Polysaccharide blended whey protein isolate-(WPI) hydrogels: A physicochemical and controlled release study

Abstract

Design and characterization of composite whey protein isolate (WPI) hydrogels are gaining interest due to their utilization as controlled delivery matrices for bioactive agents. In this study, black carrot extract (BC) loaded composite WPI hydrogels, containing xanthan (XN), pectin (PC) and gum tragacanth (GT) were prepared by conventional water bath (CV) and infrared (IR) assisted microwave heating (MW). Release and swelling experiments were conducted at pH 7.0 phosphate buffer solution for 24 h. Highest swelling ratio (SR) was observed at CV XN hydrogels and only XN hydrogels showed a distinct increase in SR (17.85%) with respect to WPI hydrogels containing no additional polymer (10.55%) (p < 0.05). CV WPI hydrogels having no added polysaccharide showed the highest release percent (77.81%). CV PC, XN and GT hydrogels with release ratios of 37.15%, 32.79% and 29.39%, respectively, were capable of retarding release with respect to sole WPI hydrogels (p < 0.05). MW increased the release rates of all polymer added hydrogels. Nuclear Magnetic Resonance (NMR) relaxometry was used to understand the polymer-water interactions in the samples. Therefore, transverse relaxation times (T2) and self-diffusion coefficients (SDC) of each hydrogel were measured. Increasing T2 and SDC values of CV XN samples were associated with better gel characteristics. Scanning electron microscope (SEM) images revealed the microstructural differences between the heating and polymer types. Mathematical modelling of release behaviors of hydrogels was also conducted to estimate diffusion coefficients. Moreover, this study introduces the effects of MW-IR heating on the physiochemical and controlled release behavior of WPI-GT composite hydrogels for the first time.