Abstract
Organoleptic and biochemical attributes in the coffee bean determine the final cup quality of coffee which is a critical factor in the price determination of coffee in the market. The study aimed at determining the genetic variability of the green coffee bean. The trial sites were located at Siaya and Busia counties in Kenya. Nineteen different genotypes were established and included Arabusta coffee hybrids, backcrosses of Arabica to tetraploid Robusta, Arabica coffee, Robusta coffee, and Arabusta coffee. Randomized Complete Block Design with three replications in each site was used in conducting the experiment. The coffee beans were harvested in the year 2018 and extraction and calculation of sucrose, trigonelline, caffeine, and chlorogenic acids was carried using the recommended methods. The cupping procedure involved the use of five judges in assessing the flavor, aroma, balance, overall standard, acidity, body, and aftertaste of the roasted coffee beans. The sensory evaluation used the Specialty Coffee Association (SCA) method. There were significant variations recorded for the traits that were measured. All the traits were highly heritable registering values of > 50% for heritability whereby, caffeine and oil were highly heritable traits with 90.8% and 88.9% respectively. Oil had a high phenotypic coefficient of variation, genotypic variation, and response values when compared to the other traits. All the organoleptic traits were positively correlated with sucrose, trigonelline, and oil but the correlation with caffeine and chlorogenic acids was negative. The genotypic effects contributed largely to the high heritability recorded with a low influence from the environmental factors.
Highlights
Coffee is an important beverage being the second traded commodity after petroleum (Sunarharum et al, 2018; Tolessa et al, 2019)
The broad-sense heritability varied within the attributes measured whereby, caffeine showed the highest percentage of heritability followed closely by oil and sucrose whereas body and balance exhibited the lowest percentages of heritability
The significant differences within the mean ranges indicate that there is a wide variation in the organoleptic and biochemical performance of the genotypes for the attributes mentioned. This indicates that genetic variability is an important criterion in the selection of high-quality coffee varieties in coffee improvement programs
Summary
Coffee is an important beverage being the second traded commodity after petroleum (Sunarharum et al, 2018; Tolessa et al, 2019). Coffee supports the livelihoods of over 125 million people in the world within the whole value chain (Bunn, 2015). In Kenya, coffee is the fourth most important commodity that contributes greatly to the Gross Domestic Product (GDP) with earnings of about US$230 million supporting over 700,000 livelihoods (International Coffee Organization, 2019). Kenya prides itself on being among the top producers of the best quality coffee in the world and this is favored by the good environmental conditions which include well-distributed rains, high altitude, red volcanic soils, and processing methods among other factors. The quality of coffee; physical quality, liquor quality, and biochemical attributes are dependent on genetics, environmental factors, agricultural practices, and the post-harvesting processing methods (Gichimu et al, 2014; Leroy et al, 2006)
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