I've seen recommended on these forums that you add your LME later in the boil if you don't want the brew to turn too dark. I'm assuming the length of the boil (typically 60 minutes) is for the benefit of the hops, which (correct me if I'm wrong) I think is to provide preservation effect on the beer, at least the hops that you add in the beginning.
My question is does this happen if I just boil water and hops with no malt extract, or must some malt extract be present for the correct effect? I'm thinking about just boiling the water and hops and finally adding the LME during the last few minutes. How would this differ (besides lighter color) to adding all the LME at the beginning if I haven't changed anything else in the recipe of procedure?