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Fruit juices from Khasi mandarin orange, watermelon, carambola and pineapple were spray dried with 20% maltodextrin and studied for physicochemical, phytochemical and antioxidant properties. Khasi mandarin orange gave the highest yield (85.27%). Viscosity of the feed sample and the particle size distribution of the powders varied among samples. Moisture content ranged between 3.41 and 5.47%. pH was in the acidic range and titratable acidity was highest in carambola (0.70%). Solubility values ranged from 57.57 to 76.75%. Hygroscopicity of the juice powders ranged from 11.63 to 11.99 g/100 g of samples. The change in color (ΔE) after spray drying was highest in reconstituted Khasi mandarin. The phytochemical content and antioxidant activity were significantly different between the spray-dried and fresh untreated juice samples. An increase in total phenolic content, total flavonoid content, ferric reducing antioxidant potential and DPPH radical scavenging activity was observed in Khasi mandarin juice powder. PRACTICAL APPLICATIONSApplication of heat treatment causes number of changes in quality parameters of spray-dried fruit juice powder. The present work studied the effect of spray drying on the physicochemical properties of four fruit juice powders as well as changes in their phytochemical and antioxidant activities. It was observed that spray drying had both positive and adverse effects on the physicochemical and antioxidant properties depending on the fruit juice type. The phytochemical and antioxidant properties were enhanced upon spray drying of Khasi mandarin juice. The results indicate that spray-dried Khasi mandarin orange and watermelon juice powders can be promoted for processing by the fruit processing industries.

A comparative study on the effect of conventional thermal pasteurisation, microwave and ultrasound treatments on the phytochemical and antioxidant activities of juices from carambola (Averrhoa carambola L.), black jamun (Syzygium cumuni L.Skeels.), watermelon (Citrullus lanatus var lanatus), pineapple (Ananas comosus L. Merr) and litchi (Litchi chinensis Sonn.) was carried out. Depending on the type of fruit sample and treatment, increase or decrease in phytochemical values was observed. Overall, sonication had a positive effect on the total flavonoid content in all the juice samples followed by microwave treatment with exceptions in some cases. High-performance liquid chromatography study showed the presence of different phenolic acids depending on the sample type. The phenolic acids in some processed carambola juice samples showed decrease or complete destruction, while in some cases, an increase or appearance of newer phenolic acid originally not detected in the fresh juice was observed as seen in conventional thermal pasteurisation, microwaved at 600 W and sonicated juices. Both microwaved and sonicated samples were found to have positive effect on the phenolic content and antioxidant activity with exceptions in some cases. Therefore, microwave and sonication treatment could be used in place of thermal pasteurisation depending on the sample requirements.

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