Effects of thermosonication on ascorbic acid, polyphenols and antioxidant activity in blackberry juice

Summary Limited research studies exist that assess the impact of thermosonication (TS) processing on antioxidant compounds in blackberry juice. Different combinations of TS parameters (temperature, amplitude power and time) were applied to blackberry juice using a pilot‐scale ultrasonic transducer (UIP500hdT). In low‐temperature treatment, the juice was treated at 10°C and 50% amplitude power for 5 min (10‐50‐5) showed the best retention of ascorbic acid (0.95 mg), total phenolic content (TPC) (459.55 mg GAE), 2, 2‐diphenyl‐1‐picrylhydrazyl (DPPH) (261.34 mg TE) and ferric reducing antioxidant power (FRAP) (604.09 mg TE). Similarly, in high‐temperature treatment, the juices were treated at 70°C and 100% amplitude power for 5 min (70‐100‐5) showed ascorbic acid (1.05 mg), TPC (166.17 mg GAE), DPPH (304.95 mg TE) and FRAP (686.93 mg TE). Both low‐ and high‐temperature treatments showed higher retentions in these attributes than untreated and pasteurised juices. The results were further supported by high retention of predominant polyphenols, namely cyanidin‐3‐ O ‐glucoside (400.58 and 336.94 mg/100 mL, for 10‐50‐5 and 70‐100‐5, respectively). A similar trend was observed in the contents of cyanidin‐3‐ O ‐rutinoside, procyanidin dimer B 2 , 5‐chlorogenic acid, epicatechin and rutin. TS treatment in overall could be a considerable alternative option to be used for antioxidant‐rich blackberry juice production as it has effects on phytochemicals similar to that of pasteurisation.