The aim of these studies was to investigate the influence of airborne ultrasound-assisted convective drying and microwave-assisted convective drying, as well as their combination, on process kinetics, total color change, water activity, content of carotenoids, polyphenols and antioxidant activity of carrots (Daucus carota L.). The global model of drying kinetics based on coupled ordinary differential equations was used to describe the moisture and material temperature profiles during drying. Application of ultrasound and microwave in convective drying reduced drying time in the range of 9-81%, but the shortest drying time was observed for simultaneous action of convection, ultrasound and microwave. The results of qualitative analysis showed a product improvement due to ultrasound as compared to convective drying and microwave-convective drying. The proposed mathematical model of drying kinetics successfully simulated real drying processes. The proposed mathematical model of drying kinetics successfully simulated real hybrid drying processes.

Vacuum impregnation is a non-destructive method of introducing a solution with a specific composition to the porous matrices of fruit and vegetables. Mass transfer in this process is a result of mechanically induced differences in pressure. Vacuum impregnation makes it possible to fill large volumes of intercellular spaces in tissues of fruit and vegetables, thus modifying physico-chemical properties and sensory attributes of products. This method may be used, e.g., to reduce pH and water activity of the product, change its thermal properties, improve texture, color, taste and aroma. Additionally, bioactive compounds may be introduced together with impregnating solutions, thus improving health-promoting properties of the product or facilitating production of functional food.

We studied the content of tocopherols, tocotrienols and carotenoids in oil extracted from the kernels of 15 apricot (Prunus armeniaca L.) genotypes and the associated oil yield of the studied samples. The oil yield in apricot kernels was in a wide range of 27.2-61.4% (w/w) dry weight basis. For each class of studied compounds (tocochromanols and carotenoids), a three-fold difference was found between the lowest and the highest content (78.8-258.5 and 0.15-0.53 mg/100 g of oil, respectively). γ-Tocopherol accounted for 91-94% of total tocochromanols detected in all tested samples. Lutein, zeaxanthin, β-cryptoxanthin and β-carotene were the main compounds among the eight different carotenoids detected in apricot kernel oils; they comprised 76-94% of the total carotenoids content, and compositions were characteristic for specific genotypes. The oil yield and content of lipophilic antioxidants in apricot kernel oils were significantly affected by the genotype. The oil yield was negatively correlated with the total amount of tocochromanols (r = −0.910) and carotenoids (r = −0.704) in apricot kernel oils.

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