Effect of microencapsulation on antioxidant and antifungal properties of aqueous extract of pomegranate peel.

The aqueous extract of pomegranate ( L.) peel compounds was freeze-dried (FDPOPx) and encapsulated using two wall forming components at two concentrations (maltodextrin: MDX and β-cyclodextrin: βCDX; 5 and 10%) with a mass ratio of 1:5 (extract/wall material). Different properties of the encapsulated powders (bioactive components, physicochemical and morphological properties) and storage stability of prepared microcapsules were evaluated during 42 days of storage at a different relative humidity (52 and 75%) and temperatures (4 and 25 °C). Encapsulated powder with βCDX-10% had the highest total phenolic compounds (TPC: 58.78 mg GA/g) and antioxidant capacity [FRAP: 1414.76 μmol Fe/g and DPPH assay (RSA): 77.83%] among other wall materials. The amounts of TPC and their antioxidant capacity decreased during the 42 days of storage. However, the highest TPC was observed in the freeze-dried MDX-10%  % encapsulated powder at 4 °C storage temperature and 52% relative humidity with a half-life (t) of 81 days, the reaction rate constant (k) of 0.85 × 10 min and the glass transition temperature of 69.73 °C. In addition, the polyphenolic extracts (both free and encapsulated) were able to control the growth of yeasts and molds, and maintaining the sensory properties of cupcakes as the model food system. The lowest growth after 9 days of storage of cupcake was observed in samples prepared with 1.5% of microencapsulated powder (MDX-10%) which was equivalent to the effect of the chemical preservative potassium sorbate.