Stability enhancement of beetroot betalains through copigmentation

Like other natural pigments, betalains have a stability problem. Copigmentation can be explored to address this issue. In this study, black carrot anthocyanins were used for the first time as copigment with betalains so that copigmented betalains with enhanced stability could be developed to withstand deteriorative processing and storage conditions.

Increase in hyperchromic and bathochromic shift with subsequent increase in black carrot anthocyanin extract (0.250 g L^-1 ) addition from 0.2 to 1.0 mL L^-1 was observed in native betalain pigments from 0.28 to 1.90 and 538 nm to 564 nm, respectively. For maximum recorded bathochromic shift, 0.8 mL L^-1 addition of copigment was optimized. Copigmented betalain pigment showed better stability in comparison with native pigment, when exposed to light, temperature more than 60 °C and ≥1.0 g L^-1 NaCl. At constant incubation time (3 h), copigmented betalains degraded up to 20.79-41.43% whereas the non-copigmented counterpart degraded up to 83.49-86.86% at 60, 75 and 90 °C, respectively. Lower rate constant (k) and enhanced activation energy (E_a ) showed higher thermostability of copigmented betalains. With constant light exposure, the half-life value of betalains was 145.2 h, which increased approximately twofold (274.08 h) after copigmentation. The t_1/2 of betalain pigment at 10%, 15% and 18% salt addition was 81.12, 75.36 and 83.52 h, which increased to 186.96, 226.56 and 152.88 h after copigmentation.

These findings support that black carrot anthocyanin is a potential and compatible copigment for water-soluble betalain pigment that enhances stability of betalains under extreme processing conditions. © 2022 Society of Chemical Industry.