Enhanced chemical stability, chromatic properties and regeneration of betalains in Rivina humilis L. berry juice

•Selenium (Se) bleaches betalains color mildly during thermal treatment.•Ascorbic acid (AA) protects and regenerates betalains to some extent after thermal degradation.•AA and Se synergistically protect and regenerate betalains efficiently after thermal degradation.•Thermal processed betalains containing juice may be stored in cold in presence of AA and Se.

Betalains are hydrophilic colorants containing chromophore betalamic acid. Owing to poor stability, its usage is limited to low acidic short shelf-life, and frozen foods. In this report, effect of metals (inorganic Se4+, Zn2+, and Cu2+) on stability of betalains in Rivina humilis L. berry juice (RBJ) was studied in presence of 10 and 40 μg metal/mL with/without ascorbic acid (AA; 0.25 and 0.5 g/100 mL). Se bleached RBJ betacyanins mildly, whereas Zn, and Cu bleached the pigments significantly. AA protected the pigments from metal-induced bleaching, and stabilizing effect of 0.25 g AA/100 mL was higher (P < 0.05) than 0.5 g AA/100 mL. AA (0.25 g/100 mL) + Se (40 μg/mL) enhanced (five-fold) the half-life time of betacyanins. RBJ betacyanins degraded up to 95% and 96% on treatment for 36 min at 90 °C and storage for 48 days at 25 °C, respectively, whereas only 15% pigment was lost on storage (5 °C, 90 days). AA (0.25 g/100 mL) + Se (40 μg/mL) regenerated the pigments on storage at 5 °C after thermal degradation. Color values of AA (0.25 g/100 mL) + Se (40 μg/mL) containing samples indicated an orange tinge, whereas other samples turned brown yellow after thermal treatment.