zach wrote: ↑Wed Mar 12, 2025 9:46 am
I think the issues is on the fermentation side of things.
Just for fun, I've been trying out Grok and asked the following question:
A corn only distillate has a pronounced ethyl acetate or acetone flavor. Synthetic enzymes were used to convert the starches. Baker's yeast was used for fermentation. What is the likely cause?
The pronounced ethyl acetate or acetone flavor in a corn-only distillate, where synthetic enzymes were used to convert starches and baker’s yeast (Saccharomyces cerevisiae) was used for fermentation, is likely due to a combination of fermentation conditions and yeast metabolism. Let’s break this down:
Key Compounds
Ethyl acetate: An ester with a fruity, solvent-like aroma, often described as nail polish-like in high concentrations. It’s produced by yeast during fermentation through the reaction of ethanol and acetic acid, catalyzed by enzymes like alcohol acetyltransferases.
Acetone: A ketone with a sharp, chemical-like smell, less commonly associated with fermentation but can arise from certain metabolic pathways or contamination.
That's probably it, I know it would make your nose burn and eyes water if you got a big enough sniff of it.
Likely Causes
High Fermentation Temperatures:
Baker’s yeast ferments optimally between 25–30°C (77–86°F), but if temperatures exceed this (e.g., >35°C or 95°F), it can become stressed. Stressed yeast increases production of fusel alcohols and esters like ethyl acetate as byproducts of sloppy metabolism. Acetone-like flavors could also hint at thermal degradation or atypical yeast activity under stress.
I would be surprised if this is the cause.The fermention was done in an insulated cabinet with a heating element and Inkbird to regulate the temperature. Ambient temps for that time period never got above 70°F and my Inkbird is set to 80°F low and 85°F high.
Yeast Stress from Nutrient Deficiency:
Corn mash, while rich in starch, is naturally low in free amino nitrogen (FAN) and other micronutrients (e.g., zinc, vitamins) that yeast needs for healthy fermentation. Synthetic enzymes break down starches into fermentable sugars (mostly glucose), but they don’t add nutrients. If no supplementation (e.g., yeast nutrients) was provided, the yeast may have struggled, leading to off-flavors like ethyl acetate.
Maybe I was low on micro-nutrients, but I did add some typical yeast nutrients to the mash when I hydrated the yeast. DAP, Epson Salt, and a liquid B complex were added.
Acetic Acid Production:
Ethyl acetate forms when ethanol reacts with acetic acid. Baker’s yeast doesn’t typically produce much acetic acid, but if fermentation was slow or oxygen was present (e.g., poor sealing of the fermenter), wild bacteria (like Acetobacter) or stressed yeast could have oxidized ethanol into acetic acid. This would then combine with ethanol to form ethyl acetate.
The fermentation lasted about 10 days, and then sat on the trub for 2 more before we racked it and cold crashed it. We racked it once more, then ran it. The fermenters both have tight lids and rings that secure the lids, both have an airlock. Typical PH for the 10 days was 5ish.
Overly High Sugar Concentration:
Synthetic enzymes might have converted the corn starch into an excessively high sugar concentration. If the mash had a high gravity (>15–20% fermentable sugars), it could overwhelm the yeast, increasing osmotic stress and triggering overproduction of esters and fusel compounds.
I don't believe the sugar concentration was high, one was at 1.055 and the other was at 1.060. Isn't that right in line with what I should have gotten with 22#s of corn to 12 gallons of water?
Acetone-Specific Possibility:
Pure acetone flavors are rare in yeast fermentation and might suggest contamination (e.g., from equipment cleaning solvents) or a misidentification of similar compounds like acetaldehyde (green apple, solvent-like) or isoamyl acetate (banana-like). Baker’s yeast doesn’t naturally produce acetone, so this could point to an external factor or sensory confusion.
Could very well be sensory confusion, these four make my 20th - 23rd runs and first AG, I got a noobie nose. After all the info I've seen since, I'm betting on the ethyl acetate.
Most Likely Culprit
The dominant ethyl acetate flavor strongly suggests yeast stress, most likely from high fermentation temperatures or nutrient deficiency in the corn mash. Baker’s yeast is robust but not optimized for high-efficiency alcohol production (like distiller’s yeast), so it’s prone to off-flavors under suboptimal conditions. If acetone is genuinely present, I’d lean toward contamination or a sensory overlap with ethyl acetate’s solvent notes.
Isn't bakers yeast the go to here? I wasn't looking for high output (high efficiency), I've had good luck with sugar and rum by keeping the abv low. I was just trying something new and hoping for a good outcome using the same basic principals.
How to Fix It
Lower fermentation temperature (keep it below 30°C).
Check
Add yeast nutrients (FAN, vitamins, minerals) to the mash.
Check
Ensure a clean, oxygen-limited fermentation environment.
Check
Consider switching to a distiller’s yeast strain bred for cleaner ethanol production.
OK, maybe, I have DADY & EC-1118.
Does this align with what you observed during the process? Any specific details (e.g., temperature, mash prep) you want to dive deeper into?
Well...not really, I don't think I had most of the issues or conditions the article talked about except for using bakers yeast.