FOOD HYDROCOLLOIDS Food Hydrocolloids 21 (2007) 537–544 Autolysis study of bigeye snapper (Priacanthus macracanthus) skin and its effect on gelatin Rossawan Intarasirisawat a , Soottawat Benjakul a,Ã , Wonnop Visessanguan b , Thummanoon Prodpran c , Munehiko Tanaka d , Nazlin K. Howell e a Department of Food Technology, Faculty of Agro-Industry, Prince of Songkla University, Hat Yai 90112, Thailand b National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, 113 Paholyothin Road, Klong1, Klong Luang, Pathumthani 12120, Thailand c Department of Material Product Technology, Faculty of Agro-Industry, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand d Department of Food Science and Technology, Tokyo University of Marine Science and Technology, Konan 4, Minato, Tokyo 108-8477, Japan e School of Biomedical and Molecular Science, University of Surrey, Guildford, Surrey GU2 7XH, UK Received 17 March 2006; accepted 22 May 2006 Abstract Autolysis of bigeye snapper (Priacanthus macracanthus) skin was studied. The maximal autolytic activity was observed at 60 1C and pH 7.5. The proteolytic activity was strongly inhibited by 0.001 mM soybean trypsin inhibitor (SBTI), whereas pepstatin A (1 mM), EDTA (20 mM), EGTA (10 mM), iodoacetic acid (1 mM), PMSF (1 mM), E-64 (10 mM) and 1,10-phenanthroline (1 mM) showed no inhibitory effect. The result suggests that the major proteinase in bigeye snapper skin was a serine proteinase. Gelatin was extracted from bigeye snapper skin in water without and with 0.001 mM SBTI using a skin/water ratio of 1:7 at different temperatures (35, 40, 45, 50, 55 and 60 1C) for 12 h. In the presence of SBTI, the degradation was markedly inhibited. However, b-chain disappeared and a-chains underwent degradation to some extent at temperatures above 50 1C. Generally, a higher yield of gelatin was obtained as the extracting temperature increased (Po0.05). Nevertheless, the addition of 0.001 mM SBTI caused a lower gelatin yield. Therefore, heat-activated serine proteinase, most likely collagenase, involved in the degradation of collagen molecule and affected the yield and proteinaceous components in the resulting gelatin from bigeye snapper skin. r 2006 Elsevier Ltd. All rights reserved. Keywords: Proteinases; Bigeye snapper; Gelatin; Soybean trypsin inhibitor; Collagen; Skin 1. Introduction Proteinases are enzymes inducing the cleavage of peptides. Collagenolytic enzymes are associated with the quality of seafoods. Collagenolytic enzymes are another proteinases which catalyze the hydrolysis of collagen and gelatin (Kristjansson, Guthmundsdottir, Fox, & Bjarna- son, 1995; Sikorski, 1990; Sovik & Rustard, 2006). The major collagenolytic enzymes are collagenase, a group of matrix metalloproteinase in a family of zinc-dependent enzymes. They can cleave triple-helical collagen at a single site, resulting in the formation of fragments corresponding to 1/4 and 3/4 of its initial length (Sano, Nishino, Ueno, & Kamimori, 2004). Metallo-collagenases in fibroblastic cell from rainbow trout are classified as MMP-13 (Collagenase- 3, EC 3.4.24) (Saito, Sato, Kunisaki, & Kimura, 2000). Apart from metalloproteinases, serine collagenases were found in the intestines of Atlantic cod (Kristjansson et al., 1995) and the hepatopancreas of northern shrimp (Panda- lus eous)(Aoki, Ahsan, Matsuo, Hagiwara, & Watabe, 2003). Furthermore, non-collagenase proteinases can cleave the collagen molecule in the telopeptide region and contribute to destabilization of the collagen molecule by disrupting the region, in which intermolecular cross-links are formed (Bornstein & Traus, 1979). Gelatin, a derivative of collagen, has been used widely by the food industry to enhance the elasticity, consistency and ARTICLE IN PRESS www.elsevier.com/locate/foodhyd 0268-005X/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodhyd.2006.05.012 Ã Corresponding author. Tel.: +66 7428 6334; fax: +66 7421 2889. E-mail address: soottawat.b@psu.ac.th (S. Benjakul).