Antioxidant Activity and Quality of Spray Dried Aonla Powder as Affected by Storage Behavior of Juice

Abstract

Good quality powder can be prepared from aonla juice by spray drying. It may be consumed as health drink after reconstitution, because of its high vitamin C content and antioxidant capacity. An experiment was conducted to evaluate the antioxidant activity and other quality parameters of spray dried powder prepared from aonla juice stored up to one year. The juice, extracted from aonla cv. Chakaiya, was pasteurized at 90°C for 2 min and preserved with 500 ppm SO₂ in food grade carboys at room temperature (18 – 40°C). The powder was prepared from stored juice (0, 2, 4, 5, 6, 9 and 12 months) in a spray dryer at inlet temperature of 190°C and 16 rpm feeding speed with 2 percent maltodextrin as stabilizing agent. The analytical data indicated that ascorbic acid in juice decreased gradually from 375.0 to 137.2 mg 100ml^–1 during 12 months of storage. The corresponding reduction of ascorbic acid in powder was from 3176 to 1632 mg 100g^–1. The content of polyphenols also decreased in juice (1.55 to 1.20%) during storage, but the changes in its content in powder were not significant. Gradual reduction in antioxidant activity (FRAP value) in juice (259.5 to 111.9 mmol ml^–1) during storage was noticed with a concomitant decrease in powder (995.1 to 578.7 mmol g^–1) prepared from stored juice. Non-enzymatic browning increased significantly in juice (0.033 to 0.262 OD) during 12 months of storage but increased marginally in powder (0.004 to 0.067 OD). The color of the powder also changed from creamy white to brownish white when prepared from fresh and 12 months stored juice. The significant decrease in ascorbic acid content (30%) and antioxidant activity (27%) was observed at 6 months of storage when room temperature increased drastically (25 to 40°C). It may be concluded that good quality spray dried powder could be prepared from aonla juice stored up to 5 months at room temperature without much deterioration in ascorbic acid content and antioxidant activity.