Microbial deterioration of lamb meat from European local breeds as affected by its intrinsic properties

Although sheep meat has a small share of ∼1.5 % of the total meat production in the EU, sheep farming is of great importance to rural development and the environment. Enhancing the quality of lamb meat of local breeds is essential to ensure both profitability for sheep producers and the conservation of endangered breeds. This study aimed to (i) characterise the evolution of spoilage microorganisms in refrigerated vacuum-packed lamb meat from a total of 10 farms housing 8 local breeds of Portuguese, Spanish, Italian and Slovenian origin raised in intensive, extensive or semi-extensive regime; and (ii) elucidate how intrinsic properties of meat can affect its microbial spoilage. Cold carcass weight (CCW), ultimate pH (pH24) and proximate analysis were quantified on carcass/meat from each of the 285 animals raised and slaughtered for this purpose; while mesophiles, lactic acid bacteria, Pseudomonas spp. and psychrotrophic bacteria were enumerated during 15-day storage at 4 °C. Substantial variability in all attributes were found between the ten farms. CCW of intensively-raised lambs (21.4 kg; 95 % CI: 20.6–22.1 kg) were higher (p < 0.05) than the ones in semi-extensive regime (14.9 kg; 95 % CI: 14.4–15.4 kg), and in turn these were heavier (p < 0.05) than the extensively raised lambs (12.4 kg; 95 % CI: 12.0–12.7). Mean contents of protein (76.5–87.4% db), fat (3.78–13.1% db) and ashes (4.62–5.65% db) in lamb meat were highly dependent on the farm. Although meat from some farms was associated to higher microbial levels, in general, microbial growth was found to be modulated by intrinsic properties of meat. Higher pH24 (p < 0.05), moisture (p < 0.05), protein content (p < 0.05) and ashes content (p < 0.01) accelerated spoilage rate; whereas meat from heavier carcasses (p < 0.001) and of higher fat content (p < 0.01) presented slower growth of spoilage bacteria. In order to improve the microbial quality of lamb meat, animal handling must be enhanced to minimise pre-slaughter stress; slaughtering practices and hygiene must be improved; and a carcass classification system could be adopted towards the selection of fatter animals and chilled carcasses of optimal pH24.