Extracting betalains from red beetroot (Beta vulgaris) by using deep eutectic solutions

Deep eutectic solvents (DESs) are high-acceptance new generation green solvents due to their stability and biocompatibility. This study aims to extract red beet betalains using 10 different DESs consisting of choline chloride-alcohols, choline chloride-organic acids, choline chloride-sugars, organic acids-choline chloride, and organic acids-sugars, as well as traditional solvents. The betalain yields extracted with different solvents were compared. In the first stage of the study to determine the most effective solvent and extraction conditions, choline chloride:glucose (1:2) was found to be the most effective DES. The electrical conductivity, pH, and viscosity results of DESs varied significantly based on their hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD) profiles, and this variation also influenced the betalain yield. Using choline chloride:glucose (DES 5) that provided the highest yield, extraction conditions were optimized using response surface methodology and central composite design. As independent variables, molar ratio (HBA=1:HBD=0.41, 0.75, 1.25, 1.75, 2.09), water content (8.18, 15, 25, 35, and 41.82%), and temperature (19.77, 30, 45, 60, and 70.23°C) were used in the optimization. The optimal conditions for betalain extraction were determined as choline chloride:glucose molar ratio of 1:0.75, water content of 30.83%, and temperature of 30°C. The respective responses for betalain, betacyanin, and betaxanthin under these conditions were 1192.17±23.63 mg/kg, 738.83±17.87 mg/kg, and 453.34±5.93 mg/kg. Bioaccessibility analysis and stability tests were conducted on the extracts obtained under optimal conditions. The bioaccessibility values for betacyanin, betaxanthin, and betalain were determined as 44.67%, 75.02%, and 56.21%, respectively. The extracts obtained under optimal conditions were subjected to storage stability tests at room temperature (20°C), in the dark, and in the refrigerator (4°C). After 9 days of storage in light, a loss of 84.90% was determined in total betalain, while in the dark, it was determined as 59.47%. This study demonstrated that DES-based solvents provide higher efficiency in the extraction of red beet betalains compared to traditional solvents. Keywords: Red beet, Betalain, Green chemistry, Deep eutectic solvent, Optimization