Search results for "Autolysis"
showing 8 items of 18 documents
Animal rennets as sources of dairy lactic acid bacteria
2014
ABSTRACT The microbial composition of artisan and industrial animal rennet pastes was studied by using both culture-dependent and -independent approaches. Pyrosequencing targeting the 16S rRNA gene allowed to identify 361 operational taxonomic units (OTUs) to the genus/species level. Among lactic acid bacteria (LAB), Streptococcus thermophilus and some lactobacilli, mainly Lactobacillus crispatus and Lactobacillus reuteri , were the most abundant species, with differences among the samples. Twelve groups of microorganisms were targeted by viable plate counts revealing a dominance of mesophilic cocci. All rennets were able to acidify ultrahigh-temperature-processed (UHT) milk as shown by pH …
Ultrastructural changes of sparkling wine lees during long-term aging in real enological conditions.
2012
Ultrastructural changes of lees of three series of sparkling wines produced using the traditional method during long-term aging (4 years) were assessed by high-pressure freezing in combination with transmission electron microscopy. The stratified structure of the cell wall disappeared throughout aging. After 18 months, the microfibrous material of the cell wall appeared more diffuse and the amorphous midzone of the inner wall layer was progressively degraded. From 30 months onward, the cell wall consisted of a tangled structure of fibers. In spite of these changes, the cell wall of yeasts remained unbroken at 48 months of wine aging. Cell membrane breakage was observed for the first time in…
Release of macromolecules by Saccharomyces cerevisiae during ageing of French flor sherry wine “Vin jaune”
2003
The French flor sherry wine "Vin jaune" spends 6 years and 3 months in the same barrel under a yeast velum. Because of temperature variations in the cellars, this velum sinks partially into the wine and a deposit of dead yeasts cells accumulates in the bottom of the barrels, favouring the formation of new velum. Growth and autolysis occur simultaneously. This study investigated the evolution of macromolecules released by yeasts during the ageing of "Vin jaune" in a model system closely simulating winemaking. It was observed that the release of macromolecules during the formation of the velums by living yeasts was low but greatly increased when the velums fell and yeast viability decreased. …
Sorption of wine volatile phenols by yeast lees
2005
The capacity of Saccharomyces cerevisiae yeast lees to sorb 4-ethylguaiacol and 4-ethylphenol was investigated in a synthetic medium and in wine. Active dried yeast was more effective when volatile phenols were diluted in red wine. Partition coefficients between wine model solution and wine yeast lees were determined and compared with those measured for dried active yeast. They showed a larger affinity of volatile phenols for wine yeast lees than for dried active yeast. The effect of yeast lees on volatile phenol sorption was sensitive to yeast autolysis level and to physicochemical parameters, such as ethanol content, temperature and pH. These results could be applied in the technology of …
(−)Geosmin sorption by enological yeasts in model wine and FTIR spectroscopy characterization of the sorbent
2010
Abstract For the first time, we report that enological yeasts or yeast cell walls can sorb (−)geosmin, an undesirable molecule that causes critical organoleptic defects in wine at low concentrations (around 50 ng l −1 ). The wine is described as “earthy” or “mouldy”. The influence of various post-harvesting processes on yeast (−)geosmin sorption capacity was studied. The dried yeast biomass obtained by the different processes was analysed by FTIR spectroscopy in ATR mode: structural differences were detected between the samples depending on the strain and the treatment used. Surface proteins and mainly phospholipids from the plasma membrane appeared to induce significantly different signals…
Yeasts and Sparkling Wine Production
2019
Sparkling wines are produced in many different countries. Among sparkling wines, some are produced from Charmat or bottle fermentation. In this chapter, the practical methods and principles of producing quality sparkling wine is given in details including each step of the production from viticultural parameters, base wine production up to secondary fermentation. After the second fermentation in bottle, the wine is aged on lees. During aging, yeast autolysis occurred. The mechanisms of yeast autolysis and the compounds released are presented. The consequences of yeast autolysis on wine quality are detailed. Finally the riddling and disgorging operation are presented
Influence of yeast autolysis after alcoholic fermentation on the development of <em>Brettanomyces</em>/<em>Dekkera</em> in wi…
2001
<p style="text-align: justify;"><em>Brettanomyces</em>, a contaminant yeast, is relatively common in wines and mainly in red wines during barrel aging. The results presented here relate to the effects of yeast lees autolysis on the growth of <em>Brettanomyces</em>. Experiments were realised in a culture medium after alcoholic fermentation, in a hydroalcoholic wine-like solution and in a red wine. <em>Brettanomyces</em> was inoculated at low level : 10<sup>2</sup> cfu/ml and the growth was controlled by counting on agar appropriate medium. Yeast lees from <em>S. cerevisiae</em> were added to these media in the presence or abse…
Proteolytic capacity in mouse cardiac muscle following strenuous exercise
1981
Proteolytic capacity in mouse cardiac muscle was analyzed 1, 3, and 6 days after exhaustive intermittent or submaximal prolonged running. No significant changes were recorded in the activities of acid or alkaline proteases, β-glucuronidase or trypsin inhibitor. Similarly, no changes were found in the rates of acid or neutral autolysis.