The primary objective of the study was to determine the effect of process conditions on extraction efficiency and the total amount of released polyphenols and antioxidant activity (AA) in black chokeberry juice. The study samples were fruits of black chokeberry ( Aronia melanocarpa (Michx.) Elliott) cv. Galicjanka. In the study, two kinds of presses—piston press and twin gear juice extractor—were used, and two raw material pretreatment methods—freezing and thawing and enzymatic liquefaction—were applied. The study showed that pressing efficiency depends on the design of press and the nature of pretreatment. The highest pressing efficiency was obtained using the twin gear juice extractor. Enzymatic liquefaction of shredded fruits significantly increased the efficiency of pressing by the piston press. The type of press and the pretreatment method used had an effect on the quality traits of the extracted juices. The highest content of soluble solids was obtained for fruits not subjected to any pretreatment and pressed using the twin gear press. The highest total phenolic content was obtained in juice extracted using the piston press from shredded fruits subjected to enzymatic treatment at 45°C. A higher total phenolic content was also a characteristic of juice obtained from fruits not subjected to any pretreatment and extracted using the twin gear press. The capacity of the black chokeberry juices for free radical quenching oscillated around the level of approximately 90%. The study showed that the application of suitable processing methods is necessary for the acquisition of products with desirable quality traits.

The paper presents the comparison of quality of six different commercial apple juices produced in Poland. The apple juices came from two different Polish companies. From each manufacturer three various juices were selected: two cloudy and clarified one produced as a mixture of different apple varieties. The following properties were evaluated: density, soluble solid content, viscosity, total phenolic contents, phenolic acid, and antiradical activity. The obtained results showed that three from fourth cloudy juices (M1Sz, M1A and M2A) differed from clarified juices. The highest differences were noticed for total phenolic contents, phenolic acids, antiradical activity and viscosity. The values of these properties ranged between 60.72–103.6 mg GAE·100−1 mL−1 for phenolic contents, 78.3–90.9% for antiradical activity and 2.68–5.79 mPa·s for viscosity. The remaining cloudy juice (M2Sz) was more similar to the clarified ones. The strong correlation between total phenolic content and antiradical activity of apple juices was found. The high correlation coefficient obtained between these features indicates that both producers do not apply excessive amounts of vitamin C during the production of cloudy apple juices. There was also a strong interrelation between the density of juice and solid soluble content. However, no correlation was found between the solid soluble content and the viscosity of the tested juices.

The effect of temperature and concentration on the rheological behavior of pasteurized apple juice has been studied using a rotational rheometer at shear rates ranging from 0.5 to 12 s −1. The rheological properties were measured at different conditions changing from 10°C to 60°C and from 15°Brix to 40°Brix. On the basis of the obtained results, flow curves were prepared and consistency coefficients and flow indexes were determined. The superposition technique was applied to model behavior of apple juice. The obtained master curve is very important for the industry because it shows the apple juice in the whole range of temperature and soluble solid content. The influence of temperature on consistency coefficient was well described by the Arrhenius equation with activation energy values between 23.3 and 33.6 kJ⋅mol −1. A single equation was proposed for describing the combined effect of temperature, concentration, and shear rate on shear stress at constant flow behavior index. The model can be useful for the easy comparison of the rheological properties of different fluid food.

The possibility of using the vacuum impregnation as a pretreatment before drying apple cubes was investigated. The impregnation was carried out for 4.5 min with the vacuum pressure of 0.01 MPa. The sucrose solution or a mixture of sucrose and the citric acid were used as infiltration liquids. Apple cubes were dried by convective drying (CD) (at temperature of 50 and 70 °C) or microwave-vacuum drying (MVD) (at power of microwaves 120 and 480 W). The drying kinetics was determined and quality factors (anti-oxidant activity, mechanical–rheological properties and colour changes) were analysed. Studies proved that the vacuum impregnation causes increasing of the drying dynamics (12.50–28.57 % during CD and 12.50–18.48 % during MVD). All impregnated apples were darker, yellower and susceptible for deformation or cutting than non-impregnated. The highest level of anti-oxidant activity was observed when two-component impregnant before MVD by power of 480 W was used.

In this paper influence of solvent polarity on the efficiency of ultrasound-assisted extraction of polyphenols from apple pomace was studied. In the experiment, three solvents were used: water, 60% ethanol and 96% ethanol. The extraction process was aided by ultrasonic waves at intensity of 60 W. Efficiency of extraction was determined by measuring total phenolic content, antioxidant activity, energy consumption and unit energy consumption. It has been shown that a 60% solution of ethanol is the most effective solvent for ultrasound-assisted extraction of polyphenols from apple pomace. The application of an appropriate solvent allows a significant reduction in the energy consumption of the extraction process, what is important for the sustainable use of energy sources in the food and agriculture sector.