Impact of Pre-treatment and Drying Temperature on Retention of Bioactives from Immature Dropped Kinnow Fruit using Ultrasonication

Background: Agri-waste including immature dropped fruits is rich in various nutrients and bioactive compounds that can be dried and utilized for beneficial purposes. Methods: Impact of pre-treatments (citric acid, steam blanching and both together) and drying temperatures (40-80°C) on retention of bioactive compounds from immature dropped kinnow fruit (IDKF) was studied using ultrasonication. Result: Highest total phenolic (6.42 g GAE/100 g and 8.68 g TAE/100 g), total flavonoid (10.58 g QE/100 g), DPPH (390.79 mg AAE/100 g), FRAP activity (9.15 g TE/100 g and 4.65 g AAE/100 g) and minimum colour difference were detected in IDKF, pre-treated with citric acid and dried at 50°C. Crude IDKF bioactive extract, prepared from this sample showed antimicrobial activity against Gram positive bacteria. Impact of citric acid pre-treatment and drying temperatures on maximizing bioactive compounds retention was indicated by principal component analysis too. Total saponins and alkaloids were better retained in sample with no pretreatment and dried at 40°C.