclusions are shown as follows:1.Optimization of antioxidant peptides from duck meat protein using response suface methodologyThree different enzymes(including Protamex,Flavorzyme,Pancreasin)were used to prepare duck meat protein hydrolysates.Considering the protein recovering ratios,the scavenging activities for DPPH radical,hydroxyl radical and superoxide radical,Protamex was the best enzyme to hydrolyze duck meat protein.Pesponse surface methodology(RSM)was used to optimize the hydrolysis conditions,including reaction temperature,enzyme to substrate(E/S)ratio,hydrolysis time and pH.The optimal processing conditions were as follows:temperature 50?,E/S ration 0.75 g/(100 g protein),time 4.0 h and pH 6.0.Under the optimized conditions,DPPH radcial scavenging activity was 78.10%which was in agreement with the predicted value(76.40%)estimated by RSM within a 95%confidence interval.2.In vitro antioxidant activity and antioxidant stability of duck meat protein hydrolysateThe hydrolysate was evaluated by the reducing power and the scavenging activities for DPPH radical,hydroxyl radical and superoxide radical.The antioxidant activities of hydrolysate increased with increasing concentration used.When protein concentration was 1.0 mg/mL,DPPH radical scavenging activity was 83.17%.Hydroxyl radical scavenging activity,superoxide radical scavenging activity and reducing power of hydrolysate was 67.51%?88.36%?0.308when protein concentration was 4.0 mg/mL.The antioxidant stability of hydrolysate was evaluated in different conditions such as temperature,pH,NaCl concentration,sugar concentration and a simulated gastrointestinal digestion.Antioxidant peptides showed good stabilities when temperature was lower than 60?;they could keep highly antioxidant ability(up to 95%)in the acidity environment,but lost its activity in the alkali environment,only 70%when pH was 10.0;NaCl and sugar had no effect on antioxidant stability;the results of a simulated gastrointestinal digestion showed that antioxidant activity increased with pepsin treatment but declined with further hydrolysis with trypsin.3.Indentification and characterization of antioxidant peptides from duck meat protein hydrolysateAntioxidant peptides were isolated and purified by ultrafiltration and consecutive chromatographic methods including gel filtration chromatographic and ion exchange chromatography.Seven peptides were identified by Nano-LC-ESI-LTQ-Obitrap MS/MS.These peptides were synthesized,and their antioxidant activity was evaluated.Among these peptides,the LQAEVEELRAALE showed the highest DPPH radical savenging activity(93.36%)and Fe2+ chelating ability(87.13%),and the IEDPFDQDDWGAWKK and NWDDMEKexhibited the highest hydroxyl radical.