Coffee is a commonly consumed beverage that is enjoyed by a large percentage of the world. However, it is a very diverse drink with each individual seeming to have a preference in the preparation of the beverage. Individuals and large corporations tend to dispose of spent coffee grounds (SCGs) after one extraction. Here, we show that SCGs that have already been used once in coffee brewing can be used to produce additional extracts containing similar compounds to the initial brew. Medium and dark roast SCGs from the same bean variety were acquired after extraction by hot brew, cold brew, and espresso methods. The total antioxidant capacity (TAC) and total caffeoylquinic acid concentrations of aqueous SCG extracts were investigated through HPLC analysis and five colorimetric assays including ABTS assay, total phenolic content, and FRAP assay. Results indicated SCG extracts from hot brew methods had the highest average TAC levels, while espresso SCG extracts had the lowest. SCGs extracts may be able to act as a substitute for standard coffee extracts in both syntheses and beverages as a part of greener chemistry.

Characterization of total antioxidant capacity in spent coffee ground extracts by roast and brewing method via UV-Vis spectrometry

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