Microbiological and sensory changes in Morcilla de Burgos preserved in air, vacuum and modified atmosphere packaging

Morcilla de Burgos is the most popular blood sausage in Spain. Traditionally, this product is distributed and sold without packaging in the local market. To extend its shelf-life and expand the market, different packaging methods have been employed and compared: morcilla stored in air (without packaging), in vacuum and in modified atmosphere packaging (MAP) using three different CO2 concentrations 30%, 50% and 80% and balanced with N2. Total viable count (TVC), psychrotrophs, lactic acid bacteria (LAB), pseudomonads, enterobacteria, moulds and yeasts, enterococci, Staphylococcus aureus, and sulfite reducing clostridia were analysed during storage at 4 C. Sulfite-reducing clostridia, pathogenic staphylococci, and enterococci were not detected in any sample. In air-stored morcilla a significant increase in all microbial groups was observed during storage. Pseudomonads were the predominant microorganisms reaching a population higher than 8 log cfu/g after 27 days of storage. On the other hand, a decrease in pH was noticed in MAP and in vacuum packaged morcilla (pH 4.73) during storage. At the same time, LAB becomes the predominant species in all these packaged samples. The rest of the microbiota did not grow during storage. In morcilla packed with 50% and 80% of CO2, counts of pseudomonads and enterobacteria were lower than found in the vacuum packs. Sensory analysis showed that shelf-life of morcilla stored in air did not exceed 17 days, while samples packed under vacuum and with 30% CO2 were acceptable until 22 days of storage. Morcillas packaged with 50% and 80% CO2 were sensorially acceptable for 32 days.