I've read that certain proteins denatured during the wort boil is responsible for causing great, delicious foam.
I don't get me no foam.
I'm also doing partial boils using extract.
So my question is twofold: I could boil 10 liters (out of 25) with the hops for ~60 minutes, and then boil an additional 10 liters of malt/water for a shorter time. How long would that shorter time have to be to denature the protein? 5 minutes? 10? 60?
Also, since I am using extract my wort comes preboiled. Does this mean it doesn't matter if I boil all malt or not? Does it mean that I will have worse head retention no matter what, compared to all-grain?