There is a specific set of standards for every commodity. Size, shape, color, taste, weight and overall appearance. Strictness vary on every company and on who the quality control officer is.
What is defect? It is an item or set of items which never conform with the standard. If the specified color is yellow, then all the incoming material should be yellow. Weigh 90 to 100 grams, then all must weigh equal to or more than 90 grams but not more than 100 grams. All unconformities are detected by human perception or by machine means. Such are removed to achieved the set specification.
What if there is no set criteria for a specific property? Then varying value means nothing. It doesn’t matter whether it is too high or too low. Quality control officer would never mind checking it.
The coffee moisture content. According to sweetmarias, green coffee beans is best stored and roasted at 12% moisture. Then if all the coffee producers will follow, all coffee having moisture content less than 12% and more than are defective.
A little explanation. If a set of green beans is too moist, it requires a longer roasting time for a specified temperature. There is an extra time required for fending off extra moist. On the other hand, if too dry, shorter roasting time is necessary. Following the standard time and temperature pattern is likely to render the batch burnt.
What should be done? On part of coffee farmers and green coffee middlemen, having the ability to check beans moisture content during and after drying period is good. Too much dried beans are lighter and means getting a lower paid value. Moist beans are heavier but dealers and roasters are unlikely to pay for it.
On part of coffee processors. Check coffee moisture content before roasting or before accepting the beans. Ask the dealer to do moisture correction or do it yourself.
Invest in an expensive moisture meter or a lower cost grain moisture meter. Or guess, guess, just guess the moisture.