Enhancing Robusta Sensory Profile using Indonesian Lactic Acid Bacteria and Yeast as Fermentation Starter

In Indonesia, the majority of coffee production consists of Robusta which is predominantly sold as green beans. However, traditional processing methods without fermentation often lead to inconsistent quality. Therefore, this study aims to enhance Robusta green coffee bean quality and consistency by conducting fermentation using the lactic acid bacteria Enterococcus faecium and the yeast Pichia fermentans as starter cultures. Fermentation was conducted for 5 days at 30 °C, then every 24 hours, coffee beans were sampled for pH analysis, total yeast, and lactic acid bacteria count. Before and after fermentation, coffee bean samples were analysed for reducing sugar content using the DNS method, as well as chlorogenic acid and amino acid content using HPLC. Sensory analysis was conducted after fermentation. The results showed that after five days of fermentation, a decrease in pH was observed in all treatments. The application of the starter culture consisting of Pichia fermentans accelerated the growth of the total yeast population, while the addition of Enterococcus faecium enhanced the total lactic acid bacteria population. Fermentation caused a reduction in the reducing sugar content of all treatments. However, a significant rise in chlorogenic acid content was found in the treatment using Pichia fermentans, the combined treatment of Pichia fermentans and Enterococcus faecium, as well as in the control. The highest amino acid content after fermentation was generally obtained using the Pichia fermentans single-starter treatment, with the highest alanine, arginine, aspartic acid, leucine, glutamic acid, isoleucine, phenylalanine, valine, threonine, and tyrosine content. The treatment also produced the highest final cupping score of 81.65, classifying the sample as Fine Robusta coffee. This suggests that Pichia fermentans has the most beneficial effect on coffee quality. The cupping scores of brewed coffee treatment above 80 also suggest that Enterococcus faecium has the potential to improve coffee quality