I've been brewing for ~40 years. IMO under-pitching means you haven't given the yeast manufacturer enough money. Assuming you rack your brew to a secondary fermenter, you may notice the amount of cream yeast in the bottom of your primary. I am a 5 gallon brewer and there is always more than a quart of slurry (cream yeast) in the bottom of my primary. The amount of yeast remaining in the primary is more important than how much was pitched in the beginning.
If your brew Kreusens in the first 12 hours, then your pitching is just right.The brewing of ales is an incredibly forgiving process. I don't pay much attention to the numbers unless something goes wrong. I find Augie Busch's approach of tasting everything to "see" what each ingredient and each process contributes to the final result a more reliable guide to a tasty brew. Biologically, the art of brewing ales is the practice of caring and feeding of yeast. ericbw's response explains that aspect quite well. May your yeast always be happy!
PS I frequently use the cream yeast as starters for making bigas into bread.
If your brew Kreusens in the first 12 hours, then your pitching is just right.The brewing of ales is an incredibly forgiving process. I don't pay much attention to the numbers unless something goes wrong. I find Augie Busch's approach of tasting everything to "see" what each ingredient and each process contributes to the final result a more reliable guide to a tasty brew. Biologically, the art of brewing ales is the practice of caring and feeding of yeast. ericbw's response explains that aspect quite well. May your yeast always be happy!
PS I frequently use the cream yeast as starters for making bigas into bread.