Logarithmic scaling and effects of severity levels of ringspot disease on sensory quality of coffee brew

Abstract

A logarithmic scale was developed to evaluate the severity of the ringspot caused by Coffee ringspot virus (CoRSV) in coffee berries to investigate the effect of disease severity on the quality of brew. The scale comprised seven severity levels (0, 1 to 4%, 4.1 to 8%, 8.1 to 15%, 15.1 to 25%, 25.1 to 50%, 50.1 to 75%, 75.1 to 90%) and was evaluated for accuracy, precision, and reproducibility of severity estimation. The accuracy and precision were determined by simple linear regression between the actual and the estimated severity, considering twelve raters. Brew quality was assessed in berries with three severity levels (4.1 to 8%, 50.1 to 75%, 75.1 to 90%) and healthy berries. The selected fruits were processed and analyzed for electrical conductivity, total sugars, reducing sugars, non-reducing sugars, activity of polyphenol oxidase, and total phenol. The logarithmic scale obtained was easy to use and able to provide quick estimates of disease, good accuracy and good precision. Biochemical analysis of berries showed that polyphenol oxidase activity decreased with increasing severity, whereas total sugars and total phenol levels increased with increasing severity. This result indicated that the higher the CoRSV severity level, the greater the change in compounds directly related to the final quality of brew, which consequently contribute to coffee depreciation.