Altitude and temperature are the two greatest variables that can “break” a fermentation model. At higher altitudes, the ambient temperature is lower, which slows microbial metabolism but can actually improve Phosphoric perception because the slow drop in pH is more controlled.
Here is how you adjust your BRIX and timing targets based on the environment:
- High Altitude / Cold Climate (e.g., >1,800m)
In colder environments, the “Dry Ferment” phase can stretch dangerously long, risking the development of “onion” flavors or butyric acid if not managed.
- The Adjustment: You may need to increase the initial BRIX density by using only the ripest cherries.
- Target Timing: Extend Dry Fermentation to 20–24 hours.
- The “Soak” Strategy: Because the water is likely colder, you can push the soak to the full 33–36 hours. The cold water acts as a preservative, allowing amino acids to develop without any risk of the beans “over-fermenting” underwater.
- Sensory Result: Maximum Phosphoric “sparkle” and a very heavy, syrupy body.
- Low Altitude / Warm Climate (e.g., <1,400m)
Heat is the enemy of Chlorogenic Acids (CGAs). High heat accelerates microbial growth, which can cause the pH to crash too fast, leading to that “phenolic” or vinegary sharp taste.
- The Adjustment: Use thermal mass to your advantage. Keep the fermentation tanks shaded or even partially covered to prevent a temperature spike above 30°C.
- Target Timing: Shorten Dry Fermentation to 12–15 hours.
- The “Soak” Strategy: Reduce the soak to 24 hours. In warm water, the beans can begin to sprout (germinate) faster; you want to stop the process before the embryo consumes the sugars you’re trying to save for the roast.
- Sensory Result: A cleaner, lighter cup with high floral notes, though potentially less phosphoric intensity than high-altitude lots.
Environmental Adjustment Table
Variable High/Cold Altitude Low/Warm Altitude Rationale
Dry Ferment Time 20 – 24 hrs 12 – 15 hrs Microbial speed is temp-dependent.
Soak Time 33 – 40 hrs 20 – 24 hrs Prevents “boozy” notes in heat.
Water Change Not needed Every 12 hours Oxygenates water to prevent staling.
Bed Thickness Thin (<2cm) Medium (3-4cm) Prevents rapid “case hardening” in heat.- The “Clean Cup” Sensory Correlation
To ensure your team is hitting the mark, look for these three indicators during the final “Washed” stage:
- Parchment Color: It should be a pale, translucent white. Any “pinkish” tint suggests the pH dropped too low (too acidic), which will lead to a phenolic, metallic taste.
- Water Clarity: During the 33-hour soak, the water should remain clear enough to see the beans at the bottom. If it turns milky, the mucilage wasn’t washed properly, and you are losing “cleanliness.”
- The “Snap” Test: Once on the drying beds, a bean that has been soaked correctly will have a distinct “snap” when bitten (even at high moisture), indicating a dense, well-developed cellular structure.
- The “Clean Cup” Sensory Correlation