Influence of keeping system on the fatty acid composition in the longissimus muscle of bulls and odorants formed after pressure-cooking

German Simmental bulls were kept either in a stable (group 1) or on a pasture (group 2). For both groups the intramuscular fat content of the longissimus muscle and the fatty acid composition in phospholipids and triacylglycerols were investigated. Significant influences of feeding were shown in most fatty acids measured in both lipid classes. In concentrate-fed bulls a higher content of linoleic acid (C18:2n-6) was detected, corresponding to the large amount of linoleic acid found in concentrate used as feed. In contrast, bulls fed grass proved to have a higher linolenic acid (C18:3n-3) content, also correlating well with the larger amount of linolenic acid found in grass. Pressure-cooking of the beef followed by an analysis of eight important meat odorants revealed that, in line with the higher concentrations of the precursor fatty acids C18:3n-3 and C18:1 in muscle of group 2, (E,Z)-2,6-nonadienal (from C18:3n-3) as well as nonanal and octanal (from C18:1) were much higher in the processed meat of animals fed grass. On the other hand, the much higher amounts of C18:2n-6 in bulls fed concentrate were well-reflected by higher concentrations of five aroma compounds known to be formed by a thermal degradation of this acid, e.g. (E,E)-2,4-decadienal.