Introduction: Dipeptidyl peptidase IV (DPP-IV) inhibitors constitute a novel approach for the management of type 2 diabetes mellitus (T2DM). A major obstacle to the commercialization of these milk-derived bioactive peptides is their susceptibility to breakdown within the gastrointestinal tract. Consequently, encapsulation has become a vital strategy for enhancing the utilization of bioactive peptides. Therefore, this study was conducted to encapsulate DPP-IV-inhibitory hydrolysates derived from milk proteins and evaluate their structural and moisture sorption properties.
Methods: A milk protein hydrolysate rich in DPP-IV-inhibitory peptides was prepared. This hydrolysate was encapsulated in a matrix of gum arabic and resistant maltodextrin through spray drying. The obtained encapsulated DPP-IV-inhibitory peptides were analysed in terms of their structural characteristics (SEM), FTIR and moisture sorption isotherm.
Results: SEM analysis confirmed the achievement of matrix-type encapsulation with a smooth, wrinkled surface and aggregated particles. The FTIR results indicated the uniform distribution of peptides within the matrix. The glass transition, crystallization and melting temperatures of the encapsulated peptides were 57.11, 181.37 and 283.49 °C, respectively. The moisture sorption isotherm (MSI) behaviour was investigated at 25, 35 and 45⁰C using an isopiestic method. The isotherm obtained for the encapsulated peptides was J-shaped, close to a type-III isotherm. Various mathematical models were used for the analysis of the experimental equilibrium moisture content. The Kuhn, Halsey and GAB mathematical models showed the best fit, whereas the BET, Caurie and Modified Mizrahi models did not fit at all the temperatures based on their RMS% and P values. The surface area of sorption decreased from 26.31 at 25⁰C to 17.70 and 17.22 m2g-1 at 35 and 45⁰C, respectively, indicating increased sorption and an increased surface area at lower temperatures. The isosteric heat of sorption showed the independence of the product to varying temperatures. Overall, the present study shows the successful encapsulation of milk protein hydrolysates. The characterization studies showed that encapsulated hydrolysates have a hygroscopic nature and can be improved with different bulking agents.
