The 4-Process Experiment: One Seed, Four Flavors

Four bags of coffee will arrive at your door from us looking nearly identical. Same origin. Same farm in Guatemala. Same harvest, same cherry density, same variety. The roast on each was pulled with the same intention. The only thing that changed between the four bags is what happened to the seed during processing, specifically which microorganisms were present, for how long, and under what conditions. That single variable produced four meaningfully different coffees. This post breaks down what each process does and how to recognize those differences when you sit down to cup them.

This is the premise of the James Hoffmann Fermentation Project, and it is a more rigorous question than most coffee experiments ask. Rather than comparing a Kenya to an Ethiopia and calling it a fermentation study, this project starts from the same seed and changes only one variable. What you taste at the end of that process belongs entirely to the fermentation.

In this post

• Why the control lot is the most important bag in the kit
• What each of the four processes does to the cup
• How to taste all four at home
• What to pay attention to, and what to write down
• Frequently asked questions

Why the control lot is the most important bag in the kit

The first coffee in this kit went through a mechanical demucilager, a machine that removes the sticky mucilage layer from the seed without allowing biological fermentation to begin. No bacteria. No yeast. No time in a tank. The mucilage is stripped, the bean is dried, and the process ends there.

This lot is the experiment's anchor. When you taste the other three coffees in the kit, you are tasting how much distance fermentation can put between a seed and its baseline character. Every note of brightness, every shift in body, every aromatic quality in the other three cups has to travel through that baseline to reach you. Without the control, you are guessing. With it, you have a reference.

In practice, the mechanically demucilaged lot tends to present the most direct expression of the coffee's terroir and variety. The acidity it carries is the coffee's own, not an artifact of microbial activity. The sweetness is what the cherry produced, not what fermentation amplified or redirected. It is not a lesser cup. It is a transparent one, and transparency is exactly what this experiment needs at its foundation.

What each of the four processes does to the cup

Here is what the science and our own sample roasting tell us to expect from each lot.

Process 1: Mechanical demucilaging (the control)

No fermentation. Mucilage removed by machine within hours of depulping. The cup reflects the coffee itself: the farm, the altitude, the variety, the drying conditions. Think of this as the artist's canvas before any paint is applied. Whatever character the other three lots carry that this one does not, that difference belongs to fermentation.

Expect: Clean, direct, terroir-forward. Acidity that is structural rather than expressive. A reference point, not a finale.

Process 2: Wild fermentation (48 hours, ambient microbes)

After depulping, this lot rested in a fermentation tank for approximately 48 hours. No cultures were added. The microorganisms present were whatever arrived naturally: ambient yeasts and bacteria from the farm environment, the water, the equipment, the air above the tank. This is essentially the traditional washed process, the same one producers have been using for generations across Central America.

Wild fermentation is place-specific in a way that inoculated fermentation is not. The microbial community that shaped this lot belongs to that farm, that season, that altitude in Guatemala. Research from the Specialty Coffee Association confirms that local ambient temperature and variety both influence microbial community dynamics during fermentation, which is part of why coffees from the same process but different origins can taste so distinct.

Expect: Familiar washed character, but with more complexity than the control. Subtle fruit development. The kind of cup that rewards attention without announcing itself. Think of this as the baseline most of the specialty coffee you have drunk in your life was built on.

Process 3: Lactobacillus inoculation (targeted bacteria)

This lot was inoculated with a specific Lactobacillus culture before fermentation began. Lactobacillus is a lactic acid bacterium. When it dominates a fermentation, it produces lactic acid as its primary metabolic output, along with a range of aromatic precursors that migrate into the seed during processing.

The effect on the cup is distinctive. Specialty coffee producers who work with lactic fermentation describe the outcome as brighter, more precise, and often creamier than wild fermentation, with a mouthfeel that some compare to yogurt without the sourness. The flavor results are distinctive: where standard fermentation tends toward variable intensity, lactic fermentation typically produces a softer, rounder cup with clean acidity that is smooth rather than sharp. It tends to amplify floral and tropical fruit notes. Producers who push it further report a finish that can carry papaya or citrus characteristics. When we cupped this lot during sample roasting, the lift in the cup was immediately apparent against the control.

Expect: Elevated brightness. Clean, structured acidity. More aromatic complexity than the wild lot. A cup that is precise and vibrant rather than layered and slow.

Process 4: Saccharomyces inoculation (targeted yeast)

The fourth lot was inoculated with a Saccharomyces yeast culture. Saccharomyces is the genus that drives fermentation in winemaking and brewing. When applied to coffee, it takes a different metabolic pathway than lactic acid bacteria. Rather than producing primarily acid, it produces aromatic precursors including esters, alcohols, and volatile compounds that tend to express as fruit and floral characteristics in the roasted cup.

Where Lactobacillus tends to work on acidity and brightness, Saccharomyces tends to work on body, sweetness, and aroma complexity. Research published in food science literature consistently shows that yeast-inoculated coffees score higher on body and fruity aromatic attributes compared to non-inoculated controls. The cup feels rounder, often heavier, with a sweetness that carries further into the finish.

