Analysis of apple beverages treated with high-power ultrasound: a quality function deployment approach

BACKGROUND

The objective of this paper was to demonstrate application of quality function deployment in analysing effects of high power ultrasound on quality properties of apple juices and nectars. In order to develop a quality function deployment model, joint with instrumental analysis of treated samples, a field survey was performed to identify consumer preferences towards quality characteristics of juices/nectar.

RESULTS

Based on field research, the three most important characteristics were 'taste' and 'aroma' with 28.5% of relative absolute weight importance, followed by 'odour' (16.9%). The quality function deployment model showed that the top three 'quality scores' for apple juice were treatments with amplitude 90 µm, 9 min treatment time and sample temperature 40 °C; 60 µm, 9 min, 60 °C; and 90 µm, 6 min, 40 °C. For nectars, the top three were treatments 120 µm, 9 min, 20 °C; 60 µm, 9 min, 60 °C; and A2.16 60 µm, 9 min, 20 °C.

CONCLUSION

This type of quality model enables a more complex measure of large scale of different quality parameters. Its simplicity should be understood as its practical advantage and, as such, this tool can be a part of design quality when using novel preservation technologies. © 2017 Society of Chemical Industry.

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

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 9 min, sample temperature: 20 ℃, for thermosonication: 40 and 60 ℃ and amplitude: 60, 90 and 120 µm). 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 µm) and '16' (amplitude 60 µm) both for 9 min and the temperature of 20 ℃ were best scored for both models. Treatment '6' (amplitude 120 µm, 3 min treatment time and the sample temperature of 20 ℃) for cranberry nectars was among the best for both models. Ultrasound treatments '6' of amplitude 120 µm, 3 min and the temperature of 20 ℃ and '11' same amplitude 120 µm and temperature, but 9 min were best scored blueberry juices for both models. Blueberry nectar had best total quality index for treatments '5' (amplitude 120 µm, 6 min treatment time and the sample temperature of 40 ℃) and '6' (amplitude 120 µm, 3 min treatment time and the sample temperature of 20 ℃).

Influence of high power ultrasound on selected moulds, yeasts and Alicyclobacillus acidoterrestris in apple, cranberry and blueberry juice and nectar

The purpose of this study was to investigate the effect of non-thermal technology, high power ultrasound (HPU) on inactivation of Aspergillus ochraceus 318, Penicillium expansum 565, Rhodotorula sp. 74, Saccharomyces cerevisiae 5 and Alicyclobacillus acidoterrestris DSM 3922 in clear juices and nectars from apple, blueberry and cranberry juice concentrate. Inoculated juice and nectars were treated by high power ultrasound (20kHz) according to procedure set by central composite design (CCD). Three operational parameters, amplitude (60, 90 and 120μm), temperature (20, 40 and 60°C), and treatment time (3, 6 or 9min) were varied in order to observe the influence of ultrasound and combination of ultrasound and slight heating (thermosonication) on growth and inactivation of selected microorganisms. Number of vegetative cells of A. acidoterrestris DSM 3922 were not significantly reduced by high power ultrasound (p>0.05), except in apple juice, where statistical significant (p<0.05) influence of quadratic interaction of amplitude on bacteria reduction were observed. In all samples of fruit juices and nectars in terms of ultrasonic treatment at 60°C and times of 3, 6 and 9min, regardless of the value of the amplitude, complete inactivation of the growth of yeasts and moulds were achieved, while at 20 and 40°C it is not observed. The value of reduction of cells of selected yeasts and moulds for ultrasound treatments at 60°C and the duration of the 3, 6 and 9min ranged from 3.556 to 5.934 log units, depending on the initial number of selected yeasts and moulds before treatment.

Aromatic profile and sensory characterisation of ultrasound treated cranberry juice and nectar

Ultrasonication is a nonthermal food processing technology that is used in several applications (extraction, pretreatment before drying, freezing, inactivation of microorganisms etc.). The objective of this study was to investigate the effect of high power ultrasound and pasteurisation on the aroma profile and sensory properties of cranberry juice and nectar. Samples were treated according to the experimental design, with high power sonicator at ultrasound frequency of 20kHz under various conditions (treatment time 3, 6 and 9min, sample temperature: 20, 40 and 60°C and amplitude 60, 90 and 120μm). The aromatic profiles of juices showed that, compared to the untreated samples of juices and nectars, the ultrasonic treatment led to the formation of new compounds or to the disappearance of compounds that were found in the untreated samples. Samples treated at the highest amplitude (120μm) were used for evaluation and comparison with untreated and pasteurised samples using electronic tongue study. Principle component analysis (PCA) confirmed the results of electronic tongue study, which showed that the ultrasound-treated and pasteurised juices had different scores compared to the untreated samples. Sensory evaluation showed that ultrasonically treated and pasteurised juices received lower scores in comparison with the untreated samples.