Functional characteristics of gelatin extracted from skin and bone of Tiger-toothed croaker (Otolithes ruber) and Pink perch (Nemipterus japonicus)

The utilization of waste from fish processing industry for production of value added products has attracted substantial attention. Tiger-toothed croaker (Otolithes tuber) and Pink perch (Nemipterus japonicus) are used for surimi production and have the potential of abundant supply of raw skins and bones. In order to evaluate the waste from Tiger-toothed croaker and Pink perch as a source of gelatin, the gelatin was extracted from skin and bones and its rheological and functional properties were examined. The skins of Tiger-toothed croaker and Pink perch yielded 7.56% and 5.57% gelatin, whereas their bones yielded 4.57% and 3.55% respectively indicating skin as an important source for gelatin production. The gel strength of gelatins from the skins and bones of Tiger-toothed croaker (170 g and 140 g respectively) were found higher than Pink perch skin and bone gelatins (150g and 130g respectively). Similarly, the viscosity, melting point, emulsifying capacity and stability, foaming capacity and stability, and water holding capacity of gelatin extracted from Tiger-toothed croaker were in general greater than those of the gelatin from Pink perch and the values of skin gelatin were higher compared to bone gelatin in both the species. Hydroxyproline contents in skin and bone of Tiger-toothed croaker were 7.77 and 7.51 mg/g and in Pink perch they were 7.63 and 7.41 mg/g respectively. It can be concluded from the present study that Tiger-toothed croaker skin is a prospective source to produce gelatin in good yield with desirable functional properties comparable to commercially available mammalian gelatins. (C) 2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.