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A long-time client and friend called me one day and said: “Listen, our production guys messed up a batch of Rye and the mash bill is all wrong. We know exactly what went into the mash/ferment, and we’ve calculated how to adjust our Bourbon mashbill so that we can blend-in this mistaken Rye distillate in small percentages over time while maintaining our existing Bourbon mashbill percentages.”
It’s natural to assume this “transitive property of mash bills”. To evaluate, let’s consider some unaged whiskey distillate, fresh off the still, sitting in tanks.
One would think that evenly blending a 51% Rye / 49% Corn distillate (Rye Whiskey) with a 100% Corn Bourbon distillate (Bourbon Whiskey) would yield a finished product that is Bourbon, with a mash bill of 75.5% Corn, 24.5% Rye. This is the mash bill ratio that you would get based on the simple math, and these mash bill percentages qualify it for Bourbon based on a quick reading (i.e. all grain, >51% corn).
In fact, this is not the case. In choosing to blend those two distillates, you have possibly run afoul of federal regulations, and you have created something other than Bourbon or Rye. You’ve created a blend which can, at most, be called “Whiskey” or “American Whiskey”. In the blending, you’ve lost the right to call the liquid Bourbon or Rye, since the mixed product no longer meets the standards of identity for either.
This remains true even if you are combining two different Bourbon mashbills. If you evenly mix some 36% Rye Bourbon with some 10% Rye Bourbon, you do not have a 23% Rye Bourbon. Instead, you have commingled (not blended) two different mash bills of Bourbon, and the resulting mix can still be labeled as Bourbon. However, if you want to make a label claim about your mash bill, you must call out the fact that it is a mix of spirit distilled from multiple mash bills.
Federal Regulations require you to establish the identity of your spirit as soon as it comes off the still. The identity is determined primarily by the fermentable type (e.g. grain, cane, fruit, etc) and the proof at distillation. Once that liquid has been collected from your still, its identity is fixed and can only change through a subsequent Processing operation. You cannot blend or mingle different types/kinds of spirit in your Production account and then re-assign its identity upon barreling/storage. There must be a straight line of consistent recordkeeping from your mash bill to your finished product illustrating that your product meets the standards of identity under which it is bottled.
