Robusta coffee cherry fermentation: Physicochemical and sensory evaluation of fermented cascara tea

This study aims to investigate the effect of Robusta coffee cherry fermentation on cascara tea produced includes color, total phenolic content (TPC), total tannin content (TTC), antioxidant activity (DPPH radical scavenging activity [RSA]) and sensory acceptability. Fermentation was carried out using a completely randomized design consisting of spontaneous fermentation and fermentation with Saccharomyces cerevisiae, and both were performed at 3 fermentation duration (24 h, 48 h, and 72 h). The data were analyzed statistically using ANOVA with Duncan's post hoc test. Principal component analysis (PCA) and hierarchical clustering analysis (HCA) were employed to examine the correlation between dependent variables and determine treatment clusters. Results revealed that fermentation affects the physicochemical of dried cascara and tea produced. The fermentation time had effect on increasing yellowness (b*); decreasing pH, total phenolic content, and total tannin content; but had no effect on lightness (L*) and sensory evaluation both of spontaneous and S. cerevisiae fermentation. In the spontaneous fermentation, moisture content (MC), b* value, and antioxidant activity of cascara tea were not significantly different with increasing fermentation time, but in the fermentation with S. cerevisiae, the MC and b* value were increased, and its antioxidant activity was decreased due to fermentation duration. PCA showed that DPPH (RSA) was positively correlated with TPC, TTC, and pH, and was conversely correlated with MC and color coordinates (a* and b*). Practical applications Coffee pulp is a by-product obtained from the coffee cherry processing. It can be used as raw material for cascara (dried skins of coffee cherries) which contains many compounds with good antioxidant activity, and it's currently being submitted to be a novel food in the European Union. During development of functional drink, it is recommendable that the cascara-based beverages have an attractive composition, and enjoyable sensory characteristics, which make it acceptable for consumers. In this work, cascara treated with fermentation duration of 24 h in both cases (spontaneous fermentation and with S. cerevisiae fermentation) were categorized in the same cluster having the highest antioxidant activity, TPC and TTC. Thus, the potential use of fermented cascara as a tea drink is quite good as an effort to utilize this previously wasted residue.