Saccharomyces cerevisiae and Hanseniaspora osmophila strains as yeast active cultures for potential probiotic applications.

This work allowed the evaluation of the gastrointestinal resistance of five yeasts (Saccharomyces and non-Saccharomyces) in order to assess some biotechnological characteristics linked to the potential probiotics, using a dynamic gastrointestinal simulator (simgi®). The best results obtained were for strains Saccharomyces cerevisiae 3 and Hanseniaspora osmophila 1056. Having optimised the method, the yeasts were subsequently lyophilised, and the one that showed the least loss of viability, S. cerevisiae 3, was used in a freeze-dried form to obtain a new functional food. On the other hand, some characteristics of the product were compared with those of probiotic supplements and other commercial probiotic foods. The obtained functional product showed better parameters than the rest of the samples containing yeasts which, together with the great acceptance shown after the consumer tests, means that it can be presented as a possible commercial functional product.

Viability of Hanseniaspora uvarum yeast preserved by lyophilization and cryopreservation.

Hanseniaspora yeasts are known to produce volatile compounds that give fruity aromas in wine and fermented fruit. This study aimed to verify the feasibility of the Hanseniaspora uvarum strain that had been isolated and identified during a previous study and preserved by lyophilization and freezing at -80 °C (cryopreservation). This strain was assessed in relation to its macroscopic and microscopic morphology and for its ability to ferment apple must. After having been subjected to lyophilization and cryopreservation, viability was assessed in relation to these characteristics during 12 months of storage. The strain showed stable colonial features and its microscopic appearance was unchanged during all recoveries. The plate count results showed consistency in both processes. Regarding the fermentative capacity, the kinetic results showed 100% viability for the strain subjected to lyophilization, as well as for those preserved at -80 °C. These results demonstrate that the preservation methods used are compatible with the maintenance of the relevant characteristics of the strain for the period of evaluation of this study (12 months).

An optimized procedure for the enological selection of non-Saccharomyces starter cultures.

The apiculate yeasts are the species predominating the first stage of grape must alcoholic fermentation and are important for the production of desired volatile compounds. The aim of the present investigation was to establish a protocol for the enological selection of non-Saccharomyces strains directly isolated from a natural must fermentation during the tumultuous phase. At this scope, fifty Hanseniaspora uvarum isolates were characterized at strain level by employing a new combined PCR-based approach. One isolate representative of each identified strain was used in fermentation assays to assess strain-specific enological properties. The chemical analysis indicated that all the analyzed strains were low producers of acetic acid and hydrogen sulphide, whereas they showed fructophilic character and high glycerol production. Analysis of volatile compounds indicated that one strain could positively affect, during the alcoholic fermentation process, the taste and flavour of alcoholic beverages. The statistical evaluation of obtained results indicated that the selected autochthonous H. uvarum strain possessed physiological and technological properties which satisfy the criteria indicated for non-Saccharomyces wine yeasts selection. Our data suggest that the described protocol could be advantageously applied for the selection of non-Saccharomyces strains suitable for the formulation of mixed or sequential starters together with Saccharomyces cerevisiae.