Freeze vs. Spray Drying for Dry Wild Thyme (Thymus serpyllum L.) Extract Formulations: The Impact of Gelatin as a Coating Material
Open Access
- 27 June 2021
- Vol. 26 (13), 3933
- https://doi.org/10.3390/molecules26133933
Abstract
Freeze drying was compared with spray drying regarding feasibility to process wild thyme drugs in order to obtain dry formulations at laboratory scale starting from liquid extracts produced by different extraction methods: maceration and heat-, ultrasound-, and microwave-assisted extractions. Higher total powder yield (based on the dry weight prior to extraction) was achieved by freeze than spray drying and lower loss of total polyphenol content (TPC) and total flavonoid content (TFC) due to the drying process. Gelatin as a coating agent (5% w/w) provided better TPC recovery by 70% in case of lyophilization and higher total powder yield in case of spray drying by diminishing material deposition on the wall of the drying chamber. The resulting gelatin-free and gelatin-containing powders carried polyphenols in amount ~190 and 53–75 mg gallic acid equivalents GAE/g of powder, respectively. Microwave-assisted extract formulation was distinguished from the others by a higher content of polyphenols, proteins and sugars, higher bulk density and lower solubility. The type of the drying process mainly affected the position of the gelatin-derived -OH and amide bands in FTIR spectra. Spray-dried formulations compared to freeze-dried expressed higher thermal stability as confirmed by differential scanning calorimetry analysis and a higher diffusion coefficient; the last feature can be associated with the lower specific surface area of irregularly shaped freeze-dried particles (151–223 µm) compared to small microspheres (~8 µm) in spray-dried powder.Keywords
Funding Information
- Ministarstvo Prosvete, Nauke i Tehnološkog Razvoja (III46010)
This publication has 38 references indexed in Scilit:
- Optimization of the extraction process of polyphenols from Thymus serpyllum L. herb using maceration, heat- and ultrasound-assisted techniquesSeparation and Purification Technology, 2017
- Microencapsulation optimization of natural anthocyanins with maltodextrin, gum Arabic and gelatinInternational Journal of Biological Macromolecules, 2016
- Optimization of microwave-assisted extraction of total polyphenolic compounds from chokeberries by response surface methodology and artificial neural networkSeparation and Purification Technology, 2016
- Review of Ethnobotanical, Phytochemical, and Pharmacological Study ofThymus serpyllumL.Evidence-Based Complementary and Alternative Medicine, 2015
- Freeze-Drying for Microencapsulation of Turmeric Oleoresin Using Modified Starch and GelatinJournal of Food Processing and Preservation, 2014
- Microencapsulation of oil droplets using freezing-induced gelatin–acacia complex coacervationColloids and Surfaces A: Physicochemical and Engineering Aspects, 2012
- Encapsulation of Natural Polyphenolic Compounds; a ReviewPharmaceutics, 2011
- Encapsulation of polyphenols – a reviewTrends in Food Science & Technology, 2010
- Interaction of functional groups of gelatin and montmorillonite in nanocompositeJournal of Applied Polymer Science, 2006
- The effect of freeze‐drying and its implications for botanical medicine: a reviewPhytotherapy Research, 2005