Yeast, and why it's important in making home brew beer
Yeast are important little beasties in home brew, yet too often are forgotten about, like the leftovers at the back of the fridge. But improving the yeast process is an easy and cheap way of brewing better beer.
Yeast feed on sugar as the beer ferments. As they feed, they turn the sugary substance into an alcoholic one. They also lower the pH to decrease the levels of bacteria, and release carbon dioxide and flavour compounds to make your home brew beer fizzy and tasty.
You need it, your dog needs it, even your car needs it. So does the yeast for your home brew. When you boil your wort, it loses oxygen, so before you pitch your yeast you need to put it back in. You’re aiming for 8-10ppm (parts per million) of oxygen.
There are a few ways you can add oxygen at this point in the beer-brewing process:
- Splashing – either pouring the wort through a tube with a spray device on the end, or transferring it between two sterile vessels a few times. It’s not the most effective method, but it does the job without needing extra bells and whistles.
- Agitation – also referred to as stirring or beating. Either rock the fermenter, or whip it with a sterilised spoon or whisk until there’s a few centimetres of foam on top. This method will get you slightly more aeration than splashing.
- Adding pure oxygen – the simplest way to do this is to use a sterile oxygen pump and filter, just like you’d use in a fish tank. For maximum results you could use an oxygen bottle.
If you want yeast to do its job to the best of its ability, you’ll need to feed it. The easiest way to do this is to add some yeast nutrient to your home brew. This is like Sunday morning bacon and eggs for yeast, giving you a better fermentation and much better home brew beer. It also reduces the diacetyl content in your beer, which is good because too much of that makes the beer taste rancid.
Keeping your home brew beer at a good consistent temperature is essential for good fermentation. In fact, if you run into problems, the temperature should be the first thing you look at if it turns out it’s not caused by contamination.
If you need to keep your home brew yeast warm and toasty, invest in a heat pad, or a heating belt that fits around your fermenter. A temperature controller is also handy to regulate your heating or cooling device to maintain a constant temperature.
Other home brew tips and tricks for yeast
- When you buy a home brew refill kit it will come with yeast. However, there’s no way of knowing what kind of quality the yeast is, and how long it’s been sitting in the kit. Instead try using a specialised yeast – this way, you’ll get the right yeast for the beer you’re brewing and the quality will be way better.
- If you’ve ever tried to make bread, you’ll know that you usually rehydrate dried yeast before using it. Do that for home brew beer, too. Rather than just sprinkling it on to your wort, dissolve it in a little bit of warm (24-30 degrees), sterile water first – it’ll make a difference. Read the data sheet for the yeast you're using to get more specific instructions.
- The quantity of yeast matters. To work out the amount of yeast you need, use this calculator. You might find you need to make a yeast starter to get the best results from your home brew beer.