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Lemon thyme contains several bioactive health-promoting compounds of high antioxidant capacity—such as polyphenols, carotenoids, and chlorophyll—which may undergo degradation during drying in incorrect processing conditions. This work is aimed at evaluating the impacts of different drying techniques and parameters on the chemical and physical properties of lemon thyme. In the experiment, lemon thyme leaves are dried using two traditional hot-air methods, convective drying (temperature 70°C or 80°C, air velocity 2 m/s), and fluidized bed drying (temperature 70°C or 80°C, air velocity 5–10 m/s); as well as two innovative drying methods, microwave-assisted fluidized bed (MFB) drying (microwaves at a power of 240 or 440 W, air temperature 40°C, air velocity 5–10 m/s) and microwave-vacuum (MV) drying (microwaves at a power of 240 or 440 W, under vacuum at 4–6 kPa). The kinetics of water delivery are described using the Page Model. After drying, the nutritional composition of the material is analyzed: polyphenol (total content and polyphenols profile by ultra-performance liquid chromatography), carotenoid, and chlorophyll total content, as well as antioxidant capacity (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt [ABTS+] and ferric reducing antioxidant power [FRAP]). Color changes ( L*, a*, b*, ΔE) are also analyzed using the visible effects of lemon thyme pigment disintegration. It is found that the MV drying method is the best for lemon thyme preservation, as it has the shortest process time and the highest retention of polyphenols (78.90%-82.14%), chlorophylls (51.54%-52.68%), antioxidant capacity (47.83%-48.63% of ABTS+ and 20.85%-45.45% of FRAP), and presented the least color change ( ΔE = 25.57-28.32). For preserving carotenoids, the most protective method is MFB (retention 68.46%-70.61 %).
Marta Pasławska; Kinga Sala; Agnieszka Nawirska-Olszańska; Bogdan Stępień; Elżbieta Pląskowska. Effect of Different Drying Techniques on Dehydration Kinetics, Physical Properties, and Chemical Composition of Lemon Thyme. Natural Product Communications 2020, 15, 1 .
AMA StyleMarta Pasławska, Kinga Sala, Agnieszka Nawirska-Olszańska, Bogdan Stępień, Elżbieta Pląskowska. Effect of Different Drying Techniques on Dehydration Kinetics, Physical Properties, and Chemical Composition of Lemon Thyme. Natural Product Communications. 2020; 15 (2):1.
Chicago/Turabian StyleMarta Pasławska; Kinga Sala; Agnieszka Nawirska-Olszańska; Bogdan Stępień; Elżbieta Pląskowska. 2020. "Effect of Different Drying Techniques on Dehydration Kinetics, Physical Properties, and Chemical Composition of Lemon Thyme." Natural Product Communications 15, no. 2: 1.
Food technology seeks ways to preserve products while maintaining high bioactive properties. Therefore, an attempt was made to assess the effect of the process of impregnation with apple-pear juice and the drying process on the content of bioactive compounds in chokeberry fruit. Chokeberry fruits were subjected to impregnation with apple-pear juice at three levels of vacuum pressure, 4, 6, and 8 kPa; then, they were dried using microwave-vacuum technology. The water activity of the obtained products, the content of fructose, glucose, sorbitol, and polyphenolic compounds, and antioxidant activity were determined. A total of 20 polyphenolic compounds were identified in the fruits and the obtained products (seven anthocyanins, six flavonols, four phenolic acids, and three flavan-3-ols). Preliminary processing, which consisted of introducing the juice ingredients into tissue of the chokeberry fruit, resulted in increased content of bioactive compounds. Moreover, a positive effect of impregnation on the antioxidant stability of the fruit after drying was noted. Water activity in the obtained products showed their microbiological safety. Impregnation at 4 kPa vacuum pressure proved to be the most desirable; in such conditions, the best product in terms of the content of bioactive compounds was obtained.
Agnieszka Nawirska-Olszańska; Marta Pasławska; Bogdan Stępień; Maciej Oziembłowski; Kinga Sala; Aleksandra Smorowska. Effect of Vacuum Impregnation with Apple-Pear Juice on Content of Bioactive Compounds and Antioxidant Activity of Dried Chokeberry Fruit. Foods 2020, 9, 108 .
AMA StyleAgnieszka Nawirska-Olszańska, Marta Pasławska, Bogdan Stępień, Maciej Oziembłowski, Kinga Sala, Aleksandra Smorowska. Effect of Vacuum Impregnation with Apple-Pear Juice on Content of Bioactive Compounds and Antioxidant Activity of Dried Chokeberry Fruit. Foods. 2020; 9 (1):108.
Chicago/Turabian StyleAgnieszka Nawirska-Olszańska; Marta Pasławska; Bogdan Stępień; Maciej Oziembłowski; Kinga Sala; Aleksandra Smorowska. 2020. "Effect of Vacuum Impregnation with Apple-Pear Juice on Content of Bioactive Compounds and Antioxidant Activity of Dried Chokeberry Fruit." Foods 9, no. 1: 108.
The purpose of the study was to evaluate the efficiency of mass transfer during vacuum impregnation (VI) of apple tissue by different process conditions. VI was carried out in two stages: Vacuum (4, 6, or 8 kPa maintained at time 10, 20, 30, 40, 60, and 80 s) and atmospheric (4 min under atmospheric pressure). As infiltration liquids, fresh squeezed apple-pear juice (J), 3% citric acid solution (C), and distilled water (DW) were used. Mass transfer was analyzed based on three factors: Mass variation (MV), dry mass variation (DMV), and solid gain (SG). The outflow of native components and inflow of infiltration liquid has been described by mathematical models. The polyphenol content and antioxidant capacity (ABTS+, FRAP) were evaluated as the bioactive potential factors confirming native component outflow and incorporation of liquid molecules into an apple tissue. It was found that during VI of an apple tissue, intensive mass transfer occurred: Native components of fruit tissue outflowed and external ingredients of impregnation liquid inflowed into the material with the intensity proportional to the vacuum level and process time. The most beneficial conditions of apple cube VI were noticed at a vacuum level of 4 kPa for a minimum of 40 s, which is when the highest polyphenol content and antioxidant capacity occurred.
Marta Pasławska; Bogdan Stępień; Agnieszka Nawirska-Olszańska; Kinga Sala. Studies on the Effect of Mass Transfer in Vacuum Impregnation on the Bioactive Potential of Apples. Molecules 2019, 24, 3533 .
AMA StyleMarta Pasławska, Bogdan Stępień, Agnieszka Nawirska-Olszańska, Kinga Sala. Studies on the Effect of Mass Transfer in Vacuum Impregnation on the Bioactive Potential of Apples. Molecules. 2019; 24 (19):3533.
Chicago/Turabian StyleMarta Pasławska; Bogdan Stępień; Agnieszka Nawirska-Olszańska; Kinga Sala. 2019. "Studies on the Effect of Mass Transfer in Vacuum Impregnation on the Bioactive Potential of Apples." Molecules 24, no. 19: 3533.