Effect of High Intensity Ultrasound and Pasteurization on Anthocyanin Content in Strawberry Juice

Igor Dubrović¹, Zoran Herceg²*, Anet Režek Jambrak², Marija Badanjak² and Verica Dragović-Uzelac<sup>2

1</sup>Teaching Institute of Public Health of the Primorsko-goranska County, Krešimirova 52a, HR-51000 Rijeka, Croatia
²Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, HR-10000 Zagreb, Croatia

Article history:
Received January 24, 2011
Accepted April 1, 2011

Key words:
high intensity ultrasound, anthocyanins, strawberry juice, response surface methodology

Summary:
The purpose of this investigation is to study the influence of high intensity ultrasound and pasteurization on the stability of anthocyanins and their content in strawberry juice. Different ultrasound process parameters for the treatment of juices are compared to the classical thermal treatments. For ultrasound treatments, three parameters were varied according to the statistical experimental design. Central composite design was used to optimize and design experimental parameters: temperature (25, 40 and 55 °C), amplitude (60, 90 and 120 μm) and time (3, 6, and 9 min). It was found that the anthocyanin content after pasteurization (85 °C for 2 min) was reduced by 5.3 to 5.8 % compared to untreated juices. After treatment with ultrasound (20 °C for 3, 6 or 9 min) or thermosonication (40 °C for 3, 6 or 9 min and 60 °C for 3 or 6 min), the degradation of anthocyanins was generally less intensive and was 0.7–4.4 % compared to the untreated juices. Only in the case of ultrasonic treatment at a temperature of 55 °C and treatment time of 9 min the total content of anthocyanins, compared to untreated juice, was reduced by 5.8 to 7.1 %, and their degradation was greater than that of pasteurized juices. From the results it can be concluded that total anthocyanin content was greater in more than 85 % of the selected ultrasound treatments compared to pasteurized juices. Ultrasound treatment can replace pasteurization in terms of preserving total anthocyanin content. The modelling approaches using response surface methodology (RSM) developed in this study exploit data in order to identify the optimal processing parameters for lowering degradation of anthocyanins in strawberry juice during ultrasound processing.

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