Wednesday 16 February 2011

Fermentation

Fermentation is where the magic begins - where the sugars and yeast are added to the wort and alcohol is made.

Clean and Sanitise all Equipment.

It is important that all equipment used at this stage is thoroughly cleaned and sanitised. This includes your fermenter vessel, the lid of the fermenter, the airlock, your thermometer and hydrometer and your brewers paddle.

If you are using a beer kit then a more detailed process of the fermentation process with beer kits can be found here.


Prepare the Yeast

Many people use dry yeast and simply sprinkle this onto the wort and then let nature take it's course however a rehydrated yeast or yeast starter is preferable as this allows the yeast to start fermenting almost as soon as it has been added to the wort. The yeast head produced during fermentation acts as a barrier to any airborn bacteria that could infect your brew.


To rehydrate dry yeast is simply a process of adding the yeast to a sanitised jug of about 225ml warm water (30°C-35°C) and after 15 minutes add a teaspoon of sugar or malt extract that has been boiled in a little water. Cover with cling film and leave to start the fermentation. The benefits of this is to check that the yeast is still alive or not too old - after about 30 minutes the yeast should start to foam. If not it may be wise to use a different batch of yeast.


A yeast starter uses liquid yeast. There are various types of liquid yeast including 'smack packs' which contain a yeast nutrient in a separate pack inside the main package. The nutrients are simply added by bursting the inner pack when needed. Liquid yeasts should be stored in the refrigerator until needed to keep the yeast dormant. Liquid yeasts need to be prepared at leat 4 days before they are added to the fermenter.

To make a yeast starter the liquid yeast must first be placed in a warm place overnight - the yeast pack (if using a smack pack) will swell overnight. Add roughly half a cup of dried malt extract to a pint of boiling water and stir to mix. Cool the mixture (putting the pan in a sink of cold water works well) until the temperature is around 30-35°C. Pour the contents including the sediment into a sanitised bottle or similar container. Pour the yeast into the bottle and cover well and give the solution a good shake to mix the contents thoroughly. Either cover the bottle with a loose fitting piece of cling film secured with a rubber band or fit an airlock to the bottle and leave to ferment. Eventually the sediment should drop to the bottom of the liquid and the liquid should clear. It is now ready to pitch when required.


Take a Hydrometer and Temperature Reading


Once the wort is in the fermenter it is time to take a hydrometer and temperature reading to find out the original gravity (OG) of the beer. We use this to calculate the alcohol content of the finished beer by comparing it to the final gravity (FG) reading we take later. Again make sure your hydrometer has been sanitised. Make a note of the readings for future reference. A hydrometer reading is affected by the temperature. Most hydrometers are calibrated for a temperature of 20°C. If the temperature is different you will need to refer to a hydrometer temperature chart.For more information on hydrometers click here. If the original gravity reading is not right you can make alterations by adding sugar or dried malt extract to raise the gravity.

Aerate the Wort

For the yeast to work correctly it is important that there is enough oxygen in the wort. This can be done by pouring the wort from one sanitised fermenter bucket to another several times or by vigorously stirring the wort with your brewers paddle for 5 minutes. Inserting the brewers paddle into a cordless drill is ideal.

Add the Yeast

Adding the yeast is simple. Dried yeast can be simply sprinkled on top of the wort and left to sink naturally with or without a gentle stir. Rehydrated yeast or a yeast starter can be added by pouring over the surface of the wort. Ideally the wort should be at a temperature of 25°C. If it is too warm then this could kill the yeast. If too cold then the yeast could remain dormant.

The Final Stage

Once the yeast has been added the lid needs to be secured to your fermenter and the airlock needs to be filled slightly with water and placed in the bung on the lid. The fermenter then needs to be placed in a warm place and left for several days.

After several days you will notice that the airlock has stopped bubbling. It is now time to take a hydrometer and temperature reading again. Leave for 24 hours and then do the same. Once the readings have stabilised the beer is ready for bottling or barreling.

If your liquor fails to start fermenting you will need to check the temperature of the liquor. If it is too cold for example below 16°C then the fermenter will need either placing in a warmer area or. a wise investment, is to purchase a brewers belt or heat tray. The brewers belts in particular are relatively cheap and simple to use. Once you have sorted the temperature of the liquor it is advisable to give the liquor a very gentle stir with a sterilised brewers paddle to agitate the yeast which may have settles to the bottom of the fermenter.

Alternatively the liquor may have been too warm at the time of pitching the yeast. If this is the case then the only way to save the beer is to pitch more yeast.

If the temperatures have been right through all the processes then you may be experiencing what is refered to as stuck fermentation. Again, a gentle stir so as not to allow excessive air into the beer, with a sanitised brewers paddle is advisable.

Go to Barreling and Bottling your Beer

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