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I get usually about 1/4in of sediment towards the end of the fermentation. Does anyone know weather this predominantly dead or live yeast.
I propose to use some and boil it to act as a natural nutrient for a troublesome ginger beer starter bug. They are different yeasts , other is a pale ale yeast. Is this a good idea or should i just buy commercial nutrient.
Yes, yeast cake can be used as a nutrient base with some caveats. It is better if it is not from a very hoppy beer if you want to use it for ginger beer using a SCOBY (the tiny little grains of gel that make a "real ginger beer bug"). Hops are usually tolerated by yeast but the lactobacillius in the ginger beer SCOBY can be inhibited by the hop acids. So adding any amount of hop essence will be detrimental to the bug. In my experience the yeast from a (low hop) lager brew can be strained, rinsed well and decanted a few times. Then the rinsed slurry, which is by then mostly hop free, can be boiled up and used as a nutrient base. Others I have talked to have used a teaspoon tip of "Marmaite" or similar yeast extract product in 2L of water with reasonable results. It might be added that the ginger beer SCOBY seems to work well (over a period of many years) with just ground (or fresh sliced) ginger and sugar. It does take a little while to start and does require oxygen to grow. A thing often forgotten by those using a demi-john with airlock rather than the more traditional muslin covered open vessel. And keep it warmer than cooler. Above 18C is a good place to start - and 20C is often better. Ginger bug tends to "hibernate" below 10C.
Yeast-wise, a yeast cake contains enough live cells to process a heavy beer, and some people brew small beers for the entire purpose of getting a yeast cake that they use in heavy beers then.
However, yeast cake contains not only yeast cells, but all sorts of hot/cold break and hop particles that you probably don't want to add to another beer, especially one that is quite different from the one that produced your yeast cake.
As an economical yeast nutrient you can just use dry baking yeast. I always have a rather big can of that at home, as I bake a lot, so occasionally boil a tablespoon of dry baking yeast together with my starter solution.
That yeast sediment is a mix of coagulated proteins, hop byproducts, dead and resting yeast.
It is possible to use this as a base in order to pitch into a new batch, however you will need to wash that sediment in order to get the yeast and make a new starter. Example of instructions here : http://homebrewacademy.com/yeast-washing/
I guess you could also use this washed yeast as a nutrient. Even maybe the complete cake, but be careful with byproducts that could bring off-tastes if you use too much.
