Abstract
Traditionally, thermal treatments for the inactivation of Listeria monocytogenes in meat products involve undesirable changes of the product quality. In recent years, efforts have been carried out to develop alternative methods to inactivate L. monocytogenes without affecting the product quality attributes. In this context, the feasibility of combined high pressure carbon dioxide and high power ultrasound (HPCO2+HPU) treatment to inactivate L. monocytogenes inoculated on the surface of dry cured ham was investigated. Inactivation data were determined at 6, 8 and 12MPa, as a function of temperature (22, 35, 45°C) and treatment time (0.5 to 30min), and compared to those obtained after thermal and HPCO2 treatments.Color, pH and acidity changes of the samples after both thermal and HPCO2+HPU treatments were measured and compared, sensorial profile of the treated samples was evaluated by a sensory panel and shelf-life was determined by a storage study for 4weeks at 4°C.The results clearly revealed that HPU alone was not able to induce any microbial inactivation while HPCO2+HPU treatment always assured a certain level of inactivation, variable with the process temperature used: the inactivation efficiency was demonstrated higher at 35°C rather than 22°C and no enhancement was observed at 45°C compared to 35°C. Process conditions of 12MPa, 35°C, at 10W for 5min assured inactivation to undetectable level of L. monocytogenes spiked on the surface of the product with an initial concentration of about 109CFU/g. No differences were detected between acidity, pH, color and sensory attributes of the untreated and HPCO2+HPU treated dry cured ham surface, while slight differences were measured between the values obtained for the untreated and thermally treated samples. Additionally, the storage study demonstrated that a full microbial and quality shelf-life was assured for 4weeks at 4°C. The results obtained may open the doors to the application of such an innovative process at industrial level, in particular to treat ham-type or meat products.