In vitro determination of the lipophilic and hydrophilic antioxidant capacity of unroasted coffee bean extracts and their synergistic and antagonistic effects

Abstract

The yield extraction, basic compositional analysis, individual antioxidant capacity and synergistic/antagonistic antioxidant interactions of unroasted coffee bean extracts with different degree of polarity from different locations and species were studied and compared. The beans were extracted with hexane followed by methanol to obtain lipophilic and hydrophilic extracts, respectively. Furthermore, an autoclave extraction was conducted as a simple representative approach to obtain an antioxidant rich powder for industrial application. The antioxidant capacity of all extracts and their synergistic/antagonistic responses was determined by using different but complementary well-known kinetic methods of β-carotene and crocin bleaching assays, which are representative of lipidic and hydrophilic oxidation processes. The results of this study indicated that the yield distribution and antioxidant capacity of the hydrophilic extract were much greater than the lipophilic ones, but similar to the industrial approach. The potential equivalent capacity of the industrial approach indicated that raw coffee beans possess a high content of antioxidants, offering an alternative source of nutraceuticals as well as preservatives in food formulations. Finally, statistically consistent synergistic and antagonistic values were found between the extracted coffee residues and some commercial antioxidants of well-known degree of polarity. Interestingly, it was found that the extracted residues with an equivalent degree of polarity act similar to the additive mode of interaction between single chemical entities, and as an independent interaction mode when their degree of polarity varies. The results if transferable to more realistic food matrices in the food industry, may guide the development and evaluation of food products and processes, underlying different phenomena that may affect the quality of products.