Search results for "fermentation"

Two-carbon metabolites, polyphenols and vitamins influence yeast chronological life span in winemaking conditions

2012

Abstract Background Viability in a non dividing state is referred to as chronological life span (CLS). Most grape juice fermentation happens when Saccharomyces cerevisiae yeast cells have stopped dividing; therefore, CLS is an important factor toward winemaking success. Results We have studied both the physical and chemical determinants influencing yeast CLS. Low pH and heat shorten the maximum wine yeast life span, while hyperosmotic shock extends it. Ethanol plays an important negative role in aging under winemaking conditions, but additional metabolites produced by fermentative metabolism, such as acetaldehyde and acetate, have also a strong impact on longevity. Grape polyphenols quercet…

Peptidases specific for proline-containing peptides and their unusual peptide-dependent regulation in Oenococcus oeni

2009

International audience; Growth of the lactic acid bacterium (LAB) Oenococcus oeni, which is involved in malolactic fermentation during the winemaking process, is stimulated by peptides originating from yeast. In this study, we investigated the impact of peptides on O. oeni growth, peptidase activity and the expression of genes encoding the studied peptidases. Low levels of PepN activity and very high levels of PepI activity were observed in O. oeni, whereas levels of PepX activity were intermediate. The level of biosynthesis of these O. oeni peptidases was shown to depend on peptides present in the culture medium. These results were confirmed by transcriptional analyses of putative pep gene…

Effect of the mechanical harvest of drupes on the quality characteristics of green fermented table olives

2015

Background: Because of damage caused by mechanical harvesting, the drupes for table olive production are traditionally hand harvested. Until now, no data have been available on the microbiological and chemical features of mechanically harvested drupes during fermentation. Results: Drupes mechanically harvested and inoculated with Lactobacillus pentosus OM13 were characterized by the lowest concentrations of potential spoilage microorganisms. On the other hand, drupes mechanically harvested and subjected to spontaneous fermentation showed the highest concentration of Enterobacteriaceae and pseudomonads during transformation. The lowest decrease of pH (4.20) was registered for the trials inoc…

Basal catalase activity and high glutathione levels influence the performance of non-Saccharomyces active dry wine yeasts.

2020

Non-Saccharomyces wine yeasts are useful tools for producing wines with complex aromas or low ethanol content. Their use in wine would benefit from their production as active dry yeast (ADY) starters to be used as co-inocula alongside S. cerevisiae. Oxidative stress during biomass propagation and dehydration is a key factor in determining ADY performance, as it affects yeast vitality and viability. Several studies have analysed the response of S. cerevisiae to oxidative stress under dehydration conditions, but not so many deal with non-conventional yeasts. In this work, we analysed eight non-Saccharomyces wine yeasts under biomass production conditions and studied oxidative stress parameter…

Natural hybrids fromSaccharomyces cerevisiae,Saccharomyces bayanusandSaccharomyces kudriavzeviiin wine fermentations

2006

Several wine isolates of Saccharomyces were analysed for six molecular markers, five nuclear and one mitochondrial, and new natural interspecific hybrids were identified. The molecular characterization of these Saccharomyces hybrids was performed based on the restriction analysis of five nuclear genes ( CAT8 , CYR1 , GSY1 , MET6 and OPY1 , located in different chromosomes), the ribosomal region encompassing the 5.8S rRNA gene and the two internal transcribed spacers, and sequence analysis of the mitochondrial gene COX2 . This method allowed us to identify and characterize new hybrids between Saccharomyces cerevisiae and Saccharomyces kudriavzevii , between S. cerevisiae and Saccharomyces ba…

2018

Tiger nut (Cyperus esculentus) is a tuber that can be consumed raw or processed into beverages. Its nutritional composition shows a high content of lipid and dietary fiber, close to those of nuts, and a high content of starch, like in other tubers. Tiger nuts also contain high levels of phosphorus, calcium, and phenolic compounds, which contribute to their antioxidant activity. From those characteristics, tiger nuts and derived beverages are particularly relevant to limit food insecurity in regions where the plant can grow. In Europe and United States, the tiger nut derived beverages are of high interest as alternatives to milk and for gluten-free diets. Fermentation or addition of probioti…

Fermentation of Jerusalem artichoke by Zymomonas and Saccharomyces

2008

PurposeThe aim of this study is to find out the appropriate fermentation conditions of Jerusalem artichoke powder (JAP) based media to obtain light beverage containing inulin.Design/methodology/approachJAP water suspension or filtrate were used for preparation of growth media with or without enzymatic hydrolysis of inulin for fermentation by Zymomonas mobilis 113 “S” or Saccharomyces cerevisiae.FindingsIf enzymatic hydrolysis of inulin was not used significantly higher amount of inulin (7.42 per cent) was unconverted by Z. mobilis than by S. cerevisiae (2.22 per cent) while the ethanol concentration was much higher (2.86 per cent) after S. cerevisiae fermentation than after Z. mobilis ferme…

Sustainable Method Using Filtering Techniques for a Fermentation Process State Estimation

2020

Winemaking is concerned about sustainable energy availability that implies new methods for process monitoring and control. The aim of this paper is to realize a comparative analysis of the possibilities offered using estimation techniques, balances, and filtering techniques such as the Kalman filter (KF) and the extended Kalman filter (EKF), to obtain indirect information about the alcoholic fermentation process during winemaking. Thus, an estimation solution of the process variables in the exponential growing phase is proposed, using an extended observer. In addition, two estimation solutions of this process with the EKF and an estimation of the decay phase of the fermentation process are …

Microbiological and safety evaluation of green table olives marketed in Italy

2011

The microbiological and safety conditions of green table olives sold on the Italian market were evaluated on 40 samples, 20 loose and 20 packed in containers, purchased at street markets and supermarkets. The olives were analyzed for microflora and food safety indices, and for aflatoxin B1 and ochratoxin A occurrence, and the results showed acceptable security. There was wide heterogeneity in the microflora, the numerical values being in relation to the olive type. The microbial population was dominated by the yeasts and lactic bacteria responsible for the fermentation process, and their numbers, together with the metabolic activity, led to conditions unfavorable for the development of path…

Potential application of lactic acid bacteria in the biopreservation of red grape from mycotoxigenic fungi

2021

Background Filamentous fungi are the main contamination agent in the viticultural sector. Use of synthetic fungicides is the regular answer to these contaminations. Nevertheless, due to several problems associated with the use of synthetic compounds the industry demands new and safer methods. In the present work, the biopreservation potential of four lactic acid bacteria (LAB) strains was studied against the principal grape contaminant fungi. Results Agar diffusion test evidenced that all four culture-free supernatant (CFS) had antifungal properties against all tested fungi. The Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (MFC) test values evidenced that medi…