Fermentation of coffee pulp using indigenous lactic acid bacteria with simultaneous aeration to produce cascara with a high antioxidant activity

Abstract

Coffee pulp which is a by-product of coffee production contains considerable amounts of phenolic compounds that can be valorised to produce cascara as an antioxidant beverage. The fermentation and drying conditions of the coffee pulp have a great influence on the bioactive compounds in the cascara. This study aimed to investigate the effect of natural fermentation with simultaneous aeration on the phenolic content and antioxidant activity of cascara. A systematic study was carried out using a response surface methodology with a face-centered central composite design to determine the effect of fermentation time (0–8 h) and temperature (27–37 °C) on the number of bacteria in the coffee pulp after natural fermentation with simultaneous aeration (an air flowrate of 4 m/s) as well as phenolic content and antioxidant activity of cascara. The experimental dataset was modelled with an empirical model using multi-variable non-linear regression. A good agreement between model and experimental data was obtained. At the optimum conditions (4.2 h, 31.8 °C), the phenolic content was 6.72% whereas the antioxidant activity was 27.6%. Indigenous lactic acid bacteria were also isolated from the coffee pulp and determined as Leuconostoc pseudomesenteroides. The isolated bacteria can be used as a starter for controlled fermentation of coffee pulp as it increased the antioxidant activity up to 15% higher than the antioxidant activity of cascara obtained at the optimum conditions for natural fermentation with simultaneous aeration and 30% higher from the fresh coffee pulp.