Process-controlled gas hydrate formation in coffee solutions for the application of cold concentration

Abstract

CO₂ gas hydrates occur in aqueous systems at elevated pressure and low temperature. They offer prospect to energy efficiency and gentle concentration of liquid foods. In current research, the formation of CO₂ gas hydrates in a batch autoclave system for pure water and pure coffee (13–40 wt%) was investigated. Hydrate formation was highly reproducible. When reducing the temperature from 4 to 1 °C, induction times in 13 wt% coffee solutions approached zero, regardless of the applied target pressure (36 vs. 41 bar). Over the used range of temperature, pressure and concentration, different gas hydrate morphologies could be observed, ranging from dispersed gas hydrate crystals in coffee slurry to ordered, large-scale structures. The formation of large continuous hydrate structures bears application potential for efficient removal of gas hydrates from the concentrated liquid.