Stability of betacyanin in red dragon fruit (Hylocereus polyrhizus) juice obtained from Lap Thach, Vinh Phuc province ☆

The red dragon (Hylocereus polyrhizus) is a potential fruit for Vinh Phuc province. In order to develop red dragon fruit products, this study aimed to evaluate the nutritional value and determine the effects of heat treatment, pH and the antioxidant addition (ascorbic acid) as well as the storage condition (light exposure, room and dark conditions) on the stability of betacyanin – the main color compound in fruit juice. The results indicated that the Vinh Phuc red dragon fruit had 12.6°Brix, pH = 4.72; contained high nutritional value with 15% dry matter, 9.60 g/100g in the total sugar content, 8.12 g/100g in reducing sugar content; 1.12 g/100g protein and 5.1 mg/100g in vitamin C content and 32.70 mg/100g in total betacyanin content. The best heating condition for the stability of betacyanin in the fruit juice was less than 80 ° C. Betacyanin was stable in acidic conditions (pH 3 ÷ 6), especially in pH 4, but this stability rapidly decreased in neutral and alkaline pH (pH ≥7). The addition of ascorbic acid at a concentration of 0.2 % increased the stability of betacyanin in the fruit juice even in light exposure. Betacyanin was more stable at 15 °C and in dark condition