Studies on texture and collagen content of commercially important tropical fishes

Abstract

Stroma proteins refer to slightly soluble proteins which are obtained after removing water and salt, soluble proteins in the muscle. The main constituent of stroma protein is collagen. The role of collagen in contributing to the texture and gaping of fish fillets has been studied using six commercially important fish species of India VIZ. sardine (SardineIla lonqiceps) ,mackeral ( RastralIiger kanaqurta ) , tilapia ( Oreochromis mossambicus ) , common carp (Cyprinus carpio), tuna (Euthynnus affinis) and shark (Scoliodon sorrakowah). The texture of raw fish meat was found to be influenced by the content of collagen in fish muscle. A significant correlation (P > 0.05) was obtained between soluble, insoluble and total collagen contents, and toughness of raw meat, as determined by sensory evaluation and two types of texturometers. Significant correlation was also obtained between actomyosin content and toughness of raw meat, determined either by subjective or objective methods (P > 0.05), but not to the extent of soluble or total collagen. In the case of cooked meat , although a significant correlation (P> 0.05 ) was obtained between actomysin content and cooked meat toughness ,no such correlation could be established between collagen content and cooked meat toughness. Stroma proteins seem to be important in deciding the texture of raw meat, whereas, In the case, of cooked meat, myofibrillar proteins are probably involved. The gaping phenomenon was studied in frozen fillets stored for a period of three months. A slight increase in gaping was noticed during storage period. However, this was not found to be statistically significant. Further studies have to be carried out to get a clear cut idea about the influence of collagen on gaping phenomenon in frozen stored fish. The two types of texturometers fabricated, spring - operated and weight - operated, were found suitable for assessing the toughness of raw fish meat, but not. Cooked meat.