CONICET | Buscador de Institutos y Recursos Humanos

Bacteriophages can cause great economic losses due to fermentation failure in dairy plants. Hence, physical and chemical treatments of raw material and/or equipment are mandatory to maintain phage levels as low as possible. Regarding thermal treatments used to kill pathogenic bacteria or achieve longer shelf-life of dairy products, neither low temperature long time nor high temperature short time pasteurization were able to inactivate most lactic acid bacteria (LAB) phages. Even though most phages did not survive 90ºC for 2 min, there were some that resisted 90ºC for more than 15 min (conditions suggested by the International Dairy Federation, IDF, for complete phage destruction). Among traditional biocides used in dairy industry, peracetic acid has consistently proved to be very fast and efficient to inactivate dairy phages, whereas efficiency of sodium hypochlorite was variable, even among different phages infecting the same LAB species. Only phages infecting dairy cocci and Lactobacillus helveticus were reasonably inactivated by ethanol, whereas effect of isopropanol was in all cases almost inexistent. Some new biocides tested showed low efficiency, but others are really promising for industrial use. Processes involving high pressure were barely used for phage inactivation, but until now most studied phages revealed high resistance to these treatments. Photocatalysis using UV light and TiO2 has been recently reported as a feasible option to industrially inactivate phages infecting diverse LAB species. Although more research is needed, an UV-A radiation emitting system proved to be safe and usable for long periods. To conclude, and given the great phage diversity found on dairies, it is always advisable to combine different anti-phage treatments (biocides, heat, high pressure, photocatalysis), rather than using them separately at extreme conditions.

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