Tenderness in lamb also seems to be less variable than in beef and pork and generally receives high scores from taste panelists. As with these species, tenderness can be greatly influenced during processing, especially by extending the aging (conditioning) period. This results in proteolytic breakdown of the muscle structure. Electrical stimulation is sometimes used in the early stages of processing to tenderize lamb and to prevent cold shortening during chilling. This can easily arise in the lamb carcass with its high ratio of surface area to weight. Another factor in the generally high tenderness of lamb could be intramuscular fat (marbling fat), which is higher than in beef and pork with similar carcass fat levels, but is not so visible in the meat.
The flavor of lamb is particularly distinctive. In comparison with beef and pork, this is explained by high concentrations of branched-chain fatty acids of medium-chain length, e.g., 4-methyloctanoic acid and 4-methyl-nonanoic acid, and perhaps by more saturated fat. Skatole is also a significant factor in the flavor of lamb. Different flavors in grass-fed and grain-fed lamb have been shown in several studies. This is associated with higher concentrations of n-3 (omega-3) polyunsaturated fatty acids in muscle after grass-feeding, whereas grain-fed lamb contains higher concentrations of n-6 polyun-saturated fatty acids (Fig. 1). The different oxidation products of these fatty acids produce different odors and flavors during cooking (Fig. 2). Grass-fed lamb also has reduced by selection of leaner animals. Conformation of the carcass varies greatly between sheep breeds; too much attention is often paid to this in the grading/classification process. Lamb meat has distinctive qualities. It has a high Grass ultimate pH and marbling fat content, and generally scores
Concentrate high for tenderness and flavor, with less variability than in beef and pork. Grass-feeding increases flavor intensity, which may not suit all tastes, because of relatively high levels of n-3 polyunsaturated fatty acids obtained from a grass-based diet.
Lamb Abnormal flavor flavor
Fig. 2 Scores from University of Bristol taste panel for flavor of loin steaks from lambs fed a grass or concentrate diet (1 100 scales increasing in intensity for each characteristic). (From Ref. 7.) (View this art in color at www.dekker.com.)
Much of the research at University of Bristol is funded by the U.K. Department for Environment, Food, and Rural Affairs (DEFRA) and Meat and Livestock Commission (MLC).
higher concentrations of vitamin E (a-tocopherol) obtained from the grass. This prevents the fatty acids oxidizing, whereas in concentrate-fed lambs, a high level of fat oxidation may explain the different flavor. It should be pointed out that in several countries where grain-feeding of lamb is more common than grassfeeding, the flavors and odors associated with this feeding practice are preferred by consumers. In one study, grass-fed lamb was preferred by a British taste panel, whereas grain-fed lamb was preferred by a Spanish taste panel.
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