What is the Purpose of Adding Malt Sugars Towards the End of the Boiling of the Wort, as Opposed to the Beginning?

Late addition also compliments partial boil. For an extract brewer, using less water and delaying additions of extract make it possible to brew on just about any stove top. A full boil with all the extract up front versus a partial boil with extract held back will have similar utilization, because the gravity and composition is made similar by the techniques. I don't know about beer smith but brewtarget has a check box for 'late addition' which doesn't affect SRM (in the software) but does increase hop utilization. This way you can take a recipe that anticipates a full boil and make it a partial boil and use late extract additions to see if you need to adjust hops for the anticipated IBU. To state the obvious; doing a partial boil without doing late additions drastically reduces your hop utilization. Also, late addition is a technique best used with LME. DME will ball up and be difficult to dissolve in solution at high temps.

This technique of holding back the extract until the end of the boil is a fairly new concept that's caught on in the last few years. Here's some reasons why its a good idea in general:

• Faster time from the start of the boil to the 1st hop addition
• Less chance of a boil over
• Less caramalization/Mailiard reactions of the extract (leading to lighter colored beer). This is probably the biggest benefit.

To answer Scott's concerns in his comment above:

• The Hop Utilization for this recipe was formulated with LATE MALT ADDITIONS IN MIND, so there's no problem there. Northern Brewer certainly knows how to account for the change in utilization. You might actually end up a few IBU's off the recipe target, since you didn't follow it precisely (but I wouldn't worry about it, human's mostly can't detect anything less than a 5 IBU difference anyway).

• Hot Break isn't a problem because malt extract has already been "hot-broken" when it was condensed into syrup. This is also the reason why DMS is less of a concern for extract brewers, because the process of turning wort into extract at the factory boils off most DMS precursors and of course also creates a hot break. The hot break proteins might still be IN the extract, but since you can't unscramble an egg, they do not require re-breaking, and will fall out just fine in the fermentor.