Antioxidant and prooxidant activity of spent coffee extracts by isothermal calorimetry
MetadataShow full item record
This work aims to determine the antioxidant and prooxidant activity of spent coffee extracts obtained with (1) a lowpressure (LP) extraction with ethanol and (2) a subcritical ﬂuid (SF) extraction with carbon dioxide and ethanol as cosolvent. The antioxidant capacity of both extracts was measured by two calorimetry-based approaches. The ﬁrst assessed the capacity of the extracts to inhibit the lipid oxidation of a standard solution of linseed oil. The second measured the capacity of the extracts to inhibit the radical decomposition of AIBN, a free radical generator. Both approaches showed that LP extracts had a higher antioxidant capacity than SF extracts. However, when SF extracts were further puriﬁed with ethanol, the resulting sub-fraction showed an antioxidant capacity comparable to that of LP extracts. Conversely, when SF extracts were puriﬁed with hexane, the resulting sub-fraction exhibited a prooxidative capacity, either speeding-up the oxidation of linseed oil and the decomposition rate of AIBN. Such prooxidative capacity was explained with the high content of unsaturated fatty acids contained in the hexane sub-fraction. Overall, this work showed that LP technique provided an extract with high antioxidant activity. Moreover, the results indicated that SF extraction could also serve as a technique for the recovery of antioxidants from spent coffee once the extract was furthermore puriﬁed and the lipid fraction removed.