Ermmmm, ok.
Which bit(s) are you referring to, because from what I have read, been told and done this seems to be correct. But I am always keen to learn more.
Which bit of your previous post, or which bit of BS&P? I'll presume the former.
Racking the beer to another vessel to perform
secondary fermentation, as opposed to racking
post fermentation, just for the sake of it (which is what, unfortunately, so many people on brewing forums think 'secondary' is), when performed correctly, does, in fact, perform a purpose. It removes the beer from spent yeast; it allows a small uptake of oxygen from the transfer process allowing the remaining yeast to finish the fermentation more thoroughly, allows the yeast to attenuate fully, and converts unwanted flavour compounds into flavourless products.
Performing a multi-stage fermentation is not everyones cup of tea, nor is it (necessarily) required (although I would never perform a double drop without also performing a secondary fermentation). Here is the last part of what is said on the subject in BS&P. The first line of this quote is of
particular importance.
In any event the yeast must have access to fermentable carbohydrate for the process to succeed. This carbohydrate is provided, as above, by residual gravity in the beer or by the addition of sugar by priming or by krausening. Krausening is the addition of wort from the active
`krausen' stage of the primary fermentation usually at 510% by volume of the green beer. In shorter secondary fermentation regimes yeast activity must be intense to achieve carbonation, purging of the undesirable volatiles, removal of all residual oxygen and chemical reduction of many compounds. This leads to immediate improvement of flavour and aroma and flavour stability.
A real world example would be in an English ale, if using a yeast that throws diacytal (I'm thinking of a particular whitelabs yeast, here, which is a great yeast, but it throws a lot of diacytal)...over time, with aging, the diacytal will clear itself up. Although, by aging the beer, the esters will also reduce. A secondary fermentation
may assist with clearing the (excess) diacytal up in a shorter timeframe, thus allowing you to retain the full ester profile.
ymmv, 2c, etc. And I can't be arsed checking to see if I've spelled diacytal correctly. But it doesn't look right. No doubt if I'm wrong, someone (and he knows who he is
) will correct me. Although checking the spelling would have been quicker than typing this paragraph.
