Influence of amino acid addition on the thermal stability of anthocyanins in pomegranate (Punica granatum L., cv. Hicaznar) and orange (Citrus sinensis L. Osbeck, cv. Valencia) juice blend.

This is the first study revealing effects of aspartic acid (AA), proline and valine as well as ascorbic acid on individual anthocyanins in pomegranate and orange juice blend (POJB) during heating at 90-150 ℃. Effect of amino acids on colour and anthocyanin stability varied depending on heating temperature. At 90 ℃ (3 h), AA, proline and valine increased (up to 4.7 times) contents of cyanidin-3-glucoside and total anthocyanin, and cyanidin-3,5-diglucoside stability. At 105 ℃ (2 h), AA and valine caused the highest absorbance value at maximum wavelength (A) and high anthocyanin stability, which pointed out copigmentation. At 150 ℃ (0.5 h), AA and valine increased (up to 11%) stabilities of cyanidin-3-glucoside, cyanidin-3,5-diglucoside and delphinidin-3,5-diglucoside, and caused the highest A. Owing to copigmentation by hydrophobic interactions/hydrogen bond, degradative effect of ascorbic acid on anthocyanins was slowed down. Thus, these three amino acids might have a high potential for copigmentation in products containing anthocyanins and ascorbic acid at high concentration.