Pollination Experiment
It is commonly known that better pollination results in better fruit set and yields. However, pollination is a fundamental yet often overlooked factor influencing coffee quality. While Coffea arabica varieties are largely self-pollinating, they are also capable of receiving and utilizing pollen from other Arabica varieties. This capacity for cross-pollination introduces the potential for genetic exchange and seed alterations, which may affect not only yield and fruit set, but also cup quality. Despite this, the role of pollination partner in shaping quality attributes has not been systematically studied under controlled conditions.
Experiment
In this study, we investigated the influence of cross-varietal pollination on the quality of Arabica coffee. Specifically, we examined whether the identity of the pollen donor could impact sensory attributes and chemical composition of the resulting seeds. To enable clear observation of any deviations in cup profile, we selected the SL28 variety as the maternal plant. SL28 is known for its highly distinctive sensory traits—particularly its pronounced blackcurrant and fruity notes—making it an ideal baseline for detecting changes associated with different pollination partners.
During flowering, we transported pollen from the donor varieties (SL28, Caturra, Geisha, Typica) to the maternal variety (SL28) where we had all the receptive flowers caged up to not receive any outside pollen. The maternal variety had the male parts removed to avoid self-pollination.
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The experimental design allowed for precise control of pollination events, ensuring that any observed differences could be attributed to the pollen source. Post-harvest, the seeds were processed using our cold washed process and analyzed using Gas Chromatography-Mass Spectrometry (GCMS) to characterize aroma profiles.
Results
The findings from this controlled pollination study reveal subtle yet meaningful variations in coffee quality and aroma composition depending on the identity of the pollination partner, even within a single maternal variety (SL28). Notably, all samples had a least the same score as the control (SL28 pollinated with SL28), indicating that cross-pollination did not detract from baseline quality. However, differences in both the cupping scores and the aroma compound profiles suggest that the pollination partner can exert a detectable influence.
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SL28 × SL28 (self-pollination) and SL28 × Caturra both yielded a cupping score of 86 and shared a common aromatic dominance by esters. This suggests that pollination by genetically similar or less aromatically distinct partners may not significantly alter the perceived sensory profile.
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SL28 × Geisha resulted in the highest score (87) and introduced a more complex aroma profile, with both esters and terpenes dominating. Terpenes are associated with intense floral, citrus, and spicy (brown sugar, cardamom) notes, which aligns with Geisha’s known aromatic intensity and may explain the enhanced score. This result supports the hypothesis that pollen from highly aromatic varieties can positively influence cup complexity.
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SL28 × Typica scored slightly higher than the self-pollinated control (86.5) and showed ester and ketone dominance. Ketones can contribute creamy, buttery, or fruity nuances, suggesting a qualitative shift in the sensory character of the cup.