Jong-Bang Eun

Nutritional composition and microflora of the fresh and fermented skate (Raja Kenojei) skins

The proximate compositions of fresh and fermented skate skin were each 75.95% and 74.5% moisture, 22.7% and 21.8% protein, 0.5% and 0.7% lipid and 0.6% and 0.9% ash, respectively. The predominant minerals were potassium and phosphorus (i.e. 53.5 and 33.0 mg/100 g in fresh skin, and 10.46 and 10.51 mg/100 g in fermented skin, respectively). Amino acid concentrations were lower in the fermented skin compared with the fresh skin. Histidine, glycine, alanine and glutamic acid were the major free amino acids in both skins. Palmitic acid (C16:0) was the major fatty acid in both fresh (16.68%) and fermented (20.38%) skate skin. Omega-3 polyunsaturated fatty acids were higher in fresh skin (22.17%) and fermented skin (24.54%) compared with omega-6 polyunsaturated fatty acids. The predominant microflora present in the both fresh and fermented skin were Photobacterium sp. and Vibrio sp. Total plate counts for the fresh and fermented skin were 2.4×104 CFU/g and 7.7×107 CFU/g, respectively.

Effect of blanching and drying temperatures on the physicochemical characteristics, dietary fiber composition and antioxidant-related parameters of dried persimmons peel powder.

The effects of blanching with hot water at 90°C for 2 min and hot-air drying temperatures (50°C, 60°C and 70°C) on the physicochemical properties, dietary fiber compositions, antioxidant activity and hydration properties of ripe, soft persimmon peels were investigated. Blanching and drying significantly reduced the retention of antioxidant-related parameters. Although there were no significant differences in total phenolics and β-carotene content at different drying temperatures for both dried unblanched and blanched peels, dried blanched peels had higher dietary fiber compositions and swelling capacity than those of dried unblanched peels at all drying conditions. In addition, blanched peels dried at 50°C had the highest dietary fiber compositions, swelling capacity and antioxidant activity compared with those at high drying temperatures (60°C and 70°C). Therefore, blanched peels dried at 50°C is suggested to obtain better quality dietary fiber powder from persimmon peel for use in food applications or in fiber-fortified foods for health promotion.

Kenojeinin I, antimicrobial peptide isolated from the skin of the fermented skate, Raja kenojei.

An antimicrobial peptide was purified from fermented skate skin extract using the solid-phase extraction and separation on HPLC reversed-phase chromatography. Amino acid sequence of the purified peptide (Peak A) having an antimicrobial activity revealed the presence of many cationic residues of the total 28 amino acids. Its molecular mass was found to be 3059 Da. This result was in excellent agreement with the theoretical molecular mass calculated from the amino acid sequence. The synthetic kenojeinin I had inhibitory effects on B. subtilis (MIC, 12 microg/ml), E. coli (28 microg/ml), and S. cerevisiae (12 microg/ml). These results indicate that fermented skate skin is potentially antimicrobial.