The Different Meaning Of Sour Mash In the 1800s


Making Fine Whiskey Without Adding Yeast

An 1881 insurance article described in some detail the production of whiskey in America (see pp. 137 et seq). It is a succinct and accurate account of the subject, necessitated by the importance of the industry and its evident risk of fire hazards. That risk, while lessened today, is always present: a good part of Heaven Hill Distillery burned to the ground 20 years in Bardstown, KY, a devastating fire whose origins were never determined.

Following some verbal play involving rosy-hued Bacchus, handmaidens, and the temperance man Gough, a clear but detailed description of whisky-making appears. In this period, there was sweet mash whisky, sour mash whiskey and “alcohol” (Cologne spirits aka neutral spirits aka plain spirit). Some producers, distilling and non-, blended whiskey and alcohol, and we have seen earlier how Ontario distillers created Canadian whisky in the process.

This was a time when sour mashing still held connotations from the early 1800s. As the author explains, sour mash meant, not even that yeast from an earlier ferment was used in the next, but that backset could create a fermentation on its own. Backset, for which there are many synonyms e.g., slops, setback, pot ale, is simply the spent beer from a distillation. It is the un-condensed liquid which drains away after the alcohol is extracted by the heat of distillation.

This liquid comprises acids, some alcohol, enzymes, proteins, dead yeast cells, maybe glucose, burned sugars, and a host of other organic and inorganic chemicals. It depends on the feedstock, and concentrations vary depending whether re-cycled process water is added: this analysis from Florida researchers is something to ponder. Adding backset to a mashing or fermentation vat was and remains a way to inhibit unwanted bacterial action. Its effects can be emulated today by acidifying mash water, yet some claim backset contributes positively to flavour – I’m not sure why since its elements were not volatile to begin with.

My understanding is Canadian distillers don’t usually do a backset sour mash, either they acidify with food-grade acids or they don’t use even these, relying on modern sterile plant conditions to ensure yeast dominance and a predictable result.

This part of the history of backset use is not controversial but another part is less well-understood. When you read, as in the 1881 article, that backset serves the function of yeast added to a ferment it seems a riddle. How can a boiled substance, one in which all live organisms are killed by high temperature, provide a source of yeast? For this reason some have thought that old books when referring to pot ale or backset as a fermenting mechanism must have meant the dregs of the cereal beer ferment, the stage just prior to distillation.

Callwood-DistilleryIn fact this is not so. The old books were correct and the key to understanding them is to examine the role of dunder in Caribbean rum distillation. As this Victorian chemical encyclopedia confirms at pg 114, fresh dunder contains no live yeast.

But the dunder used as backset in mashing or fermentation is not fresh. As the account explains, by exposure to air it acquired a new fermentative capability, a “regeneration”. Wild yeast sought the dead yeast as a nutrient source in addition to sugars and caramel in the backset. Dunder was stored in pits dug in the forest and became bioactive, indeed an innoculum; one can imagine that vegetation fell in and provided yet further material for wild yeast propagation. Use of dunder in a new ferment was enough to turn the grain sugars into alcohol without any yeast being added.

Obviously exactly the same thing happened with corn and rye liquor backset on the American frontier. The effect was noted as early as 1818 by Pennsylvania distiller Harrison Hall, see the footnote at pg. 125 where he wonders how Kentucky and Tennessee distillers achieved the results they did without adding yeast. He did not understand the causes but science gleaned them later in the same century.

This hand made way of fermenting was slower and less efficient – less attenuating in technical terms – than adding measured amounts of a fresh yeast of known properties. By the end of the 1800s, it is doubtful many distillers were sour-mashing in the old way, but one or two may have continued into the 1950s. The term “small tub distilling” may in some cases have pointed to the old method.

Thus, sour mashing today, practiced by all Kentucky and the large Tennessee distillers, is different from what it meant in the 1800s.

The old sour mash was said to produce a richly fruity whiskey, just as dunder is said to produce estery and complex heavy rums. Also, it required a different aging regimen, a couple of years longer to get optimum results.

The new Last Barrels Canadian whisky from Wiser, which I discussed a couple of posts ago, is a sour mash whiskey, apparently a little sour milk was used to impart the lactic acid needed. This would be a modern sour mashing – and it is very good.

I am not aware any modern distiller has made sour mash in the 19th century sense, any information to the contrary would be gratefully received.

Note re images above: the first image is from this distiller’s yeast supplier’s site. The second, from this resort’s website. All intellectual property therein belongs solely to their lawful owners. Images are believed available for educational and historical purposes. All feedback welcome.