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Characterisation of the Convective Hot-Air Drying and Vacuum Microwave Drying of Cassia alata: Antioxidant Activity, Essential Oil Volatile Composition and Quality Studies

Chua LYW 1 , Chua BL 2 , Figiel A 3 , Chong CH 4 , Wojdyło A 5 , Szumny A 6 Show all authors , Lech K 7

Affiliations 

  • 1 School of Engineering, Taylor's University, Lakeside Campus, No. 1, Jalan Taylor's, Subang Jaya, Selangor 47500, Malaysia. [email protected]
  • 2 School of Engineering, Taylor's University, Lakeside Campus, No. 1, Jalan Taylor's, Subang Jaya, Selangor 47500, Malaysia. [email protected]
  • 3 Institute of Agricultural Engineering, Wrocław University of Environmental and Life Sciences, 37a Chełmońskiego Street, 51-630 Wrocław, Poland. [email protected]
  • 4 School of Engineering and Physical Sciences, Heriot-Watt University Malaysia, No. 1 Jalan Venna P5/2 Precinct 5, Putrajaya 62200, Malaysia. [email protected]
  • 5 Department of Fruit, Vegetable and Plant Nutraceutical Technology, Wrocław University of Environmental and Life Sciences, 37 Chełmońskiego Street, 51-630 Wrocław, Poland. [email protected]
  • 6 Department of Chemistry, Wrocław University of Environmental and Life Sciences, Norwida 25, 53-375 Wrocław, Poland. [email protected]
  • 7 Institute of Agricultural Engineering, Wrocław University of Environmental and Life Sciences, 37a Chełmońskiego Street, 51-630 Wrocław, Poland. [email protected]
Molecules, 2019 Apr 24;24(8).
PMID: 31022967 DOI: 10.3390/molecules24081625

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.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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