| Summary: | 碩士 === 國立臺灣海洋大學 === 食品科學系 === 94 === Abstract
The objectives of this study are to investigate the proximate composition, amino acid constituents, decalcifying condition for extraction of collagen, collagen type and characteristics of fish scales from tilapia (Oreochromis niloticus x O. aureus), striped mullet (Mugil cephalus), and milkfish (Chanos chanos). The antioxidant activities and cell viability of collagen hydrolysates were also studied. The crude protein contents of tilapia, striped mullet, cultured and wild milkfish scales were 48, 54, 61 and 56%, and ash contents were 45, 41, 36 and 38%, respectively. The decalcification condition for milkfish scales (cultured and wild) was 0.2 M HCl treatment for 30 min, and tilapia and striped mullet were 0.3 M HCl for 40 min. The yield of collagen extracted from all fish scales was higher than 45%. Four kinds of fish scale collagen were heterotrimers with α-chain, α1 and α2, indicating that these scale collagen were Type I collagen. No difference was observed between cultured and wild fish. The profiles of SDS-PAGE were also similar to that of calf skin collagen Type I. The dominant amino acids of collagen were Gly, Pro, Hyp and Ala. The crude fish scale collagen of tilapia was treated with 2% Alcalase (w/w), 3% Protease type ⅩⅣ and 1% Collagenase for 0, 1, 2, 3, 4 and 5 hour. The antioxidant activites of the hydrolysates were measured using the methods including the scavening effect on α,α-diphenyl- β-picrylhydrazyl (DPPH) radical, reducing power and chelating ahilities of metal ion Cu2+. Results showed the highest antioxidant activity was found in 2% Alcalase hydrolysates at 50℃ for 4 hour. Free and combined amino acids increased by 3.5 and 2 times after 1 hour hydrolysis. The increased free and combined amino acids might be associated with the increase of antioxidant activity. The Alcalase hydrolysates were then separated by ultrafiltration, and the fraction with MW 5~10 kDa and <5 kDa were observed to have the highest scavening effect on DPPH radical. Reducing power increased with increasing MW of the UF fraction. The chelating of Cu2+ for MW 5~10 kDa and <5 kDa were higher than that of >10 kDa. Results indicated the peptides of hydrolysates possessed antioxidant activities. The cell viability of human keratinocye treated with tilapia scale collagen and it hydrolysate with MW >10 kDa, 5~10 kDa and <5 kDa were 113%, 149%, 136% and 133%, respectively. Results revealed that tilapia scale collagen and its hydrolysate with proper concentration could enhance the growth of human keratinocyte.
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