Effect of pulsed electric fields (PEF) on physico-chemical properties, β-carotene and antioxidant activity of air-dried apricots

Fresh apricots pre-treated by pulsed electric fields at different intensities [LPEF, 0.65 kV/cm, 100 Hz, 20 mu s and total treatment time 30 s; HPEF1, 1.25 kV/cm, 100 Hz, 20 mu s and total treatment time 30 s; HPEF2, 1.25 kV/cm, 100 Hz, 20 mu s and total treatment time 60 s], along with controls [non-treated, non-treated and sulphite treated, and heat pre-treatment at 80 degrees C, for 10 min (HC)] and soaked in 0.2% sodium sulphite solution for 1 h and then were subject to hot air drying. The changes in drying rate, polyphenol oxidase, peroxidase, and beta-carotene contents as well as antioxidant activity and colour in pre-treatment and hot air-dried apricot samples were investigated. PEF and heat treatments increased the drying rate of apricots. PEF treatments had no effect on the PPO activity and decreased the POD activity (p < 0.05). HPEF2 treatment retained more beta-carotene, higher antioxidant activity and suffered less browning during processing. Overall, the results indicate that combining sulphite treatment with PEF produces dried apricots with more beta-carotene and antioxidant activity, and better colour.