Evaluation of Physicochemical Characteristics of Kenyan Coffee Variety ‘Ruiru 11’ according to Green Bean Processing Method

Abstract

This study examined the characteristics of green coffee beans and extracted coffee solutions based on processing methods to understand their quality impact factors. Nine samples of the Kenyan coffee variety ‘Ruiru 11’ were analyzed. The study measured defects, moisture content, density, and color of green beans, as well as the pH, Brix (%), and total dissolved solids (TDS) of extracted coffee after roasting. Different processing methods showed varying characteristics, with the honey processing method having the highest defects but the natural processing method receiving the most deductions when scored. The washed processing method exhibited the highest moisture content, likely influenced by fermentation in water. The natural processing method had the lowest density, which was consistent with previous studies. The color, redness (a*) and yellowness (b*) values were highest for the natural processing method because the cherry was dried with its pulp intact, affecting the sugar content. Brix (%) was highest for honey processing, while TDS was highest for natural processing due to sugars from cherry mucilage transferring to the beans during drying. The pH results did not meet expectations, possibly influenced by uncontrollable roasting intensity or unselected pH-affecting defects in samples. The study highlights the physicochemical differences in ‘Ruiru 11’ coffee based on processing methods, providing foundational data for coffee processing understanding and Kenyan coffee product development. Nevertheless, additional research in connection with sensory evaluation is necessary.