Fish muscle quality-Influence of carbohydrates in feed and the composition of extracellular matrix

Carnivore fishes as salmon, trout and cod have low capacity to metabolically handle high glucose loading and act in a similar way as diabetic animals. The connective tissue plays an important role in maintaining fish flesh quality; a firm connective tissu e seems to reduce the ability of gaping that is a major quality problem in fish. Gaping is shown to occur in the sarcolemma/basement membrane complex. In this area of the connective tissue, collagen and proteoglycan as decorin and heparan sulfate proteogl ycans contribute to maintain tissue integrity and mechanical strength in mammalians. We have by biochemical and immunological methods found a difference in glycosaminoglycan and proteoglycan composition in bovine muscles with different textural properties as measured by Warner Bratzler Shear Force analyses. In humans and terrestrial animals a high blood glucose level as in diabetics are found to cause a change in the synthesis of heparan sulphate proteoglycans and a reduction in the content of sulphate. T he degradation rate was furthermore increased. If simi lar mechanisms are taking place in fish, the addition of carbohydrate in feed may have adverse consequences for the textural properties. By use of available biochemical and microscopical methods as de scribed, we should be able to clarify these aspects.