Original papersThe use of optical coherence tomography for the evaluation of textural changes of grapes exposed to pulsed electric field

- Hibernal, Johanniter and Marechal Foch grapes were exposed to the electric field.
- OCT imaging shows the effects of PEF interaction on the near skin fruit structure.
- LBP histograms, lacunarity, and entropy quantify structural changes in grapes.
- Marechal Foch red grape cultivar was found the most robust to the electrical field.

Application of pulsed electric fields (PEF) to food is a nonthermal technology of food processing. The short pulses of high intensity electric field can modify the internal structures of fruits and vegetables by affecting the cell permeability. In the presented study three popular grape wine cultivars - Johanniter, Hibernal and Marechal Foch were exposed to PEF at electric field strengths of 3.3 kV/cm and 5 kV/cm. The significant textural changes of near peel grape layers influenced by electric field were observed in optical coherence tomography (OCT) images, using infrared light of 1300 nm. These changes were expressed by the variation of entropy, standard deviation or lacunarity features and evaluated in a dedicated software tool developed by the authors in Matlab environment. The OCT is a non-destructive technique in which no sample preparation is needed and grapes still remain intact (undamaged) during imaging. The OCT cross-sections revealed the progressive process of expanding zone with strong echo in sub-peel layers what may indicate cell permeabilization or even loosing parenchyma cells integrity. Also grape surface deformations under PEF were quantified. It has been shown that the values of considered textural features in near peel grape tissue were related to the intensity of electric field. Marechal Foch cultivar appeared to be more resistant to PEF than two other grape varieties.