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From the UK vineyards association (David Cowderoy of wineskills)
Dear all,
I have been asked by some of the wineries I consult to for some recommendations on yeast strains. A difficult task, seeing as there are over 250 yeast strains commercially on the market!
However here are some general recommendations to help you all decide on what strain to use. Attached to this email is a summary of the majority of the strains available. This is by no means definitive. The characteristics are taken from the manufacturer’s data sheets and are not my own comments. The spreadsheet has auto-filters so you can select from any column the criteria you want.
I will happy to discuss this in more detail at the WineSkills event on Thursday 2nd September at Denbies
Basic selection criteria
Availability
Only some of the manufacturers have distributors in the UK. Whilst you can always import, it is not a good idea to over order as even unopened packets will lose viability when kept from one year to the next.
Optimum fermentation temperature
Select a strain that matches your refrigeration capabilities. If a tank has no refrigeration, then don’t select a stain that is an active fermenter, normally indicated by a low optimum fermentation temperature. This is particularly important if fermenting in barrel as the heat of fermentation cannot escape. On the other hand for late varieties, when the ambient air temperature is much lower, a more active stain will be used.
Freedom from faults
Try and select strains that produce low VA and low H2S.
Nitrogen requirement
Strains with high nitrogen requirement can be problematic if the juice has insufficient free available nitrogen (FAN). Whilst this can be supplemented with DAP, it is not uncommon to reach the maximum legal addition and still have a reduced fermentation.
For organic producers this selection criterion is particularly important as DAP additions are not allowed.
Un-justified statements
Beware of marketing spiel such as ‘expression of fruit and spice’ and ‘structured and fruity’. With a few important exceptions, these comments are very subjective.
Quality enhancing characteristics
Malic acid metabolism
Some strains can metabolise malic acid and reduce acidity. However they will only remove some of the malic acid and not all.
Ester producers
There are now several strains that produce significant quantities of esters during fermentation. These can be extremely useful in enhancing quality for young wines. Bear in mind that most of these esters hydrolyse fairly rapidly, within a period of a few months.
Improved palate structure
Glycerol, polysaccharides and mano-proteins all have a positive effect on palate structure, softening tannins, balancing acid and supporting fruit flavours. Yeasts ability to produce these varies greatly, for instance up to 10g/l of Glycerol.
Flavour improvement
This is perhaps one of the only areas in which the winemaker has the opportunity to significantly improve the quality of the wine. These strains fall roughly into three groups.
Beta-glycosidase activity – Glucosidically bound mono-terpenes can be cleaved, releasing aromatic volatile mono-terpenes if the yeast possesses this activity. This is particularly relevant for varieties like Siegerebe, Schoenberger, Riesling and Muller Thurgau.
Thiol producing – There are now several strains that actively enhance the levels of thiols in the finished wine. This flavour compounds are particularly important in the flavour profile of Sauvignon Blanc and Bacchus but are also present in Kerner, Muller Thurgau and Scheurebe.
Beta-damascenone enhancing – In a similar way, some yeast strains can increase the level of nor-isoprenoids, in particular beta-damascenone, improving overall flavour. This is particularly important in Chardonnay, Ortega and Riesling.
As you can see, a particular variety could have flavour contribution from more than just one group of compounds. Don’t be afraid to used mixed cultures. This technique can be very useful and manufacturers themselves are now producing pre-mixed preparations.
One final word. Problems during fermentation often can be traced back to poor re-hydration and inoculation. This can be avoided by closely following the manufacturer’s instructions and most importantly, never subject the culture to a temperature shock of more than 5oC over a 15 minute period.
Best regards
David Cowderoy
Dear all,
I have been asked by some of the wineries I consult to for some recommendations on yeast strains. A difficult task, seeing as there are over 250 yeast strains commercially on the market!
However here are some general recommendations to help you all decide on what strain to use. Attached to this email is a summary of the majority of the strains available. This is by no means definitive. The characteristics are taken from the manufacturer’s data sheets and are not my own comments. The spreadsheet has auto-filters so you can select from any column the criteria you want.
I will happy to discuss this in more detail at the WineSkills event on Thursday 2nd September at Denbies
Basic selection criteria
Availability
Only some of the manufacturers have distributors in the UK. Whilst you can always import, it is not a good idea to over order as even unopened packets will lose viability when kept from one year to the next.
Optimum fermentation temperature
Select a strain that matches your refrigeration capabilities. If a tank has no refrigeration, then don’t select a stain that is an active fermenter, normally indicated by a low optimum fermentation temperature. This is particularly important if fermenting in barrel as the heat of fermentation cannot escape. On the other hand for late varieties, when the ambient air temperature is much lower, a more active stain will be used.
Freedom from faults
Try and select strains that produce low VA and low H2S.
Nitrogen requirement
Strains with high nitrogen requirement can be problematic if the juice has insufficient free available nitrogen (FAN). Whilst this can be supplemented with DAP, it is not uncommon to reach the maximum legal addition and still have a reduced fermentation.
For organic producers this selection criterion is particularly important as DAP additions are not allowed.
Un-justified statements
Beware of marketing spiel such as ‘expression of fruit and spice’ and ‘structured and fruity’. With a few important exceptions, these comments are very subjective.
Quality enhancing characteristics
Malic acid metabolism
Some strains can metabolise malic acid and reduce acidity. However they will only remove some of the malic acid and not all.
Ester producers
There are now several strains that produce significant quantities of esters during fermentation. These can be extremely useful in enhancing quality for young wines. Bear in mind that most of these esters hydrolyse fairly rapidly, within a period of a few months.
Improved palate structure
Glycerol, polysaccharides and mano-proteins all have a positive effect on palate structure, softening tannins, balancing acid and supporting fruit flavours. Yeasts ability to produce these varies greatly, for instance up to 10g/l of Glycerol.
Flavour improvement
This is perhaps one of the only areas in which the winemaker has the opportunity to significantly improve the quality of the wine. These strains fall roughly into three groups.
Beta-glycosidase activity – Glucosidically bound mono-terpenes can be cleaved, releasing aromatic volatile mono-terpenes if the yeast possesses this activity. This is particularly relevant for varieties like Siegerebe, Schoenberger, Riesling and Muller Thurgau.
Thiol producing – There are now several strains that actively enhance the levels of thiols in the finished wine. This flavour compounds are particularly important in the flavour profile of Sauvignon Blanc and Bacchus but are also present in Kerner, Muller Thurgau and Scheurebe.
Beta-damascenone enhancing – In a similar way, some yeast strains can increase the level of nor-isoprenoids, in particular beta-damascenone, improving overall flavour. This is particularly important in Chardonnay, Ortega and Riesling.
As you can see, a particular variety could have flavour contribution from more than just one group of compounds. Don’t be afraid to used mixed cultures. This technique can be very useful and manufacturers themselves are now producing pre-mixed preparations.
One final word. Problems during fermentation often can be traced back to poor re-hydration and inoculation. This can be avoided by closely following the manufacturer’s instructions and most importantly, never subject the culture to a temperature shock of more than 5oC over a 15 minute period.
Best regards
David Cowderoy
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