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Time for giving back to the community and saying thank you for everyone that has provided information and references. Here are notes that I have made. I hope they are useful to everyone making mead.
Yeast cells are 5 – 10 microns in size.
Most American Ale yeasts are considered as medium flocculation.
With high flocculation yeast it is a good idea to stir 2x a day until the 1/3 sugar break and then 1x daily until the 2/3 sugar break. This is to bring the yeast out of the settled cake at the bottom of the fermenter.
Yeast will produce minimal flavor compounds and ethanol at this stage. Yeast will not make esters until there is an appreciable amount of alcohol. As a result of this, fermentation can be left at a warmer temperature during the lag phase to let the colony grow and then cool/temperature control later. In general, yeast should be pitched at fermentation temperature or slight below and then left to rise for the first 12 to 36 hours.
Check the specifications of your specific yeast for tolerance range and if there is any specific information regarding pitching temperature. As an example, Lalvin D47 has a fermentation range of 59F-86F with specific directions to pitch at 62F or higher.
Some brews may contain up to 50 different esters. Three common ester types are:
Pre-Fermentation oxygen is used by yeast to produce Sterols in preparation for budding new cells. This Sterol production takes away from Acetyl-CoA. This results in lower esters. Higher aeration can result in lower esters.
The majority of esters are produced in fermentation and are influenced by:
The opposite is true in that not as much oxygen will create an increased Acetyl-CoA and ester formation. Not having enough oxygen can create yeast that struggles and might produce some off flavors in addition to a higher ester production. A lack of dissolved oxygen can also lead to stuck fermentations. It is likely best to shoot for increased oxygen aeration and use strains of yeast that produce esters that you want.
Oxygen uptake by yeast is swift with the yeast deleting the oxygen in as little as 30 minutes of inoculation. To produce ethanol the yeast need to enter an anerobic fermentation; they do this once there is low oxygen or high sugar levels. Oxygen is used to bud more daughter cells. If there is high enough glucose concentration, even without oxygen, the yeast will produce alcohol. It enters anerobic fermentation.
Once your must is greater than 1.092 SG, using oxygen should be considered mandatory for proper yeast health; a must with a SG above 1.083 will benefit from additional oxygen somewhere between 12 to 18 hours after yeast pitch as this will increase fermentation speed and yeast attenuation. This second dose can speed fermentation by as much as 33%.
Aeration while using oxygen will provide an oxygen level in the must in the range of 8-10 PPM. Using a ½ micron stone will provide the desired oxygen levels.
Hand stirring the must will provide an oxygen level of ~4 PPM.
Aeration with a drill and wine degasser can provide an oxygen level approaching 8 PPM.
A filtered air pump with an aeration stone will provide ~8 PPM after ~60 minutes.
The above O2 numbers are with ½ micron aeration stone at 75F. This is from test data by White Labs.
If harvesting yeast for use again, higher O2 levels are desired as low O2 levels will increase the lag phase.
Many English ale yeasts are known to have a high ester production while American ale yeast have less ability and lager yeasts have even less ester capability.
All yeast type will produce a lot of esters if stressed. The health of the yeast is important to avoid strange fruity flavors that may not be very palatable.
Pitching an adequate amount of yeast that has plenty of oxygen is critical to avoiding off flavors. The amount of yeast pitched has some minor effect on ester production with a higher amount of yeast producing less esters and a lower yeast pitch producing more esters. When in doubt, remember that you can’t over pitch an amount of yeast and go for more if unsure.
In general, it is considered best practice to rehydrate your yeast before pitching and to attemperate the yeast with some of the must to acclimate it to the amount of sugar and the pH of the must before the entirety of the yeast is pitched. The Go-Ferm product is recommended with yeast hydration.
When adding yeast to an ongoing fermentation, the yeast need to be in an active state as there is no oxygen and alcohol is present. You need to use a starter or yeast from 1 to 2 day active fermentation. A yeast with a high kill factor may make adding a different yeast difficult.
Controlling for temperature 1 to 3 days after yeast pitch is critical for controlling ester production. If you want as little ester production as possible then you would want to start controlling after 1 day. If you are shooting for more esters than you would wait until after that third day.
Reducing fermentation temperature will create lower ester production while higher temperatures create more. This goes back to yeast selection and which produce desirable esters or lack of. It has been documented that Kveik yeast has a very large fermentation temperature range and has been anecdotally noted that higher temperature ranges can produce some very fruit flavors with some brewers choosing to leave the fermentation vessel out in the sun to increase these esters.
