FREQUENTLY ASKED QUESTIONS - YEAST & FERMENTATION
General Information
Trouble Shooting
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Yeast is a single cell organism which multiplies vigorously in the presence of oxygen. When all oxygen is used up yeast will convert sugar into alcohol.
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Simply, fermentation is the process by which yeast converts sugar into alcohol and carbon dioxide.
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| Why does fermentatin have to be enclosed in a fermenter under airlock? | 1. Yeast needs to have a controlled access to oxygen. During the first stage of fermentation (aerobic) oxygen is used by the yeast to multiply. The second stage (anaerobic) takes place when the oxygen is exhausted and the yeast looks to the sugar for it's food source. It then stops multiplying and starts producing alcohol and Carbon Dioxide.
2. With all forms of fermentation we are producing a sweet mix with good nutrients suitable for a very wide range of organisms to thrive. We then introduce the organisim that we want to multipy ie. yeast. It is important to restrict access to other organisms by sanitising everything and keeping the mix sealed in an air tight fermenter. Regardless of how careful you are with your sanitising, some bacteria and unwanted organisms will make their way into your mix. Yeast multiply approx every 2 hours and bacteria every 20 minutes however when yeasts start to multiply they reduce the ph (increase acidity) and remove the oxygen. Both of these factors will destroy the bacteria. For that reason it is essential for good fermentation to keep everything sanitised and sealed and to get the yeast added as soon as possible.
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An airlock is a device which allows carbon dioxide to escape during fermentation without letting oxygen or unwanted organisms in.
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| Why is sediment formed during fermentation? | As the yeast convert sugar into alcohol and carbon dioxide, other byproducts are produced. These include dead or dormant yeast cells along with unfermented solids.
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| Why do you need to ferment at a certain temperature? | Yeast is a living organism. Most yeasts used in distilling are active and produce fermentation in a temperature range of between 18o and 26o C.This is the temperature range where we have the best chance of achieving good results. Above this temperature very rapid fermentation may produce unwanted byproducts. If the temperature is too high the yeast will die. At lower temperatures fermentation will be slower and may cease completely (stuck ferment) meaning the yeast has become dormant. The latest release from Still Spirits, the new temperature tolerant yeast, will even ferment in temperatures as high as 40o C.
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| How do I warm my wash during fermentation in cold climates? | The only sure way is to use a heating pad or heating belt which will maintain a constant temperature. These devices are almost essential in the winter months.
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| How can I stop my brew from overheating when my room temperature is too high? |
There are two methods that you can use.
1. Fill some PET soft drink bottles with ice and freeze them. You can add them throughout fermentation to control the temperature.
2. Another method is to use the evaporation technique. Sit the fermenter in a tray with about 25mm of water. Drape some fabric over the fermenter so it dangles in the water (towelling or an old sweatshirt is ideal). If it is still too hot, turn a fan onto the fermenter.
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| What do I do if my yeast stops working before all the sugar is used up? | Make sure that your mix has not actually finished by checking the Specific Gravity(SG) with a hydrometer. The SG should be around 990. If the SG is higher and all sign of fermentation has stopped, first try restarting the mix. This can often be achieved by stirring the yeast that has settled on the bottom of the fermenter back into the liquid and also ensuring that the mix is at the correct temperature for the yeast strain used. If the SG is below 1005 and fermentation has stopped and you can not restart by the method above, then distill as normal but use some Distilling Conditioner. This will ensure that unfermented sugar in the mix does not cause frothing during distilling. You will also get a slightly lower yield of distilate. If the SG is higher than 1005 then try adding some Bayanus yeast. This is a particular strain of yeast which will start in the presence of alcohol and is used in Champagne making for the secondary fermentation in the bottle. Most yeast varieties will be destroyed by being added to a mix which contains alcohol as they need to build up a resistance to alcohol during the normal process of fermentation. Do not add more Turbo or Nutrients as excess nutrients at this stage will result in problems distilling and may actually make the mix more difficult to ferment. The best method to get the yeast going again is to get a 1 litre jug, rehydrate your Bayanus yeast in 100 mls of water at 30o C with 1 teaspoon of dextrose. When this is fermenting, add 100 mls of stuck mix. When this is fermenting add a further 200 mls of stuck ferment. When this is fermenting add a further 400 mls of stuck mix. When this is fermenting add half to the stuck mix and top up with the same. Continue until fermentation has restarted.
In extreme cases the wash may not start again. If this happens do not dispair. Distill it anyway and accept a lower yield rather than discarding it and getting no return.
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| Why did my yeast stop working before all the sugar was used? | The most common cause of this is overheating of the mix. During fermentation a lot of energy is released which results in an increase of temperature sometimes by as much as 8o C . For this reason, do not cover the fermenter nor use heating of any sort for the first 24 hours unless you are in an extremely cold area. If you do believe you need to do this then monitor the temperature regularly. Remember if the mix gets too cold you can start it again by stirring and heating. If the mix gets too hot then you may weaken or kill the yeast. Also leaving the mix in a position where the sun will shine directly on the fermenter during the day may result in excessive temperatures. Try to keep the fermenter in a position where the temperature will be constant throughout the day. Most damage to yeast occurs in the first 24 hours of fermentation but does not show up until the end off fermentation when a higher SG is noticed. Another reason for stuck or slow fermentation can be sanitiser left in the fermentation vessel. Always ensure you have used one of the Still Spirits range of Turbo yeast. Our yeast and nutrient mixes are balanced and will guarantee trouble free fermentation if the correct temperatures are maintained. Do not use more sugar or less water than what is recommended. The ratio of sugar, nutrients, yeast and water are essential. High temperatures coupled with higher concentrations of sugar will result in stuck fermentations as you have two adverse conditions working together.
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| My wash has turned to jelly! | The problem described is the result of a bacterial contamination from Leuconostoc. Under certain conditions, this bacterium produces a polysaccharide. This polysaccharide looks like jelly. Whilst it is totally harmless, customers would definitely complain if they saw such a contamination.
This bacterium can live on surfaces within a brewing environment, especially where there is a lot of repeat brewing, this is likely to be the source of contamination. But, for leuconostoc to contaminate a brew would require very low temperatures - under such conditions, very little ethanol would be produced during the first 48 hours allowing the Leuconostoc to take hold.
Also ensure that all equipment is sterlised with a chlorine based cleaner. We recommend Fermtech Sterliser Cleaner or Pink Steriliser. It would also be advisable to spray the walls of the brewing room or if possible move to another location.
The simplest answer is to ensure start liquid and fermentation temperatures between 20o - 30o C. (See the section on Turbo's and their uses for more information). It is important to start the brewing process by preparing the correct volume of water at the correct temperature and then adding the sugar to it. These are all detailed in the Turbo flyer or on the web at this link. Or at least for the start liquid temperature to be 30o C - then, even when the air temp is low, enough ethanol will be produced during the first 24 hours to protect against such contamination.
Click here to go to the Distillation FAQ
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