The effects of the diet on flesh quality of farmed dentex ( Dentex dentex)

Abstract

The aim of this study was to assess the potential effects of replacing part of the dietary protein by lipid or carbohydrate on the characteristics of dentex muscle. Dentex were hand-feed four isoenergetic diets (22.6 MJ kg − 1 gross energy) with protein:lipid:carbohydrate ratios 43/16/28 (D1); 43/24/4 (D2); 38/19/28 (D3), and 38/24/13 (D4). At the end of the feeding period, biometric parameters, textural properties of muscle, as well as protein, lipid and collagen contents, and electrophoretic protein profiles of this tissue were studied. The decrease in dietary protein content improved textural parameters (increased firmness and water holding capacity). Within each dietary protein level, diets with high carbohydrate and low lipid contents resulted in lower values of muscle firmness than diets with low carbohydrate and high lipid contents. This increase in firmness matched with a lower muscle lipid and higher muscle collagen contents. SDS-PAGE separation of muscle extracts showed a higher relative contribution of myosin to total optical density in muscle from those animals fed lower dietary protein, although no significant difference in fish texture could be attributable to this finding. Results indicate a favourable effect of replacing protein by alternative energy sources (lipids or carbohydrates) on the rheological properties of muscle in this species, this improvement was more noticeable when protein was replaced by lipid than by carbohydrate.