Evolution of Physico-Chemical and Microbiological Parameters During Large-Scale Coffee-Pulp Silage

Abstract

Coffee-pulp (CP) is an agricultural by-product produced in tropical regions. The high moisture and high carbohydrates content promote rapid spoilage by microorganisms together with detrimental consequences for the environment. Proper conservation of this biomass could be useful as a substrate for other processes. The feasibility of CP silage without any additive was studied at a large scale. Four silages were carried out each one containing 4.5 t of CP. Coffee-pulp silage was monitored during three months and samples were collected at regular intervals of time. Samples were used to determine microbiological parameters (lactic acid bacteria and yeasts population) and physicochemical variables like dry matter, pH, water-soluble carbohydrates, organic acids and ethanol. In all the 4 silages carried out, a high level of lactic acid was rapidly reached, decreasing the pH. Additionally, acetic and propionic acids were produced inducing an antifungal effect. Limited ethanol production was observed in the first days of silage due to the yeast´s activity. The internal temperature of silos rose indicating residual aerobic activity. Stable silage conditions in terms of high lactic acid concentration (> 8% DM), low pH (3.9) and no butyric acid production, were established during the first 72 h. These CP silage variables were kept constant after 30 days and until 90 days. Coffee-pulp is a suitable agricultural by-product for in situ conservation at large-scale silage process without addition of inoculum.