Full Sour / Partial Sour

Full Sour

Partial Sour

Español: Agrio o fermento completo / parcial
Français: Fève sure / Fève demi-sure

Full Sour is a Primary (Category 1) defect: 1 sour bean (> 50% damaged) = 1 full defect
Partial Sour is a Secondary (Category 2) defect: 3 partially sour beans (< 50% damaged) = 1 full defect
Sour beans are recognized by a yellow or yellowish-brown to reddish-brown color and sometimes-waxy texture. It is often possible to see a dark or black spot (sometimes hollow) in the tip of the seed, which represents a dead embryo. When cut or scratched, a sour or vinegar-like smell is released. Do not confuse sour beans with amber or foxy beans, which are only discolored on the surface and not considered defective.
Cup: Varies depending on the degree of bean fermentation: when slight, partially sour beans may exhibit pulp, sour and mellow flavors. When strong, full sour beans may produce biting and pungent sourness, ferment, rotten fruit, onion, sweat, rancid, foul and stinker tastes.
Consideration: Affects aroma and physical appearance of the green beans.
Cause(s): AGRICULTURAL & PROCESSING: Sour beans are caused by the death of its internal embryo, which may result from over-fermentation (extended microbial activity) and high temperatures at multiple points during harvesting and processing. Specific causes include: picking of overripe cherries, picking of fallen cherries, contamination of water during processing, over-fermentation in the fruit still attached to trees under humid conditions and drying up at high temperatures (>45°C).
Remedies: AGRICULTURAL: Harvest ripe cherries only and sort/remove over-ripe cherries, do not collect fallen cherries, always use clean bags, and do not cultivate coffee in low altitude areas near lakes, rivers or dams.
Avoid sour beans in PROCESSING by:
  1. pulping cherries immediately after harvesting, avoiding storage of the cherries for extended periods;
  2. (in natural processing) spreading and drying up of cherries in 1 to 2 inch layers;
  3. (in fully washed coffees) maintaining cleanness of patios, raised beds, fermentation tanks and water and appropriate fermentation time when in tanks
  4. maintaining best practices during the drying process: cleanness, proper aeration and temperature control, avoiding interruptions, contact with and protection from rain or condensation; and
  5. using an electronic color sorter to remove full sour beans.