Dear Mr. Wizard,
Is it okay to mash and lauter your grain and then store the wort in the fridge until you have time to go through the boiling/cooling/racking-to-fermenter procedure?
Mr. Wizard replies: Some brewers use a technique called flotation to separate cold trub (the solid matter) formed during wort cooling from the wort. The old method of flotation occurs before yeast is pitched and lasts up to a day. Brewers who still use the flotation method add yeast prior to flotation because of the microbiological problems associated with storing unpitched wort. I know of at least one manufacturer of malt extract that stores the wort near 30° F for about a day prior to concentrating the wort. This process helps make the finished beer clearer, and the very cold temperatures greatly slow microbiological growth.
The rule of thumb is to cool your wort, add yeast, and get a vigorous fermentation going in the shortest period possible. The result of this practice is that the wort pH is quickly reduced from about 5.2 to 4.5, and the population of yeast in the wort rises. These two factors are strong inhibitors to microbiological spoilage and help the brewer produce a beer from a single strain of yeast. Contrast this to the technique used by Belgian lambic brewers in which the hot wort is cooled in large, shallow coolships exposed to outside air. The result of that practice is a fermentation by many species of yeast and bacteria.
If you really want to homebrew but find the brew day too long and don’t mind the possibility of a bad batch, try wha you propose. I would cool the wort as fast as possible and store it very cold in a closed container. You might be able to hold the wort for a day or two before boiling it, but I wouldn’t shoot for the moon and attempt to store it for a week with such a perishable ingredient.
Mr. Wizard, BYO's resident expert, is a leading authority in homebrewing whose identity, like the identity of all superheroes, must be kept confidential. To see more of Mr. Wizard, check out the latest issue of Brew Your Own available at better homebrew shops and bookstores.