Freeze vs. Spray Drying for Dry Wild Thyme (Thymus serpyllum L.) Extract Formulations: The Impact of Gelatin as a Coating Material

Freeze drying was compared with spray regarding feasibility to process wild thyme drugs in order obtain dry formulations at laboratory scale starting from liquid extracts produced by different extraction methods: maceration and heat-, ultrasound-, microwave-assisted extractions. Higher total powder yield (based on the weight prior extraction) achieved freeze than lower loss of polyphenol content (TPC) flavonoid (TFC) due process. Gelatin as a coating agent (5% w/w) provided better TPC recovery 70% case lyophilization higher diminishing material deposition wall chamber. The resulting gelatin-free gelatin-containing powders carried polyphenols amount ~190 53–75 mg gallic acid equivalents GAE/g powder, respectively. Microwave-assisted extract formulation distinguished others polyphenols, proteins sugars, bulk density solubility. type mainly affected position gelatin-derived -OH amide bands FTIR spectra. Spray-dried freeze-dried expressed thermal stability confirmed differential scanning calorimetry analysis diffusion coefficient; last feature can be associated specific surface area irregularly shaped particles (151–223 µm) small microspheres (~8 spray-dried powder.