For anyone that is fermenting under pressure, this lowers ester production.
The concentration of fusel alcohol increases with fermentation temperature. Additionally, too much or too little nitrogen can increase fusel alcohols. This should be kept balanced with the need for nitrogen to produce esters.
More or less nitrogen than the necessary YAN amounts needed by the yeast will affect ester production but going too far can cause fusel alcohols. Interestingly fusel alcohol provides opportunity for ester production with any Acetyl-CoA present. Avoiding “hot” fusel alcohol while allowing for ester production is likely a balance act between temperature control, free nitrogen, and proper yeast health and appropriate yeast selection.
Yeast use sugars in the following order: Glucose, Fructose, and then Sucrose. More complex sugars are used last. The more flocculent strains are less able to handle complex sugars.
Biotin is the most important vitamin for yeast. A deficiency in this vitamin can result in slow yeast growth and stuck fermentations. Biotin is found in Fermaid K and Fermaid O and a proper nutrient schedule should provide what is needed.
Zinc is an important mineral and is often limited. An ideal amount in a fermentation is .1mg to .15mg per liter. Honey typically has .05mg to 2mg per 100g of honey. Fermaid O contains zinc, but I don’t know at what level. I am assuming that recommended dosage contains the needed amount of zinc.
For Lalvin yeast the recommended amount of yeast to pitch changes based upon the SG/gallon.
Rehydration of dry yeast should always be done in place of just sprinkling into the must/wort. Skipping hydration can kill 50% of the yeast pitched. Those dead yeast start to break down and affect flavor.
Dry yeast is dormant and is not dead or inert. Stored at 75F, a dry yeast will lose ~20% viability per year. Stored at 38F it only loses ~4% per year. During the first moments of rehydration, the cell cannot regulate what passes through the membrane. This allows high levels of sugar, nutrients and acids to enter freely and potentially damage cells. This is why directly pitching to the must/wort can have such a negative effect on the yeast pitched.
Using a product like Go-Ferm allows proper nutrients, minerals and vitamins to be absorbed while the yeast is acting like a sponge.
Everything used should be sanitized.
Use 1.25 grams of Go-Ferm for every gram of dry yeast to be used.
Multiply by 25 to determine how much water is to be used. 5 grams of yeast will need 6.5 grams of Go-Ferm. That amount multiplied by 25 means you will need 156 ml water.
Heat water to ~104F and stir in Go-Ferm until dissolved in water. It will dissolve faster in hotter water, but you will need to allow it to cool below 102F before you can pitch yeast. If you choose to not use Go-Ferm, your water should have a mineral content of 250-500 ppm hardness. You should never use distilled water for rehydration as it will kill the yeast while the cell cannot regulate the outside and inside in those first moments and the cell will burst.
Sprinkle yeast on top and avoid clumping. A wider container with a larger surface area will be preferred for this. Let sit for up to 15 minutes to start hydrating and then gently stir into the solution.
Allow yeast to acclimate for 10-15 minutes and then check temperature. If the yeast slurry and must are within 10F of each, the yeast can be pitched into the must. If not, a small amount of the must (~25% of slurry amount) can be added to the yeast slurry to lower temperature.
Even if the yeast slurry and must are within 10F of each other, you can add a small amount of the must to the yeast to acclimate it to the pH of the must. Wait another 10 minutes and then pitch yeast.
71B (eats fructose before glucose) and also converts some malic acid to lactic acid.
Cyser
QA-23
Most of this information has been taken from Yeast, The Practical Guide to Beer Fermentation, Hombrewer’s Lecture Series: Esters, Misc Podcasts on Got Mead, and personal experience.
Yeast Notes
A yeast that is listed as having high flocculation is one that clears faster. Calcium is needed for flocculation with a level of at least 50 ppm. Soft water may need calcium added.Yeast cells are 5 – 10 microns in size.
Most American Ale yeasts are considered as medium flocculation.
With high flocculation yeast it is a good idea to stir 2x a day until the 1/3 sugar break and then 1x daily until the 2/3 sugar break. This is to bring the yeast out of the settled cake at the bottom of the fermenter.
- There are times that you may want to use multiple strains in a single brew.
You might use a higher ABV tolerant strain to help finish a stuck ferment or to use on a too sweet brew. Use of a neutral yeast strain will help avoid changing flavors. Lalvin EC 1118 is a good candidate. - If you are trying to increase complexity or unique flavors you should add all the desired yeast at the beginning of fermentation as most fermentation derived flavor compounds are produced in the first 72 hours.
