Segureño lamb meat from protected Geographical Indicationmethods to promote nutritional andtechnological quality in sustainable farming system

Abstract

This doctoral thesis is part of the national project (RTA 2013-00104-C02-00) developed by the University of Murcia and the Institute for Agri-Food Research and Development of Murcia (IMIDA). The global objective was to establish more sustainable dietary strategies that contribute to enhancing the quality attributes of Segureño lamb meat in line with new meat consumption habits. Spring and autumn lambs reared indoors with maternal grazing or not in a farm included in the "Segureña Lamb Protected Geographical Indication" were compared. The concentrate feeds for weaned lambs were manufactured with local sage by-products (SDB) whose polyphenol content was analysed. The combined effect of maternal rearing (seasonal grazing of cereal straw and fallow vs. intensive rearing with cereal grain with lucerne pellets) and lamb diet supplementation with 10% SDB on the meat quality were evaluated. Loin fillets were packed under modified atmosphere (70% O2 and 30% CO2) and kept for up to 12 days, simulating retail conditions. Moreover, the fat composition and oxidative stability of freshly cooked meat kept under catering conditions will be studied, taking into account only the effect of maternal grazing. For this, patties were made using the legs from autumn lambs. The patties were alternately grilling (150ºC for 2 min) or cooked under vacuum in a thermostatic bath (75 ºC for 35 min), reaching in both cases a similar final internal temperature (72 ºC). Subsequently, the hamburgers were kept at 65ºC for 4 h simulating hot catering conditions. The results obtained reveals that the contribution of dietary antioxidant and / or antimicrobials compounds through graze did not improve the results obtained when the ewes were fed indoors. The incorporation of SDS also did not produce any technological preservative effect in meat, possibly due to insufficient bioavailability of the active compounds present at the dietary doses used. Maternal grazing resulted in a higher proportion of n-3 polyunsaturated fatty acids (PUFA) (linolenic and eicosapentaenoic) compared to n-6 (arachidonic and docosatetranoic), thus reducing the n-6 / n-3 ratio in lamb meat, which implies a nutritional improvement. For its part, dietary supplementation with SDS had no clear effect on the lipid profile of lamb meat in both seasons. The improvements in the lipid profile associated with maternal grazing were maintained, both in freshly cooked meat and after subsequent hot keeping. In short, semi-extensive sheep rearing improves the nutritional quality of Segureña grain-fed lamb meat, although does not increase its preservation capacity. On the other hand, SDB can be included up to 10% in the diet of weaned lambs without sensory, nutritional and technological detriment to the meat quality, although it would be convenient to improve the supplementation method and, if necessary, using antioxidant strategies to enhance meat preservation. Finally, sous vide cooking may contribute to reducing the degree of oxidation of meat during cooking and subsequent catering-type hot keeping, increasing the retention of healthy fatty acids and reduces the intake of potentially harmful compounds.