Effect of Maillard reaction conditions on the degree of glycation and functional properties of whey protein isolate – Maltodextrin conjugates

The Maillard reaction has been used as a natural alternative to improve protein functionality by covalent coupling with saccharides. However, if reaction conditions are not properly selected, glycation can lead to a loss in functional properties. The objective of our research was to study the effect of temperature, time, water activity and reactants molar ratio on the degree of glycation and color development in whey protein isolate conjugated with maltodextrins. Three different levels of glycation (low, medium and high) were selected to investigate functional properties. The extent of glycation was assessed by quantifying the loss of amino groups using the o-phthaldialdehyde technique. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to evaluate the molecular weight of the glycoproteins. Color changes were determined using a Minolta colorimeter and calculating the browning index. Functional properties evaluated were solubility, rheological behavior, foam overrun and foam stability. Temperature and water activity were the most influential factors determining the degree of glycation and color change. The correlation coefficient between blocked amino groups and color was of 0.743. Whey protein isolate exhibited lower solubility at pH 5 and conjugates at pH 4. Consistency index and foaming properties improved according to the level of glycation achieved.