Betalains Stability and Antioxidant Activity of Beetroots: As a Function of Maturity Stage

Beetroots are an excellent source of colourant (betalains) and antioxidants. Betalains are the most popular emerging food colourants but undergo degradation due to harsh processing and storage conditions. In this study, beetroot (cv. ‘Crimson Globe’) extract from four different maturity stages (60, 75, 90 and 105 days after sowing) were subjected to different thermal, pH, light and oxygen exposure conditions to see the impact of maturity stages and processing conditions on the stability of betalains and antioxidant activity. Exposure to different temperatures revealed that betalains showed minimum degradation (6.27%) at 10 °C while 90 °C showed the maximum (99.23%) degradation but with maximum retention of antioxidant activity after 4 h of incubation. Among the different pH, i.e., 2–7 studied at ambient temperature (~ 25–27 °C), pH 5 showed the minimum (21.93%) and pH 2 showed the maximum (40.85%) betalains degradation but with maximum antioxidant activity. After 8 days of incubation, betalains degraded up to 84.45%, 76.01%, 85.63% and 76.35% when exposed to natural light, dark, aerobic and anaerobic conditions, respectively. Temperature (> 60 °C), pH ~ 2, light and air exposure were the most deteriorative conditions for betalains stability for each maturity stage. Under all incubations, each maturity stage showed a similar trend of betalain and antioxidant degradation but at varied rate. Unlike for betalains stability, exposure to harsh conditions was conducive for antioxidant retention. In nutshell, beetroots harvested 90 days after sowing were found most suitable to harness their potential as most stable betalains (colourants) and antioxidants enriched source.