Determination of an Antioxidant Capacity Index by Immobilized Tyrosinase Bioreactor

Immobilized tyrosinase on aminopropyl-controlled pore glass support (AMP-CPG) was used to determine the antioxidant capacity index and the total phenol content in juices, integrators, infusions, jams, and drugs containing bilberry fruits. The method is based on the chromatographic determination of the decrease of total ingredients content, absorbing at 280 nm, by mushroom tyrosinase oxidation. In comparison with the widely used Folin-Ciocalteu method (FC), this enzymatic method appears to be more specific and rapid and as whole is not affected by interfering compounds such as citric acid and sugar. The results were also compared with those obtained by 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)/persulfate antioxidant assay, expressed as Trolox equivalents (TEAC). Using all 17 samples, a good linear correlation (r(2) > 0.94) was observed between the enzyme assay and both the FC and TEAC assays. Poor correlation (r(2) < 0.4) with the other tested methods (pH-differential, vanillin index, and butanol-HCl assays) was evidenced. This shows that the enzymatic assay cannot be applied for a specific phenol class determination, but it is sensitive to the total phenolic content.