Abstract
Whey protein is a common food additive for enhancing product stability and texture, while phenolics are considered food antioxidants. As a consequence, combining whey protein with phenolics is an effective way to improve protein functionality while also maintaining polyphenol bioactivity. Herein, the functional properties and antioxidant activity of whey protein modified with various types and concentrations of oxidized phenolic compounds, including gallic acid (OGA), ferulic acid (OFA), and tannic acid (OTA), were studied. In general, the modified whey protein had a decrease in free amino content, but an increase in total phenolic content. Whey protein modified with 5% OTA showed the highest total phenolic content and the lowest free amino content. Modification of whey protein with OTA and OGA resulted in a loss of surface hydrophobicity in contrast to whey protein modified with OFA. However, no significant difference in surface activity including foam and emulsion properties in the whey protein with/without modification was observed. The modified whey protein had an increase in antioxidant activity when compared with that of the control.
Highlights
Whey protein is a by-product of cheese and casein manufacture, and it serves as an ingredient widely used in the food and drink industry due to its valuable nutritional and bioactive characteristic, and multiple functional properties such as solubility, viscosity, and emulsifying and foaming properties [1,2]
Gallic acid was used as a standard, due to number of hydroxyl groups, and results were reported as mol gallic acid equivalent (GAE)/g dry weight (DW) basis
For the whey proteins modified with OGA and OFA, the whey protein modified with OGA showed a higher total phenolic content than the whey protein modified with OFA, OFA showed a higher interaction with the whey protein, as evidenced by the lower free amino group content of the modified whey protein. This result might be because gallic acid had more hydroxyl groups on the aromatic benzene ring than ferulic acid, resulting in a higher total phenolic content in the whey protein modified with OGA
Summary
Whey protein is a by-product of cheese and casein manufacture, and it serves as an ingredient widely used in the food and drink industry due to its valuable nutritional and bioactive characteristic, and multiple functional properties such as solubility, viscosity, and emulsifying and foaming properties [1,2]. Covalent interaction appears to play a crucial role in proteinphenolic interaction, which is used to enhance the functional properties of proteins [4]. Such an interaction affects the functional properties of proteins, such as emulsion formation [6], gelling properties [7] and antioxidant activity [5]. Due to cross-linking and complex formation, the conformation of proteins is changed and the exposure of some additional hydrophobic regions previously buried takes place [4–6,8]. The increase in phenolic groups in modified protein can increase hydrophilicity and antioxidant activity [9]. Linking and complex formation, the conformation of proteins is changed and the exposure of some additional hydrophobic regions previously buried takes place [4–6,8].
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