Ultrasound‐assisted extraction of red beet pigments ( <i>Beta vulgaris</i> L.): Influence of operational parameters and kinetic modeling

Abstract

This study investigated the extraction of betalains from red beet by an ultrasound-assisted process using water as solvent. For this purpose, the effect of time and temperature on ultrasound-assisted extraction (UAE) was evaluated, and together the effect of ultrasound on the process was investigated by comparing the results with orbital shaking extraction (OSE). From the ideal conditions of these parameters, defined in the UAE, the effects of the ultrasound power and the solvent/sample ratio were evaluated and the experimental data obtained in the kinetics with different solvent/sample ratios were correlated with the diffusion coefficient of betalain in water. The results showed that the betalains content present in the extract decreased with temperature and the same occurred with the increase in time at higher temperatures, therefore, 30°C and 30 min were the first conditions established. Under these conditions, the UAE showed better results in obtaining betalain compared to OSE. The increase in ultrasound power improved the extraction and 83 W was sufficient for maximum removal of the compounds. The highest betalains content was obtained using solvent/sample ratio of 75 ml/g and this result is attributed to the highest diffusion coefficients determined in this condition. This extract showed high sugar content, being sucrose the main component (~96%), and also exhibits high antioxidant activity by ABTS, DPPH, and FRAP methods. Practical applications Betalains are safe alternatives to synthetic pigments that are widely used in the food and pharmaceutical industries. In addition to exercising a coloring function, these compounds have antioxidant capacity and their consumption can attribute health benefits. However, due to the low heat stability, most of these compounds are lost during the extraction process, which makes research by alternative methods necessary. UAE is suitable for obtaining heat-sensitive compounds, since the extraction time and temperature should be minimized. The study of kinetics and modeling are important in the extraction process, since it allows the determination of the ideal operating conditions and the prediction of the dynamic behavior of the process for future applications on an industrial scale.