Microbiological Quality of Filled Pasta in Relation to the Nature of Heat Treatment

Abstract

The microbial population present in 49 samples of Italian industrially processed filled pasta was characterized and its changes during refrigerated storage were evaluated. The most frequently isolated species belonged to the genus Bacillus. No pathogenic organisms were isolated from the processed industrial pasta. As a consequence of the diversity of composition and thermal treatment a wide variability was observed (from less than 3 days to more than 1 month) in the shelf life at 4°C of the industrial “fresh filled pasta.” However, the results obtained suggested that the shelf life of the processed products depended not only on the number of surviving cells but also on the textural or microstructural changes induced by the heat treatment. Challenge tests using Staphylococcus aureus showed that even pasteurization values (P7010, expressed as an equivalent process time, in minutes, necessary to obtain at 70°C the same lethal effect as during the actual process) not exceeding 2 were able to remarkably reduce the cell load of this organism. Subsequent growth of the surviving S. aureus cells occurred only at temperatures >7°C, particularly when the water activity (aw) values were higher than 0.97.