Assessment of the Textural Variations of Muscle Tissues of Labeo rohita and Scoliodon sorrokawah with Emphasis on Their Collagen Content

Abstract

Structural proteins specifically myofibrillar protein and collagen play a very significant role in determining the texture of the product. Shark (Scoliodon sorrokawah) is a cartilaginous fish having high collagen content and its crude protein content (22.01%) is comparatively higher than rohu (Labeo rohita) viz. 17.73%. The present study investigates the rheological differences between the two species differing in their collagen content. During freezing, an increase in the toughness was observed which was possibly due to the aggregation of myofibrillar proteins and collagen. Histographs and texture profile analysis data obtained indicated a two – phase toughening process in both the species. In both unfrozen and frozen samples, a two to three fold increase in toughening occurred during cooking. Though the first phase of hardening on cooking (50°C) was similar in both species, the second phase of hardening varied in frozen samples as 70°C and 75°C for fresh and frozen shark and 70°C and 80°C for fresh and frozen rohu respectively. These slight variations in the two species might be possibly due to the difference in their connective tissue protein content, distribution and properties. In raw muscle tissue, the toughness is very much a product of hardening of the connective tissue proteins. During the second phase of tissue hardening the weight loss and cooking shrinkage was observed which was possibly due to the loss of water holding capacity and conformational changes in the protein configuration.