Over the course of the harvest, Cuatro M has been receiving and processing coffees from its varietal plot, El Palmero, in Finca El Manzano. Within this plot are three different varieties of coffees, Pacamara, Red Bourbon, and Yellow Bourbon, all planted at the same time, five years ago.
On each of the four days that the coffees were harvested, Beneficio El Manzano used a different processing method, the Natural, Pulp Natural, Machine Washed, and now, after receiving coffees on Saturday, February 4, the Fully Washed processing method.
Within the fully washed processing method, coffee beans are washed of their mucilage, via natural fermentation, which takes place as the parchment is soaked and stirred within water for “16-36 hours” (www.coffeeresearch.org), depending on several contributing factors.
“The coffee fermentation time depends on a number of factors including the amount of coffee fermenting, water temperature, and humidity. The mucilage is made up of pectin materials including protopectin (33%), reducing sugars including glucose and fructose (30%), non-reducing sugars such as sucrose (20%), and cellulose and ash (17%) (Wrigley, 455). Protopectin is not water soluble and will hydrolyze to pectinic acid in the fermentation tanks (Wrigley, 455). Hydrolysis of the protopectin and degradation of the pectin by enzymes is the process that occurs to remove the mucilage during fermentation (Wrigley, 455). Currently, the best way of determining the end of coffee fermentation is to feel the coffee beans to determine if they are still encased in mucilage. If the coffee beans are fermented for 36-72 hours, stinker beans develop. Lactic, acetic, and propionic acids are produced in this process and are believed to prevent the traditional fermentation taste by inhibiting mold growth that regularly occurs during drying on a patio in humid conditions” (Wrigley).
The holding tanks for the water are typically called, ‘fermentation tanks,’ and range in width and length depending on the operation or mill, however they must be shallow enough for coffees to be stirred and rinsed.
In order to process a sample of the varietal coffees, we prepared the tanks and calculated the amount of water needed for fermentation.
According to www.informedfarmers.com, the conversion ratio for fermentation is 0.6 cubic meters of water, per 1,000 kg of ripe cherry. The total weight of the cherries for each sample variety had to then be measured, and converted, in order to determine the amount of water needed for fermentation.
Yellow Bourbon: 1.63 pounds = 1.8 cups of water
Red Bourbon: 2.23 pounds = 2.5 cups of water
Pacamara: 2 pounds = 2.2 cups of water
The measurement accounts for the total weight of cherries, but in reality, the amount of water is added to the wet parchment, taken once the cherries have been de-pulped.
Once each of the samples had been de-pulped, the weight of the wet parchment was taken, in order to determine the total weight ratio of cherry to wet parchment, and the amount of weight lost for each variety, once it had been stripped of its cherry.
Yellow Bourbon: Cherry = 1.63 pounds; Wet Parchment = .995 pounds
Weight Percentage Loss = 39%
Red Bourbon: Cherry = 2.23 pounds; Wet Parchment = 1.26 pounds
Weight Percentage Loss = 43.5%
Pacamara: Cherry = 1.995 pounds; Wet Parchment = 1.21 pounds
Weight Percentage Loss = 39.4%
The wet parchment was then ready to begin fermentation.
- Wrigley, Gordon. 1988. Coffee. New York: John Wiley and Sons.