Process optimization of ultrasound-assisted betalain extraction from beetroot waste stalks

Abstract:

Beetroot stalks are considered as agro-industrial waste, by ignoring its nutritional properties and colorant ability. In this study, betalain pigments present in beetroot waste stalks were extracted using ultrasonication technique. The Betacyanin pigment (BC) which imparts red-violet color ranged from 1.80-6.5 mg/g and Betaxanthin pigment (BX) responsible for imparting orange-yellow color ranged from 1.26-4.56 mg/g over entire experimental conditions. For optimization of the extracted pigments, response surface methodology was adopted three factor/five level Central Composite design with pH, solid-solvent ratio (g/ml) and sonication time (min) as the main process parameters. A maximum yield of BC and BX of 6.31 and 4.43 mg/g respectively, were achieved under the optimized conditions (pH 4.7, solid-solvent ratio 50 g/ml and sonication time 30 min). It was also found that pH has no significant effect on the betalain pigments. It is evident from the study that the beetroot waste stalks contain considerable amount of pigment and can be used as a food additive in form of colorant, rather than discarding it as a residue. Thus, extraction of colorant from beetroot waste stalks could be one of the sources of betalain pigments and helps in reducing the environmental pollution.