Full/Partial Sour Green Coffee Bean Defects
Defect Name: Full/Partial Sour Green Coffee Beans
Description: Sour beans can be recognized by their yellowish brown to reddish brown colour. Once roasted, a single sour bean can taint an entire pot of coffee. Sour beans are caused by fermentation that is a direct result of microbial contamination at various points during processing. Some particular causes include: overripe cherries, fallen cherries, water contamination during processing as well as humid conditions as the cherries are ripening.
Effect on the Cup: As you might expect, the main effect on cupped coffees is that of a sour taste. Other taints can include a fermented or ‘stinker’ flavour that is imparted in the cup. The secondary taints depend on the degree of the beans fermentation .
Remedies:
Agricultural: Only harvesting ripe cherries is the number one method of preventing sour beans. Avoid picking cherries from the ground and cultivating trees at low elevations near large water sources.
Processing: Pulping must occur in a timely fashion to avoid storage of harvested cherries for prolonged periods of time. Controlling the time of fermentation in fermentation tanks. Avoid using contaminated or recycled water during the washing process. It is not until after the pergamino is removed that sour beans become apparent. This is by extensive monitoring of the processing stage is required.
