Typically, the 5 g packets sold are fine for batch size up to 5 gallons. If you scale a recipe down to a 1 gallon batch, you can use the whole packet, so increasing the amount of yeast is certainly not going to hurt anything. I don't yet know enough about beermaking to spot if there's anything exceptional about this recipe that might require it...
Some folks here regularly "over-pitch" for their meads, but I usually don't, I figure if I double the amount of yeast required, all it's doing is taking 90-120 minutes off the time it takes to get it going (this is the approximate amount of time it takes for a single yeast cell to multiply, so the doubling time for the whole culture). If you've ever seen a graph of something that doubles over time, it'll start off slow but get very high very fast (logarithmic, if I recall correctly), even if you start with 1 cell, soon you have 2, then 4, then 8, then 16, then 32, then 64, then 128, 256, 512, and so on... of course, in a closed environment, they'll slow down the rate and stop reproducing when they start nearing the maximum colony for the environment. My point is, one doubling in the grand scheme of things really isn't much, they only get to their population threshhold one doubling time faster... Of course, having tried under-pitching running on this same theory, it often works out fine, but every now and then, it doesn't. And yeast packets are cheap, for a $1 purchase, it's not really worth the risk of having something else get there first.
Last edited by Chevette Girl; 05-13-2012 at 02:21 PM.
"The main ingredient needed is 'time' followed closely by 'patience'." - The Bishop 2013
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