Pulsed electric field treatment prior to freezing carrot discs significantly maintains their initial quality parameters after thawing



The interaction of pulsed electric fields (PEF) with different cryoprotectant and texturizing agents in quality retention of carrot discs was analysed. Increasing the permeability properties by PEF may lead to better accessibility of intracellular materials to freezing and thus reducing the freezing time, leading to better maintaining the texture after thawing. Carrot discs of 5 mm thickness were immersed in different solutions of CaCl2, glycerol, trehalose and tap water, and subsequently were treated with PEF (1 kV/cm, 100 pulses, 4 Hz). Then, the samples were drained and packed along with a control group in separate prepared polypropylene pouches. All the samples were frozen at −18 °C for 24 h and thawed during 3 h at ambient temperature (20 °C) the following day. The quality of the thawed carrot discs was certified by measuring weight loss, firmness, microscopic studies and CIE colorimetric attributes. All the PEF-treated samples, no matter what solution they were soaked in, could significantly (P < 0.05) maintain the firmness as well as colour attributes. However, it was deducted that application of CaCl2 in conjunction with PEF can result in a firmer texture. Firmness analyses determined that application of PEF alone results in 5.84 N, while its combination with CaCl2 leads to higher value of 6.63 N. Firmness in control samples was found to be 3.46 N. The SEM studies supported the results of firmness analysis and depicted more integrity in the cell walls of the samples treated with CaCl2 and glycerol. The weight loss values varied among different samples, and the highest amount and lowest amount were reported in CaCl2 and solely PEF-treated samples, respectively. There was no significant difference between the colour attributes measured in different groups including control sample (P > 0.05).