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

•High pressure at 700 MPa caused colour change in purple kernel similar to steaming.•Pressurized kernels had higher antioxidant activities than steamed kernels.•High pressure resulted in the loss of anthocyanin in the purple kernels.•Higher pressures, in range of 250-550 MPa, decreased the phytochemical contents.•At 700 MPa, the anthocyanin content in the kernels was higher than that at 550 MPa.

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 ho (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.