The fermenting yeasts can be classified into three groups with respect to their influence in this process:
Start yeast fermentation
It is usually apiculate yeasts, ie lemon-shaped, having a low fermentative power (up to 4-5% Vol.). Many of them are of little benefit because they produce volatile acid rather except Schizosaccharomyces veronae.
We can cite as yeast Kloeckera apiculata this most common type in most of the vinification.
Based on this negative influence by formation of volatile acidity called "fermentation super-four," which consisted of lead musts with alcohol to 4% Vol was created. in order to avoid such yeast. Today is a method of use, mainly due to the use of feet of Cuba selected yeasts or the use of active dry yeast.
Yeast fermentation medium-high power
ImagenUna once they have exceeded 4-5% Vol. alcohol, other yeast species dominate the process as is the case of Saccharomyces cerevisiae var. ellipsoideus, Saccharomycespastorianus, and others.
High yeast fermentation power
On reaching 10-11% Vol alcohol, other yeast species begin to exert their dominance because they enjoy a high fermentative power oviformis such as Saccharomyces, Saccharomyces bayanus, Saccharomyces and other ellipsoideus, among others. Except microvinifications laboratory where they have reached as high as 18-20% vol. Of alcohol, it is usual that can not ferment beyond the 13.5-14.5% vol. Of alcohol. Within this group they are also typical of the second yeast fermentation of sparkling wines.
Within the post-fermenting yeast two groups, one extremely damaging and other highly beneficial differ.
The first are aerobic yeast under fermentative power called "wine flower" forming a thin white veil on the surface of low alcohol wines kept in poor conditions. They are extremely harmful because they form large amount of acetic acid and ethyl acetate (smell of glue) from ethanol, paving the way for a subsequent bacterial acetic chopped. It is micoderma Candida, Hansenula anomala and Picchias.
The second, called "flor yeast," are typical of the wines of biological aging as they are fine, manzanilla and amontillado in their biological aging yeast. Forming a much thicker, yellowish, very flocculant veil. It is yeast with high fermentative power that form the veil once concluded must fermentation unlike earlier than they do from the beginning. It is moltuliensis Saccharomyces, Saccharomyces cerevisiae and beticus mainly italicus. These yeasts are acetaldehyde (almond flavor) from ethanol, and acetals more acetaldehyde from ethanol; consume virtually all the glycerol favor the oxidation-reduction potential of the must under the veil for malolactic fermentation, among other things. It is for this reason that the wines based on these developments would lead to the 15 to 15.5% Vol. with wine alcohol in order to prevent other species of yeast and which may form the characteristic veil of biological aging in boots .
You might think to perform the alcoholic fermentation with yeast we only wanted, as in many other fermentation industries, which is totally unworkable in wine cellar. To do so would first have to sterilize the wort, which lead to a complete loss of enzymes, vitamins, metabolites, ... and especially aromas.
The use of feet Cuba with selected yeasts or active dry yeast, is extremely workable and sometimes preferred, but their performance is limited, occurring mainly at the beginning whereas eventually the yeasts present imposed in the bloom of grapes and the winemaking facilities, much more adapted.
As a curiosity, and to conclude this section, arguably seem totally blind as a deposit, for example, 100 Hl., Have reached a whopping 10,000,000,000,000 yeast, and yet not see or a.