The Effect of Pulsed Electric Fields (PEF) on Nanostructure and Monosaccharides Composition of Pectin Fractions Extracted from Green and Red Tomatoes

PEF technology is a non-thermal food process gaining popularity for treating fruits and vegetables. However, there has been little investigation into the impact of PEF on the biomolecular components of plant tissues. This study assesses the influence of PEF at low (1.5 kJ/kg) and medium (151 kJ/kg) intensities on the physicochemical parameters of pectin fractions isolated from green and red tomatoes. Monopolar exponential decay pulses of 1.0 and 10.0 kV/cm were delivered to alcohol-insoluble residue (AIR) recovered from mature green and ripe red tomatoes. Topography and recognition imaging were performed using atomic force microscopy (AFM) on three pectin fractions: water-soluble pectin (WSP), chelator-soluble pectin (CSP), and diluted alkali-soluble pectin (DASP). Image analysis has been used to characterize the geometrical properties of pectin. PEF treatments generated considerable structural alterations in all pectin fractions. The effect varied depending on the stage of tomato ripening and the energy input applied. The average length of WSP fibres in red tomatoes decreased dramatically (up to 50% shorter) as the intensity of the electric field increased. Green tomatoes showed the opposite effect, with the length of the WSP fibres increasing as the applied electric field increased. The monosaccharide composition revealed that PEF decreased pectin linearity independent of the fruit ripening stage. The data obtained on PEF-pectin interactions might assist in building tailored food processes that rely on pectin’s functional qualities and a better understanding of the effect of the ripening stage on PEF efficacy.