Thanks for your thorough reply!
Thanks for providing this information. It's really interesting stuff. I'm not surprised by the use of sugar which is fairly common for making table wines all over. The spontaneous fermentation for wine is also not too surprising. I am curious how they are spontaneously fermenting a bread beer because neither baked bread nor refined sugar are good sources of wild yeast. I wonder if it's environmental inoculation or they have a way to transfer yeast from one batch of beer to the next. I'd also be curious to know whether the bread used is the same type of bread you eat or if they make a special kind of bread for brewing.
I can't say this with a 100% certainty, but with my general knowledge of rural Georgian cooking and brewing habits, I can say that:
They don't bake special bread, the stories I've heard about it always involved a source of bread - like a big wedding celebration, or a funeral meal - whenever a fair amount of this traditional bread is baked and then left untouched by the feast, women brew beer.
I have to add that in soviet times, there were sugar-beets grown there in a mass scale and I've also heard adding those to mashing - Russian kvass-making does this too - though I'm not sure whether this is an old tradition or a new one like adding table sugar.
But they must be also using malt, don't know the shares, but these villages also have a tradition making barley malt, so there's some malt and hence maltose, this would start the wild yeast.
I don't believe there is a culture of preserving yeast anywhere in Georgia, thy only culture people store and nurture here are the local yoghurt bacteria.
I am now culturing some yeast from a kombucha colony that appeared in apple juice on it's own and makes very nice kombucha, tastier then another scoby I ordered on ebay. I put some brew in hopped sugar solution, the hopps killed the bacteria, as anticipated, and the yeasts are showing progress on fermenting that sugar; I'll see what the end-result tastes like when the airlock stops bubbling =D
Definitely looks like it's just amylase enzyme. I'm not sure at those volumes you even need to add enzymes. Most base malt has more enzyme than it needs to self-convert, usually by several times. Not knowing the diastatic power of the base malt you have I did a quick calculation using conservative numbers. You should be ok going even as high as half bread and half base malt without needing to add enzymes.
I would mash for longer than normal (75-120 minutes) and test conversion with an iodine test. If you don't have good conversion then I would add enzymes and mash for another 15-20 minutes to give them time to finish the job.
I think of going 40% Malt and 60% Bread. With lots of protein and all the other rests for all the needed time. I like your tip, if the gravity isn't nice enough at the end, just use the enzyme-help for that occasion^^
Something like this:
For 10 litres of ale.
1.1 kg Basemalt
1.6 kg roaster and crumbled bread
Perle hops for bittering - 20 grams, 1 hour
Perle hops for flavouring - 5 grams, 10 minutes
As for yeast, I have US05, S04 and S-33 available. I don't want the yeast to interfere in the tasting of the bread flavor, so I think of using US05 - do you think this is a good choice?