Betalain Extraction from Beetroot Using Supercritical Carbon Dioxide and Microwave Pretreatment by Response Surface Method (RSM)

Extensive research has begun on the production of naturally occurring red colorants as permitted food additives. The Betalain in Beetroot (Beta vulgaris) cells can be used to prepare a natural red color additive for food products. Betalains are more resistant to acidic conditions and high temperatures than other red pigments such as anthocyanins. However, the low stability of Betalain compared to synthetic colorants is considered a big challenge in its extraction, processing, and storage. Therefore, it is very important to use a suitable extraction method for it. In recent years, the use of supercritical carbon dioxide (scCO2) for isolation and extraction of natural products instead of conventional methods such as extraction with organic solvents has attracted interest because the final product may become contaminated with the solvents. In the same vein, this research evaluated the effects of microwave power (100-450 W), carbon dioxide flow rate (1-3 mL/min), temperature (30-70℃), and pressure (15-40 MPa) on extraction efficiency, 2,2-diphenyl-1-picrylhydrazyl, and the quantities of phenolic compounds extracted from Beetroot. The results suggested that temperature, pressure, flow rate, and microwave power significantly influenced the amounts of phenolic compounds, extraction efficiency, and antioxidant properties of the compounds extracted from Beetroot. Increases in temperature, pressure, microwave power, and carbon dioxide flow rate in the (50-60℃), (20-30 MPa), (300-400 W), and (1-2 mL/min) ranges, respectively, increased the quantities of phenolic compounds, ability to suppress free radicals and extraction efficiency as the response. However, increases beyond the mentioned ranges caused decreases in the response variables. Optimal extraction of Betalain from Beetroot using supercritical carbon dioxide and microwave pretreatment was achieved at a temperature of 45 °C, pressure of 27.5 MPa, CO2 flow rate of 2 mL/min, and microwave power of 300W.