A review on protein-phenolic interactions and associated changes

Polyphenols have become an intense focus of research interest due to their health-beneficial effects especially in the treatment and prevention of several chronic diseases. Polyphenols are known to form complexes with proteins leading to changes in the structural, functional and nutritional properties of both compounds. In this review, the effects of protein-phenolic interactions under various conditions on protein and phenolic compound's structure and functionality are described. The parameters thatare defined to affect protein-phenolic interactions are basically temperature, pH, protein type and concentration, and the type and structure of phenolic compounds. Even though the exact mechanism of how proteins influence polyphenols is still not yet known, studies on the changes in the structure and functional properties were investigated. According to these studies, secondary and tertiary structures of the proteins are changed, and solubility of the protein is decreased whereas its thermal stability might be improved. In addition, the amount of some amino acids and protein digestibility might be reduced as a result of this interaction. It is also concluded that proteins significantly decrease the antioxidant capacity in general, but there are some controversial results which might be due to the differences in the analytical techniques performed in these studies. Similarly, different results were obtained in the bioavailability experiments. Factors affecting these results as well as lacking parts of these studies are discussed in detail in this review. In conclusion, interaction of proteins and phenolic compounds is a complex phenomenon and should be further investigated. On the other hand, optimum conditions should be studied in detail to improve the food processes and provide maximum beneficial health effects to the consumers with optimum nutritional and functional properties. (C) 2013 Elsevier Ltd. All rights reserved.