Fatty acid composition and eating quality of lamb types derived from four diverse breed × production systems

Abstract

Carcass composition, muscle fatty acids and eating quality of loin chops were examined in ram lambs from four diverse breed × production system groups: pure Welsh Mountain off upland flora, pure Soays off lowland grass, Suffolk crosses off lowland grass and Suffolk crosses off concentrates. The two Suffolk groups had heavier and better muscled carcasses than the others and Soays were particularly lean. Fatty acid composition was different between the groups. The forage-fed lambs all had high concentrations of n-3 polyunsaturated fatty acids (PUFA) including 18:3 (α-linolenic acid) and 20:5 (eicosapentaenoic acid) compared with Suffolks-concentrates which had high concentrations of the n-6 PUFA 18:2 (linoleic acid) and 20:4 (arachidonic acid). Soays were high in both n-3 and n-6 PUFA. Flavour characteristics in grilled chops were similar in Welsh Mountain and Suffolks-grass which differed from Soays and Suffolks-concentrates. The latter two groups had low scores for lamb flavour and overall liking and high scores for abnormal lamb flavour, metallic, bitter, stale, and rancid. Soays had the highest score for livery. These results extend previous findings of the association between feed, PUFA composition and lamb flavour profile and confirm that forage-fed lamb is preferred by UK taste panellists. They also identify a specific breed effect on the quality of meat from lambs raised on forage. These findings suggest that possibilities exist for the production of meat with specific quality characteristics.

Introduction

Several factors affect consumers' decisions to purchase meat but an important one is the perception of quality. The perceived ‘healthiness’ of a food is becoming a key quality issue for consumers and, in the case of meat, this is largely related to its fat content and its fatty acid composition. Previous studies suggest that the fatty acid composition of ruminant meats can be influenced by diet, with consequences for other important quality attributes, most notably flavour which is a major determinant in eating satisfaction (Wood, Enser, Fisher, Nute, Richardson & Sheard, 1999). For example, grain diets which result in raised concentrations of n-6 polyunsaturated fatty acids (PUFA) in muscle produce a different flavour profile to grass diets which increase muscle concentrations of n-3 PUFA (Kemp, Mahyuddin, Ely, Fox & Moody, 1981, Larick & Turner, 1990). The preference of taste panellists for meat from grain-fed or grass-fed lambs seems to depend on previous experience: although Spanish taste panellists identified British grass-fed lamb as having more intense/pronounced lamb flavour, they preferred the flavour of younger, Spanish, grain-fed lamb. British panellists, assessing the same lambs, were in agreement on the flavour intensity ratings but preferred the flavour of the British lamb (Sanudo et al., 1998).

In addition to diet, the effect of breed may be important. There is anecdotal, but little scientific, evidence that the meat from lambs of certain breeds reared on particular diets (i.e. ‘systems’) has unique or characteristic flavours. Such meat could qualify for premium quality status if it were shown that it was genuinely different. One hypothesis to support differences in taste is that they are, in large part, a result of variation in fatty acid composition which, in turn, varies according to the breed and feed used. Ruminants preferentially deposit PUFA in phospholipids (Enser, Hallett, Hewett, Fursey, Wood & Harrington, 1998) so very lean breeds could have relatively high proportions of PUFA compared with fatter lambs in which the phospholipid effect is diluted by higher levels of neutral storage lipid (marbling fat). Variations in the absolute concentration and the relative proportions of different fatty acids would affect the flavour profile. In order to investigate these ideas further, fat content, muscle fatty acid composition and flavour profile have been studied in four lamb types. Three of these represent diverse breed × production systems found in the UK, whilst the fourth type was genetically similar to one of the others but was fed a different diet to provide information on the effect of diet per se. The aim in selecting animals from different breed × feed combinations was to determine the extent of natural variation in fatty acid composition and flavour characteristics.