Effect of different polysaccharides on swelling of composite whey protein hydrogels: A low field (LF) NMR relaxometry study

Abstract Hydrogels are usually prepared from hydrophilic polymers and when different types of polymers are blended or emulsified with an oil phase the resulting gel is usually known as a composite gel. The objective of this study was to analyze the water uptake characteristics of whey protein‐polysaccharide containing composite hydrogels. Composite and composite emulsion gels were formulated in this study using whey protein, xanthan (XN), pectin (PC), alginate (AL), and sunflower oil. Water absorption of hydrogels was studied using Nuclear Magnetic Resonance (NMR) relaxometry through transverse relaxation time (T 2 ) measurements, and Non‐Negative‐Least‐Square (NNLS) analysis. Swelling ratios (SR) of different gels were determined. Swelling of the gels was also evaluated mathematically and water uptake of hydrogels was explained by the power law model and diffusion rate constants based on power law model were determined. Results showed that NMR relaxometry could be used to differentiate water uptake mechanisms of composite hydrogels. Practical applications Biodegradable hydrogels provide controlled delivery of nutrients, bioactive agents such as antioxidants and antimicrobial agents at a desired site and time and at a specific rate. Incorporating bioactive agents to these gels also protects sensitive nutrients and may increase the shelf life of some potential food products. The swelling characteristics of hydrogels provide information about the possible release behavior of the hydrogels. When a hydrogel is loaded with an agent and placed in an aqueous medium, usually the release rate of the agent from the gel and the swelling ratio (SR) of the gel due to solvent uptake from the surrounding medium is proportional to each other. In this study, effects of different polysaccharides on the SR of composite whey protein hydrogels were determined by NMR relaxometry. NMR enabled fast and easy monitoring for hydrogel swelling. Furthermore, NMR provided more detailed information on swelling mechanism than conventional methods proving potential for further applications.