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Variations in diet, age and castration were employed to generate a range of flavours that were chemically analysed to find the cause of 'pastoral' flavour in sheepmeat and its relationship to species flavour. Lambs were raised on pasture (ram or castrate) or on a maize-based or lucerne-based concentrate diet (ram only). They were slaughtered at 132 and 232 days. Fat from animals raised on concentrates had lower proportions of fat-hardening stearic acid and higher proportions of oxidationprone fat-softening oleic and linoleic acids. Concentrations of species-characterising short branchedchain fatty acids (BCFAs), typified by 4-methyloctanoic acid, were lower for pasture-fed lambs, particularly at 232 days, although between-animal variation was high. Castration did not statistically affect BCFA concentration at this age. Correlations between BCFAs and testes weight were not significant, suggesting that they were not acting as sex pheromones. Concentrations of 3-methylindole (skatole) in perirenal fat were higher for the pasture diet at both slaughter dates. Concentrations of 4-methylphenol in the fat were not affected by diet. However, 3-methylphenol was more abundant in pasture treatments. A sensory panel found that the intensity of 'sheepmeat' flavour was higher for pasture-raised animals, but that associations of 'barnyard' flavour (which has been linked to pastoral flavour) with diet were more complex. The issue was resolved by fat sniffing. Panel responses to heated subcutaneous fat were recorded as frequency of descriptive terms drawn from a limited lexicon. Volatiles from fats pooled by treatment were resolved on a gas chromatographic column whose effluent was monitored by odourport sniffing. Compounds were identified by parallel chromatographic/mass spectrometric runs. The headspace concentrations of these compounds were then measured for individual animals. These data were related to frequency data by the principal component method. 'Mutton' and 'sheepmeat' odour notes were clearly linked to indoles (skatole particularly) and, to a lesser extent, methylphenol, setting these notes apart from 'lamb', an odour note more associated with lucerne and maize diets through higher concentrations of BCFAs. It was concluded that 3-methylindole was the major cause of pastoral flavour in sheepmeat, and that fat oxidation products represented a background flavour that varied quantitatively but not qualitatively with fatty acid profile.

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Lamb has a unique flavor, distinct from other popular red meats. Although flavor underpins lamb's popularity, it can also be an impediment to consumer acceptance. Lack of familiarity with sheepmeat flavor itself can be a barrier for some consumers, and undesirable feed-induced flavors may also compromise acceptability. Against the backdrop of climate uncertainty and unpredictable rainfall patterns, sheep producers are turning to alternatives to traditional grazing pasture systems. Historically, pasture has been the predominant feed system for lamb production in Australia and around the world. It is for this reason that there has been a focus on "pastoral" flavor in sheep meat. Pasture-associated flavors may be accepted as "normal" by consumers accustomed to meat from pasture-fed sheep; however, these flavors may be unfamiliar to consumers of meat produced from grain-fed and other feed systems. Over the past few decades, studies examining the impacts of different feeds on lamb meat quality have yielded variable consumer responses ranging from "no effect" to "unacceptable", illustrating the diverse and sometimes inconsistent impacts of different forages on sheepmeat flavor. Despite considerable research, there is no consensus on which volatiles are essential for desirable lamb aroma and how they differ compared to other red meats, for example, beef. In contrast, comparatively little work has focused specifically on the nonvolatile taste components of lamb flavor. Diet also affects the amount of intramuscular fat and its fatty acid composition in the meat, which has a direct effect on meat juiciness and texture as well as flavor, and its release during eating. The effect of diet is far from simple and much still needs to be learned. An integrated approach that encompasses all input variables is required to better understand the impact of the feed and related systems on sheepmeat flavor. This review brings together recent research findings and proposes some novel approaches to gain insights into the relationship between animal diet, genetics, and sheepmeat quality.