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© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.

Abstract

The preservation of active constituents in Cassia alata through the removal of moisture is crucial in producing a final product with high antioxidant activity. This study aims to determine the influences of various drying methods and drying conditions on the antioxidant activity, volatiles and phytosterols content of C. alata. The drying methods used were convective drying (CD) at 40 °C, 50 °C and 60 °C; freeze drying; vacuum microwave drying (VMD) at 6, 9 and 12 W/g; and two-stage convective pre-drying followed by vacuum microwave finish drying (CPD-VMFD) at 50 °C and 9 W/g. The drying kinetics of C. alata are best described by the thin-layer model (modified Page model). The highest antioxidant activity, TPC and volatile concentration were achieved with CD at 40 °C. GC–MS analysis identified the presence of 51 volatiles, which were mostly present in all samples but with quantitative variation. The dominant volatiles in fresh C. alata are 2-hexenal (60.28 mg 100 g−1 db), 1-hexanol (18.70 mg 100 g−1 db) and salicylic acid (15.05 mg 100 g−1 db). The concentration of phytosterols in fresh sample was 3647.48 mg 100 g−1 db, and the major phytosterols present in fresh and dried samples were β-sitosterol (1162.24 mg 100 g−1 db). CPD-VMFD was effective in ensuring the preservation of higher phytosterol content in comparison with CD at 50 °C. The final recommendation of a suitable drying method to dehydrate C. alata leaves is CD at 40 °C.

Details

Title
Characterisation of the Convective Hot-Air Drying and Vacuum Microwave Drying of Cassia alata: Antioxidant Activity, Essential Oil Volatile Composition and Quality Studies
Author
Lisa Yen Wen Chua 1 ; Bee Lin Chua 1   VIAFID ORCID Logo  ; Figiel, Adam 2   VIAFID ORCID Logo  ; Chong, Chien Hwa 3   VIAFID ORCID Logo  ; Wojdyło, Aneta 4   VIAFID ORCID Logo  ; Szumny, Antoni 5   VIAFID ORCID Logo  ; Lech, Krzysztof 2 

 School of Engineering, Taylor’s University, Lakeside Campus, No. 1, Jalan Taylor’s, Subang Jaya, Selangor 47500, Malaysia 
 Institute of Agricultural Engineering, Wrocław University of Environmental and Life Sciences, 37a Chełmońskiego Street, 51-630 Wrocław, Poland 
 School of Engineering and Physical Sciences, Heriot-Watt University Malaysia, No. 1 Jalan Venna P5/2 Precinct 5, Putrajaya 62200, Malaysia 
 Department of Fruit, Vegetable and Plant Nutraceutical Technology, Wrocław University of Environmental and Life Sciences, 37 Chełmońskiego Street, 51-630 Wrocław, Poland 
 Department of Chemistry, Wrocław University of Environmental and Life Sciences, Norwida 25, 53-375 Wrocław, Poland 
First page
1625
Publication year
2019
Publication date
2019
Publisher
MDPI AG
e-ISSN
14203049
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2549007115
Copyright
© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.