Enhancing phenolic content in carrots by pulsed electric fields during post-treatment time: Effects on cell viability and quality attributes

The impact of pulsed electric fields (PEF) and post-treatment time on the phenolic content and quality attributes of carrots was studied. Additionally, their influence on cellular permeability and viability was analyzed. Carrots were subjected to different electric field strengths (0.8, 2 and 3.5 kV.cm(-1)) and number of pulses (5, 12 and 30). The largest increases in phenolic content were produced 24 h after applying 30 pulses of 0.8 kV.cm(-1) (40.1%) and 5 pulses of 3.5 kV.cm(-1) (39.5%). At such conditions, the colour was not affected but softening occurred after applying the highest electric field strength. Moreover, the increase in the specific energy input correlated with the decrease in cell viability. Carrot weight loss over time, media conductivity increase and cell viability decrease are related to the destabilization of cell membranes, which would entail a physiological response to stress, leading to a higher content in phenolic compounds. Industrial relevance: Determining the response of plant tissues to processing technologies is of great interest from an industrial point of view. Pulsed electric fields (PEF), as well as other processing technologies, may trigger metabolic responses that are directly related to the quality of final products. This paper studies the impact of PEF treatments on the phenolic content and quality attributes of carrots. Results show that PEF application allows improving the polyphenol content in carrots. However, it must be considered that firmness, weight, and colour may suffer modifications if PEF parameters are not properly selected. The information provided could be beneficial to develop processed foods with enhanced health-related compounds content. Furthermore, in order to optimize treatments, it is critical to study structural changes as affected by PEF processing. In this study, tetrazolium staining and conductivity measurements were used to visualize and determine the cell damage on carrot tissues. Industry can apply PEF to achieve other aims such as enhancing intracellular metabolite extraction or improving the drying efficiency; therefore, PEF treatment suitability could be evaluated based on this approach. Results show that PEF could be a promising pre-treatment to enhance the phenolic content of carrots and obtain derived products with improved nutritional value.