Peaberries, while sometimes considered a defect, are not associated with any flavour taints. In fact, many roasters tell us that because of the characteristic rugby ball-like shape of peaberries, they are easier to roast than ordinary beans. It is simply the loss of yield that is the problem.
Research into the formation of peaberries indicates that they are the result of environmental stress, but some plants are more prone to the production of peaberries than others. In some cases, the peaberry may account for as much as 40 percent of the crop. Plants prone to peaberry formation are usually removed from a farm because for every 1 percent of peaberries in a crop, there is a 0.75 percent loss of yield (A. Carvalho and L. C. Monaco, 1969, p. 219).
A research study looking into drip irrigation of coffee plants found that in the first year of cultivation, the test plot without irrigation had a very high percentage of peaberries, at 21 percent of the total crop (Barbosa et al., 2015). The report states, ‘The production of peaberries is partially related to adverse environmental factors, mainly in the flowering and fruiting. So appropriate management of irrigation in these phases provided better conditions for the formation of beans, thus reducing the percentage of peaberries.’ Research demonstrated that air temperatures close to 24º C (1 degree above the upper limit of what is considered optimum for arabica coffee) increases the amount of peaberries harvested (Pezzopane et al., 2007 and Barbosa et al., 2015).