Effects of ultrasound treatments on wine microorganisms

Ultrasound is one of the most promising non-thermal an emerging technique in food technology. The objective of the present work was to evaluate the effect of different ultrasonic treatments on the most important wine microbiota (Saccharomyces and non-Saccharomyces yeasts and lactic acid bacteria). Two stages were carried out: the assessment step, where six different ultrasonic treatments (with varying power, time, and pulses) were used on Saccharomyces cerevisiae, Brettanomyces spp., and Lactiplantibacillus plantarum; and the validation step, where two chosen ultrasonic treatments were used on Zigosaccharomyces bailli, Brettanomyces spp., Saccharomyces cerevisiae, Saccharomyces bayanus, Pichia membranifaciens, Schizosaccharomyces pombe, and Hanseniaspora osmophila. The most sensitive microorganism was Brettanomyces spp., and the most resistant was Lactiplantibacillus plantarum. Ultrasonic treatments had varying effects on vitality (delay of growth or maximum OD reduction) and on viability (reduction of microbial growth)

Influence of microwave treatments on viability and vitality of wine-origin microorganisms

Microwave has been used in food industries to enhance or replace conventional techniques. In Enology, its potential use is not clear since references indicate that can be intended for both inactivation of microorganisms and maceration treatments. In this context, it is important to know the effect of microwaves on microorganisms. This study focuses on the application of microwave (MW) on Saccharomyces and non-Saccharomyces yeasts and Lactiplantibacillus plantarum (from oenological ecosystems) to evaluate their behaviour under different conditions of power, duration and presence of pulses on; viability and vitality were studied. MW affected microorganisms in different ways. In general, yeasts were less resistant than L. plantarum. Counts after treatments showed inactivation in some cases. Nevertheless, ODmax after 96 h presented values closer to the controls. This effect shows that in some cases the treatment exerts an antimicrobial effect after application, but after some time, microorganisms can restore their biological structures and growth, which is reflected in an increase in the lag phase. On a few occasions, treatments were able to improve the kinetic parameters. Thus, this technique could be useful for inactivation, attenuation or even activation of associated food microorganisms

Optimization of a rapid method for studying the cellular location of β-glucosidase activity in wine yeasts

Aims: To improve a method for determining β-glucosidase activity and to apply it in yeasts isolated from wine ecosystems from 'La Mancha' region and to know its cellular location. Methods and Results: A total of 82 wine yeasts were identified (PCR/RFLP) and evaluated for their β-glucosidase activity. First, they were qualitatively evaluated by growth on YNB cellobiose, the activity was quantified using different culture media, under aerobic and anaerobic conditions and cells after 24-72 h of growth. To study the location activity, five fractions were obtained (supernatant, whole cell, cell wall, cytosol and cell membrane). The enzymatic assays were optimized, being: growth in YP cellobiose for 72 h in aeration conditions and, after cell removing, enzyme analysis with 128 g 1-1 of cellobiose as substrate, for 30 min at 30°C. The genus that displayed the greatest activity were Pichia, Hanseniaspora and Rhodotorula, and the activity was intracellular. Conclusions: The study showed that β-glucosidase activity was induced by the carbon source and was aerobic dependent. The non-Saccharomyces species displayed the greatest activity, which was intracellular and strain-dependent. Significance and Impact of the Study: This study developed a reliable method for screening β-glucosidase activity in yeasts isolated from wine ecosystems. This activity is very important in the release of monoterpenols from glycoside precursors for the enhancement of wine aromas. © 2005 The Society for Applied Microbiology.Articl

Probiotic characteristics in Saccharomyces cerevisiae strains: Properties for application in food industries

In this work, the probiotic or health-beneficial potential of 142 Saccharomyces strains isolated from food ecosystems belonging to the collection of the Yeast Biotechnology Laboratory (University of Castilla-La Mancha) have been studied. They were screened for their ability to resist and grow when exposed to simulated in vitro digestion conditions. As a result, 44 strains showed good kinetic properties and were chosen through k-means and one-way ANOVA and used to assess other important probiotic characteristics. For the second step, a Principal Component Analysis was run with the results from auto-aggregation and hydrophobicity at 30 °C assays, antibiotic resistance and antimicrobial activity, and 10 yeasts were then selected in order to study their biofilm formation capability, auto-aggregation and hydrophobicity at 37 °C, viability and biofilm formation after simulated sequential salivary-gastric-intestinal digestion. The most relevant results were those that showed the biofilm formation and hydrophobicity behaviour, so they were used for characterized the most promising probiotic candidates. The final results showed that the strains 132, 139 and 146 were the best ones

Biotechnological application of yeasts in food science: Starter cultures, probiotics and enzyme production

This review is an account of experiences of two research teams (from Italy to Spain); the leading idea is the following: yeasts represent valuable sources in food science and microbiology and are a kind of food factories, because of the potentiality of whole cells or for their produced compounds. This review covers three major areas: the first section addresses the role of yeasts as starter cultures with a special focus on wine. The second section is an update on probiotic yeasts. Finally, the focus of the last section is on enzymes produced by yeasts, with a short description of the removal of mycotoxin

Effects on varietal aromas during wine making: a review of the impact of varietal aromas on the flavor of wine

Although there are many chemical compounds present in wines, only a few of these compounds contribute to the sensory perception of wine flavor. This review focuses on the knowledge regarding varietal aroma compounds, which are among the compounds that are the greatest contributors to the overall aroma. These aroma compounds are found in grapes in the form of nonodorant precursors that, due to the metabolic activity of yeasts during fermentation, are transformed to aromas that are of great relevance in the sensory perception of wines. Due to the multiple interactions of varietal aromas with other types of aromas and other nonodorant components of the complex wine matrix, knowledge regarding the varietal aroma composition alone cannot adequately explain the contribution of these compounds to the overall wine flavor. These interactions and the associated effects on aroma volatility are currently being investigated. This review also provides an overview of recent developments in analytical techniques for varietal aroma identification, including methods used to identify the precursor compounds of varietal aromas, which are the greatest contributors to the overall aroma after the aforementioned yeast-mediated odor release