Effect of osmotic agents and freeze drying on bioactive compounds and sensory quality of dried strawberries

Abstract

The rationale of this study was to find out the possibility of using a sugar and honey as osmotic agents and use of freeze-drying method to obtain pro-health-promoting dried strawberries. The research material was Chandler strawberries, which were dehydrated using sugar and honey syrups in a concentration of 50, 60 and 70°Brix followed by freeze drying. Analysis were conducted to determine the influence of the osmotic agents and freeze drying process on colour values (Hedonic scale), total phenols, antioxidant activity, total flavonoid content and sensory properties of the final dried product. Osmotic drying enhanced the total phenol and total flavonoid content of freshly dried whole strawberries from 64.55 to 138.64 mg/100g and 250.30 to 406.74 mg CE/100g in T1 (control) and T4 (70°Brix sugar), respectively. Better retention of antioxidant activity 87.68 per cent in T7 (70°Brix honey) and L* values of 36.64 in T4 (70°Brix sugar) were observed. The sensory scores were higher for osmotically freeze- dried strawberries when compared to control (strawberries dried without any osmotic agent). The shelf life was enhanced markedly upto three months after packing them in laminated pouches. Hence, osmotic drying can prove to be a promising technology for extending shelf life of strawberries for three months with better retention of nutritional and sensory characteristics.