Pigment and color stability of beetroot betalains in cow milk during thermal treatment

• Thermal stability of betalains in cow milk was determined during heating at 70–90 °C.
• Degradation of betalains in milk followed first order kinetics at 70–90 °C.
• The changes of Hue angle and L* in milk fitted zero order kinetics during heating.
• Regression models were established between betalains content and color values.
• Significant correlations were observed between betalains content and L* and Chroma.

Thermal stability of beetroot betalains in cow milk was determined during heating at 70–90 °C. Changes in color values of colored milk were also investigated. Degradation of betalains followed first order kinetics while changes of L∗, Hue angle and Chroma values fitted zero order and first order kinetic, respectively. Reaction rate for degradation of betalains, L∗, Hue angle and Chroma values ranged between 1.588–30.975 × 10−3 min−1, 90.50–379.75 L∗ min−1, 0.581–5.008 Hue angle min−1 and 3.250–19.750 × 10−3 min−1, respectively. Between 70 and 90 °C, activation energy for the degradation of betalains was 42.449 kJ mol−1. L∗ values was more stable than Hue angle and Chroma color values in colored milk during heating. 74.150 kJ mol−1, 111.174 kJ mol−1 and 93.311 kJ mol−1 of activation energy values were found for L∗, Hue angle and Chroma values of milk, respectively. Significant positive and negative linear correlations were determined between betalains and color values. Multiple regression models were also established to predict the content of betalains in milk during thermal process by using color values.