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Sanitising and infections - Understanding how sanitising protects your precious brew.

Info BeerLab

Written by Nick Birkby

Every brewer knows that sanitising is important, but when and where is it most crucial? Sanitising is the primary safeguard against bacterial infections that can spoil your beer, so it’s also good to understand what causes them (and where) in order to keep our beer safe. Let’s find out a bit more.

Firstly, the most likely place for a beer infection is in your fermenter, followed by in the bottle used to carbonate the beer. Yes, the primary cause of infections in beer is, surprise, the residue of old beer that now has bacteria and wild yeast living on it! The number one reason brewers lose their precious beer to unpalatable funky flavours is from not scrupulously cleaning their fermenters after bottling the previous batch, or by not sanitising their bottles well enough before bottling. The beer goes in and a Trojan Horse of bacterial baddies awaits to take over.


Of course, this is a broad generalisation, but its largely true. What is an infection exactly? An infection is picked up by the drinker primarily as an ‘off’ flavour- a flavour that you don’t expect or want in your beer. Sourness is a common one, followed by strange aromas like cloves or overly carbonated gushing bottles. You will notice immediately when an infection is bad, you will sense it when it is mild and sometimes it is hardly noticeable and the beer even still drinkable (though infections tend to worsen with time). There are a multitude of funky off-flavours out there, and a lot depends on how badly the beer has been infected. Fortunately, an off beer is not dangerous to drink it just tastes bad!

The two main causes of these off flavours are bacteria and wild yeasts. Both love beer wort (all that sugar) and cause off flavours by metabolising it and creating nasty compounds and aromas during fermentation. If there are enough of them around, they get a head start on the brewing yeast and take over and spoil the party. But, if they are limited to a minimum by careful sanitising, the brewing yeast gets the job done with no complaints or competition.

So, when and where do we sanitise? Well the good news is that during the first two thirds of the brewing session we simply follow good hygienic kitchen practice -keeping things clean - there is no need to use sanitiser yet.

The simple reason for this is that the wort is boiled with hops for a full hour before being cooled and transferred to the fermenter. This sterilises it completely and absolutely, and, only once it has dropped below 70 degrees do we need to step into action with our sanitising regime. -For extract or kit brewers who don’t boil, make sure to sanitise your can opener, spoons and fermenter
before opening and the diluting the extract (which is already sterilised in the container).

We then sanitise any and all utensil making contact with it, be it a thermometer or stirring spoon- the wort is now at its most vulnerable. This isn’t a time to take a break for a beer. You should transfer the wort to the fermenter as soon as it is cooled! A well washed, sanitised fermenter and utensils at this crucial time will avoid problems later down the line.

To prepare for fermentation, bottling and in general, brewers follow a two-step process for cleaning brewing equipment. It’s pretty simple- a powerful powdered brewery soap such as Oxydet dissolves off any organic matter (beer or wort residue, hop gunk) followed by a sanitiser that kills any bacteria or wild
yeast that may still be on the surface.

Two popular brewers’ sanitisers are Iodophor or Acidisan. Both are food grade and are ‘no rinse’ meaning that the dilution is so low that there is no need to rinse with water after sanitising. This is good news as it saves time (and water). Mix up a half bucket to have on hand for sanitising various things as you go- your transfer hose, fermenter, thermometer and so on. You should wash and sanitise your fermenter immediately after bottling and then sanitise again just before the next use. The same applies for your bottles when bottling. A brand-new fermenter should only need to be well sanitised.



Ask any pro brewer and they will quickly tell you that cleaning and brewing go hand in hand, and that there is never a ‘leave cleaning for later’ approach (tired as you may be!). The simple reason for this is that any brewing or beer residue left behind will attract bacteria and invites trouble into the brewery.
So, get into a habit of cleaning as you go and rinsing and washing as soon as an item has been used. Even the beer bottle you just finished that you plan on re-using! This new habit will ensure you hopefully never have to deal with the heartbreak of a bad batch.

Lastly, a few other things can help against infections as well as help brew better beer. A healthy yeast starter (or two sachets of yeast) will kickstart a strong vigorous fermentation with no room for competitors. Perhaps add a yeast nutrient? Bottle your beer as soon as you are sure it is finished fermenting, there is no need to let it languish in the fermenter.

Lastly, let your beer condition properly- a perfectly aged beer (two to three weeks at room temperature from bottling) -will taste smooth, balanced and fresh. Young beers often taste very slightly of green apples, or a bit harsh, and are not at their optimum flavour yet- so have patience -it will be well worth it!

Enjoy, keep things clean and happy brewing!

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