Flavor Creation in Whiskey
A NAFFS STAFF REPORT
Corn, wheat, rye and malted barley – more than 99% of whiskeys around the world are made with one or a combination of these grains, Tom Gibson, flavor architect and director at Flavorman, told attendees of the 104th Annual NAFFS Convention.
Corn’s flavor notes consist of sweet, corny and grassy, he said. Gibson said corn was historically used because of its abundance and high level of starch. Corn is readily available, has a high starch content which equals more fermented sugars. “More fermented sugar equals more alcohol,” he said, adding that corn has a very specific profile. (At this point, he instructed attendees to taste the first of the 11 samples of whiskey they’d been given.) He said it had a corny character but for the experts in the room, he said it had notes for nickel sulfide, some sulfuric notes – maybe like sulfuryl – and a little bit of pheromones in the background.
Distillers buy grains at 14% moisture levels, he said. Corn is mid- to high- 70% starch. Other grains are lower, which is why corn, when used, is generally a high percentage of the mash bill – more starch will ultimately equal more spirits, Gibson said.
The first sample was non-aged, 100% corn at 100 proof. Descriptive words from the audience were creamy, sweet, corny notes. Gibson said once it goes into the barrel during fermentation, distilling and aging most of these aroma chemicals will dissipate and only sweetness will prevail. Of the popular whiskeys made with corn, the Buffalo Trace series is well-known on the market, he said.
He offered a wheat whiskey sample, known as soft and subtle with a creamy profile and yet he noted some sour faces in the room. He said wheat is less intense but more complex than corn and holds up through fermentation distilling and into barrel aging. The sample was 100% wheat non-aged and 80 proof and can offer a nutty flavor. Some people picked up some notes of baking spices and vanillin. An example of a wheat-based whiskey on the market, he said, is the Van Winkle series and also Maker’s Mark.
Gibson said with the third grain, rye, you “either love it or hate it” because rye is sharp and powerful. He said it is less “punchy” than corn and it is very unstable. But with rye, Gibson said, “a little goes a long way!”
Upon tasting the next sample, the audience noted some flavor notes including spicy, floral finishes and herbal notes. Gibson said rye is used as either a flavoring grain or as its own whiskey. Malted rye is uncommon but not unheard of; it’s much more common in craft distilling. He said examples include Basil Hayden, which has more rye than we realize, as does Four Roses and Old Granddad.
Barley (malt) is the fourth grain used in American whiskey. Gibson said it’s primarily used for starch conversion and less so for flavor profile since it creates a more delicate spirit that doesn’t hold up as well to new, charred cooperage.
When the audience sampled it, they noticed a light taste (pyrazine) and Gibson said there would be signs of sweet, fruity, grainy and malty note. Tasters may sense brown notes and some piercing like metal fire and a little bit on the chocolatey side with a weird fruity finish, he said. Barley is used in other whiskeys around the world in Scotch, Irish and Japanese whiskeys as a base for these single malts.
Gibson said fermentation is very important to the development of flavor; it’s the formation of alcohol. “You’re getting all those notes in every permutation; even those 100% grains have those notes as well,” he said. Only about 5-10% is used in American whiskey, he noted.
Fermentation makes dozens of alcohols, acids, aldehydes and esters. The next important part of this whiskey flavoring process is the yeasts, he said. Yeasts produce very standard aroma chemicals. Selection of the yeast is very important for the signature of chemical whiskeys, he added.
“It’s often said that yeast is as important to whiskey as grape selection is to wine” since “it forms the path on where you are going,” Gibson said. “Yeast is an art and comes in how you make the cuts and dig into your flavor profile on the heads, hearts and tails.” The heads, he said, are low boilers; the first things that come off. The hearts are ethyl alcohol and the tails are the high boilers coming at the end. It takes a lot of energy to get these off the column but Gibson promised it was going to change in the barrel and “you will see these in your finished product.” One was a general ester-producing yeast. “Grains may be predominant but if you look beneath, you will find orchard fruit type esters, ethyl 2 methyl butyrate, hexyl acetate,” he said.
Gibson had the audience taste a few more samples. He explained that smelling them can have a similar result without the alcohol ingestion. He said the yeast was designed to kick out ethyl alcohol. The samples had different alcohol burns and notes – some smoky, some creamy. He said the use of different yeasts helps pull through more flavors such as pineapple, strawberry, nutty and caramels.
The next sample was made with a high alcohol-producing yeast. He said outside the alcohol burn, one can find hexyl compounds and grassy notes. Yet another was heavy with creamy light caramelic notes; gamma and delta lactones, hydroxy furanones (berry, pineapple, caramel, nutty and spice).
Gibson said grain selection and fermentation aims for aroma chemical consistency because the next step is anything but consistent: “barrel aging” he said “is chaos.”
When it comes to oak and aging, the main factors that will impact flavor extraction and creation are heat treatment of the wood, the entry proof into the barrel and aging. Charring creates a layer of carbon that will act as a filter. Toasting will deepen the natural toast layer that happen on the outer boundary of charring.
Gibson offered more samples while he explained the charring process. He said charring of the barrel is important to the finished product. The toasting can happen before the charring to deepen the toast layer to convert/increase different aroma chemicals. He said it’s imperative to convert the wood lignins and sugars to unique compounds from the oak staves. He said charring beforehand is preferable because it expands the toast. “That way you have a char layer – which is smokey – and a toast layer which can be vanillin, syringaldehyde, eugenol. He noted that the age spirit in an uncharred barrel will still taste like new make after aging years.
Entry proof plays a significant role, Gibson said. “Most large players used to go no higher than 110-115. Alcohol-to-water ratio determines what is pulled out of the barrel – water-soluble compounds vs. alcohol-soluble compounds. The higher the entry proof the more alcohol soluble compounds will be extracted and less water-soluble.”
The first and main extractives from the barrel are wood sugar, vanillin and tannins, he said. “But there are also dozens of other compounds that are extracted that will start to build a more complex flavor profile as they concentrate in the whiskey. This is the additive phase of barrel aging,” Gibson said. “A handful of aroma chemicals get extracted and concentrate in the liquid over time. The liquid gets pushed in and out of the wood, and through the char/toast/red layer, due to changes in temperature and barometric pressure. The materials extracted are very important for the next stages of barrel aging.”
The oxidation cycle is, according to Gibson, “is where the rubber meets the road. Flavor compounds aren’t just created during fermentation and extracted from the barrel. The vast majority of whiskey flavor compounds get created through the aging process by oxidation which creates additional alcohols, acids, aldehydes and esters.”
He said the subtractive phase of barrel aging includes several factors: 1) the movement of the liquid in and out of the char layer. This is the removal of long chain fatty acids and other tailsy materials; 2) evaporation – or “the angel’s share” can be 6-8% the first year, 3-4% in subsequent years; 3) oxidation is the headspace created that allows the oxygen to work its magic.
Alcohol + O2 = Acid
Acid + O2 + Aldehyde
Aldehyde + Alcohol + ester
“You can’t taste the effect of aging until two years, with more noticeable change after three to four years,” Gibson said. “Any longer, it just takes like wood.”