Process characterization and optimization of cold brew coffee: effect of pressure, temperature, time and solvent volume on yield, caffeine and phenol content

BACKGROUND Cold brew coffee, based on cold extraction, is rapidly attracting consumers' preference worldwide. Low total solids yield and long extraction times (up to 24 h) are the main drawbacks of this process. Five different treatments were investigated: the traditional cold extraction method, freezing, lyophilization of coffee beans, use of chaotropic salt and reduced pressure extraction. The latter was optimized by applying a Box-Behnken design. Pressure, vacuum cycles, duration of each cycle and mass of ground coffee to water ratio were the optimization parameters. Yield, caffeine and phenol concentration were the response variables. RESULTS Caffeine concentration and yield were significantly affected by vacuum cycles and by the combination of vacuum cycles and duration of each cycle. Validation of the derived quadratic models for each response variable was performed. Optimum values for highest extraction yield (22%) and phenol concentration as well as mass transfer coefficients of phenol and caffeine were also determined. CONCLUSIONS Extraction under reduced pressure might be the best treatment for the acceleration of cold brew coffee extraction. (c) 2021 Society of Chemical Industry

Automated summary

In this study, it was found that extraction under reduced pressure may be the best method for accelerating cold brew coffee extraction, with vacuum cycles and duration of each cycle significantly affecting caffeine concentration and yield. Experimental results indicate that optimal values can be determined to obtain the highest extraction yield and phenol concentration.