Development of Freeze-Dried Red Dragon Fruit Yoghurt Containing Probiotics ☆

Yoghurt, a product prepared by fermentation of milk with bacterial cultures consisting of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, has been popular for a long time, however, dehydrated yogurt is still uncommon. Freeze drying is well-known as an effective method to preserve the nutritional and sensory characteristics of the food product compared to other dehydration ways. This study developed a protocol to produce freeze-dried yoghurt fermented by commercial probiotic starter culture containing betacyanin – a bioactive component from red dragon fruit on laboratory scale. The freeze-dried red dragon yoghurt was produced by the following steps: (1) plain yoghurt preparation: Milk with 12% milk dry matte was heated at 95oC for 5 min, cooled down to 42oC, followed by the addition of commercial probiotic bacteria starter, then fermented for 3 hours until the pH reached to 4.6 and the milk coagulated (2) obtained yoghurt was mixed with 30 % red dragon fruit, molding in the tray (3) Freeze at -20oC and freeze-dried (4) packaging to obtain the final product. Betacyanin – well-known as a bioactive compound from red dragon fruit of the obtained products and viable bacteria remained during 30 days storage at room temperature.