| Summary: | 碩士 === 國立嘉義大學 === 食品科學系碩士班 === 91 === In this study, the salted duck egg white was treated by electrodialysis desalination and hydrolyzed with the addition of 0.5% (w/w) protease (Protease N, Protease A or Prozyme 6) for 24 hours at 45℃ in a reactor. The hydrolysates were then freeze-dried into powder, and the antioxidative activity and antioxidative mechanism of freeze-dried hydrolysates were investigated. When the concentration of the hydrolysates was 5 mg/ml, for the samples without treatment of electrodialysis desalination, Protease N had the strongest antioxidative activity up to 73.0% but, for the samples treated by electrodialysis desalination, Protease A showed a higher antioxidative ability up to 70.7%. However, wheather treated or untreated by electrodialysis desalination, the total antioxidative ability of hydrolysates with Prozyme 6 was about 60-62%. The analysis of different antioxidative mechanism of hydrolysates, the scavenging effects on H2O2, superoxide anion, DPPH radical, hydroxyl radical and chelating effects on Fe2+. Results of the antioxidative mechanism on hydrolysates which hydrolyzed with Protease N, Protease A and Prozyme 6 were followed: the scavenging effectson hydroxyl radical were 68.8%, 60.7% and 65.5%; the scavenging effects on superoxide anion were 58.1%, 52.1% and 58.5%; the chelating effects on Fe2+ were 17.7-21.7%; the scavenging effects on DPPH radical were 31.8-45.0%; reducing power of hydrolysates was weakest. The hydrolysates were further screened by membranes of different pore size and then to confer the effect of antioxidative mechanism between all kinds of membrane fractionation. Membrane fractionations hydrolyzed with Protease N, Protease A and Prozyme 6 with the molecular weight range at 10-30kDa, 3-10kDa, 1-3kDa and <1kDa could raise the scavenging effects on hydroxyl radical and had a better effect than original hydrolysates. The membrane fractionations of Protease N and Prozyme 6 with molecular weight range between 10-30kDa could raise the scavenging effects on superoxide anion. The membrane fractionations of Protease N and Prozyme 6 with molecular weight range >30kDa could raise chelating effects on ferrous ion slightly. The membrane fractionations of Protease N, Protease A and Prozyme 6 with molecular weight <10kDa could raise the scavenging effects on DPPH radical. The molecular weight range between 1-3kDa of the hydrolysates with Protease A could raise the scavenging effects on H2O2 up to 14.8%, but the others were not effective. The change of molecular weight did not raise reducing power at all. Further application of hydrosate powders can be made to investigate the TBARS amount produced during storage. On storage at -18℃, fresh meat with added salt could promote TBARS production. After 5 months storage, fresh meat with added hydrolysates but no salt addition had a fewer TBARS content. But fresh meat with added salt and hydrolysates had raised the content of TBARS to a certain degree, only the hydrolysates treated with Protease A by electrodialysis desalination showing fewer TBARS content. If stored at 4℃, fresh meat with added salt and hydrolysates and treated with heat could promote the increase of TBARS immediately. Among all groups, the content of TBARS with meat heated at 90℃ was the highest. The hydrolysates treated with Protease A and Prozyme 6 by electrodialysis desalination and Protease N treated by non-electrodialysis desalination could reduce TBARS content effectively when heated at 160℃. Their contents were about 30.0%, 31.3% and 44.0% respectively if compare with cases without hydrolysates addition. Furthermore, the hydrolysates treated with Protease N and Prozyme 6 by electrodialysis desalination had the highest antioxidative ability and combined with commercial antioxidants — BHA and Carnosine. Results showed that any of the combinations could inhibit TBARS production and had better effects than individual one but, not better than the sum of two individual effects. Therefore, they only demonstrated synergistic effects.
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