Effect of UV-C treatment on the microbial population of white and red wines, as revealed by conventional plating and PMA-qPCR methods

• Published in: Food control Vol. 47; pp. 407 - 412
• Main Authors: Rizzotti, Lucia, Levav, Nir, Fracchetti, Fabio, Felis, Giovanna E., Torriani, Sandra
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.01.2015; Elsevier
• Subjects: acetic acid bacteria; Biological and medical sciences; cell viability; Food industries; Fundamental and applied biological sciences. Psychology; General aspects; Hygiene and safety; irradiation; lactic acid bacteria; microbial load; Microbial quality; PMA-qPCR; propidium; red wines; sulfur dioxide; turbulent flow; Turbulent flow reactor; ultraviolet radiation; UV-C light; White and red wine; white wines; winemaking; yeasts; PMA-qPCR; UV-C light; Turbulent flow reactor; Microbial quality; White and red wine; White wine; Method; Red wine; Alcoholic beverage; Ultraviolet irradiation; Quality; Microorganism; Reactor
• ISSN: 0956-7135; 1873-7129
• DOI: 10.1016/j.foodcont.2014.07.052

Ultraviolet C (UV-C) irradiation is one of the emerging techniques for the inactivation of microorganisms in liquid food products, and it holds considerable promise also for treatment of wine. This application can be of particular interest to reduce or even eliminate the use of sulphur dioxide as a preservative in winemaking, given its potential health risks. In this study, UV-C light treatment was applied to ten different white and red wines during winemaking, for the first time at industrial scale, using a commercial turbulent flow system. The effect of 1.0 kJ/l dosage treatment on the viability of the natural microbial population, i.e., total yeasts, lactic acid bacteria and acetic acid bacteria, was investigated both with conventional plating and optimized specific propidium monoazide (PMA)-qPCR. Results of the two methods were mainly concordant for control and UV-C treated samples, and, in some cases, PMA-qPCR was able to detect small amounts of viable cells, probably in the VBNC state. Remarkably, PMA-qPCR allowed to obtain reliable results much faster than conventional plating methods. Data indicated that the UV-C irradiation was effective in reducing microbial counts for up to five log CFU/ml, depending on the wine (white or red) and on the microbial load of the sample. The treatment was much more effective in white wines: a statistically significant decrease was observed for putative spoilage-related bacteria, besides the most pronounced effect on yeast cells. Outcomes strongly support the applicability of UV-C treatment for white wine production, thanks to its efficacy towards all the microbial groups considered. •Low dosage UV-C irradiation can efficiently reduce microbial count of white wine.•UV-C treatment is a suitable alternative to limit the use of SO2 in winemaking.•PMA-qPCR is a fast and effective method to detect viable cells in UV-C treated wine.