Yeast is vital in home brewing, as without it, fermentation couldn’t take place. All wine, beer and cider kits come with a packet of dried yeast, while many brewers also use dried yeast when making their own wine beer or cider from raw ingredients. In many cases, the instructions on the packet, or supplied with the kit, will tell you to sprinkle the yeast directly onto the wort (beer) or must (wine & cider), leave for a few minutes and then stir in.
While this certainly works, it’s not the optimum way of starting your fermentation. Dried yeast first of all need to rehydrate, before they can start to multiply. To do this, they need to absorb water through the cell wall. However, by pitching directly into wort, or must, you are adding the yeast to a high-sugar environment, which can inhibit the yeast’s ability to rehydrate, or put strain on the yeast cells. In many cases, 50% of the yeast cells pitched straight into wort or must, will die of straight away. This means that it takes longer for the surviving yeast to multiply enough to form a healthy colony which is able to start fermenting that sugar into alcohol. This is a bad thing!
Rehydrating yeast before pitching will produce a much healthier colony, which will start fermenting sooner, reducing the lag before you first start to see airlock activity. You are also less likely to see a stuck fermentation, when you rehydrate your yeast correctly. Some packets of yeast do come with rehydration instrucitons, but if not, here’s how you rehydrate your yeast for maximum effect:
How to rehydrate yeast
Using boiled water which has been allowed to cool to 35-40°C, measure out 10-times the volume of water, as you have yeast. So, for a 12g packet of yeast, measure out 120ml of water, into a sterilised glass. For a 7g packet, measure out 70ml, and so on. Use a sterilised thermometer to check the temperature is correct, then sprinkle the yeast onto the water. Cover with cling-film and leave for 10-15 minutes. After 10-15 mins, the yeast should have sunk to the bottom and you should see some foam on the water’s surface. If there is still a lot of yeast on the surface, give it a gentle stir with the thermometer to ensure all the yeast is wet and leave for a few more minutes. Don’t leave the yeast for longer than 20-30 minutes though, as the yeast will start to deteriorate without food.
Ensure that your must or wort is at the correct temperature and that there is no more than 10°C difference between the yeast and the wort or must. If the difference is too much, you can shock the yeast, leading to mutations or cell death. Pitch the yeast into the wort or must and give it a good stir. Fit the airlock and leave to ferment.
Feed your yeast!
To give your fermentation even more of a boost, add nutrient to the wort/must. This will ensure that the yeast have plenty of food to get started, helps to reduce lag, decreases fermentation time and reduces the chance of a stuck fermentation. You can use Yeast-Vit for beer & cider, Vitamin B1 tablets or yeast nutrient for wine, cider and mead.