| Summary: | 博士 === 國立臺灣大學 === 食品科技研究所 === 89 === Abstract
Protein isolates and roasted, defatted peanut kernel, prepared from fresh commercial Tainan 11 strain peanuts, were acid-, alkaline- and enzyme-hydrolyzed to various extents to investigate their antioxidative activity during hydrolysates preparation. Among the hydrolysates prepared, those treated with Esperase for 2 hr exhibited the satisfactory activity. Esperase hydrolysates permeates were further screened by membranes with MWCO 3 and 5 kD, and those with MWCO 3-5 kD was selected to conduct the reduction power test (using linoleic acid in emulsion as substrate), inhibition of oxidation induced by FeCl2/H2O2, chelation of Fe+2, prevention of autooxidation of linoleic acid, scavenging activity on H2O2 and on DPPH. This membrane fraction (MWCO 3-5 kD) was further separated by a SP Sephadex C-25 and a QAE Sephadex A-25 chromatographies to collect the fractions to investigate the correlation between the properties of compositional amino acid and their antioxidative activities. Among the fractions collected, sample eluted with 2 N NH4OH displayed strong polarity and remarkable antioxidative activity, which were further fractionized by a HPLC to show containing 7 peptides.
Roasted (180°C) and defatted peanut kernel (RDPK) exhibited increasing antioxidative activity when roasted for longer period of time (0-60 min) in an oven. RDPK was acid- (6 N HCl), alkaline- (4 M BaOH2) or Esperase-hydrolyzed, and the antioxidative activity of the collected fractions were compared. It was found that the antioxidative activity of Esperase hydrolysates was the synergistic combination of all molecular weight fractions (＜1 kD, 1-5 kD, 5-10 kD, 10-30 kD, ＞30 kD). The main antioxidative mechanism of Esperase hydrolysates was the scavenging ability on DPPH, chelating ability on ferrous ion and reduction power.
In food model system, contribution of Esperase hydrolysates in biscuit formulae to antioxidation was significant when biscuits were incubated at 37°C for up to 10 weeks. Results from Ames Test showed that RDPK was non-toxic and inmuatgenic in the presence of S9. In indirect mutagenecity test induced by B(a)P, RDPK exhibited satisfactory antimutagenic ability using Salmonella typhimurium T98 and T100 as bacteria strains. Besides, RDPK showed antimutagenic effect when directly induced by 4-NQO. During the toxicity test on cells, RDPK (100 mg/ml) showed 50-60% inhibition growth effects on leukemia cells, U937 and HL-60, while no apparent inhibition on the growth of MRC-5 cells was observed.
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