In Portugal, sheep and goat meat production constitutes 2.8% of the total meat production, with a self-sufficiency of ~82%. The main autochthonous sheep breeds exploited for meat production are Churra-Galega-Bragançana (CGB) and Bordaleira-de-Entre-Douro-e-Minho (BEDM), whose quality must be optimised in order to ensure adequate income levels for sheep producers. The study aimed to characterise the evolution of spoilage microorganisms in refrigerated vacuum-packed (VP) lamb meat from BEDM and CGB breeds; and elucidate how intrinsic properties of meat can affect its microbial spoilage. Meat from BEDM breed presented higher (p<.0001) populations of mesophiles, lactic acid bacteria, Pseudomonas spp. and psychrotrophic bacteria, since its higher ultimate pH (means: 5.77 for BEDM vs. 5.58 for CGB) accelerated spoilage rate (p<.0001). While water activity and protein content were not found to modulate microbial deterioration (p>0.05), the growth of spoilage bacteria was found to be exacerbated by higher moisture (p<.0001) and higher ash content (p<.001). By contrast, a higher fat content retarded (p<.0001) the growth of spoilage bacteria in VP lamb meat. In order to extend the shelf-life of Portuguese-origin lamb meat, animal handling must be enhanced to minimise pre-slaughter stress, and a carcass classification system should be adopted towards the selection of fatter animals and chilled carcasses of optimal ultimate pH. Keywords: BioSheep, local breeds, proximate composition, pH, lactic acid bacteria, Pseudomonas, psychrotrophic bacteria, shelf-life.
