Detection of critical contamination points of Zygosaccharomyces rouxii during processing concentrated grape juice.

ROJO M.C.; TORRES PALAZZOLO C.; LERENA M.C.; MERCADO L.; COMBINA M.

Recife

Jornada; V Jornadas Latinoamericanas de Biología y Biotecnología de Levaduras; 2015

Red Latinoamericana de Levaduras

Grape juice and by-products represent an important part of the food industry in the world. Concentrated grape juices have a great importance as additive in several massive consume products. Due to their natural qualities, they are employed to elaborate baby foods, pharmaceutical products, foods and drinks. Concentrated grapes juices (CGJ) are microbiologically more stable than other fruit products due to the combination of high sugar concentration and low pH. Osmophilic yeasts represent the primary spoilage cause in high sugar food and drink industries, where the genus Zygosaccharomyces rouxii is the most frequent described spoilage yeast. CGJ production includes several processing steps where some microbial contamination points could take place. The aim of this study was to identify osmophilic yeast contamination points during processing of CGJ. Three grape juice concentrator industries were included, concentrated and pre-concentrated grape juices and the associated surfaces (soil, walls, tank, pipes, etc) were sampled during processing. Osmophilic yeasts were count in MY50G media and identified by sequencing the 5.8S-ITS gene. The results showed that Z. rouxii was the main species found in the CGJ, representing 100% of the yeasts isolated in most of the samples. Storage periods of pre-concentrated and concentrated juices allowed a significant increase in the population of Z. rouxii, being a critical point. Surfaces showed high counts of osmophilic yeast, however Z. rouxii was only detected in two surfaces which had traces of JUC. The yeast species identified on surfaces were: Wickerhamomyces anomalus, Torulaspora delbrueckii, Citeromyces matritensis, Lachancea thermotolerans, Metschnikowia pulcherrima, Candida orthopsilosis and Candida apicola. These yeast species have been described as associated with processing plants sugary product environments, but they have not been classified as spoilage yeasts. Therefore, it was concluded that there was no incidence of Z. rouxii on cleaned surfaces. This fact suggests that cleaning practices performed in the industries would be able to eliminate the Z. rouxii populations on the surfaces. Juice residues must be completely removed from all areas in contact with the product to avoid Z. rouxii presence