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Autolysis in winemaking relates to the complex chemical reactions that take place when a wine spends time in contact with the lees, or dead yeast cells, after fermentation. While for some wines - and all beers [1] - autolysis is undesirable, it is a vital component in shaping the flavors and mouth feel associated with premium Champagne production.
Autolysis (alcohol fermentation), the complex chemical reactions that take place when wine or beer spends time in contact with the (dead) yeast after fermentation; Breadmaking#Preparation, the rest period in which dough is left without yeast or starter to autolyse for improved gluten development
Fermentation typically begins when viable baker's yeast or a starter culture is added to flour and water. Enzymes in the flour and yeast create sugars, which are consumed by the yeast, which in turn produce carbon dioxide and alcohol. Specifically, the grain enzyme diastase begins to convert starch in the grain to maltose.
The addition of additional ethanol kills yeast, leaving a wine that is high in sugar and alcohol content. [3] Fruit wine – Fruit wine is a fermented alcoholic beverage made from a variety of base ingredients and can be made from virtually any plant matter that can be fermented. The fruits used in winemaking are fermented using yeast and aged ...
Autolysis is uncommon in living adult organisms and usually occurs in necrotic tissue as enzymes act on components of the cell that would not normally serve as substrates. These enzymes are released due to the cessation of active processes in the cell that provide substrates in healthy, living tissue; autolysis in itself is not an active process.
Yeast handling conditions that might lead to autolysis include: - Warm temperatures – cause an increase in the yeast metabolic rate speeding up the use of the yeast nutritional reserves - Long storage times – this extends the time that the yeast relies on its reserves and increases the risk that the reserves might be depleted
Yeast need a reliable source of nitrogen in forms that they can assimilate in order to successfully complete fermentation. Yeast assimilable nitrogen or YAN is the combination of free amino nitrogen (FAN), ammonia (NH 3) and ammonium (NH 4 +) that is available for a yeast, e.g. the wine yeast Saccharomyces cerevisiae, to use during fermentation.
The dying yeast cells are then heated to complete their breakdown, after which the husks (yeast with thick cell walls that would give poor texture) are removed. Yeast autolysates are used in Vegemite and Promite (Australia); Marmite (the United Kingdom); the unrelated Marmite (New Zealand); Vitam-R (Germany); and Cenovis (Switzerland).