Enhancement of the extraction of betanine from red beetroot by pulsed electric fields

A systematic study about the influence of pulsed electric fields (PEF) and other operating parameters on betanine extraction from red beetroots has been carried out in this investigation. Thin disks of red beetroots were subjected to PEF at different intensities (number of pulses and field strengths), and the release of betanine into media of different pH and at different temperatures was determined. The influence of mechanical pressing after PEF treatments on betanine extraction was also investigated. The use of extracting media having pH 3.5 and temperatures of 30 °C gave the highest yields and rates for betanine extraction from PEF treated samples. When subjected to 5 pulses of 2 μs at 7 kV/cm, the samples released about 90% of total betanine in 300 min, a rate that is fivefold quicker than the non-PEF-treated samples. Pressing the samples during the extraction process at all pressures investigated further reduced the extracting time. A general mathematical expression was developed to determine the percentage of betanine extracted from red beetroots treated at different electric field strengths (1–9 kV/cm), and then pressed (0–14 kg/cm2). Based on this equation, a treatment of 5 pulses at 7 kV/cm (2.5 kJ/kg) and 10 kg/cm2 at room temperature permitted the extraction of 90% of the total red colouring in 35 min.