The amount you need is less than a bee's wienerblackbeard2 said:I know it's not strictly a "nutrient" for the yeast, but have you tried or considered adding a minute amount of olive oil?
https://www.google.com.au/webhp?tab=ww&ei=6afLUovlJ8WBlQXb8oHgBw&ved=0CBUQ1S4#q=olive+oil+yeast+starter
Seems to be lots of homebrewers claiming that it improves fermentaion in one way or another, meets your criteria for being a readily accessibly, common ingredient. The biggest issue I see with it is being able to accurately measure a small enough quantity of it for ~ 20L of wort.
Don't know what boiling would do to the nutrients in the dried grape. Have only ever used commercial yeast nutrient in beer and raisins as described previously in meads and ciders.TimT said:Superstock - boil to kill the wild yeasts. Though this may not matter either - stronger yeasts will almost always dominate. Perhaps boil as a precautionary measure.
Commercial yeast nutrients are concentrated chemical salts, ignoring the dead yeast type, and as such are probably not affected by the boiling. But use too much and you can affect the taste. Natural nutrients are less concentrated and so you need more of it by volume but it is almost impossible to overdose, although I imagine large volumes may add flavour. Also if you put the raisins in whole, the yeast have to wait until the skin becomes permeable before they can access the nutrients. This may inhibit the yeasts growth.TimT said:I wonder a bit about the boiling too Superstock, though given that others recommend throwing yeast nutrient into the boil anyway maybe FAN isn't particularly affected by a boil.
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