Effect of encapsulation on hygroscopic, structural, physico-thermal and in vitro release properties of DPP-IV inhibitory peptides-rich sodium caseinate hydrolysates

Abstract

Considering the increasing worldwide prevalence of Type 2 diabetes mellitus (T2DM), utilizing milk protein-derived bioactive peptides offers a promising and sustainable solution to manage hyperglycemia. However, formulating functional foods rich in Dipeptidyl peptidase-IV (DPP-IV) inhibitory peptides is hindered by their poor physicochemical stability and high hygroscopicity. To overcome these limitations, this study specifically aimed to encapsulate a DPP-IV inhibitory peptide-rich sodium caseinate hydrolysate (SCH) within the gum Arabic and resistant maltodextrin polysaccharide matrix using spray drying. The hygroscopic profiles of SCH (without encapsulation) and the resulting encapsulated powder (EP) were evaluated comparatively. Structural and thermal transitions were mapped using Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray Diffraction (XRD). FTIR and SEM analyses demonstrated that encapsulation had adequately protected the peptides within the matrix. DSC revealed that encapsulation has increased the glass transition temperatures (Tg) from 52.89 °C (SCH) to 89.66 °C (EP). XRD patterns demonstrated improvement in crystallinity after encapsulation. Moisture sorption analyses indicated that EP was effectively predicted by the Halsey, Kuhn, and GAB models at 25 and 35 °C and exhibited type-II sigmoid isotherm. Further, EP shows ∼6-fold higher DPP-IV inhibition than SCH in the intestinal phase. The findings demonstrated that encapsulation has markedly reduced hygroscopicity and insolubility index (by 0.6 mL), enhanced dispersibility (by 5.6%), of DPP-IV inhibitory peptide-rich sodium caseinate hydrolysates, besides offering better protection during gastro-intestinal transit. This could help to develop a shelf-stable, DPP-IV inhibitory peptides-rich sodium caseinate hydrolysate powder for better management of T2DM.