Comparison and prediction of UV-C inactivation kinetics of S. cerevisiae in model wine systems dependent on flow type and absorbance

Abstract

UV-C (254 nm) treatment can be an alternative or supplement method to adding sulfite to wine for stabilization. There are various types of UV-C reactors using different flow types. However, literature data often refer to specific microorganisms in specific food using specific UV-C reactors. Therefore, a statement about the influence of the flow conditions on the inactivation of microorganisms is difficult. This study examined the inactivation of Saccharomyces cerevisiae dependent on the flow conditions. Different flow conditions were realized in three UV-C reactor types. In order to minimize the influence of the natural fluctuations of the ingredients in wine, a model medium was introduced and validated to mimic the inactivation of S. cerevisiae in wine. The absorbance of the model solution was adjusted to resemble wine available on the market by applying variable concentration of food coloring (sunset yellow). These model solutions with inoculated microorganisms were UV-C treated using different flow conditions (Dean vortices, turbulent and laminar tube flows, and laminar annular thin film flows with a 3 mm and a 0.6 mm gap). Mathematical models were established to predict the inactivation of S. cerevisiae dependent on the flow type, the absorbance of the (model) wine and the UV-C dose.