Pitching rate

Now that you have defined your dry yeast weight depending on the number of viable yeast cells you target in your brew, we need to get to another point : what are the effects of low or high pitching rates ?

Pitching low

A low pitching rate will have the effect of slowing the start of the fermentation and increasing the competition from bacteria and wild yeast that are present in the fermentation vessel.

It has been noted, that low pitching rats increase the undesirable aroma levels such as acetaldehyde that reveal grassy and green apple aromas as well as estery levels characterized by fruity banana flavours.

A low removal level of yeast combined to a low pitching rate will increase diacetyl in the brew.  The diacetyl level will also increase in case of pediococcus infection.

High pitching effects

A high pitching rate generates high heat and influences the rapidity of start of fermentation. Pitching at high levels will decrease the Ph and help reduce the bacterial growth; in the same way, the formation of diacetyl will be reduced.