When increasing a starter in steps, should the steps be a certain size?
Yes, but there is plenty of leeway in the size of the steps. A “step” is when you take an active starter and increase the volume with more wort. Brewers do this to increase cell mass, while keeping the rate of growth consistent. The size ratio of one step to the next can affect the health of the yeast and the amount of cell growth. A very large step can result in a change in yeast metabolism, where the sugars that are fermented last can fall out of favor with the yeast. The yeast become lazy and subsequent generations can become lower attenuating. Making a greater number of small steps increases the chance of contamination. Every transfer, every feeding, every bit of handling you do increases the chance of contamination. Five to ten times the size of the prior step is considered correct. You should try to balance the practical considerations of handling, sanitation, and cell growth.
