Effect of high-pressure processing on colour, phytochemical contents and antioxidant activities of purple waxy corn (Zea mays L. var. ceratina) kernels

High-pressure processing (HPP) at 250-700 MPa for 30-45 min affects the colour parameters, phytochemical contents and antioxidant activities of purple waxy corn kernels (p < 0.05). The higher pressure-level, the lower L*, a*, b*, C* and h(o) (p < 0.05). However, pressure-treated kernels at 700 MPa showed a similar colour profile to steam-treated kernels. HPP caused a loss in the total phenolic, flavonoid, and anthocyanin contents and antioxidant activities. The pressure-treated kernels had a higher phytochemical content than the steam-treated kernels. The phytochemicals and antioxidant activities decreased as the pressure increased from 250 to 550 MPa, but the levels recovered at 700 MPa. The longer holding-time, the greater loss of the compounds and antioxidant activities (p < 0.05). Pressure treatment at 700 MPa yielded the highest total phenolic and anthocyanin contents (p < 0.05). Water-soluble compounds can leach from food materials due to cell rupture. Nevertheless, HPP is a potential process to preserve the phytochemicals in food.