Physicochemical and Sensory Attributes of Robusta Coffee as Influenced by Sorbitol Concentration and Roasting Time

Many studies have reported several methods to improve the quality of Robusta coffee such as fermentation, but it takes a relatively long time. In this study, a new processing method for Robusta coffee quality enhancement was investigated. Robusta coffee cherry was immersed using sorbitol solution under different concentrations (10%, 15%, and 20%), then the green bean coffee was roasted with several roasting duration (1, 3, and 5 minutes after coffee beans cracking) to determine the characteristic of coffee produced. Characteristics examined were chemical responses consisted of water content, pH, caffeine content, and anti- oxidant activity (IC50); physical responses consisted of L* color attribute; and organoleptic responses consisted of color, aroma, taste, and aftertaste. Principal component analysis (PCA) was employed to examine the qualitative correlations between dependent variables. The results demonstrated that the concentration of sorbitol of 10% to 20% altered the organoleptic reaction but not the physical and chemical responses. The roasting time impacted the coffee’s water content, pH, antioxidant activity (IC50), color, flavor, and aftertaste, but not its caffeine content and aroma. The interaction between sorbitol concentration and roasting time influences the color, flavor, and aftertaste characteristics of coffee. This finding led to an improvement in the quality of Robusta coffee. Furthermore, PCA showed that IC50 value was positively correlated with pH value and was conversely correlated with water content and L*, and slightly correlated with caffeine. Sensory attributes had no correlation with variables of IC50, caffeine and pH, and L*

Evaluation of Fluidized-Bed and Drum Roaster Performance in Roasting of Robusta Green Bean

The roasting process is essential in producing ground coffee as it is where coffee's distinctive aroma and flavour are developed. There are two coffee roasters: drum and fluidized bed roasters, each with benefits and drawbacks. This study aimed to determine the effects of roasting machine type and roasting level on the characteristics of Robusta coffee. The experimental design used was a 2x3 factorial of a Randomized Block Design. The results indicated that the water content, ash content, caffeine content, total phenol content, bulk density, colour, coffee ground aroma, brewing colour, brewing aroma, bitterness, acidity, and sweetness were all affected by roasting level. The interaction between roaster type and roasting level affected the water content, total phenol content, bulk density, colour, ground coffee aroma, brewing aroma, bitterness, and acidity. The analysis of volatile compounds in ground roasted coffee by hot-air and drum roasters at light, medium, and dark levels revealed 40, 20, 18 and, 46, 48, 48 volatile compounds, respectively. As a conclusion it was found that the type of roasting machine and the degree of roasting have a strong influence on different characteristics of coffee powder, including moisture content, ash content, total phenol content, volatile compounds, bulk density, colour, and sensory qualities like aroma, bitterness, acidity, and sweetness. However, they didn't have a significant impact on the caffeine content