Introduction
No matter how clever we are or how hard we try, there is still always scope to make a stronger beer. Sometimes, just using the right ingredients, the right yeast and optimum fermentation conditions are simply not enough.
There are many ways we can make our beer, or other fermented beverage, stronger but here we just going to focus on one technique – cryoconcentration. Although this looks like a long fancy scientific word, all it means is that we freeze the hell out of the beer and separate out the ice leaving whatever is left behind much stronger. The Germans are famous for their Eis-Bock beer which, if you’ve never tried it, I suggest you go out and buy some and drink it on a quiet evening at home when there’s no one else around.
The cryoconcentration step can be performed before fermentation to concentrate dissolved sugars prior to fermentation – which is how ice-wine and ice-cider are produced. For beer, this benefit is not so obvious, after all if you want a stronger wort, you just use more grain (or malt extract) or boil it longer.
Alternatively, cryoconcentration can be used after fermentation has finished to concentrate the alcohol as in Eis-Bock or Apple-Jack cider. This technique is regarded by most authorities as a type of distillation and is generally regarded as being illegal (as it is avoiding tax payment) – so you have been duly warned. However, I understand that this sort of thing can be carried out for educational purposes (like doing background work for a book like this).
Note that concentrating the alcohol will also concentrate other products of fermentation including those that will give you a heavy hangover or even poison you, so you have been duly warned, twice.
In this section, I’m going to cover the production of beverages using pre-fermentation (legal) and and post-fermentation (educational) cryoconcentration techniques.
Freezing Stuff in Water
Despite our best efforts, the main constituent of any beer (or cider) is water. When water cools, it freezes to form (pure) ice. If we can remove this ice, we increase the concentration of whatever is left dissolved in the water. As we all know, pure water will freeze at 32°F (or 0°C). If sugar or alcohol (or in fact anything else that is dissolved) are present, then the freezing point of water is reduced. What happens is that, as water freezes, it arranges itself into a highly structured tetrahedral lattice which bonds adjacent water molecules together and ice crystals are formed. If other molecules like sugar or alcohol are present, they get in the way and bugger up this crystallization process and so that the freezing is inhibited. As the temperature is further reduced, the attraction between the water molecules increases and a point is reached when the sugar and alcohol molecules just can’t keep them apart any longer and the crystallization of water proceeds. This is a thermodynamic effect involving free energy considerations. For most molecules, the freezing point depression of water is directly proportional to the number of sugar or alcohol molecules in the water.
What this also means is that, if we know the temperature of the ice, we can calculate the concentration of sugar or alcohol in the remaining liquid. If we put the vessel into a deep freezer, as more ice is formed the concentration of the sugar or alcohol increases in the residual liquid and the temperature decreases still further. If we’re looking at achieving a target concentration, we just need to monitor the temperature and wait until it reaches the value known to give the required concentration.
There’s a lot of theory and equations involved in predicting the relationship between freezing temperature and concentration of sugar or alcohol. I thought about stuffing it all in here and making the readers suffer – but I probably don’t fully understand it either. So, as a public service, I’m going straight to the practicalities of performing cryo-concentration in the comfort of your own home.
Pre-Fermentation Cryo-Concentration
As mentioned earlier, it’s relatively straightforward to increase the strength of a beer by adding more malt or sugar or boiling down the volume of the wort to increase its strength. For drinks like hard cider (and wine), boiling is not an option and adding more juice won’t increase the strength. Cryo-concentration is very applicable to making stronger hard cider as the only ingredient in the cider continues to be apple juice.
A typical raw apple juice will contain a total of 10 to 12% of the following sugars fructose, glucose and sucrose. It’s specific gravity will be around 1.045 to 1.050.
Based on my experiences and that reported by others, it would seem that a reasonable target for ice-cider would be to concentrate the sugars by a factor or 3 with a yield of about 1/4 of the initial volume of the apple juice. Thus 1 gallon of would produce 1/2 gallon of concentrated juice of SG 1.135 to 1.150 – the starting gravity for a typical ice-cider.
Here is my procedure for cryo-concentrating apple juice to make 1 gallon of ice-cider:
- Fill an empty 1-gallon plastic milk carton (or some other suitable plastic container with a sealed cap) with apple juice. Fresh apple juice often comes packaged in plastic containers that are very suitable for this. Leave a 1″ air gap at the top of the container.
- Screw on the cap and check that there are no leaks.
- Put the container of apple juice upside down in a plastic bucket (just in case there are leaks).
- Put the bucket into a chest freezer at 0°F (-16°C) and leave for 2 days. Periodically check the container for leaks or damage during this time. Pour the apple juice into a second container if there is a problem.
- After 2 days, the apple juice should be frozen hard.
- Remove the cap from the container.
- Place the container upside down (i.e. with the opening downwards) into a clean and sanitized glass jar or cup with a 1 quart level marking on it.
- To get a good concentration effect, it’s very important that the frozen apple juice should thaw very slowly. I’ve used two methods to achieve this:
- Place the glass jar and the container with the frozen apple juice into a beverage cooler (I use one of my mash tuns) and replace the lid.
- Adjust the temperature of a chest freezer to about 34°F (1°C) and put the jar and apple juice container in that. The chest freezer will require an external temperature controller to enable this – this will be a new project that will be published on this site shortly.
- Once the frozen apple juice is in a environment slightly above freezing point, it should start to slowly melt. As the liquid melts it will drip into the glass jar. The process should be slow and may take over 24 hours.
- Periodically check the level of the liquid collected in the glass jar and, once the 1 quart mark is reached, take out the container with the residual frozen apple juice and pour the quart of concentrate into a suitable clean and sanitized 1-gallon container.
- Let the residual frozen apple juice thaw and then either discard it or drink it (it’s still very drinkable).
- Fill the container with another gallon of raw apple juice and repeat the process to get another quart of concentrate.
- Repeat this a further 2 times to get in total a gallon of concentrate.
A recipe for ice-cider will be given (soon) under the Recipes section of this website.
Post-Fermentation Cryo-Concentration
LEGAL WARNING: If you’re going to try freezing beer to get more alcohol, then there’s a few things you should consider beforehand. Firstly, it’s almost certainly illegal to do this and, secondly, the resultant beer may contain unhealthy levels of toxins like methanol, aldehydes and fusel compounds. Although, I’m going to describe the process for cryo-concentrating fermented beer, I will take no responsibility for any ill effects you or those around you may suffer in health or from legal prosecution from doing this stupid thing.
First start by studying the laws in your area – they may be different. In the USA, use of cryo-concentrated beer is allowed under the following three circumstances [##]:
- The alcohol concentration is only increased by 0.5% or less (i.e. totally useless).
- Concentrated beer doesn’t leave the brewery and is diluted back to the beer’s original strength before consumption (i.e. also totally useless).
- The concentrated beer is used for some purpose other than drinking – for example fuel for a lawn mower (I’m not feeding beer to my lawnmower). An official license must be obtained to do this.
Cryo-concentration of wine (and cider) is always illegal (except for use in lawnmowers).
Once you know how long you will spend in prison, if you wish to proceed, then read on.
I might add at this point, that all the concentrated beers and ciders I made using cryo-concentration after fermentation were immediately diluted back to their original strength prior to tasting.
The process instructions are the same as they were for the pre-fermentation cryo-concentration.