Abstract
Sour cherries were first dried by vacuum drying and then used as material for obtaining extracts rich in bioactive compounds by ultrasound-assisted extraction (UAE). The first step was to apply a factorial design for the preliminary experiments to determine the most influential UAE factors, and thus the three studied parameters were chosen as the most suitable for the design of the main experiment (temperature, liquid–solid ratio and ethanol concentration). In this part, the contents of total phenols and the total content of monomeric anthocyanins were taken for responses. For the further optimization of UAE, experimental design (face-centered) was applied, and the yield, total phenolics, flavonoid content and content of monomeric anthocyanins and antioxidant activity (DPPH, ABTS and FRAP assays) were analyzed. Temperature (40–80 °C), ethanol concentration (40–80%, w/w) and liquid–solid ratio (10–30 mL/g) were investigated as independent variables. The obtained experimental results were fitted to a second-order polynomial model and analysis of variance was used to determine the fit of the model and the optimal conditions for investigated responses. High quality extracts with high concentrations of polyphenols and anthocyanins were also obtained, which could be used as food additives.
Highlights
The sour cherry (Prunus cerasus L.) is one of the fruits that originated in areas around the Caspian Sea
After the previous screening of ultrasound-assisted extraction (UAE) factors, it was found that three investigated parameters showed the greatest effect on total phenolics and monomeric anthocyanin content throughout the ultrasoundassisted extraction of vacuum dried sour cherry samples
After the preliminary screening of the studied UAE factors, it was found that three investigated parameters showed the highest influence on total phenolic and monomeric anthocyanin content throughout the UAE of previously vacuum dried sour cherry samples
Summary
The sour cherry (Prunus cerasus L.) is one of the fruits that originated in areas around the Caspian Sea. Sour cherries are characterized as an important industrial fruit variety, and they are a valued raw material in the area of food production. Thanks to their high postharvest respiration and susceptible structure, numerous methods must be applied in the fruit processing industry to control and maintain adequate quality of sour cherries [4]. The results of the comparative analysis of the effects of convective drying, vacuum drying and lyophilization (freeze drying) on the physical, chemical and biological properties of stone fruits in the research of Vakula et al [9] showed that the highest total phenolic and flavonoid content of all dried stone fruit samples were obtained in the vacuum dried sour cherry samples
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