The role of drying methods on enzymatic activity and phenolics content of impregnated dried apple

Infusion of antioxidants into vegetables is a new food strategy managed by matrix processing. Raw and blanched apple were air- or freeze-dried. In the case of freeze-dried samples, different freezing methods were previously applied: conventional (-28 degrees C), blast freezing (-30 degrees C), and liquid N-2 (-196 degrees C). Afterwards, air- and freeze-dried samples at different conditions were impregnated with a concentrated (40 degrees Brix) tea extract and finally, air-dried for their stabilization. Total phenolic content (TPC), antioxidant capacity (AC), enzymatic activity, and microstructure were analyzed. Regardless of pretreatments, the impregnation and the further drying improved the antioxidant potential. Samples with the most porous microstructure free of degradative enzymes provided high AC (78.5 +/- 0.9mg Trolox/g dried matter) and TPC (16.7 +/- 0.2mg GAE/g dried matter).