Volume: 2, 2023
2nd International PhD Student’s Conference at the University of Life Sciences in Lublin, Poland:
ENVIRONMENT – PLANT – ANIMAL – PRODUCT
Abstract number: T021
DOI: https://doi.org/10.24326/ICDSUPL2.T021
Published online: 19 April 2023
ICDSUPL, 2, T021 (2023)
Subcritical water extraction of walnut bark (Juglans regia L.): The effect of temperature, raw material fraction size and process time
Piotr Kamiński1,2*, Katarzyna Tyśkiewicz2, Zygmunt Fekner2, Marcin Gruba2, Zbigniew Kobus1
1 Department of Technology Fundamentals, University of Life Sciences, Głęboka 28, 20-612 Lublin, Poland
2 Łukasiewicz Research Network – New Chemical Syntheses Institute, Al. Tysiąclecia Państwa Polskiego 13a, 24-110 Puławy, Poland
* Corresponding author: piotr.kaminski@ins.lukasiewicz.gov.pl
Abstract
Phenolic compounds are secondary metabolites present in various parts of plants and are used as protective substances against various types of stress that can be caused by environmental conditions, pathogens and injuries. Green walnut, shell, husk, kernel, bark, root and leaves of Juglans regia L. are widely used in the pharmaceutical and cosmetic industries. Walnuts are considered a good source of tocopherols and essential fatty acids, moreover contain other compounds including polyphenols, tannins, folate, dietary fiber, protein, melatonin and sterols. The bark of Juglans regia L. contains chemical components such as β-sitosterol, ascorbic acid, juglone, folic acid, gallic acid, regiolone, and quercetin-3-O-α-l-arabinoside. These bioactive compounds are separated from plant material by conventional extraction methods using organic solvents such as n-hexane and others. In this manner organic solvent can remain in final products and organic waste is generated. A green alternative to organic solvent application is the Subcritical Water Extraction (SWE). In order to produce a high amount of valuable extract from bark of Juglans regia L. in an environmentally friendly manner, the SWE process was tested at temperatures 110, 140, and 170°C, raw material fraction size 0.9, 1.4 and 1.9mm, and process duration 10, 30 and 50min. Obtained extracts were characterized by the polyphenols and flavonoids content, as well as antioxidant activity measured using the DPPH and FRAP methods. The total polyphenols (TPC) and flavonoid (TFC) were determined using the spectrophotometric (UV-Vis) method. The response surface methodology (RSM) was employed to optimize the yield of bioactive compounds. On the basis of developed model, the highest polyphenols (192.2 mg (GAE)/100 g (dry mass)) (GAE – gallic acid equivalent), flavonoids (88.3 mg(QE)/100 g (dry mass)) (QE – quercetin equivalent) contents and antioxidant activity (21.3×10-6 MTE/1 g (dry mass)) (TE-Trolox equivalent) were obtained under the following extraction conditions: temperature 131.6°C, raw material fraction size 0.9mm and process time 10min. The greatest impact on the extraction yield was observed in the case of the temperature, whereas the raw material fraction size and the process time had a secondary impact. Obtained results indicate that a smaller particle size and a shorter time may improve the process; however, a reduction in particle size can be challenging for a pressure cell filtration system and consequently increase the cost of the raw material pretreatment process. With the reduction in the process time, a lower cost of extract production can be achieved. This study confirmed the importance of a proper selection of extraction parameters to obtain the demanded extract composition.
How to cite
P. Kamiński, K. Tyśkiewicz, Z. Fekner, M. Gruba, Z. Kobus, 2023. Subcritical water extraction of walnut bark (Juglans regia L.): The effect of temperature, raw material fraction size and process time. In: 2nd International PhD Student’s Conference at the University of Life Sciences in Lublin, Poland: Environment – Plant – Animal – Product. https://doi.org/10.24326/ICDSUPL2.T021