Total quality index of ultrasound-treated blueberry and cranberry juices and nectars

Abstract

The influence of ultrasound in combination with elevated temperature (thermosonication) is important in inactivation effects on microorganisms. However, overall quality of these products can be deteriorated. The aim of this study was to examine the use of a single quality index in evaluating effects of ultrasound technology on quality characteristics of blueberry and cranberry juices and nectars. For the purpose of this study based on 10 quality parameters, two mathematical models for calculating a single total quality index have been introduced. Samples were treated according to the experimental design, with high power ultrasound frequency of 20 kHz under various conditions (treatment time: 3, 6 and 9min, sample temperature: 20?, for thermosonication: 40 and 60? and amplitude: 60, 90 and 120 mu m). Mathematical index of total quality index in order to evaluate total quality of ultrasound-treated juices and nectars was established. For cranberry juices, treatments 11' (amplitude 120 mu m) and 16' (amplitude 60 mu m) both for 9min and the temperature of 20? were best scored for both models. Treatment 6' (amplitude 120 mu m, 3min treatment time and the sample temperature of 20?) for cranberry nectars was among the best for both models. Ultrasound treatments 6' of amplitude 120 mu m, 3min and the temperature of 20? and 11' same amplitude 120 mu m and temperature, but 9min were best scored blueberry juices for both models. Blueberry nectar had best total quality index for treatments 5' (amplitude 120 mu m, 6min treatment time and the sample temperature of 40?) and 6' (amplitude 120 mu m, 3min treatment time and the sample temperature of 20?).