Contribution of the Connective Tissues on the Texture Difference of Various Fish Species

Abstract

Contribution of the connective tissue content on the meat texture of fish species was studied. Firmness of texturometer tests and collagen content of the raw and cooked dorsal muscles of five fish species were determined. Five species selected were skipjack, flying fish, common horse mackerel, plaice and channel rock fish. The firmness value of raw meat varied in a decreasing order: plaice, channel rock fish, flying fish, skipjack, and common horse mackerel. That of cooked meat varied in a decreasing order: skipjack, flying fish, common horse mackerel, plaiceand channel rock fish. The order of the above series was in reverse between raw meat and cooked meat. The species with softer raw meat textures, on cooking gave a firmer texture.
The amount of connective tissues as expressed by collagen content was determined on the muscle portion as the same with the texture measurements. Higher the collagen content, firmer the raw meat. There was a significant correlation (r: 0.697) between the collagen content and the firmness. The species with firmer raw meat texture contained higher collagen content than the species with softer texture. The amount of water soluble collagen at 20°C pH 7.0, assumed as an index of the exuding collagen during mustication, increased with the decrease of the firmness of raw meat (r: 0.650). The amount of water insoluble collagen gave higher correlation coe-fficient(r: 0.744) with the firmness. These results suggest that the properties and/or composition of collagen is varied by spies.
However, between the cooked meat and the collagen content, such relationships was hardly recognized, and this was attributed to the collagen which is solubilized during cooking. There was no appreciable correlation between the amount of water soluble collagen at 70°C and the fumness of cooked meat, though cooked beef muscle has been reported to give such correlation.
The connective tissue proteins must contribute to the raw meat texture, while the cooked meat texture does not depend upon the connective tissue proteins, but, probably on the other factors, like the muscle fiber characteristics as reported before.