- For stuck fermentations, you want an active and health yeast before adding to a stuck fermentation. You want a health yeast starter that has been attempered to the must.
- Lag phase – lasts 0 to 15 hours
- Exponential growth phase - lasts 1 to 4 days
- Stationary phase – 3 to 10+ days
Lag Phase
In the lag phase the yeast takes up oxygen, minerals, vitamins and nitrogen. Fermaid-0 should provide the minerals and nitrogen needed by the yeast. Oxygen needs to be added and present at the beginning of fermentation. Oxygen is not, generally, added later as it can disturb balance of flavor and aroma compounds. The exception to this is higher gravity where large reserves of oxygen are needed for fermentation to complete. A second addition of oxygen added between 12 to 18 hours after pitch can make a big difference in full attenuation; this can be greater than a 10% difference.Yeast will produce minimal flavor compounds and ethanol at this stage. Yeast will not make esters until there is an appreciable amount of alcohol. As a result of this, fermentation can be left at a warmer temperature during the lag phase to let the colony grow and then cool/temperature control later. In general, yeast should be pitched at fermentation temperature or slight below and then left to rise for the first 12 to 36 hours.
Check the specifications of your specific yeast for tolerance range and if there is any specific information regarding pitching temperature. As an example, Lalvin D47 has a fermentation range of 59F-86F with specific directions to pitch at 62F or higher.
Exponential Growth Phase
This phase can happen anywhere from 4 hours to 4 days after inoculation of the yeast to the must. The cell count is increasing rapidly, CO2 is produced, ethanol and flavor compounds are being produces and sugar is being eaten. Temperature control would be started after ~24 hours if trying to minimize Esther production.Stationary Phase
This typically happens somewhere to 3 to 10+ days after yeast innoculation. Most flavor compounds and esters are produces by this point. With most ale yeast the majority of alcohol will have been produced. The yeast will start to clean up fermentation Diacetyl and Acetaldehyde. Hydrogen Sulfide is escaping with CO2 and the yeast starts to flocculate.Esters
Esters are formed from organic acid and alcohol. These can produce fruity aromas and flavors.Some brews may contain up to 50 different esters. Three common ester types are:
- Ethyl Acetate – this can provide a solvent kind of flavor, though it may likely provide a pear like flavor.
- Ethyl Caproate – this provides an apple flavor.
- Isoamyl Acetate – this provides a banana flavor. Bavarian wheat beers.
Pre-Fermentation oxygen is used by yeast to produce Sterols in preparation for budding new cells. This Sterol production takes away from Acetyl-CoA. This results in lower esters. Higher aeration can result in lower esters.
The majority of esters are produced in fermentation and are influenced by:
- Wort-must composition
- Aeration of the wort-must
- Yeast strain and its health
- The fermentation conditions
The wort-must composition
In general, the higher the sugar concentration, the more Acetyl-CoA that is produced and the more esters that can be generated. The amount of nitrogen also affects the number of esters produced and a higher nitrogen concentration will produce more esters along with the amino acids that are used for yeast cell wall growth.Aeration
The short story here is that higher oxygen aeration will develop a stronger yeast colony. The higher oxygen aeration does result in a lower amount of Acetyl-CoA which in turn affects how many esters can be produced. Without proper aeration yeast are unable to control membrane fluidity through to the end of fermentation which leads to stuck fermentation and off-flavors.The opposite is true in that not as much oxygen will create an increased Acetyl-CoA and ester formation. Not having enough oxygen can create yeast that struggles and might produce some off flavors in addition to a higher ester production. A lack of dissolved oxygen can also lead to stuck fermentations. It is likely best to shoot for increased oxygen aeration and use strains of yeast that produce esters that you want.
Oxygen uptake by yeast is swift with the yeast deleting the oxygen in as little as 30 minutes of inoculation. To produce ethanol the yeast need to enter an anerobic fermentation; they do this once there is low oxygen or high sugar levels. Oxygen is used to bud more daughter cells. If there is high enough glucose concentration, even without oxygen, the yeast will produce alcohol. It enters anerobic fermentation.
Once your must is greater than 1.092 SG, using oxygen should be considered mandatory for proper yeast health; a must with a SG above 1.083 will benefit from additional oxygen somewhere between 12 to 18 hours after yeast pitch as this will increase fermentation speed and yeast attenuation. This second dose can speed fermentation by as much as 33%.
