A Feast for the Yeast: Starters
Oxygen is very important to making a proper starter. Unlike in your wort, aerating the starter as frequently as possible is necessary. Those yeasties can’t grow if they can’t breathe!
There are a few ways to oxygenate the starter – stir plate, O2, or shaking.
A stir plate can be costly if bought as is, but there are many tutorials out there that show you how to make one for like $20 – the main part being the extra strong magnet. The stir plate keeps the liquid constantly moving in a spiral, allowing oxygen to consistently aerate the liquid inside. It’s like a giant water ride for your yeast.
Many pros like to use O2 pumps to oxygenate the starter. This way, the brewer has complete control of how much oxygen is hitting the liquid, and ensures the yeast have plenty of oxygen to use up. However, it is possible to over-oxygenate the yeast, so if you plan to go this route – be careful! I’m a fan of Mr. Malty. He has all the answers to how many ppms of oxygen to throw into your starter depending on the size of your mini-batch.
My preferred method is the shake. Just shake your starter as often as possible to keep the oxygen flow. The only caution here is to watch for an overflow of foam – remember, those yeasties are making CO2 in there!