Increasing the quality and complexity of pulped coffee fermentation with Lactiplantibacillus plantarum and selected yeasts

Abstract

Volatile and nonvolatile compounds directly impact the quality of coffee beverages. This study demonstrated how chemical and sensory compounds were affected by three starter cultures (Saccharomyces cerevisiae, Torulaspora delbrueckii, and Lactiplantibacillus plantarum) inoculated separately and co-inoculation using the self-induced anaerobic fermentation (SIAF) method for pulped coffee.High-Performance Liquid Chromatography (HPLC) analyzed carbohydrates, bioactive compounds, and organic acids. Gas chromatography (GC‒MS) examined volatile compounds, monitored microbial composition by quantitative real-time PCR (qPCR), and performed sensory analysis using the cupping test. During fermentation, fructose was the predominant carbohydrate. Lactic acid concentrations were more expressive at the end of the process in the liquid fraction, with higher levels detected in the control (6.93 g·kg⁻¹). In all fermentations, the concentrations of chlorogenic acids and trigonelline decreased after the roasting process, while the levels of caffeine increased. Esters, such as methyl salicylate and 2-hydroxy benzoic acid ethyl ester, which contribute to the perception of fruity and caramelized notes, were formed during the fermentation process. The fermentation with S. cerevisiae and T. delbrueckii presented different descriptors from spontaneous fermentation, such as chocolate, nuts, and almonds. L. plantarum fermentation showed blackberry, spices, and nut/cocoa flavors. Fermentation using co-inoculation (S. cerevisiae and L. plantarum) produced coffees with unique aromas, including honey, brown pepper, nutmeg, and cinnamon. Therefore, wet coffee processed using the SIAF method, adding inoculum of yeasts and lactic acid bacteria, delivers a more complex and exquisite beverage.