Pure yeast

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Pure yeasts are used to make alcoholic beverages such as wine or beer.

There are already natural yeasts on the surface of grapes and fruits , but leaving them to ferment alone, i.e. allowing spontaneous fermentation to take place, can lead to unpredictable results in terms of quality and stability. Natural yeasts are always a mixture of different types of yeast. It is therefore uncertain which type of yeast will ultimately prevail. The product can also spoil if z. B. Apiculatus yeasts or even other microbes prevail. For these reasons, pure yeasts are used. A suitable strain of yeast is selected and fermentation is not left to chance.

The term pure-bred yeast contains:

  • "Pure": The product contains only the named yeast strain (no mixture!). The pure yeast is free from contamination such as mold, bacteria, etc.
  • "Breeding": The yeast strain was bred and optimized for a specific area of ​​application .

Classification

Purpose:

Wine yeasts (red wine yeasts , white wine yeasts , etc.), brewer's yeasts (top-, bottom-fermenting yeast)

Temperature:

Wine yeasts usually ferment in a temperature range of 15 ... 30 ° C. Their full performance usually only develops at temperatures above approx. 20 ° C. Special cold fermentation yeasts ferment at temperatures from approx. 6 ° C, whereby at low temperatures only significantly lower alcohol contents can be achieved than at temperatures above 20 ° C. Brewer's yeasts usually tolerate lower temperatures than wine yeasts.

Alcohol tolerance:

There are yeasts for light wines with a low alcohol tolerance (9… 11% vol). Wine yeasts with an alcohol tolerance of approx. 16 to 18% by volume are widespread. On the other hand, there are also distilling yeasts that are used for liqueur / schnapps production (alcohol tolerance of up to 20% by volume and higher). Brewer's yeasts ( Saccharomyces cerevisiae ) are alcohol-tolerant up to 8 percent by volume on average, top-fermenting yeast strains even higher. So-called super fermenters, primarily from Belgium (Trappist and farmhouse yeasts), ferment up to 15% alc. Vol. Recommendations for strong beers to use wine yeast are now considered out of date. In the creative brewing scene, so-called over-fermenters have been rediscovered among the yeast strains and are often used.

Fermentation by-products:

During fermentation, yeasts not only produce alcohol, but also various by-products, e.g. B. glycerin , and various flavorings such as esters and phenols . There are clear differences here between the various yeast strains.

Delivery forms:

Liquid yeast (yeasts suspended in small amounts of water or white wine), dry yeasts (dormant yeasts in the form of granules)

Dry yeast versus liquid yeast

  • Pro dry yeast
    1. Dry yeast has a longer shelf life.
    2. It has often been shown that dry yeast has a higher purity / quality than liquid yeast.
  • Pro liquid yeast
    1. It is not absolutely necessary to prepare a fermentation starter or to first dissolve the yeast in a large amount of water before adding it to the fermentation mixture. However , a fermentation starter is recommended for the production of wine-like drinks .

See also

literature

Web links

Individual evidence

  1. ↑ https://www.lallemandbrewing.com/wp-content/uploads/2017/03/TDS_LALBREW_PREM_BELLESAISON_ENGLISH_DIGITAL.pdf
  2. ↑ vlb-berlin.org ( Memento of the original from May 25, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.vlb-berlin.org