3.3. Effects on NEB, viscosity and color attributes
The effects of combined treatment of sonication and PEF on NEB of grapefruit juice are shown in Table 2.
NEB values of sonicated and PEF treatments were significantly increased (p < 0.05) when compared with control, but the highest value of NEB was observed in the combined treatment.
Increase in NEB might be attributed to the breakdown of coloring pigments, and reaction and variation of natural pigments, respectively.
The results were in agreement with that of sonicated apple cider (Ugarte-Romero, Feng, Martin, Cadwallader, & Robinson, 2006) while Tiwari, Muthukumarappan, et al. (2008) observed an increase in browning of orange juice with increasing ultrasonic intensity (8.61e22.79 W/cm2) and treatment time (2e10 min).