| Summary: | 碩士 === 東海大學 === 食品科學系 === 97 === Defatted spent duck breast meat was hydrolyzed by alcalase or flavourzyme with different degree of hydrolysis (DH). In DH was positively correlated with enzyme concentration and hydrolysis time, but there was no significant difference between 7.5 % and 10 % (p>0.05) for alcalase. The conditions used for alcalase or flavourzyme to produce defatted duck breast meat hydrolysates were: 7.5 %, 60℃, pH 8.5, hydrolysis times were 0, 8, 16 and 360 minute for alcalase; 7.5 %, 50℃, pH 7.0, hydrolysis times were 0, 120, 240 and 360 minute for flavourzyme. The DH, molecular weight (MW) distribution and yield (total nitrogen) in the hydrolysates were determined. Results showed that the DH and yield increased with the increase of hydrolysis time (p<0.05). The DH for alcalase was significantly higher than that for flavourzyme (p<0.05). The yield for flavourzyme hydrolysates (360 min) was 1.5 mg/mL, and the yield for alcalase hydrolysates (360 min) was 3.5 mg/mL, which was 2.3 times higher (p<0.05) than that for flavourzyme. The hydrolysis time and DH increased with the decrease of MW of the hydrolysates. In order to study the effect of MW of hydrolysates, all samples were adjusted to contain the amount of crude protein (40 mg crude protein/mL). And then the contents of their carnosine, anserine and non-heme iron were determined. Antioxidative activities including α, α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging activity, reducing power, ferrous ion chelating ability, inhibition of β-carotene bleaching activity and hydroxyl radical scavenging activity were also evaluated and compared those with butylated hydroxyl toluene (BHT), α-tocopherol or EDTA.
The results showed that the carnosine, anserine and non-heme iron contents of hydrolysates increased with the increase of hydrolysis time. The antioxidant activities of hydrolysates were affected by the contents of dipeptides and non-heme iron. Differences in DPPH radical scavenging activity and reducing power were not significantly different between the hydrolysates (alcalase and flavourzyme) and the unhydrolyzed samples. However, DPPH radical scavenging activities of all hydrolysates were about 77%, which was closed to that of BHT (250 μg/mL). The reducing power of hydrolysates were significantly stronger than that of the control (p<0.05), which were closed to BHT at 1,000 μg/mL. Ferrous ion chelating activities in the hydrolysates were higher than those in the unhydrolyzed samples; but the chelating activity of the hydrolysates for alcalase (360 min) was significantly lowered (p<0.05). The chelating activities of flavourzyme hydrolysates were significantly higher (p<0.05) than those for alcalase, and were closed to EDTA at 31.25 μg/mL. Both inhibition of β-carotene bleaching activity and hydroxyl radical scavenging activity of hydrolysates were significantly higher than those of the unhydrolyzed samples (p<0.05). And the results were comparable to α-tocopherol (1,000 μg/mL) and BHT at 7.8 μg/mL, respectively.
In order to enhance the antioxidative activity of hydrolysate, hydrolysates for alcalsae (360 min) was further fractionated into five fractions using four different molecular weight cut-off (MWCO) membranes. Hydrolysates could enhance the hydroxyl radical scavenging activity by 1.3 times using 10,000 Da MWCO membrane to obtain hydrolysates containing peptides or free amino acids with molecular weight of below 1,355 Da.
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