Incidencia de levaduras osmófilas en tres plantas concentradoras de jugos de uva

ROJO M.C.; PONSONE L.; LERENA M.C.; TORRES A.; COMBINA M.

Mendoza

Congreso; 37° Congreso Mundial de la Vid y el Vino; 2014

Organizacion Internacional de la Vid y el Vino (OIV)

Concentrated grape juice (CJ) is a commodity which is considered as natural additive in soft drinks and pharmaceutical industries. Argentina is a main producer of grape and their sub-products. Currently, Mendoza produces 51% and San Juan 49% of the CJ respectively, which is mainly exported to USA, Canada and Japan. Concentrated grape juice is a relatively microbiological stable food, but there are some yeasts that can spoil it. In a previous work, we have characterized the population of osmophilic and osmotolerant yeast in CJ of Argentina, showing that Zygosaccharomyces rouxii was the major contaminating yeast species. The elaboration process of concentrated grape juice includes several steps which are: obtaining juice by grape stemming and crushing, filtration, sulphited juice, pre-concentration, concentration, pasteurization and packaging. The identification of osmophilic yeast contaminating points during processing could contribute to the proper development of a quality program for this industry. The aim of this work was to identify stages of the process where osmophilic yeast contamination occurs and to detect surfaces that may constitute a reservoir and source of contamination. Samples were taken from three grape juice concentration industries located in Mendoza and San Juan provinces. Samples of grape juice and the different surfaces were determined "in situ" depending on the processing plant and included: sulphited grape juice, pre-concentrated grape juice, concentrated grape juice and swabs from the surface of pipes, pools, tanks, floors and walls. Samples were spread on selective medium for osmophilic yeasts (MY50G) and were incubated at 28 ° C for 5-7 days. No osmophilic yeasts were found in samples obtained prior to the pre-concentrated or concentrated grape juice stages. A large population of osmophilic yeasts was detected in pre- concentrated and concentrated grape juices and on surfaces associated with the storage and transfer of this product. The concentration stage eliminated completely osmophilic yeast population in all cases, but a subsequent contamination was found when concentrated juices were stored in tanks until packing. On the other hand, a large population of osmophilic yeasts was detected in different surfaces as filter plates, floors and pipes, and even at the filler peak. These surfaces may constitute reservoirs of osmophilic yeasts and introduce contaminant yeast once juice has been concentrated.