Obviously it is better to immediately boil the wort when it is freshest, giving any wild yeist or bacteria as little time as possible to grow and contaminate the product. It is also a well established practice to mash all of a recipe's different grains together simultaneously. These practices work wonderfully when brewing a single recipe at a time.
I am knocking around the idea of brewing multiple, smaller (2-3 gallon) batches simultaneously to allow more experimentation in my recipes. Beyond just revising the hopps/add-in timings, I want to play with the grain-bill, changing the quantities of each grain slightly for each batch. With extracts, that would be easy, but mashing each small batch seperately would be far too time consuming.
So here is what I have in mind...
Mashing each of my malts and adjuncts seperately in 5-10 gallon batches, then after sparging, cold-crash the resulting "single-malt" wort in a chest freezer. By recording the OG and volume of each seperate batch, I should be able to calculate a grain-weight to wort-volume ratio which I can use later, when translating my grain-bills from weight-based to volume-based. The mashing could all be done ahead of time, over time and in volume, so that on brew-day, I can start with a freezer full of different, nearly frozen, "single-malt" worts. From there, boiling up a bunch of small custom batches should be quick and easy; just mix in the appropriate ratios of each wort, and proceed to the boil.
So my questions "boil down to"...
Assuming that the freezer keeps the un-sterilized wort free of wild growth, what other negative-effects should I expect from the wort's time in cold-storage?
What time scale is safe for storing un-sterilized wort at cold-crash (but not frozen) levels? (a day, a few days, a week, or hopefully... weeks)
If any of you have tried something like this before, or if you've come up with another method of efficiently experimenting with small all-grain batches, please share your wisdom!