Effect of pulsed electric field coupled with vacuum infusion on quality parameters of frozen/thawed strawberries

In this study, pulsed electric field (PEF) was coupled with vacuum infusion (VI) to impregnate strawberries with cryoprotectants. Electroporation of fruits was reached with 5 bi-polar, rectangular pulses of 100 ms width with a nominal electric field strength of 850 V/cm. After PEF treatment, the strawberries were vacuum infused with a cryoprotective solution (12 g/100 g trehalose and 0.2 g/100 g acclimated winter wheat extract containing antifreeze proteins) for 14 min. The strawberries were frozen in liquid nitrogen and thawed in air at 20 C. Cell survival, texture and color were evaluated before and after freezing and thawing cycle. The fruit pre-treated with PEF prior to VI exhibited higher cell viability in epidermal layer and 30% more red color retention compared to just VI samples. However, no further improvement on strawberry quality in terms of drip loss and texture was observed upon the application of PEF.