Investigation of extraction phenomena in continuous circulation coffee brewing and comparison with other brewing methods

Abstract

This study investigated a continuous circulation cold brewing (CCCB) process using a modified single‐serve brewer that allowed recirculation of the brew within the single‐use capsules. The changes of total dissolved solids (TDS), titratable acidity (TA), caffeine and 5‐caffeoylquinic (5‐CQA) concentrations over time during the CCCB process were evaluated using two masses of coffee grounds (10 and 12.5 g). To elucidate the extraction process, Weibull distribution, pseudo‐first order, and pseudo‐second order models were fitted to the extraction kinetics data. The physicochemical quality of the brews produced from the CCCB process were also compared to brews produced though traditional cold brew steeping (separated by gravity and forced filtration) and single‐serve hot brewing processes. Significantly lower (p < 0.05) TDS, TA, and 5‐CQA concentrations than traditional cold brew methods were observed. This observation was due to flow channeling/detachment phenomena in the coffee bed which resulted in localized flow and reduction of coffee‐water contact area. In comparison, the 30 min full immersion processes resulted in approximately 70% of the TDS, TA, and caffeine levels during the first 30 min of brewing, suggesting that cold brewing processes may not have to be >8 h in length if these are the targeted brew quality indices.Practical applicationsThis study examined the kinetics and physicochemical quality of continuous circulation cold brewing of coffee and compared it to traditional full immersion cold brewing methods. The findings in this study indicated that: (1) The brew recirculation method explored was not on par with traditional full immersion cold brewing methods in terms of extraction yield due to flow channeling issues present in single‐use capsules; (2) The extraction time of traditional cold brewing processes can potentially be shortened on the basis of TDS, TA and caffeine content; (3) The choice of filtration mechanism is significant when considering the extraction yield of a brewing process.