Aeration while using oxygen will provide an oxygen level in the must in the range of 8-10 PPM. Using a ½ micron stone will provide the desired oxygen levels.
Hand stirring the must will provide an oxygen level of ~4 PPM.
Aeration with a drill and wine degasser can provide an oxygen level approaching 8 PPM.
A filtered air pump with an aeration stone will provide ~8 PPM after ~60 minutes.
| Method of Aeration for 5 gallons | Oxygen PPM |
| Shaking for 5 minutes | 2.71 PPM |
| Pure 02 for 30 seconds | 5.12 PPM |
| Pure O2 for 60 seconds | 9.2 PPM |
| Pure O2 for 120 seconds | 14.08 PPM |
If harvesting yeast for use again, higher O2 levels are desired as low O2 levels will increase the lag phase.
Yeast strains and its health
Some yeasts produce more esters than others. If you desire more impact from esters then choosing an appropriate yeast will help with that. Lalvin’s D47 yeast is known and marketed for its “accentuated fruit and volume” as well as “enhanced aroma and flavor”. This yeast is listed as having a low nitrogen demand and is a low producer of Hydrogen-Sulfide in low nitrogen environments. Proper nutrients should provide all the nitrogen needed for the yeast as well as contributing toward ester production. This yeast is also known to make hotter fusel alcohols at higher fermentation temperatures and is best kept below 75F and even better in the low 60’s even if its listed temperature range is up to 86F.Many English ale yeasts are known to have a high ester production while American ale yeast have less ability and lager yeasts have even less ester capability.
All yeast type will produce a lot of esters if stressed. The health of the yeast is important to avoid strange fruity flavors that may not be very palatable.
Pitching an adequate amount of yeast that has plenty of oxygen is critical to avoiding off flavors. The amount of yeast pitched has some minor effect on ester production with a higher amount of yeast producing less esters and a lower yeast pitch producing more esters. When in doubt, remember that you can’t over pitch an amount of yeast and go for more if unsure.
In general, it is considered best practice to rehydrate your yeast before pitching and to attemperate the yeast with some of the must to acclimate it to the amount of sugar and the pH of the must before the entirety of the yeast is pitched. The Go-Ferm product is recommended with yeast hydration.
When adding yeast to an ongoing fermentation, the yeast need to be in an active state as there is no oxygen and alcohol is present. You need to use a starter or yeast from 1 to 2 day active fermentation. A yeast with a high kill factor may make adding a different yeast difficult.
Fermentation Conditions
The state of the fermentation has a large impact on the production of esters with temperature being the biggest factor. Higher temperatures produce more activity which in turn produce more Acetyle-CoA which is needed for ester production. As stated above the first 72 hours is where most aromas and flavors are produced.Controlling for temperature 1 to 3 days after yeast pitch is critical for controlling ester production. If you want as little ester production as possible then you would want to start controlling after 1 day. If you are shooting for more esters than you would wait until after that third day.
Reducing fermentation temperature will create lower ester production while higher temperatures create more. This goes back to yeast selection and which produce desirable esters or lack of. It has been documented that Kveik yeast has a very large fermentation temperature range and has been anecdotally noted that higher temperature ranges can produce some very fruit flavors with some brewers choosing to leave the fermentation vessel out in the sun to increase these esters.
For anyone that is fermenting under pressure, this lowers ester production.
| Increase Esters | Decrease Esters |
| Higher gravity must | Lower gravity must |
| Lower oxygen aeration | Higher oxygen aeration |
| Higher fermentation temperature | Lower fermentation temperature |
| Lower yeast pitch rate | Higher yeast pitch rate |
| Higher free nitrogen | Lower free nitrogen |
Fusel Alcohols
Fusel alcohol produced during fermentation can result in that “hot” flavor and burn you feel when drinking your brew. When dealing with beer yeast, ale strains produce more of this than lager strains. Not all fusel alcohols produce that "hot" alcohol.The concentration of fusel alcohol increases with fermentation temperature. Additionally, too much or too little nitrogen can increase fusel alcohols. This should be kept balanced with the need for nitrogen to produce esters.
More or less nitrogen than the necessary YAN amounts needed by the yeast will affect ester production but going too far can cause fusel alcohols. Interestingly fusel alcohol provides opportunity for ester production with any Acetyl-CoA present. Avoiding “hot” fusel alcohol while allowing for ester production is likely a balance act between temperature control, free nitrogen, and proper yeast health and appropriate yeast selection.
