Zoran Herceg

Effects of cold atmospheric gas phase plasma on anthocyanins and color in pomegranate juice

The aim of the study was to evaluate effects of cold atmospheric gas phase plasma on anthocyanins and color in pomegranate juice. Outcomes of plasma treatment were observed at different operating conditions: (i) treatment time (3, 5, 7 min), (ii) treated juice volume (3, 4, 5 cm(3)), and (iii) gas flow (0.75, 1, 1.25 dm(3)/min). The greatest anthocyanin stability was found at: 3 min treatment time, 5 cm(3) sample volume, and 0.75 dm(3)/min gas flow. Plasma treatment yielded higher anthocyanin content from 21% to 35%. Multivariate analysis showed that total color change was not associated with sample volume and treatment time, however it declined with increased gas flow. The change of color increased in comparison treated vs. untreated pomegranate juice. Constructed mathematical equation confirmed that increase of anthocyanin content increased with gas flow, sample volume and change in color. In summary, this study showed that plasma treatment had positive influences on anthocyanins stability and color change in cloudy pomegranate juice.

Stability of polyphenols in chokeberry juice treated with gas phase plasma

Chokeberry juice was subjected to cold atmospheric gas phase plasma and changes in hydroxycinnamic acids, flavonols and anthocyanins were monitored. Plasma treatments were carried out under different treatment times and juice volumes under constant gas flow (0.75dm(3)min(-1)). The results were compared against control (untreated) and pasteurized chokeberry juice (80°C/2min). During pasteurization, the most unstable were hydroxycinnamic acids with losses of up to 59%, while flavonols and anthocyanins increased by 5% and 9%, respectively. On the contrary, plasma treated chokeberry juice showed higher concentrations of hydroxycinnamic acids and 23% loss of anthocyanins in comparison to untreated juice. In order to obtain the optimal cold plasma treatment parameters principal component and sensitivity analysis were used. Such parameters can be potentially used for pasteurization in terms of phenolic stability of chokeberry juice. Optimal treatment was at 4.1min and sample volume of 3cm(3).

Gas phase plasma impact on phenolic compounds in pomegranate juice

The aim of the study was to evaluate the effect of gas phase plasma on phenolic compounds in pomegranate juice. The potential of near infrared reflectance spectroscopy combined with partial least squares for monitoring the stability of phenolic compounds during plasma treatment was explored, too. Experiments are designed to investigate the effect of plasma operating conditions (treatment time 3, 5, 7 min; sample volume 3, 4, 5 cm(3); gas flow 0.75, 1, 1.25 dm(3) min(-1)) on phenolic compounds and compared to pasteurized and untreated pomegranate juice. Pasteurization and plasma treatment resulted in total phenolic content increasing by 29.55% and 33.03%, respectively. Principal component analysis and sensitivity analysis outputted the optimal treatment design with plasma that could match the pasteurized sample concerning the phenolic stability (5 min/4 cm(3)/0.75 dm(3) min(-1)). Obtained results demonstrate the potential of near infrared reflectance spectroscopy that can be successfully used to evaluate the quality of pomegranate juice upon plasma treatment considering the phenolic compounds.

Tribomechanical micronization and activation of whey protein concentrate and zeolite

Tribomechanics is a part of physics that is concerned with the study of phenomena that appear during milling under dynamic conditions. Tribomechanical micronization and activation (TMA) of whey protein concentrates (WPC) and zeolites (type clinoptilolite) were carried out. Samples of powdered WPC and zeolite were treated with the laboratory TMA equipment. The treatment was carried out at two various rotor speeds: 16,000 and 22,000 r.p.m. at ambient temperature. Analyses of the particle size and distribution as well as the specific area and scanning electron microscopy were carried out on the powdered WPC and zeolite, before and after the TMA treatment. Suspensions of the WPC and zeolite were treated with ultrasound, just before determining the particle size distribution, at 50 kHz. The results showed that tribomechanical treatment causes significant decrease in particle size, change in particle size distribution and increase in specific area of WPC and zeolite. These changes of the treated materials depend on the type of the material, the level of inserting particles, the planned angle of the impact, internal rubbing and the planned number of impacts. The effects found became stronger as the rotor speed of the TMA equipment increased (16,000 to 22,000 rpm). Ultrasonic treatment of suspension of tribomechanically treated WPC resulted infurther breakdown of partly damaged protein globules as proved with the statistic analyses. No further changes in their granulometric composition were caused by ultrasonic treatment of a suspension of tribomechanically treated zeolite.

