Evidence of marbling as a single connected entity in beef striploins

Serial sections of Angus striploins that varied in marbling were analysed in three dimensions to assess potential differences in intramuscular fat structure. The majority of the intramuscular fat appeared to be connected along the 100 mm of muscle in both the highly marbled and less marbled striploins. Thus, rather than having dispersed individual flecks of marbling, the intramuscular fat was a single entity within the striploin. The local shape patterns of this entity varied with marbling level in that the structure had an increased diameter in the highly marbled striploins. However, the amount of branching in the intramuscular fat did not vary with the level of marbling. The results suggest that marbling may occur along an internal structure, such as the vascular system or interstitium, in the longissimus muscle. It is postulated that when beef marbling increases, additional intramuscular fat is not deposited in isolated sites but along this internal structure, widening the existing entity rather than changing the shape.