Effect of pulsed electric fields (PEFs) on the pigments extracted from spinach (Spinacia oleracea L.)

In order to investigate the effect of PEF on the pigments of spinach, pigments were extracted and were treated by different electric field strength at different temperatures (20, 35 and 45 °C). Results showed that with the increasing temperature, the degradation of chlorophyll content was appeared for pigments without PEF treatment. However, the concentrations of chlorophyll a, b and carotenoids were increased by the PEF treatment, especially for the higher electric field strength. Moreover, the structure of spinach pigments treated by PEF also was determined by UV–Vis, FT-IR and XRD. From the structural information, it was indicated that the effect of PEF treatment mainly focused on the hydrogen bonds and the pyrrole ring of chlorophyll, as well as the crystal structure of the compound was modified. In addition, the PEF treatment also significantly increased the antioxidation activity of pigments over the series of temperatures.Industrial relevanceThis study provide evidences that the PEF treatment can inhibit the degradation of chlorophyll and carotenoids, and can increase the antioxidation activity of extraction solution compared to the thermal treatment. From the structural information, it was indicated that PEF can promote the crosslink reaction with other chlorophyll moleculars, and formed the chlorophyll-aggregated structures, such as dimers and oligomers chlorophyll. Therefore, the PEF treatment is an efficient food processing method, especially foods rich in pigment.