Antioxidant capacity retention rose when both the frequency and pulse width were increased from 50 to 200 Hz and from 1 to 7 ls, respectively. In addition, antioxidant capacity retention was the lowest at 30 kV/cm and the highest at about 35 kV/cm. Thus, antioxidant capacity retention was best maintained after HIPEF treatment at 200 Hz. and 35 kV/cm applying 7 ls bipolar pulses for 1050 ls (Fig. 3).The antioxidant capacity is related to the amount and composition of bioactive compounds present in food (Sánchez-Moreno et al.,2005). Watermelon contains small amounts of vitamin C and phenolic compounds, whereas it has been reported to be an excellent source of carotenoids. In fact, a 75% of the total carotenoid content in some watermelon cultivars was lycopene (Gil et al., 2006). In this study, the antioxidant capacity of HIPEF-treated watermelon juice could be mainly attributed to lycopene content, as antioxidant capacity retention was highly correlated with lycopene relative content (R2 = 0.964).