The impact of pulsed electric fields on quality parameters of freeze-dried red beets and pineapples

The effect of pulsed electric fields (PEF) on the cell disintegration index (Zp), the freeze-drying process and the final product quality of red beet and pineapple tissue was studied. Red beets and pineapples were PEF-treated at an electric field strength of 1.07 kV/cm and specific energy inputs of 1 kJ/kg and 4 kJ/kg (PEF1 and PEF2, respectively). Freeze-drying was performed at a pressure of 1 mbar and heating plate temperature of 50 degrees C for red beet and 40 degrees C for pineapple. The quality of freeze-dried tissue was evaluated by the analysis of residual moisture content, macrostructure, texture, colour and rehydration properties. For freeze-dried red beets, the betalain content from extracts was studied. It could be stated that PEF pre-treatment had no significant influence on drying time reduction, however significantly improved the final quality of freeze-dried product. Moreover, the effect of PEF was strongly depending on type of plant material used.

Automated summary

The study investigated the impact of pulsed electric fields (PEF) on the cell disintegration index (Zp), freeze-drying process, and final product quality of red beet and pineapple tissue. While it did not reduce drying time, PEF pre-treatment significantly enhanced the quality of the freeze-dried product. The effectiveness of PEF was found to be dependent on the type of plant material used.