Osmotic dehydration of organic kiwifruit pre-treated by pulsed electric fields and monitored by NMR

- NMR is an excellent technique for quantifying water molecules according to their situation in fruit tissue.
- NMR allows us to obtain the adsorbed water of tissue (membranes and cell wall).
- NMR opens the possibility to apply the BET model over the whole range of water activity.

Osmotic dehydration (OD) is a widely used preservation technique that consists in the reduction in food water activity by the immersion of the biological tissue in hypertonic solutions. The aim of this work was to analyze the effect of pulsed electric fields (PEF) in mass transfer as a pre-treatment of the OD using NMR. In this sense, PEF pre-treatments were done using three different voltages (100, 250 and 400 V/cm) and 60 number of pulse. The OD of kiwifruit was carried out in 61.5% of sucrose solution at 25 °C, for a contact period from 0 to 120 min. The water distribution into the cellular tissue was studied by NMR relaxometry. In conclusion, NMR is an excellent technique for quantifying water molecules according to their interactions in the fruit tissue, obtaining the adsorbed water and opening the possibility to apply the BET model to fit the adsorbed isotherm over the whole range of water activity.