Wyeast Beer Nutrient Blend usage

[Junket]

The instructions for Wyeast Beer Nutrient Blend say to dissolve in water, then add to boil at 15 minutes.

Any ideas about why I can't just add the nutrients directly to the wort at any time in the boil?

[ajdelange]

The instructions on the tubes I have say to dissolve in warm water and add 10 minutes before the end of the boil. One can only assume that something in the composition is heat labile so that exposure to heat should be limited.

[Junket]

Just got this info back from Jess at Wyeast:

It is not necessary to [add nutrient at the beginning of boil], but realistically, I don't think it will drastically alter anything vs adding it at 15 minutes prior to end of boil. The thought behind adding it at the end is to allow time for sterilization, but minimize the time interacting at high temps with the trub, etc that is in the kettle that could "chelate" or bind up some of the nutrients and not allow them to pass through to the wort.