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Impact of High Power Ultrasound (HPU) on the stability of phenols and antioxidant capacity in cloudy apple juice

The aim of this study was to investigate the influence of the ultrasound treatment on the stability of phenolic compounds and antioxidant capacity in cloudy apple juice (cv. Golden Delicious) during seven days storage at 4 °C. For this purpose, the High Power Ultrasound (HPU) (100 W, 20 kHz frequency) was operated at following conditions: (i) amplitude 40 % and 80 %, (ii) ultrasound probe 7 and 10 mm, and (iii) treatment time of 3, 6 and 9 minutes. The temperature did not exceed 41 °C during any of the ultrasound treatments. Total phenols, flavan-3-ols and antioxidant capacity (DPPH and FRAP) were determined according to previously described spectrophotometric methods. Obtained results demonstrated that ultrasound treatment decreased total phenols and antioxidant capacity in cloudy apple juices with no significant impact of the amplitude, ultrasound probe and treatment time. Moreover, seven days of storage at 4 °C also has negative impact on polyphenols stability and antioxidant capacity. However, during shelf-life, the greater stability of both, polyphenols and antioxidant capacity, was observed in all un-treated samples.

apple juice ; ultrasound ; total phenols ; flavan-3-ols ; antioxidant capacity ; storage time

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