Recently Bryan Davis, organic chemistry “hacker” and co-owner of Lost Spirits Distillery walked me through his presentation on creating highly flavorful rum that he gave at the Miami Rum Renaissance in April 2014. In this post I’ll present a summarized version, yet still filled with details you don’t normally hear about in distiller descriptions. While I’m focused mostly on rum, Lost Spirits Distillery also makes other spirits including some award winning Whiskeys. Almost all of the “science” below applies equally to rum, whiskey and their other spirits.
At the 30,000 foot level, the flavoring of a spirit involves a series of steps in a pipeline. At each point, biological and chemical reactions occur that add, modify or remove the organic compounds that are ultimately what we perceive as flavor. The basic steps of rum production: creating a mash (molasses in the case of rum), fermenting it, distilling it, then barrel aging it are essentially the same from producer to producer. What Bryan Davis does particularly well is understand exactly the chemical reactions taking place at each stage, was well as knowing how to impact the steps so that the desired flavor compounds come through and the unpleasant compounds are minimized.
When you read tasting reviews of a spirit, you’ll hear terms like “fruity”, “pineapple”, “cloves”, and “smokey”, used to describe the taste. Those flavors come from esters which are organic compounds. Each ester has its own particular smell and we humans sense some esters at very low concentrations while others require a much higher concentration before we notice them.
What I find particularly fascinating after talking with Bryan is that all the esters in the final rum aren’t necessarily there in the beginning phases. In fact there are points along the way where downright awful smelling acids undergo chemical bonding to alcohols (becoming esters) and come out smelling like wholesome fruity goodness.
Let’s look at a few examples – Don’t worry, I won’t go total biochemist on you, and don’t need to know what Phenylethyl Acetate is. Bryan says that to understand the flavor of rum, you need to understand pineapple, honey, and chocolate. Easy enough, right? Not so fast! Consider this set of organic compounds:
Hopefully you’ll never encounter all that, right? As it turns out, this is the set of esters found in pineapple. While all are present, it’s the ethyl butyrate (ninth down on the left) and ethyl octanoate (top right corner), that are the core flavor of pineapple – By themselves you’d smell the essence of pineapple but not the full spectrum present with an actual pineapple in front of you. Now, if you took this mix of esters, lowered the amount of ethyl butyrate and increased the amount of octyl acetate (third down on the right), you’d get the smell of oranges. Doing the same with decyl acetate (bottom, right) would give you a pear smell. The science of rum that Bryan Davis practices is knowing which esters he wants, which he doesn’t and creating the right conditions so that the desired esters dominate.
So how does this relate to pineapple, honey and chocolate? To get to the desired esters, sometimes you start with something very unpleasant, then make it undergo a chemical process with other compounds to produce a desired ester. Some examples:
Ethanol (the alcohol produced via fermentation)
Butyric Acid (Smells like vomit)
Ethyl Butyrate (The smell of Pineapple)
Now, let’s be very clear – This isn’t simply mixing the two together that produces the desired result. It must be actual chemical bonding.
What about spice? Let’s take cinnamon for an example:
Cinnamic acid (Oak barrels are a good source)
Ethyl Cinnamate (The smell of cinnamon)
Ethyl Cinnamate and related compounds are a subcategory of esters called phenols. Phenols are the spicier, woody part of the smell spectrum.
What would happen if you chemically bonded a fruity ester with a spicy phenol? This is where the honey comes into play:
Ethyl Butyrate (Pineapple smell)
Phenol Ethyl Butyrate (A honey, floral smell)
This last ester above is a “long chain” ester composed of simpler esters. Bryan points out that these types of esters are solely the result of the barrel aging part of the process.
What we’ve just walked through is a very small set of esters. In reality, there are hundreds of esters in play in a rum, typically around 300, as opposed to 80 in a fruit. The entire rum making process is about coaxing all these good and bad esters into a desirable combination.
Seven ways to supercharge flavors
Step 1 – Material selection – What to ferment?
Lost Spirits uses baking grade molasses as their starting point for rums, whereas other distillers will often use lesser quality molasses. This isn’t just a nicety. Sulfur is often used to aid the extraction of sucrose from the pressed sugar juice, and if they used a lesser grade of molasses, the sulfur would need to be removed during the distillation process via higher distillation. While you could do that, you’d also extract out more of the good flavors you’d worked hard to introduce.
A fun side note here – In his presentation, Bryan talks about lignins, which are the complex polymers that give sugar cane stalks their structure. When they stalks are crushed to extract the juice, some amount of lignin remains in the juice. When the juice is later boiled, the lignins undergo thermal decomposition into simpler phenolic acids that we perceive as the smoky flavor from molasses.
Step 2 – Dunder – A bacteria farm
The topic of dunder a “rum story” favorite of mine and amusing to watch people’s reaction when you tell it. During the fermentation process you need a good, plentiful source of bacteria. The dunder “pit” is where you “grow your pet bacteria” as Bryan puts it. It doesn’t really matter what organic materials you put in your dunder pit as long as it helps your target bacteria grow. In old-school rum production the spent mash after distillation was thrown into a pit in the ground to replenish the dunder. Over time all sorts of interesting bacteria fester and multiply in the pit. It’s said that some distilleries even added bat carcasses into dunder pits along with who knows what else. Dunder pits are just a really awful, vile cesspool of bacteria. The bacteria in the dunder form carboxylic acids which have a rotting smell but will eventually be converted into something much better.
