Changes in physicochemical properties and volatile compounds of roselle (Hibiscus sabdariffa l.) calyx during different drying methods

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Fresh roselle are high in moisture and deteriorate easily, which makes drying important for extending shelf-life and increasing availability. This study investigated the influence of different drying methods (oven-drying, freeze-drying, vacuum-drying, and sun-drying) on the quality of ro-selle calyx expressed as physicochemical properties (moisture content, water activity, soluble solids, color), volatile compounds, and microstructure. Oven-drying and freeze-drying reduced moisture content most while vacuum-drying and sun-drying were not as efficient. All drying methods except sun-drying resulted in water activities low enough to ensure safety and quality. Vacuum-drying had no impact on color of the dry calyx and only small impact on color of water extract of calyx. Drying reduced terpenes, aldehydes, and esters but increased furans. This is expected to reduce fruity, floral, spicy, and green odors and increase caramel-like aroma. Sun-drying produced more ketones, alcohols, and esters. Scanning electron microscopy revealed that freeze-drying preserved the cell structure better, and freeze-dried samples resembled fresh samples most compared to other drying techniques. The study concludes that freeze-drying should be considered as a suitable drying method, especially with respect to preservation of structure.

OriginalsprogEngelsk
Artikelnummer6260
TidsskriftMolecules
Vol/bind26
Udgave nummer20
Antal sider14
ISSN1431-5157
DOI
StatusUdgivet - 2021

Bibliografisk note

Funding Information:
Funding: This research was funded by Ministry of Higher Education, Malaysia and Universiti Putra Malaysia, through its Skim Latihan Akademik Bumiputera (SLAI) Scholarship Program.

Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.

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