I have read that it is very difficult for homebrewers to over-pitch yeast. (For example, in Palmer's "How To Brew.") Can anyone explain why this is the case? Or the extent to which it is the case? For example, I would *love* to split 5 gallons of wort into five 1-gallon mini batches, and pitch a different liquid yeast package into each batch to see the differences in the yeast character, but I worry that this will finally be a homebrew scale over-pitch. Any advice?
It's no easier and no harder to overpitch with homebrew than it is with commercial beer. Overpitching tends to be more forgiving than underpitching, but that applies to beers regardless of where they are brewed. If you don't already have a pitch rate in mind, I'd recommend using one of the yeast calculators to figure out how much yeast to pitch. There's nothing that says you can't use a partial tube/pouch, if that's the appropriate amount.
I suspect the statement that it is difficult for homebrewers to overpitch conflates the reality that it is more likely that homebrewers will underpitch. Reasons for underpitching are that much of the yeast sold to homebrewers is low in volume/cellcount, and may be subject to uncontrolled conditions during shipping that reduce viability and vitality of the yeast. To add to this, many homebrewers want to make big IPAs and stouts that require even more yeast, and many new homebrewers may be uncomfortable or ill-equipped to make yeast starters. Is it easier to underpitch? Well, only in as much as it is difficult to obtain enough yeast to overpitch. And +1 to using a calculator and pitching partial packs of yeast if that is what is called for. If you are set up for it, you can save the yeast (there are at least a few youtube videos to show you how), and if you are not, no big deal.
