In contrast, a great synergistic effectwas obtainedwhen applying+heat in the presence of citral or lemon EO. Interestingly, although (+)-limonene is the major IC in mandarin and lemon EO, citral is also present in lemon EO (Espina et al., 2011). Furthermore, differences in the structure or function of each compound could account for differences in the sensitizing thermal effect of PEF in the presence of each additive.