Increase in thermal stability of strawberry anthocyanins with amino acid copigmentation

Copigmentation effects of aspartic acid, proline and valine on individual anthocyanins in strawberry juice (SJ) were investigated during heating at 90, 105 and 150 °C. Aspartic acid increased (4.5-45.6%) total anthocyanin stability at all temperatures, while proline and valine had no effect at 90 °C but reduced (2.2-19.4%) stability at 150 °C. At 90 °C, aspartic acid and valine caused the highest Amax. Evaluating changes in individual anthocyanin contents, Amax, colour density and polymeric colour of SJs together revealed that aspartic acid had copigmentation effects on pelargonidin-3-glucoside and pelargonidin-3-rutinoside, whereas valine on pelargonidin-3-glucoside and cyanidin-3-glucoside. At 105 °C, all amino acids increased (7.9-33.1%) stabilities of pelargonidin-3-glucoside, pelargonidin-3-rutinoside, Amax and colour density all of which together pointed out the copigmentation. At 150 °C, interactions between "aspartic acid-pelargonidin-3-glucoside," "proline-pelargonidin-3-rutinoside" and "valine-pelargonidin-3-rutinoside" resulted in high colour density. Thus, among these amino acids, selection should be based on the heating temperature and anthocyanin profile of the product.