Proper drying and storage of parchment is likely the single most important post-harvest quality step, even greater than fermentation and roasting.
There are several key aspects for those drying their coffee on-farm.
1. Get beans visibly dry, as fast as possible.
a. The longer your parchment stays wet, the greater the risk that sugars on the bean will continue to ferment or even mold.
b. Ideally, within 4-12 hours your coffee will be dry to the touch. Mauka farms can struggle with this and may need more space to thin out wet coffee, or a mechanical dryer.
2. Rake frequently and turn your coffee so all layers dry equally.
a. Raking wet coffee into rows will speed up initial drying through convection.
i. Once “touch dry, spread out rows into a layer no more than 4” thick.
b. On a hot day, frequent raking will keep your coffee safe from high heats as some makai hoshidanas can reach above 115F.
3. Once your coffee is touch-dry, be sure to prevent your coffee from getting wet again.
a. Parchment that gets rained on will cup with off-flavors as it ages.
4. Coffee will typically reabsorb 1-2% moisture overnight.
a. This normal cycle will cause degradation if allowed to persist for too many days.
b. Rake into small piles and cover with a tarp to prevent this.
5. Measure moisture levels often when approaching the 11% range.
a. Be sure your meter is calibrated. (compare your readings to a commercial dry mill if you are unsure).
b. State law is 9-12% moisture, green coffee buyers prefer 11%.
c. Coffee will often drop moisture rapidly, once below 14%. Check often!
d. On a wood deck, 11% will take 4-14 days, depending on weather/elevation.
i. Longer dry times are not necessarily a bad thing, as it usually indicates a slower drying process at lower heats, which is safer for the beans.
e. Coffee stored above 12% moisture will age poorly, and possibly even mold. It will introduce bad flavors to your crop and reduce your cupping scores.
f. Coffee below 9% can negatively impact flavor, as well as cost you weight and lower your green value.
6. Properly dried parchment should be stored it in reusable Grainpro bags (available through KCFA) or in a climate-controlled room.
a. Industry standard is a 30-day resting period before dry-milling, which will allow green bean pores to close and provide for a more stable roast.
b. Grainpro will lock out insects, oxygen and humidity. Over the year, grain pests (moths) can attack and destroy parchment stored without Grainpro.
c. Recognize the challenges you face, mauka or makai, and plan for the season ahead
d. Ultimately, quality is our key goal, as that brings repeat customers and allows us to build our markets.