What – exactly – is Sour Mash?

Have you ever been to San Francisco?

Ah, you gotta go.  It’s great.  I could go on and on about all the wonderful things to do in the city, but of all of it, one of the things at the top of the list is to make sure you enjoy a meal including San Francisco Sourdough Bread – specifically from the Boudin Bakery.  They’ve been making sourdough bread – from the same culture, which they call their “Mother Dough” – since 1849.  It’s this mother dough that has given a ‘unique tang’ to their traditional-style french bread.  So what does this have to do with whisky?

Danger – geek stuff ahead: Whisky is made using 5 steps (sometimes known by different names); Malting, Mashing, Fermenting, Distilling and Maturing.  Malting converts complex sugars and carbohydrates into fermentable sugars.  After Malting, you mill the grain into something called ‘grist’ – which is a combination of meal, husk and flower.  Put the grist into warm water to create Mash – something like porridge – which is sweet (remember – fermentable sugars).  To this, we add yeast which will eat up all the sugars and convert it into CO2 and Alcohol.  What once was sweet, is now sour.  At this point, we’re going to separate the solids from the liquid.  The solids will be sent for animal food; happy cows.  The liquids (which is 8-10% Alcohol-By-Volume – called ‘Wash’ or ‘Beer’) is sent on to distillation.

Jim Beam, Jack Daniels and a host of other whisky makers include the statement on their label – “Sour Mash.”  This commercial from the 1980’s for Kraft Cheese Singles talks about how their cheese is made from 5oz of milk in every slice.  It takes about 6 ounces of milk to make an ounce of cheese (with Kraft singles at only 2/3 of an ounce it’s a little on the low side, but we’ll leave that one alone) – so why don’t other cheese-makers put the info on their packaging or in their commercials?  In a word – Marketing.

If you make a product, one of the ways to ensure the consistency is by taking a little bit of the previous batch and including it in the next – which is exactly what whisky-makers do.  Remember that sweet mash?  When we separate the solids from the liquids after fermentation, we hold back a portion of those solids and add them to the next batch of sweet mash going in for fermentation.  The industry term for this is “Set-Back” – and just about everyone does it.  At least the US whisky-makers do.  This set-back acts much like a sourdough starter.  Just like our friends over at the Boudin Bakery, whisky-makers in the US could trace portions of their mash back decades.  It gives us a taste of what whisky was like back them, but more importantly it ensures the whisky will be the same for years to come.

Next time you’re at the pub, raise your glass to sour mash – whether it says it on the label or not.