Non Thermal Pasteurization of Foodstuff by Dense Gases: Experimental Data, Sensorial Analysis and Inactivation Mechanism

Sara Spilimbergo, Department of Materials Engineering and Industrial Technologies, University of Trento, via Mesiano 77, I-38050, Trento, Italy, Alberto Bertucco, Department of Principles and Plants of Chemical Engineering, University of Padua, Via Marzolo,9, Padua, Italy, Giulio Bertoloni, Histology, Microbiology and Medical Biotechnologies Department, University of Padua, Via Gabelli 63, Padua, 35121, Italy, and Flavia Gasperi, Agrifood Quality Department, IASMA Research Center, Via E. Mach 1, San Michele all'Adige (TN), 38010, Italy.

Nowadays commercial pasteurization process uses thermal energy to eliminate potential foodborne illness. Recently the interest towards emerging technologies, that ensures microbiological safety while leaving sensory and nutritional features of foodstuff essentially unaffected, leading to a high fresh-like sensory quality product available for the consumer, is growing particularly towards high pressure pasteurization technologies (1). In particular, as far as dense gases treatments is concerned, in last years a review on dense phase CO2 (2) confirms the feasibility and the effectiveness of this innovative technique. The main advantage of the CO2 treatment if compared to heat treatments consists on the mild conditions of temperature applied which do not affect the nutritional and chemical-physical properties of the food (3). Also other gases can be usefully added to CO2 to improve the process effectiveness. In this poster presentation results concerning pasteurization of different fruit juices with CO2 or N2O under pressure are shown: different experimental runs have been performed at different operative conditions (P=80i200, T=28i45 CX), with fresh orange, peach and apple juices in different apparatuses. Subsequently sensory analysis have been carried out to investigate the effects of the CO2/N2O treatments on the sensory quality of fresh juice by means of discriminative test. Results obtained have been compared and discussed. In particular, the effect of stirring system and operative pressure on the inactivation efficiency have been deepened. Simultaneously, the problem of inactivation mechanism has been addressed by performing test on microbial and enzymatic deactivation of sample systems: different enzymes activity -namely ATPase, pectinase, acid and alkaline phosphatase- were measured before and after high pressure treatments. Data obtained from simultaneous measurement in both cellular and realized fractions demonstrate a cellular enzymatic activity drop, but show that a large amount of enzymes was present in the realized fractions of treated cells. The decrease in cell-bound enzymatic activity probably depends on dense CO2 capability to modify cell envelopes properties, which must cause a realise of intracellular molecules. Accordingly, a contribution to definitely clarify the interaction between dense CO2 and microorganisms/enzymes has been suggested.

1.Barbosa-Canovas, G. V., Pothakamury, U. R., Palou, E. and Swanson, B. S. Nonthermal preservation of foods (Marcel Dekker, New York, 1998). 2.Spilimbergo, S. and Bertucco, A. Non-thermal bacteria inactivation with dense CO2. Biotechnology and Bioengineering 2003, 84, 627-638. 3.Connery, K. A., Shah, P., Coleman, L. and Hunek, B. Commercialization of Better than Fresh Dense Phase Carbon Dioxide Processing for Liquid Food. Road to Commercialization, Orlando, Florida, USA, ISSF 2005.