碩士 / 國立高雄海洋科技大學 / 水產食品科學研究所 / 94 / Cobia (Rachycentron canadum) is one of the most important cultured fish in Taiwan providing for Sashimi use. Their skin wastes produced from fillet processing contain a great amount of collagen which can be utilized to make high value-added products. Many researches reported that hydrolyzed peptides and proteins have functional properties and can be used as supplement or health food. For the reasons, the aim of this study is to investigate the molecular weight (M.W.) profiles (ranges) of hydrolyzed gelatins and their antioxidative activities including linoleic acid peroxidation inhibition, DPPH radical scavenging activity, reducing activity, and cheating activity on ferrous ions.
Cobia skin was employed as raw materials for gelatin extraction. After scraping off the scales by alkali treatment, cobia skin was extracted at 121
˚C for 30 min for crude gelatin. Then four commercial enzymes, bromelain, papain, pancreatin, and trypsin, were used to hydrolyze cobia gelatins at 50˚C for 0~3 h. The results of SDS-PAGE showed that the molecular weights of most of samples treated with enzymes for 30 min were generally below 10.6 kDa. Moreover, the four hydrolyzed products were individually analyzed by HPLC with Superdex peptide 10/300 column. It indicated that the main M.W. profiles of the four hydrolyzed products ranged from 6,511 to 686 Da. No obvious alteration of M. W. profiles was found when hydrolysis times were extended to 2 or 3 h. The results of antioxidative assay demonstrated that samples treated with pancreatin and trypsin for 3 h had stronger DPPH scavenging activities than others. The pancreatin-treated samples exhibited higher linoleic acid peroxidation inhibition percentages than those of other samples. However, comparing to 1000 ppm ascorbic acid, all treated samples with dosages of 2~30 mg/mL didn’t show significant capacity in reducing activity and cheating activity on ferrous ions.
Secondary, crude gelatin and the four enzyme-treated products after 3 h hydrolysis were fractionated by ultrafilitration with various centrifugal concentrators (MWCO: 10 kDa, 5 kDa, and 3 kDa). After analysis by HPLC with the above gel filtration column, the smaller pore size of centrifugal concentrators was used and the smaller molecular mass of peptide was obtained. The main M.W. profile of the fraction by ultrafilitration with 3 kDa cut-off was from 686 to 189 Da and this fraction was selected to further evaluate their antioxidant activities. It demonstrated that all ultrafilitrated samples had much higher DPPH radical scavenging activities than samples without ultrafilitration. Particularly the DPPH radical scavenging effects of papain- and pancreatin-treated samples were 92.4% and 91.2%, respectively. Similarly all ultrafilitrated samples also displayed higher linoleic acid peroxidation inhibition percentages than those of samples without ultrafilitration.
Furthermore, gelatin samples without enzyme treatment were obtained by heating at 121˚C for 0.5, 1, 2, 3 h. The heated samples were also to profile their molecular weight ranges and evaluate their antioxidant activities. The results of SDS-PAGE indicated that peptides with smaller molecular weight were generated by heating with longer time. The HPLC analysis showed that the main M.W. profile of the gelatin heated for 2-3 h was 6,511 to 686 Da and meanwhile the amount of peptides with M. W. ranging from 686 to189 Da also increased. It also showed that smaller peptides displayed stronger DPPH radical scavenging activity. Besides, the linoleic acid peroxidation inhibition percentages of different heated samples generally maintained about 60~70%.
| Identifer | oai:union.ndltd.org:TW/094NKIMT084003 |
| Date | January 2006 |
| Creators | Ho, Hsin-Yi, 何心怡 |
| Contributors | Chow, Chau-Jen, Yang, Jing-Iong, 周照仁, 楊景雍 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 81 |
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