A cup defect is rarely decided in the cup

Two years ago, we had a problem at each end of the chain, and no one saw that it was the same one.

On one side, in Central America, natural coffees remained difficult to produce. The natural process means drying the whole cherry, with its pulp, instead of pulping it first. The sugar of the pulp passes into the bean during drying, and that is what gives those round, sweet cups our customers look for. But in a humid climate, this drying takes a long time, and all that time the lot can go into over-fermentation.

For a producer, that means tied-up space, equipment, and the risk of losing the harvest. Many prefer not to try, and one understands them.

On the other side, thousands of kilometers away, our most widely distributed blend in automatic machines lacked body and crema, and varied from one cup to the next. The same coffee, extracted as manual espresso, showed none of these defects.

That is how these two problems turn out to be one.

Letting the cherry rest

The idea of Sweet Rest is simple to state and long to dial in: ripe cherries are left to rest for forty-eight to seventy-two hours in breathable bags, then washed normally. That's all. There is no prolonged drying, no fermentation tank, no equipment to buy.

What makes the difference between a process and an accident is control. During those hours of rest, we track the ripeness of the cherries, temperature, humidity and pH, the measure of acidity that tells whether the fermentation is drifting. Without these readings, the rest becomes just another over-fermentation, and we fall back on the problem we wanted to avoid.

What happens during this rest comes down to the mucilage, the sticky layer that clings to the bean under the skin of the cherry. It is rich in pectins, the molecules that hold the fruit's tissues together. A moderate enzymatic and microbial activity begins to break them down. The bean therefore detaches more easily at pulping.

What it changes for the producer, and this is where it counts

This pre-degradation is not a technical detail. It reduces mechanical losses at pulping, and among coffee growers we have observed a yield improvement on the order of ten percent. Ten percent more coffee, on the same surface, for the same labor.

Tested in Nicaragua in 2023 on small lots, in arabica as well as canephora, the process was extended gradually. We now import about two hundred tonnes of it, three quarters arabica and one quarter canephora, with a quality premium maintained for the producers.

I specify “premium maintained” because that is the point where this kind of project is usually lost. A process that improves the cup and is then used to negotiate the price down is not an improvement, it is a transfer. Here the producer keeps their premium and gains yield. Otherwise there would be no interest for them, and a process that does not interest the person applying it does not last a season.

The other end of the chain

Let's return to the automatic machine and its missing crema.

The reflex would have been to push the roast. A darker roast gives more body and more stability, it works, and it costs the coffee's aromatic profile. We preferred to understand first.

The defect did not come from the coffee, it came from the machine. Two constraints, precisely. The tunnel between the hopper, the bean reservoir, and the grinder gave irregular doses depending on bean size. And the brew group had been designed to last, not to be precise.

To understand the first point, we drew on the work of physicist Christophe Perge on the flow of grains in a silo, and on Beverloo's law, which describes the flow rate of a granular material through an opening. It says something that seems counterintuitive: the larger the grains relative to the opening, the more the flow jams. Arches form above the orifice, like an arch of stones holding one another up, and the coffee stops flowing steadily.

Our blend was made up three-quarters of beans of screen size above fifteen, screen size being the measure of bean caliber, and for the rest of screen size above eighteen. In other words, big beans, exactly what we should not have had.

We changed two things. The caliber first: three-quarters Peaberry, those small round beans that grow singly in the cherry instead of in pairs, completed with screen fourteen to fifteen. And the process second, by introducing Sweet Rest for sweetness and roundness. The roast followed, with a slightly shorter profile and a gentler heat input, to preserve what we had just gained.

The result was seen immediately: a stable flow toward the grinder, a regular extraction, a more intense body, a persistent crema, and the aromatic profile intact.

What I take from it

The defect was in a hopper, in France, and part of the answer was in the way a cherry rests in Nicaragua. Between the two, there are not two trades, there is only one.

That is why I don't much like the idea that specialty coffee would be reserved for certain uses. That coffee goes into automatic machines, in lobbies, gas stations, hospitals. These are the cups nobody talks about, and they are the ones that reach the most people.

What this does not prove

The ten percent yield is a field observation on our partner lots, not a controlled study. The protocol requires monitoring that not all producers can provide, and Sweet Rest is not transposable everywhere. As for the effect measured on consumption in vending, on the order of five to seven percent at rollout, it measures a consumer preference, not a quality in the cup.