Conservation of conjugated linoleic, trans-vaccenic and long chain omega-3 fatty acid content in raw and cooked lamb from two cross-breeds

Available literature mainly describes the fatty acid (FA) content of raw meat, with only limited data explaining the effect of different preparation and cooking temperatures on health-promoting FA such as conjugated linoleic acid (CLA), its metabolic precursor trans-vaccenic acid (TVA), and long chain omega-3 FA (LC omega-3 FA). We collected m. longissimus thoracis (LT) from rib chops of Poll Dorset x East Friesian (EF) and Poll Dorset x Romney (R) lambs raised together. The FA composition of raw LT was compared with LT prepared with bone and all fat trimmed away or bone and fat left intact before cooking under a fan-grill. The LT from EF lambs had less cooking loss, lower lipid and total fatty acid (TFA) contents, and a lower proportion of saturated fatty acids (SATFA) than the LT from R lambs. Raising cooking temperature from medium to well-done increased cooking losses and dry matter (DM) yield but did not affect FA content or composition. Compared with raw LT, cooking of the trimmed LT resulted in more TFA and lipids in the DM, and these were greater still in the intact LT. Similar increases occurred in the DM content of most individual and groups of FA, except for CLA and LC omega-3 FA which increased with cooking of trimmed LT without further significant increase with cooking intact LT. The proportions of SATFA and TVA in the TFA increased after cooking trimmed LT and increased further after cooking intact LT. In contrast, proportion of polyunsaturated fatty acid (PUFA) was reduced at each step, while the proportion of CLA was not affected by cooking. Thus, the FA content of raw lamb underestimates that of cooked meat, especially if the lamb is cooked with bone and fat left intact allowing infiltration of FA from the surrounding intermuscular and subcutaneous fat. This influx of lipids from the surrounding adipose tissue dilutes the proportions of PUFA and LC omega-3 FA in the TFA.