Ohmic Heating-Assisted Extraction of Natural Color Matters from Red Beetroot

The main objectives of this investigation were to investigate the combined impact of the ohmic heating-assisted extraction (OHAE) parameters (voltage gradient and frequency) and the green extraction mediums (aqueous, aqueous ethanol, acidified aqueous ethanol) on betalain yield, extraction yield, color quality, energy, and exergy efficiency, and to compare them with the effects of conventional extraction (CE) process. During the OHAE process, the betacyanins yield increased as voltage gradient increased, and the betalain was extracted better in aqueous ethanol than other extraction mediums. The color changes (Delta E, Delta C, hue angle, chroma) of the extract due to diffusion of color matters during OHAE process were higher than the CE process (p < 0.05). As the voltage gradient in OHAE increased, the energy and exergy efficiencies decreased (p < 0.05). The energy efficiencies of applications for 11 V/cm, 17 V/cm, and 23 V/cm were determined in the range of 52-64%, 38-61%, and 37-55%, respectively. On the other hand, the exergy efficiencies of aqueous, aqueous ethanol, and acidified aqueous ethanol extraction mediums were determined in the range of 29-51%, 34-64%, and 44-62%, respectively. The optimum OHAE condition was predicted by applying the desirability function method in the optimization procedure as the voltage gradient of 17 V/cm, the frequency of 400 Hz, and aqueous ethanol extraction medium. This optimum condition of OHAE for the purpose of extraction of betalains from red beet root was recommended to industrial and academic applications by taking criteria of higher exergy/energy efficiencies, lower quality changes, and shorter process times.