FERMENTATION IS THE TRANSFORMATION OF A SUGARY SOLUTION INTO ALCOHOL, THROUGH THE ACTION OF YEASTS. THE YEAST ACTUALLY CONSUMES THE SUGAR AND PRODUCES CARBON DIOXIDE, ALCOHOL AND HEAT AS BY-PRODUCTS.
THE CHOICE OF YEAST CAN HIGHLY INFLUENCE THE RESULTING SPIRIT.
WHAT IS FERMENTATION AND HOW DOES IT WORK?
During the fermentation process, the yeast "eats" the sugar, and in doing so, metabolizes the sugar into ethyl alcohol, carbon dioxide, and energy.
Fermentation is an important step into spirits making, especially for darker spirits as it is during fermentation that flavors compounds a.k.a. congeners come to existence. These flavors will be concentrated by the distillation afterward. Not only does the type of yeasts play an important role but the final spirit is also affected by the length of the fermentation. A long fermentation creates a wider range of different aromas, as it produces more congeners, a short fermentation gives fewer congeners and a lighter-bodied spirit.
Yeasts can be commercial, in-house, or wild (more about yeasts below). As mentioned above, the yeasts actually feed themselves on the sugar, and, while doing so, produce carbon dioxide, and different types of alcohol. The alcohols produced are ethanol, propanol, butanol, methanol, amyl alcohol, as well as aldehydes, esters, and acids. It is up to the distiller which ones to retain or to discard (some are actually harmful, and others only convey an unpleasant taste), same with the lees. Lees is the name given to the resulting dead cells, once yeasts have consumed the sugar. They are often discarded but one can decide to keep them to give additional flavor to a spirit.
Fermentation ends naturally when the yeast runs out of sugar or produces too much ethanol so that the mixture becomes toxic to itself. It is therefore sometimes desirable to cut the process sooner if you want to keep sugar or want yeast flavors in the final product. This is achieved through temperature control.
Fermentation is an important step into spirits making, especially for darker spirits as it is during fermentation that flavors compounds a.k.a. congeners come to existence. These flavors will be concentrated by the distillation afterward. Not only does the type of yeasts play an important role but the final spirit is also affected by the length of the fermentation. A long fermentation creates a wider range of different aromas, as it produces more congeners, a short fermentation gives fewer congeners and a lighter-bodied spirit.
Yeasts can be commercial, in-house, or wild (more about yeasts below). As mentioned above, the yeasts actually feed themselves on the sugar, and, while doing so, produce carbon dioxide, and different types of alcohol. The alcohols produced are ethanol, propanol, butanol, methanol, amyl alcohol, as well as aldehydes, esters, and acids. It is up to the distiller which ones to retain or to discard (some are actually harmful, and others only convey an unpleasant taste), same with the lees. Lees is the name given to the resulting dead cells, once yeasts have consumed the sugar. They are often discarded but one can decide to keep them to give additional flavor to a spirit.
Fermentation ends naturally when the yeast runs out of sugar or produces too much ethanol so that the mixture becomes toxic to itself. It is therefore sometimes desirable to cut the process sooner if you want to keep sugar or want yeast flavors in the final product. This is achieved through temperature control.
CURIOUS ABOUT YEAST?
Yeast is added to the just "converted" liquid during fermentation. Yeast are single-celled fungi that contain special enzymes. Good producers are careful when selecting their yeasts, as the choice of yeast influences the resulting spirit.
The choices are:
- commercial yeasts, which give spirit with less complexity but allow good control over fermentation. Yeast products are available in many different forms such as cream yeast, block yeast, dried yeast or dried instant yeast. Lactobacillus Brevis will give more mushroom impression, or Oenococcus Oeni will tend toward pineapple hints*.
The spirit industry is a major consumer of yeast but not any yeast can be used as for distilled spirits you need yeast that can resist high alcohol (yeasts allowing wine fermentation die by 17% abv. for ex).
- house yeasts or yeasts isolated by the distiller, which allows a good control over fermentation and good complexity.
- wild yeasts, which less control over when and if fermentation will occur but convey high complexity to the final spirit.
To increase complexity or limit risks, multiple strains can be used.
Check this post here in which you can see how yeast can affect the final spirits, with the example of mezcal.
The choices are:
- commercial yeasts, which give spirit with less complexity but allow good control over fermentation. Yeast products are available in many different forms such as cream yeast, block yeast, dried yeast or dried instant yeast. Lactobacillus Brevis will give more mushroom impression, or Oenococcus Oeni will tend toward pineapple hints*.
The spirit industry is a major consumer of yeast but not any yeast can be used as for distilled spirits you need yeast that can resist high alcohol (yeasts allowing wine fermentation die by 17% abv. for ex).
- house yeasts or yeasts isolated by the distiller, which allows a good control over fermentation and good complexity.
- wild yeasts, which less control over when and if fermentation will occur but convey high complexity to the final spirit.
To increase complexity or limit risks, multiple strains can be used.
Check this post here in which you can see how yeast can affect the final spirits, with the example of mezcal.
This fermentation wheel is coming from the book Distilled Knowledge by Brian Hoefling.
It shows the impact on flavours of type of yeast.
The book is a fascinating read and this wheel clearly pictures a scientific fact: the "impression" of banana or of chocolate in an alcohol is not a question of imagination from spirits critics, this is the ability to discernate taste at a molecular level through years of training !
It shows the impact on flavours of type of yeast.
The book is a fascinating read and this wheel clearly pictures a scientific fact: the "impression" of banana or of chocolate in an alcohol is not a question of imagination from spirits critics, this is the ability to discernate taste at a molecular level through years of training !
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