Factors affecting contributions of volatile branched-chain fatty acids to the species-related flavors of lamb and mutton

Species-related flavors in lamb and mutton with emphasis on the volatile branched-chain fatty acids (BCFA) were investigated using sensory and chemical methods. The presence of fat in lamb broth was required for sensory recognition of their species-related flavors. Aroma threshold values and aroma descriptions for 23 branched-chain, odd-number or unsaturated fatty acids were determined. Aroma threshold values for individual fatty acids in acidic solutions ranged from 0.006 ppm (4-ethyloctanoic acid) to 82.4 ppm (2-ethylhexanoic acid). Fatty acids with chain-lengths of eight to nine carbon atoms and with branching at the 4-position had goaty/muttony/sheepy aroma notes.;Volatile BCFAs were more concentrated in subcutaneous adipose tissue (rump, shoulder, breast) than in perinephric adipose or muscle tissues of lambs. Lean lamb meat contained BCFAs, but 4-methyl- and 4-ethyloctanoic acids were present at subthresholds concentrations. Greater variations existed in fatty acid profiles of similar subcutaneous adipose samples from different lambs than from different carcass sites of subcutaneous adipose tissue from the same lamb. 4-Methyl- and 4-ethyloctanoic acids were present in all lamb subcutaneous fats tested at concentrations well above threshold levels, and would be expected to contribute species-related flavors to lamb. 4-Methylnonanoic acid concentrations in lamb fats were variable and usually lower than the threshold value, which indicated that this compound would not consistently contribute to lamb flavor.;Forty-five volatile free fatty acids (VFFA) in various fractions obtained during and after roasting, frying or boiling mutton, lamb, goat and venison were quantitatively measured. 4-Methyl- and 4-ethyloctanoic acids were released from lipids into cooking vapors, pan drip and meats of lamb, mutton and goat in adequate concentrations to provide distinctive mutton- and goat-like aromas. Alkyl- and thiophenols were measured in mutton samples and suprathreshold concentrations of thiophenol, o-, m- and p-cresol, phenol, 2-isopropylphenol, 3- and/or 4-isopropylphenols, thymol and carvacrol were found in cooked mutton fractions at concentrations adequate to provide distinctive sheep-like flavor notes.