Comprehensive Characterisation of the Robusta Coffee Postharvest Processes: Insight into Physicochemical, Volatile Compounds, and Sensory Preferences

This study investigated how different postharvest processes, specifically wet, semi-wet, and hybrid methods, affect the physicochemical quality and aroma profile of Menoreh Robusta coffee. We mapped the volatile composition of roasted coffee beans using solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GCMS). All samples met the physical standards of the Indonesian National Standard for green beans and the Specialty Coffee Association, but their chemical compositions varied significantly. Principal component analysis (PCA) revealed distinct clustering, confirming that each processing imparts unique chemical signatures to the final product. The hybrid process proved superior in maintaining nutrient density, resulting in higher glucose, fructose, chlorogenic acid, caffeine, fat, protein, and crude fibre contents compared to the other methods. The wet process maximised antioxidant properties, evidenced by the lowest DPPH IC₅₀ value (7.51 ppm) and the highest ABTS radical scavenging activity (88.32), as well as the highest total flavonoid (181.22 mg QE/g) and phenolic (139.45 mg GAE/g) levels. Meanwhile, the semi-wet sample had the highest carbohydrate content (65.66). Analysis of volatile compounds revealed a complex chemical matrix involving ketones, pyrazines, and esters, among others. Sensory assessments showed that although approximately 35 of flavour attributes were similar across treatments, the flavour profile was dominated by distinctive aromas of brown sugar, spices, coconut milk, chocolate, and rubber. All postharvest treatments yielded cupping scores exceeding 80, validating the classification of the Robusta Menoreh as a Fine Robusta regardless of the processing strategy used. © Universiti Putra Malaysia Press.