A yeast starter is a fluid in which you have created lots of yeast cells in their perfect environment. In wine and beer making it is not uncommon to make a yeast starter the day before wine or beer making.
The main reasons are:
You know for sure that your yeast is working. When a yeast is stored for a longer time or at higher temperatures it is possible that the yeast cells will die. When you add this yeast to the must there will be no activity and you risk losing your must. In this case you also do not know why the fermentation did not start.
To increase the number of working yeast cells. When you want to ferment a big amount of must you want to add a lot of yeast cells so that wild yeasts or bacteria are not able to spoil your must. The sooner it is fermenting, the better.
When you are making only a limited amount of wine you should not add too much starter or make the starter from the juice that you want to turn into wine. You can imagine that a red wine would be influenced when you add a starter made from apple juice.
I do not make a starter in most cases because I know that the yeasts that I use are ok. I rehydrate the yeast 15 minutes before I need it. I put the yeast in a cup of room temperature water. It is best to use water because when yeast becomes active it may not be resistant to all elements in the juice. After 15 minutes you can smell the yeast and perhaps notice a little activity.
Making a starter is not only useful, it is also interesting to see what happens. In fact you are creating wine on a very small scale. And it is spectacular to watch. Especially when you use a bottle with a small diameter.
It is very simple and you do not need any special equipment. As usual you have to clean everything thoroughly.
Put 50 gram of sugar in a bottle.
Add 1 gram of citric acid.
Add 1 gram of yeast nutrition
Add 500ml apple juice
Shake until everything is dissolved. This introduces oxygen in the fluid which is good for the yeast.
Add the yeast (Do not shake)
Close the bottle with some paper towel and a rubber band (No cap)If you don’t have citric acid or yeast nutrition you can omit them. After a few hours you will see the yeast forming CO2 gas which drags the yeast upwards causing these explosions in the bottle.If you do not have special yeast for wine or beer making you can do this experiment also with bread yeast. Leave it until the fermentation has stopped and the fluid clears up. The finished product is cider.Hans