Ka'u Cloud Red Caturra & How We Used Yeast to Boost Coffee Quality

Being at origin, while challenging, affords us the opportunity and privilege to work closely with farmers to co-create better, distinct and unique coffee experiences. That's what this coffee story is about...

We first bought coffee from Miles in 2020 to showcase his gorgeous Ka'u farm to our Coffee Club.Silver Cloud Coffee Farm, as he calls it, nestles in the heart of Wood Valley where mornings bless the trees with sun rays and afternoons enrobe them with misty clouds (hence the name). Miles retired after a long career as an engineer and applied his skillset to farming. He grew up in India where his family cultivated a small coffee and cardamom estate. So, for him, there's a particular nostalgic joy in his work. And it shows. His farm radiates majestic beauty. The coffee lives very happily under his care.

Miles and just one other full-time person manage the entire 10-acre farm and all the coffee processing. Harvest help, as it is for most coffee farms, depends entirely on seasonal labor. This presents a challenge because, much of the time, harvesting occurs inconsistently. Coffee doesn't ripen uniformly, so trees must be harvested many times each season to maximize quality by picking the ripest fruits. While there is an acceptable “spectrum of ripeness”, different people picking various coffees at differing ripeness levels at different times undoubtedly creates inconsistencies in the final product. This was something we first noticed in 2020, when we began working with Miles. We also noticed issues with how natural processed coffees were being dried.

At the time, Miles was looking for a consistent buyer, and we wanted to purchase Miles' coffee and develop a long-term, fruitful relationship.

To do so, we realized we needed to achieve two things together first: create more uniformity and create a coffee that tasted distinct from others in Ka'u.

While lovely, his coffee was sometimes sweet, other times it was more earthy. We'd all have a better chance at long-term success if Miles' coffee was more uniform and different.

How We Use Yeast to Boost Coffee Quality

This is where I'm grateful to have had a career introubleshootingcoffee production. Over the years, I've run multiple experiments in different processing and fermentation styles: washed, double washed (also called "Kenya-style" fermentation), dry natural, full natural,red and yellow honey processed, and, the newest, using different yeast strains in the washing process to change to the flavor and texture.

I tested different yeast strains that had originally been manufactured for a variety of beverages, champagne, mead beer, coffee, and several types within each category. As one might expect, what we experienced on the cupping table was a whole bunch of variation. Sometimes it enhanced the body, sometimes it made the texture rough. Sometimes it added buttery characteristics, sometimes it reduced sweetness. Sometimes it intensified fruit flavors, sometimes it muted floral notes.

The takeaway: yeast in coffee fermentation

Controlled yeast fermentation can do good things or bad things to coffee, but it does either more consistently than “wild” fermentation, which is the norm. Regardless of whether or not we liked the results, we found using yeast during fermentation increased uniformity from cup to cup. And, equally exciting, yeast created very interesting, distinct qualities in the cup.

How? There's a bit of a give and take relationship between yeast and coffee during fermentation. Each seed, or “bean”, is surrounded by a layer of mucilage composed of pectin and sugar. In a “wild” fermentation, naturally present yeast and enzymes break down the pectin layer, making it easy to wash the sticky-sweet pectin away from the surface of the seed. Hence the term “washed” coffee. As the yeast eats the sugar, they create several by-products, some of which the seeds absorb. So the seeds provide the sugar to the yeast, and the yeast provides by-products to the coffee. Some of the by-products create desirable results while others create neutral or undesirable results.

With this experience, I knew yeast was the first thing to test with Miles' coffee because it gave us the greatest likelihood of achieving both the uniformity and uniqueness we desired. We just needed to find the right yeast, used in the right amount, fermented for the right time, to achieve the uniqueness and consistency we needed.

Coffee quality comes neither easy nor fast

So, in the harvest season of late 2020/ early 2021, Miles and I got to work. And there was plenty to do! Quality coffee comes neither easy nor fast. It's a team sport, and it takes everybody working together each step of the way to execute well to create great coffee. I gathered a wide variety of yeasts used for white/red wine, cider, mead, and coffee-specific applications. Miles coordinated harvest times as best he could to maximize the amount of ripe fruit at each picking. At the end of his harvest day, I'd drive 90 minutes up to his farm, set up multiple 5 gallon buckets of pulped coffee, then prep and pitch different yeasts in each one. Next, we'd stir, wash, rinse, and Miles would dry and label the coffee. And then… wait. Over the harvest season, I'd make the 3 hour round trip drive several times.

The Results

I'm a bit impatient with the step of “resting” (curing), which should last 90 days. Instead, I started roasting samples of our yeast experiments after 60 days. With many years tasting the full spectrum of just-off-the-drying-racks fresh to sitting-in-burlap-for-5-years coffee, our palates have learned to recognize a coffee's potential a bit early.

Luckily, the yeasts created clear outliers on the cupping table, and, interestingly, the results differed greatly from the yeast trials performed at our coffee farm in Puna. In fact, our favorite yeasts and formulas from those experiments produced some of the worst results on Miles' coffee, and vice versa.

Caturra makes up the majority of coffee on his farm, and it's known to produce herbaceous qualities in the cup (think fresh peas or mint).The yeast we liked best edged out the herbaceousness, enhanced the body and sweetness, and harmoniously married the malic (pear and apple) and citric (citrus) acids into a white wine-like experience.

It was akin to a buttery chardonnay with honey and chamomile. That was a distinct, unique coffee experience for us.

So we decided to test the formula at scale. We moved from 5 gallon buckets to a single 150 gallon trough. Oh, how I love the efficiencies gained with growth. It was much easier only having to use a single type of yeast. It also made the 3 hour drive time more worthwhile! By the end of the harvest season in 2021, we'd produced enough yeast-fermented coffee at Silver Cloud Coffee Farm – dubbed Ka'u Cloud Red Caturra – to showcase to the Coffee Club later that year.

miles wood valley taste testing kau coffee
Now, with 2022 nearly finished, it's time to release Ka'u Cloud Caturra once again. Fortunately, more than double was produced this year compared to 2021, so we have enough to share publicly.