While Lost Spirits is all for authenticity, there are numerous reasons why a dunder pit in the middle of Monterey County, CA farmland would be problematic, not the least being the health inspector. Instead, Bryan uses five gallon plastic buckets and things like overripe bananas for his dunder pit. It took him many iterations to find the right set of ingredients to make a good dunder. By starting with an optimal dunder, Bryan is able to obtain many desired esters during the fermentation process, rather than waiting years for them slowly to form in a barrel.
Step 3 – Creating carboxylic acids from yeast
At this point in the process, you have a pool of bacteria. This is combined with yeast and the molasses to start the fermentation processes which produces a number of compounds including various alcohols such as ethanol, and esters. You’ve got fuel (the molasses), and two living organisms, bacteria and yeast fighting for resources to grow and multiply. Ordinarily, the bacteria would always win as they multiply faster than yeast does. However, yeast knows how to cheat – It creates carboxylic acids which slow the growth of the bacteria and when combined with alcohol become esters which as we now know are generally desirable, flavor-wise. Different strains of yeast produce different carboxylic acids so knowing the types of bacteria you have in your dunder, you can select yeast strains that result in desirable tasting esters.
Step 4 – Stressing the yeast
When yeast is under stress, i.e. less than optimal conditions it will combine alcohols with carboxylic acids to create esters. There are apparently many ways of stressing the yeast. Bryan uses nitrogen deprivation to weaken the cell walls. It’s during this phase many of the nasty smelling components mentioned earlier get turned into better tasting compounds.
Step 5 – Distillation
Distillation uses the fact that different types of liquid, e.g. ethanol, methanol, water, etc… boil at different temperatures. By heating the fermented mash and selectively capturing the vapor at the right intervals you can concentrate the desired parts and reduce the undesired components such as methanol.
Some distillers, especially vodka producers go to great lengths to distill their product multiple times to make it as pure and as possible. However, as you’ve seen already the Lost Spirits process focuses on creating the best possible “input” as possible – More of the desirable elements and less of the bad elements that need to be filtered out. With such an optimal input heavy distillation would only serve to remove many desired flavor elements. Thus, Bryan built a pot still that does less separation than a still used for something like Irish whiskey or vodka. For the still-wonks out there, his still has a relatively short neck.
Step 6 – Barrel Aging
For barrel aging the Navy Style and Polynesian Rums, Bryan uses heavily charred new American oak barrels seasoned with Oloroso sherry. While no sugar is directly added to the rum post-distillation, the sherry does impart a very small sugar content which adds to the flavor profile.
Regarding the effect of barrel aging, Bryan mentions that the oak trees rigidity comes from lignin, the same thing I mentioned earlier when talking about sugar cane and molasses. The charring of the barrels acts as a “knife” to break up the lignins into phenolics, which you may recall are the “smoke” aromas, and will go on to form the spice flavored esters. American oak barrels were chosen because the phenols resulting from it are disproportionately high in phenolic precursors to vanillin and other vanilla smelling chemicals. It’s during the barrel aging process that the simpler fruity and spicy esters are converted into the more complex honey-like esters.
Step 7 – The Holy Grail of Rancio
Rancio, or Benzaldehyde & related compounds to be formal, is the “nutty” flavor you find in spirits that have aged for a relatively long time. Sherry is the most familiar example of rancio. Bryan points out that Rancio formation is a separate process from “regular” barrel aging described above and that rancio is a chemical decomposition by-product of the wood lignins after very long exposure to a solvent (water and alcohol).
In the case of sherry and some rums, the rancio comes from the solera method, wherein the spirit spends time in a series of barrels. The first barrel only holds new make spirit, the second barrel only holds spirit drawn from the first barrel, the third barrel only holds spirit drawn from the second barrel, and so on. Eventually, the spirit is removed from the oldest barrel for bottling. It should be obvious that the oldest barrel(s) have had spirits in them for a very long time, and as such are imparting the most rancio.
While there’s a lot of tradition with Rancio, it can take a very long time before you have barrels that are capable of adding rancio. Bryan’s innovation was in figuring out how to treat his barrels so that the lignins have started to decompose by the time of their first use. Simply put, he’s supercharged the rancio process and put it under his control.
If all this merely wets your appetite for more detail, be sure to read Bryan’s Rum Super Geekdom page over at http://spiritsjournal.klwines.com/
During our conversation, Bryan mentioned that his first rum (Navy Style) was created to show off all aspects of his technical innovations in the spirit making process. Subsequent rums may not use all these tricks, or may add others. In my next post I’ll talk about the Polynesian Inspired rum and how it differs from the Navy Style. Finally, a big thanks to Bryan for reviewing this post for technical accuracy.