Comparative study of physicochemical and thermal stability of different commercial soluble dietary fibres as alternative glass formers for spray-dried food powders

The rising demand for functional low-calorie ingredients with improved powder stability has increased interest in soluble dietary fibers (SDFs) as alternatives to conventional maltodextrins. These fibers differ in molecular structure and water interaction, influencing their ability to form stable amorphous matrices during spray drying. However, direct comparative evaluations of their intrinsic physicochemical and thermal properties remain limited. This study compared commercial Orafti® inulin (inulin), TIC PRETESTED® GUM ARABIC FT POWDER (gum arabic), Nutriose®FB 06 (nutriose), and STA-LITE®III Polydextrose (polydextrose) to elucidate their structure – function relationships as standalone glass formers. Each fiber was characterized for moisture content, water activity, solubility, hygroscopicity, morphology (field emission scanning electron microscopy (FE-SEM), particle size distribution (PSD), universal attenuated total reflectance-fourier transform infrared spectroscopy (UATR-FTIR), X-ray Diffraction (X-RD), water sorption isotherm WSI, and differential scanning calorimetry (DSC). All fibers exhibited very high solubility >99%, with inulin achieving 100±0.00%. Gum arabic showed the highest moisture content 7.22±0.001% but the lowest water activity 0.167±0.008, while polydextrose recorded the highest aW 0.335±0.01. Hygroscopicity ranged from 0.000063gH2Og−1solid24 h−1(inulin) to 0.000085gH2Og−1solid24 h−1 (gum arabic). The Guggenheim – Anderson – de Boer (GAB) model accurately described sorption data R2>0.90, revealing differences in monolayer moisture 0.062−0.175 and multilayer adsorption. Gum arabic and nutriose exhibited higher glass transition temperatures 124.19±1.00 degC−102.19±1.00degC,respectivley, indicating greater resistance to plasticization, whereas inulin showed lowest Tg43.52±1.00 degC due to its semi-crystalline structure. Overall, synthetic resistant dextrins (gum arabic and nutriose) provided the most balanced performance in solubility, hygroscopic stability, and thermal resistance, supporting their potential use as sustainable glass formers in spray-dried food systems with extended shelf life