Effect of PEF pre-treatment on drying kinetics and quality parameters of kiwifruit chips

Nowadays, product diversity, longer shelf-life and great volume reduction are the reasons for the popularity of dried fruits and vegetables, and this could be further expanded with the improvements in product quality and process applications. In particular, osmotic dehydration (OD) and/or pulsed electric field (PEF) combined with air drying allow to obtain dried products by accelerating mass transfer phenomena. The aim of this work was to investigate the effect of PEF and OD pre-treatment on the drying kinetics, texture, color, polyphenol content, vitamin C, antioxidant activity and sensorial analysis of dried kiwifruit. Kiwifruits slices (5 mm thick) were subjected to OD process (40% trehalose, 35°C, 2.5h). PEF treatment was applied before and/or after OD by using electric field strength of 200 V/cm and 100 near-rectangular shaped pulses, with fixed pulse width of 100 μs and repetition time of 10 ms. The differently treated samples were subjected to air drying at 70°C. The results showed that the application of OD process reduced the drying time and further combining the PEF application. All treated samples maintained a good crispiness as well as non-treated kiwifruits (control) while better retention of hue color parameter was observed for OD pre-treated samples. Kiwifruit snacks treated with OD showed a better preservation of antioxidant activity, polyphenol and vitamin C content; on the contrary for PEF kiwifruit slices was noticed a reduction in comparison to the other samples. Panelists appreciated more kiwifruit slices pre-treated with a combination of PEF and OD compared to control ones. Based on the results the combination of PEF and OD allowed to reduce drying time for the production of kiwifruit slices whit high quality characteristics.