Degradation kinetics of anthocyanins and polyphenols during storage of red apple juice produced from red-fleshed apples

The aim of this study was to determine the stability of various anthocyanins in red-coloured apple juice for the development of a new attractive beverage. Red-coloured apple juice was generated from red-fleshed apples of cultivar “Maggy” to analyse the composition of anthocyanins and the effect of storage at various temperatures. Cyanidin-3-galactoside (cy-3-gal) was identified as the main component of the anthocyanin profile, next to 5-carboxypyranocyanidin-3-hexoside, tentatively carboxypyranocyanidin-3-galactoside, and two cyanidin-3-pentosides. In addition, we found cyanidin-3-glucoside, another 5-carboxypyranocyanidin-3-hexoside, probably 5-carboxypyranocyanidin-3-glucoside, one 5-carboxypyranocyanidin-3-pentoside, two unknown anthocyanins, and another cyanidin-3-pentoside. The loss of anthocyanins during storage can be described as a first-order reaction as it is the case also for other red-coloured fruit juices. The T1/2 value of cyanidin-3-galactoside varied between 53 and 84 days after storage at 4 °C, and between 15 and 13 days at 20 °C. Storage at 37 °C reduced the T1/2 values from 7 to 6 days. A much longer half-life was observed for 5-carboxypyranocyanidin-3-galactoside. The T1/2 values at 4 °C were 250–315 days and 50–112 days at 20 °C. At 37 °C, T1/2 decreased from 23 to 25 days. The antioxidant capacity (TEAC) was constant during storage for at least 1 year. The colour of red apple juice, however, is less stable than in aronia, black currant and red grape juices, for example. Taken together, red apple juice, generated of the cultivar “Maggy”, is an attractive new fruit juice, but other cultivars of red-fleshed apples with higher anthocyanin concentrations would achieve a more colour-intense product.