Fruit Pigmentation Experiment
At POMA, we're continually exploring the factors that influence the sensory profile and overall quality of coffee. In this controlled experiment, we examined whether the pigmentation of coffee cherries, specifically comparing coffee fruits with orange ripening colour with the traditional red ones - and whether it plays a role in the final cup quality. While fruit color mutations are common in coffee varieties (often arising from changes in anthocyanin or carotenoid pathways), their direct effects on coffee quality and chemistry have been greatly underexplored. This study aimed to isolate pigmentation as a variable by growing both clones of the same variety ‘Caturra’ under identical conditions.
Experimental Design
To ensure any observed differences stemmed solely from the genetic variation in fruit pigmentation, we conducted the trial in a climate chamber in a climate-controlled greenhouse. This setup allowed precise regulation of temperature (maintained at 22°C daytime, 16°C nighttime), humidity (80%), light exposure (simulating moderate shade with LED grow lights at 300 µmol/m²/s and a photoperiod of 12 hours), and drip fertigation (drip system delivering consistent nutrients via a balanced nutrition mixture).
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Both the orange Caturra (a stable mutation selected for its orange fruits, rich in carotenoids) and red Caturra (the standard form with anthocyanin-dominant red pigmentation) were propagated from cuttings to ensure genetic uniformity.
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Plants were grown side-by-side in identical pots with the same soil mix (peat moss for optimal retention and drainage and pH 5.8).
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All agronomic practices were synchronized: pruning, thinning, harvesting etc.
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Post-harvest processing followed our standard cold-washed protocol: depulping, 48-hour cold storage at 8°C, washing, and controlled slow and cold drying to 11% moisture.
This rigorous control eliminated confounding factors like weather, soil heterogeneity, agronomical factors, processing, etc., allowing us to attribute outcomes directly to the pigmentation differences.
Key Findings
After roasting and cupping, we analyzed the coffee for sensory attributes and chemical composition via Gas Chromatography-Mass Spectrometry (GCMS).
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Cupping Scores: The red Caturra achieved an average score of 87.25, showcasing its classic profile of dense sweetness, creamy body, and notes of red fruits and caramel, with a pleasant vibrant acidity and aroma complexity. The orange Caturra scored slightly lower at 86.75, with a richer sweetness - adding subtle tropical yellow fruit (mango, apricot) and buttery mouthfeel alongside the base notes.
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Aroma Chemistry: The GCMS analysis revealed higher levels of carotenoid-derived compounds in the orange clone as the outlier, introducing compounds such as beta-ionone (tropical fruit-like aromas) and beta-damascenone (honeyed, fruity aromas), which were 27% more abundant than in the red variant - yielding those sweet honey-like aromas and yellow tropical fruit profile. However, the overall intensity and diversity of esters (providing fruit-forward aromas) is higher in the red variant, contributing to a more complex red fruit-forward profile.
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Titratable Acidity: Looking at the concentrations of titratable acidity in the fruit and seeds, the red variant generally shows higher levels of individual acids and overall acidity, suggesting a more vibrant cup profile - supporting the cupping evaluation. The lower acidity level in the orange variant could also explain the higher perceived sweetness.