Expect: Enhanced body and mouthfeel. Sweetness that is amplified and sustained. Fruity aromatic notes, potentially wine-like or floral. A cup that feels more substantial than the other three without necessarily being louder.

How to taste all four at home

You do not need a professional cupping setup to get real information from this kit. You need four identical vessels, hot water, a gram scale, and 20 undistracted minutes. Here is the simplest approach that will actually work.

Grind consistently. Use the same grinder, the same grind setting, and the same dose for all four coffees. Any difference in grind size between cups introduces a variable that has nothing to do with fermentation. Weigh your doses. Even 0.5g of variance between cups can shift the balance. We use 11g per 200ml of water as a starting ratio for cupping, but your preferred pour-over ratio works fine as long as it stays identical across all four.

Brew the same way. Pour-over, French press, or even a simple immersion steep all work. The method matters less than the consistency. If you are brewing pour-over, use the same water temperature, the same pour pattern, and the same total time for all four. If one cup develops faster than another, that difference belongs to the coffee, not your pour.

Taste them in order. Start with the control and move through the wild lot, the Lactobacillus lot, and the Saccharomyces lot in sequence. The control sets your baseline. Every cup after it is a measurement of distance from that reference. When you return to the control mid-session, you will likely taste it differently than you did at the start, because the other fermentations will have given you language for what is absent.

Let them cool. Hot coffee compresses flavor perception. The differences between these four lots become most audible at around 55 to 65 degrees Celsius, roughly when the cup is warm but no longer too hot to hold comfortably. A lot of what fermentation contributes is aromatic complexity that heat mutes, and acidity that heat softens. Give them time.

What to pay attention to, and what to write down

You do not have to use industry vocabulary to get something useful out of this tasting. Three questions will get you most of the way there:

Where does the acidity land? Not whether there is acidity, but where it registers. At the sides of your tongue. At the front. As a brightness that arrives with the first sip and then fades. As something that builds across the swallow. The control gives you a baseline. The Lactobacillus lot will likely move that baseline higher and forward. The Saccharomyces lot will likely soften it and shift it toward the middle of the palate.

How long does the sweetness last? Every coffee has some sweetness. The question is what happens to it after you swallow. Does it cut off sharply, or does it carry forward into a 10-second finish? The Saccharomyces lot is the one most likely to extend that finish. If you notice a sustained sweetness after the sip, that is yeast fermentation doing work that the coffee's terroir alone could not.

What is the texture? Body in coffee is the weight of the liquid on your palate, distinct from flavor. Run the coffee across your tongue before you swallow and notice the resistance. The mechanical lot will feel lighter. The Saccharomyces lot will feel fuller. The Lactobacillus lot may surprise you with a softness that its brightness does not suggest.

Write it down. Not because the notes matter later, but because writing forces a decision. When you have to choose a word, you commit to having tasted something specific. That commitment is the difference between drinking and learning.

Frequently asked questions

Do I need special equipment to participate in the Hoffmann tasting event?

No. Any brew method that produces a consistent cup works. Pour-over, French press, AeroPress, and even a basic drip machine will give you enough information to taste the differences between the four lots. The most important variable is consistency across the four brews, not the method itself. Use the same dose, the same grind, the same water temperature, and the same timing for each cup.

Which fermentation process is the "best" one?

That is exactly the question this experiment is designed not to answer for you. Hoffmann and Lucia Solis designed the project to make the differences legible, not to declare a winner. What you prefer will depend on how you drink coffee, what you are looking for in a cup, and which qualities you find most satisfying. Some people will finish this tasting convinced that the cleanest, most direct cup won. Others will not be able to put down the Saccharomyces lot. Both responses are correct.

Can I brew the four coffees on different days instead of side by side?

You can, but you will lose information. The value of a side-by-side tasting is that your palate is calibrating in real time. When you taste the Lactobacillus lot immediately after the control, the brightness is unmistakable because the baseline is still fresh. If you wait a day between cups, memory is doing the comparison instead of your palate, and memory is a poor instrument for sensory work. Brew them together once if you can. You can always go back to a favorite on its own afterward.

Will all four coffees taste good on their own, outside of the experiment?

Yes. These are specialty-grade coffees from a single well-managed Guatemalan lot, and each process was executed with precision by Lucia Solis. The experiment framing is useful for learning, but once you have done the comparison, any of the four bags makes an excellent everyday cup. If you find yourself reaching for one process more than the others in the weeks after the tasting, that is your preferences talking, and that is worth knowing about yourself.

When is the James Hoffmann global tasting event?

The live tasting will be on the 3rd of October 2026 at 3pm GMT. There is no need to watch it live if the timing is inconvenient. It will be available afterwards and you can watch it as if live to still have the same guided experience. If you have not already ordered your kit, the link is below.