dtapke said:
from my pretty brief reading up on the enzymes, it would seem the glucoamylase or Alpha-glucosidase debranches maltose to two glucose units.
Maltose is 2 glucose, joined at the (1-4) bond. Beta Amylase makes this. Alpha Amylase breaks the (1-6) bond. Given enough time, Amylase can produce both glucose and maltose, but not as effectively as Beta Amylase.
whereas alpha-amylase is primarily responsible more for breaking down starches into maltose and glucose. I'm still mostly an idiot when it comes to all of this so perhaps my understanding is wrong, as it would seem an addition of both would be beneficial at certain points.
For fermentation, maltose and glucose matter. Polysaccharides (aka dextrines) are not usable by beer yeast because they don't produce the enzymes. The flora associated with "wild" fermentation do have the enzymes, but that's not part of making a Brut.
What's important is the cell walls of the yeast. Healthy yeast will utilize maltose. Unhealthy, under pitched, under oxygenated yeast tend to make cell walls that process only glucose. In any all malt wort, glucose is 3% to 4% of the available sugars. Once the glucose is consumed, the yeast stalls out. OTOH, in even high alcohol environments (>6%), yeast will consume glucose (and dextrose). The speed of consumption is determined by how much contact the yeast has, meaning flocculated yeast is slower than when it;s in suspension, of course.
However glucoamylase seems to be the enzyme thats "making the style" in some ways, which seems mildly odd to me as my understanding of yeast is that they can use glucose and maltose with no issues, so an enzyme that breaks down maltose into 2xglucose isn't really that helpful?
There is a whole family of amylases that all pretty much end up in the same place: digestible sugars.
Glucoamylase is a "digestive" enzyme that has two parts, each working on different substrate. It'll break existing starches into polysaccharides, then break those into simple sugars that yeast can consume.
In terms of fermentation results, there really shouldn't be any functional difference. However, the types of sugar produced and the yeast strain can always interact to give unexpected flavors.