Characterisation of acid-soluble collagen from skin and bone of bigeye snapper (Priacanthus tayenus)

Abstract

The compositions and some properties of acid-soluble collagens (ASC) of the skin and bone of bigeye snapper, (Priacanthus tayenus) were investigated. The collagens were extracted with the yields of 10.94% and 1.59% on the basis of wet weight, from skin and bone, respectively. Similar electrophoretic patterns of collagens from the skin and bone were observed. Both collagens comprised two different α chains, α1 and α2 and were classified as type I collagen. However, peptide maps of collagen from the skin and bone of bigeye snapper, digested by V8 protease and lysyl endopeptidase, revealed differences between collagens from skin and bone, and both were completely different from those of calf skin collagen. Collagen rehydrated in acetic acid had lower T_max and enthalpy than those rehydrated in deionised water, suggesting a conformational change caused by acid. Collagens form the skin and bone had the highest solubility at pH 2 and 5, respectively. No changes in solubility were observed in the presence of NaCl up to 3% (w/v). However, a sharp decrease in solubility was found with NaCl above 3% (w/v).

Introduction

Thailand is one of the largest surimi producers in Southeast Asia. At present, twelve surimi factories are located in Thailand, with a total production of about 60,000 metric tonne per year (Morrissey & Tan, 2000). The fish used for surimi production are mostly threadfin bream (Nemipterus spp.), bigeye snapper (Priacanthus spp.), croaker (Pennahia and Johnius spp.) and lizardfish (Saurida spp.) (Benjakul, Chantarasuwan, & Visessanguan, 2003). During surimi processing, numerous wastes, both liquid and solid form, are generated (Morrissey, Park, & Huang, 2000). The solid wastes constitute 50–70% of the original raw material, depending on the processing used. These wastes are a mixture of heads, viscera, skin and bone (Morrissey et al., 2000). Although the nutritional values of these wastes are fairly high, these useful resources have been mainly used as fish meal or fertiliser with low value (Nagai & Suzuki, 2000a). Also, improper disposal of these wastes may cause pollution and emit an offensive odour. Hence, optimal utilisation of surimi processing wastes, especially in the production of value-added products is a promising means to increase revenue for the producer and to decrease the cost of disposal or management of these wastes.

Collagen has a wide range of applications in leather and film industries, pharmaceutical, cosmetic and biomedical materials and food (Bailey & Light, 1989; Cavallaro, Kemp, & Kraus, 1994; Hood, 1987; Hassan & Sherief, 1994; Nimni, 1988; Slade & Levine, 1987; Stainsby, 1987). Generally, pig and cow skins and bones are the main sources of collagen isolation. However, the outbreak of mad cow disease has resulted in anxiety among users of cattle gelatin. Additionally, the collagen obtained from pig bones cannot be used, due to religious constraints (Sadowska, Kolodziejska, & Niecikowska, 2003). As a consequence, increasing attention has been paid to alternative collagen sources, especially fish skin and bone from seafood processing wastes. About 30% of these wastes consist of skin and bone, which are very rich in collagen (Gomez-Guillen et al., 2002; Shahidi, 1994). However, fish collagens have lower thermal stability than mammalian collagens because fish collagens contain lower imino acid contents than mammalian collagens (Foegeding, Lanier, & Hultin, 1996). So far, skin and bone collagen from several fish species have been isolated and characterised (Ciarlo, Paredi, & Fraga, 1997; Kimura, Miyauchi, & Uchida, 1991; Kimura, Ohno, Miyauchi, & Uchida, 1987; Nagai, Araki, & Suzuki, 2002; Nagai and Suzuki, 2000a, Nagai and Suzuki, 2000b; Sadowska et al., 2003; Yata, Yoshida, Mizuta, & Yoshinaka, 2001). However, no information regarding the collagen from tropical fish, particularly from surimi processing waste, has been reported. Bigeye snapper (Priacanthus tayenus) is commonly used for surimi production due to its high gel-forming ability (Benjakul, Visessanguan, Ishizaki, & Tanaka, 2001). Therefore, the objective of this investigation was to isolate and characterise acid-soluble collagen from skin and bone of bigeye snapper.