Improving red radish anthocyanin yield and off flavor removal by acidified aqueous organic based medium
In view of the high content of the highly stable anthocyanin in red radish roots, the plant is considered as a potent source of natural anthocyanins. However, the presence of off flavor in their anthocyanin extracts is the only limitation as far as their application in food and pharmaceutical industries is concerned. The aim of this work was to develop a suitable method for extracting the off flavor free red radish root anthocyanin, while conserving high anthocyanin yield. Results showed that phosphoric and citric acidified hexane (pH 2.5) extracts yielded maximum anthocyanin levels of 208.37 mg/100 g and 202.89 mg/100 g fresh radish, respectively with lower percentage polymeric color and higher color density, chroma and hue angle compared to other extracts at different pH values. Tentative anthocyanin identification by UPLC-TQ-MS showed 12 glycosylated anthocyanins substituted at C3 and C5 in phosphoric acidified extracts and only 10 in citric acidified extracts. In addition, analysis of total glucosinolates (GSLs) revealed significant inhibition of glucosinolate degradation in acidified hexane extracts (pH 2.5) compared to the other extracts. The off flavor evaluated by GC-MS revealed a significant decrease of isothiocyanates, sulfides and nitrogen containing compounds in acidified hexane (pH 2.5) compared to other extracts. Furthermore, dehydration and rehydration of extracts showed that over 70% of off flavor compounds could be removed in two phases (aqueous and hexane) during hexane removal. Results of sensory evaluation confirmed that the red radish root anthocyanin from the phosphoric acidified hexane (pH 2.5) was closer to the color and odor characteristics of the commercial red radish anthocyanin. Therefore, the phosphoric acidified hexane method could be a suitable method to extract off flavor free anthocyanin from red radish roots.