Antioxidant properties of ready-to-drink coffee brews

The influence of some technological variables on the changes of the antioxidant capacity of ready-to-drink coffee brews was investigated. Results showed that, depending on the roasting degree as well as on the packaging conditions adopted, redox reactions, which can take place during storage, are responsible for significant changes in the overall antioxidant capacity of the product. In particular, the redox potential of air-packaged coffee brews, obtained from light- and medium-roasted beans, showed maximum values after 2 days of storage, which corresponded to a minimum in the chain-breaking activity, while, in the case of the dark-roasted sample packaged under ordinary atmosphere, both the redox potential and the chain-breaking activity showed a maximum around 2-3 days of storage. In contrast, in the absence of oxygen, the coffee brews maintained the initial reducing properties over all the storage time, although the radical-scavenging activity values changed in a way very similar to that of the air-packaged sample. These results suggested that the changes in the antioxidant properties of the coffee brews may be attributed to a further development of the Maillard reaction during storage.