Adding tails to the mash pre-fermentation?

[Still_Holler]

Would there be a downside to adding tails back into your mash pre-fermentation rather than waiting to add before distillation? Intuitively it seems like a bad idea but I can't pinpoint why. Working with say a 6% all grain mash and EC1118 yeast there is still plenty of room for extra alcohol without stressing the yeast.  

[DrDistillation]

It's a bad idea because it's taking away from what could be fermented ABV wise.  Typically you would want your mash to be so that when fermented it's the "perfect" ABV to carry the flavor you're looking for.  For example 8.5% for a whiskey or brandy.

Now if you were making a wash for a vodka you may use grains or cane sugar or combination and maybe upward of 14% if you can keep the wash from developing off flavors.  So again you would want to maximize the ferment with sugar conversion to alcohol.

The point of the ferment is to create alcohol on it's own.  If you already have some alcohol like feints then you can combine that with the ferment when it's done and about to strip it.  If you strip first then do a spirit run for vodka you may want to add the feints in during the strip to get a distillation from it and help remove flavor.  But if these feints are for a whiskey you would likely not want to strip them again (loosing flavor) but would only add them back to the next strip run to help build a consistent flavor for each run.

Make sense?

[JustAndy]

Pitching yeast into a mash that already has alcohol in it is stressful and damaging to them. At the beginning the yeast are building their membrane walls and reproducing and the presence of alcohol can affect this behavior. There are some components of heads/tails that can be consumed & cleaned up by yeast during fermentation, but I would add to an already working fermentation if that was the goal.