Development of an innovative and rapid method to measure antioxidant compounds in red wine

Caffeic acid (CA) is an important antioxidant from hydroxycinnamic acid group found in wine, and in plants, can be extracted from by-products of food industry. The role of caffeic acid in wine is that can prevent it from oxidation and during wine aging, the phenyl pyranonathocyanin Pinotin A is formed from the direct reaction of caffeic acid with malvidin3-glucoside moreover, caffeic acid has moderate puckering astringency and bitterness effect; however, its impact on overall wine taste remains unclear. Lastly, caffeic acid could also be used as a potential inhibitor of aroma loss during aging with a consequent reduction in the SO2 addition during winemaking. The aim of this studies was to conduct an easy, fast, less expensive and especially a specific method to detect the caffeic acid (CA) for this matter a molecularly imprinted polymer specific to caffeic acid (CA-MIP) was prepared by radical polymerization using methacrylic acid as functional monomer, ethylene glycol dimethacrylate as cross-linker, and 2,2-Dimethoxy-2-phenylacetophenone as initiator, in the presence of CA as template molecule. Rebinding activities between the molecularly imprinted polymers (MIP) and non-imprinted polymers (NIP) toward CA were promoted by an indirect method and characterized by cyclic voltammetry (CV) using a screen-printed carbon electrode (SPCE). It is a fast method, which requires portable and easy to use instrumentation. The polymer (MIP) showed a high selectivity toward CA, good stability and repeatability. CA-MIP was then applied in red burgundy wine samples spiked with CA, and the results were compared to those obtained by a chromatographic (HPLC) method. With a limit of detection of 0.06 mM in wine, the recovery values confirm that the method is suitable for further applications.