Effect of pH and Whey Protein Isolate to Glucose Ratios on the Formation of Maillard Reaction Products as Antioxidants

Abstract

A Maillard reaction is one of the common non-enzymatic browning reactions in foods subjected to heat treatment and involves an interaction between protein and reducing sugars. Whey protein isolate (WPI) contains at least 90% soluble proteins. It was hypothesized that WPI could interact with glucose (Glu) leading to the formation of Maillard reaction products (MRPs) and the development of antioxidant activities. The results of this study showed that WPI-Glu developed browning MRPs after heating for 20 min at 90 °C and pH 7 or pH 8. Additionally, the generated browning MRPs developed some antioxidant activities. WPI-Glu mixtures heated at pH 8 revealed the highest free radicals scavenging activity among all examined samples. The highest 2,2-diphenyl-1-picrylhydrazyl scavenging activities of heated WPI-Glu mixtures were 18 and 26% at pH 7 and pH 8, respectively. The results also showed a positive relationship between antioxidant quantities and the amount of added glucose. Sodium dodecyl sulfatepolyacrylamide gel electrophoresis results proved that bovine serum albumin and β-lactoglobulin were the main proteins that reacted with glucose. High performance liquid chromatography analysis detected the presence of hydroxy methyl furfural (HMF) at all tested pH values. However, the data showed that the HMF quantity reached the highest value (6.58 ± 1.79 µg.mL-1) at pH 8 and a WPI:Glu ratio of 1:3. These findings demonstrated that WPI in heat processed foods could be considered as a good source of proteins as well as antioxidants.