The effect of high power ultrasound and gas phase plasma treatment on Aspergillus spp. and Penicillium spp. count in pure culture

The aim of this study was to investigate and compare two nonthermal techniques in the inactivation of moulds.

Experimental Design and Optimization of Ultrasound Treatment: Functional and Physical Properties of Sonicated Ice Cream Model Mixtures

The aim of this study was to determine the effect of high power ultrasound on functional properties of ice-cream model mixtures. Mixture composed of sucrose, glucose, whole milk powder, whey protein concentrates (WPC) and distilled water was ultrasonically treated according to different parameters. Amplitude of ultrasounds, percentage of WPC in the sample and time of treatment are the three variables considered. Effect of ultrasound parameters on rheological properties (measurement of coefficient of consistency), thermal properties (measurement of initial freezing point) and foaming properties (measurement of maximal foam capacity) was observed. Experiment was designed using model called Central Composite Design (CCD) permitting to consider the significant factors for each property, and results were analyzed and process was optimized through response surface methodology-RSM. Through study, optimal conditions of ultrasound treatment (amplitude, treatment time and percentage of WPC) by which experiment should be performed were obtained. The factor “percentage of WPC” is significant from a rheological and thermal point of view. Regarding foaming properties, the significant factor that is to say affecting most the value of the maximum foam capacity is the duration of ultrasound 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.

Effect of treatment by non-thermal plasma jet on the growth of various food spoilage bacteria in superfluous

The efficiency of gas phase plasma at atmospheric pressure by using an electrical discharge in gas argon on the inactivation of microorganisms was examined. The gas phase plasma was applied to suspensions of pure cultures Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella sp. 3064, Listeria monocytogenes ATCC 23074 and Bacillus cereus 30. The experiments were planned and performed according to a statistical experimental design, specifically central composite design, which considered three independent variables: volume (2, 3 and 4 mL), gas flow (0.75 l and 1.25 l/min) and treatment time (3, 4 and 5 min). Two studied parameters, volume and treatment time, substantially affected the inactivation. For plasma treatment, the inactivation can be attributed to UV radiation and plasma reactive oxygen species (ROS). It was found that Gram- negative bacteria were more susceptible to the plasma treatment than Gram-positive bacteria, and that the susceptibility of Gram-positive bacteria was remarkably species-dependent. Complete inactivation of Escherichia coli, Salmonella sp., and Listeria monocytogenes was acheived when optimal combination of parameters was applied.

The Effect of Tribomechanical Micronization and Activation on Rheological, Thermophysical, and Some Physical Properties of Tapioca Starch

The aim of this research was to investigate the effect of tribomechanical treatments on rheological, thermophysical, and some physical properties of tapioca starch. Samples of tapioca starch were treated using laboratory equipment for tribomechanical micronization and activation (TMA equipment). Before and after the TMA treatment, analysis of the particle size and particle size distribution was carried out, in addition to scanning electron micrography in tapioca starch. Scanning electron micrography showed that tribomechanical processing of tapioca starch resulted in breaking accumulations of starch granules in the form of granules. Pasting parameters have shown that maximal viscosities of model starch suspension have been decreasing after tribomechanical treatment. On the basis of gelatinization curves, it can be concluded that there are changes in the gelatinization point after treatment, and there is decrease in enthalpy of gelatinization for model suspension. After tribomechanical treatment, changes in physical properties of starch suspensions were determined, as well as specific swelling capacity, solubility index, and turbidity of tapioca starch suspensions.