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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., (Copyright © 2013 Elsevier B.V. All rights reserved.)

This study was conducted to evaluate the combined effects of blanching and sonication on carrot juice quality. Carrots were blanched at 100 °C for 4 min in normal and acidified water. Juice was extracted and sonicated at 15 °C for 2 min keeping pulse duration 5 s on and 5 s off (70% amplitude level and 20 kHz frequency). No significant effect of blanching and sonication was observed on Brix, pH and titratable acidity except acidified blanching that decreased pH and increased acidity significantly. Peroxidase was inactivated after blanching that also significantly decreased total phenol, flavonoids, tannins, free radical scavenging activity, antioxidant capacity and ascorbic acid and increased cloud and color values. Sonication could improve all these parameters significantly. The present results suggest that combination of blanching and sonication may be employed in food industry to produce high-quality carrot juice with reduced enzyme activity and improved nutrition.

Fresh apple juice treated with ultrasound (for 0, 30, 60 and 90 min, at 20 °C, 25 kHz frequency) was evaluated for different physico-chemical, Hunter color values, cloud value, antioxidant capacity, scavenging activity on 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical, ascorbic acid, total phenolics, flavonoids, flavonols and microbial characteristics. No significant effect of sonication was observed on pH, total soluble solids (°Brix) and titratable acidity of apple juice. Sonication significantly improved ascorbic acid, cloud value, phenolic compounds, antioxidant capacity, DPPH free radical scavenging activity and differences in Hunter color values. Moreover, significant reduction in microbial population was observed. Findings of the present study suggested that sonication treatment could improve the quality of apple juice. It may successfully be employed for the processing of apple juice with improved quality and safety from consumer's health point of view., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Microbial and enzymatic inactivation in fresh pear juice were studied under conventional and ultrasound-pasteurizations. The ultrasound-pasteurization conditions were 25, 45 and 65 °C for 10 min using a 750 W probe sonicator (frequency 20 kHz and amplitude 70%) while conventional pasteurization conditions were 65 °C for 10 min and 95 °C for 2 min. Complete inactivation of enzymes (peroxidase, pectinmethylesterase and polyphenol oxidase) and microbes (total plate count, yeast and mould) were observed in conventional pasteurization at 95 °C but this treatment also showed highest losses of ascorbic acid, total phenols, flavonoids and antioxidant capacity. Ultrasound-pasteurization at 65 °C for 10 min showed the best results in retention of ascorbic acid and other phenolic compounds with significant reduction in enzyme activities and complete inactivation of microbes. Values of pH, acidity and °Brix showed no significant changes under conventional or ultrasound-pasteurization treatments. The findings of the present study indicate that pasteurization at low temperatures in combination with ultrasound can successfully be employed for commercial processing of pear juice with improved quality. [ABSTRACT FROM AUTHOR]

Abstract: A study was conducted to evaluate the influence of blanching and sonication on important quality parameters of carrot juice. Blanching of carrots was done in normal water and acidified water (45 g/L citric acid, pH 1.3) at 100 °C for 4min and juice was extracted. Sonication of juice was done (frequency 20 KHz and amplitude level 70%) at 15 °C for 2 min. Significant increase (P < 0.05) was observed in total carotenoids, lycopene and lutein in blanched samples, however, this increase was more in simultaneously blanched and sonicated samples. Additionally, highest increase was observed in all these pigments as a result of combined treatment of acid blanching and sonication. Sucrose, glucose, fructose, chlorogenic acid and mineral elements (Na and K) were decreased significantly in all blanched samples while increased significantly (P < 0.05) in all sonicated samples. Significant decrease was observed in some minerals (P and Mg), total plate count, yeast and mold in all samples treated with blanching and sonication but this decrease was more in samples treated with acid blanching and sonication. The results suggest that combined treatment of blanching and sonication may successfully be employed for processing of carrot juice to improve quality. [Copyright &y& Elsevier]