Thermosonication as a potential quality enhancement technique of apple juice

• Quality enhancement of apple juice by thermosonication has been investigated.
• Thermosonication enabled inactivation of enzymes and microbes of apple juice.
• Retention of ascorbic acid and polyphenolic compounds was observed.
• The pH, titratable acidity and °Brix remained unaffected.
• The technique could be efficiently utilized for apple juice processing.

Enzymatic browning and microbial growth lead to quality losses in apple products. In the present study, fresh apple juice was thermosonicated using ultrasound in-bath (25 kHz, 30 min, 0.06 W cm−3) and ultrasound with-probe sonicator (20 kHz, 5 and 10 min, 0.30 W cm−3) at 20, 40 and 60 °C for inactivation of enzymes (polyphenolase, peroxidase and pectinmethylesterase) and microflora (total plate count, yeast and mold). Additionally, ascorbic acid, total phenolics, flavonoids, flavonols, pH, titratable acidity, °Brix and color values influenced by thermosonication were investigated. The highest inactivation of enzymes was obtained in ultrasound with-probe at 60 °C for 10 min, and the microbial population was completely inactivated at 60 °C. The retention of ascorbic acid, total phenolics, flavonoids and flavonols were significantly higher in ultrasound with-probe than ultrasound in-bath at 60 °C. These results indicated the usefulness of thermosonication for apple juice processing at low temperature, for enhanced inactivation of enzymes and microorganisms.