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.

Original languageEnglish
Article number6260
Issue number20
Number of pages14
Publication statusPublished - 2021

Bibliographical note

This article belongs to the Special Issue Volatile Compounds and Smell Chemicals (Odor and Aroma) of Food—Second Edition.

    Research areas

  • Drying, Dynamic headspace sampling, Microstructure, Physicochemical properties, Roselle (Hibiscus sabdariffa L.), Volatile compounds

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