Abstract: To explore the changes in the stability and antioxidant activity of betalains in the presence of different amino acids, different amino acids were added into the pigment solution. The stabilities of betalains against light, temperature, pH, and metal ions were investigated based on their retention rate and the antioxidant activity was assessed by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging activity. The findings showed that serine (Ser), histidine (His), and phenylalanine (Phe) enhanced the thermal stability of betalains, with the most pronounced effect being observed at a concentration of 5‰. Under light conditions, the retention rate of betalains was 16.8% higher in the presence of His than with no added amino acid. At pH 5.0, the retention rate was increased by up to 20% in the presence of His. Addition of His significantly improved the stability of the pigment solution containing Ca2+. Additionally, Phe addition enhanced the stability of betalains against metal ions, acids, alkalis, and light. All three amino acids enhanced the scavenging ability of betalains against DPPH radical and ABTS radical cation and inhibited their oxidation reaction. These results indicated that different amino acids had different effects on the stability of betalains. To stabilize natural pigments, appropriate amino acids should be selected according to actual requirements.

Key words: betalains; amino acids; stability; antioxidant activity; pigment retention rate