Sulphur compounds
Large amounts of Sulphur compounds are created during fermentation. These compounds are generally volatile and a vigorous fermentation along with the generated CO2 carries these compounds away. Lower fermentation temperatures will be less vigorous and can retain more of these compounds. Manual degassing of the must will help carry these compounds away. The best way to reduce having these compounds affect your brew is to have a health fermentation.Yeast Pitching and additives
Over pitching yeast will decrease the lag phase of the fermentation but the individual cells will not be as health at the end of the fermentation. We also know that over pitching yeast can decrease the impact of esters in the brew.Yeast use sugars in the following order: Glucose, Fructose, and then Sucrose. More complex sugars are used last. The more flocculent strains are less able to handle complex sugars.
Biotin is the most important vitamin for yeast. A deficiency in this vitamin can result in slow yeast growth and stuck fermentations. Biotin is found in Fermaid K and Fermaid O and a proper nutrient schedule should provide what is needed.
Zinc is an important mineral and is often limited. An ideal amount in a fermentation is .1mg to .15mg per liter. Honey typically has .05mg to 2mg per 100g of honey. Fermaid O contains zinc, but I don’t know at what level. I am assuming that recommended dosage contains the needed amount of zinc.
For Lalvin yeast the recommended amount of yeast to pitch changes based upon the SG/gallon.
| SG | Lalvin pitch rate in grams per gallon | TOSNA pitch rate in grams per gallon |
| 0 – 1.106 | 1g | 2g |
| 1.106 – 1.129 | 1.3g | 2g |
| 1.129 – 1.154 | 1.49g | 3g |
| 1.154 – 1.189 | 1.92g | 4g |
Dry yeast is dormant and is not dead or inert. Stored at 75F, a dry yeast will lose ~20% viability per year. Stored at 38F it only loses ~4% per year. During the first moments of rehydration, the cell cannot regulate what passes through the membrane. This allows high levels of sugar, nutrients and acids to enter freely and potentially damage cells. This is why directly pitching to the must/wort can have such a negative effect on the yeast pitched.
Using a product like Go-Ferm allows proper nutrients, minerals and vitamins to be absorbed while the yeast is acting like a sponge.
Rehydrating yeast
Allow yeast packet to come to room temperature.Everything used should be sanitized.
Use 1.25 grams of Go-Ferm for every gram of dry yeast to be used.
Multiply by 25 to determine how much water is to be used. 5 grams of yeast will need 6.5 grams of Go-Ferm. That amount multiplied by 25 means you will need 156 ml water.
Heat water to ~104F and stir in Go-Ferm until dissolved in water. It will dissolve faster in hotter water, but you will need to allow it to cool below 102F before you can pitch yeast. If you choose to not use Go-Ferm, your water should have a mineral content of 250-500 ppm hardness. You should never use distilled water for rehydration as it will kill the yeast while the cell cannot regulate the outside and inside in those first moments and the cell will burst.
Sprinkle yeast on top and avoid clumping. A wider container with a larger surface area will be preferred for this. Let sit for up to 15 minutes to start hydrating and then gently stir into the solution.
Allow yeast to acclimate for 10-15 minutes and then check temperature. If the yeast slurry and must are within 10F of each, the yeast can be pitched into the must. If not, a small amount of the must (~25% of slurry amount) can be added to the yeast slurry to lower temperature.
Even if the yeast slurry and must are within 10F of each other, you can add a small amount of the must to the yeast to acclimate it to the pH of the must. Wait another 10 minutes and then pitch yeast.
Yeast selection for Mead
Heat tolerant yeasts (try and keep in the lower 20% of range)- D21
- DV10
- K1-V1116
- EC-1118
- dv10
- ec1118
- D21
- D47 (Keep in low 60's)
- D80
- D254
- D47 (Keep in low 60's)
- 71B
- k1-V1116
- RC212
71B (eats fructose before glucose) and also converts some malic acid to lactic acid.
Cyser
- K1-V1116 (esters)
- EC1118
- D47 (Keep in low 60's)
- RC212
- BM 4x4
- DV10
- ec1118
Metheglin - k1-V1116
- D47 (Keep in low 60's)
- D47 (Keep in low 60's)
- k1-V1116
- CY3079
- D21
QA-23
Most of this information has been taken from Yeast, The Practical Guide to Beer Fermentation, Hombrewer’s Lecture Series: Esters, Misc Podcasts on Got Mead, and personal experience.
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