Protein is an important nutrient in the food system, and active ingredients (such as polyphenols, flavonoids, and terpenes) have a variety of physiological effects because of their unique chemical structures, such as antioxidant, antitumor, and chronic disease-preventive effects. They form complexes through covalent or noncovalent interactions, thus changing their functional structure, nutritional properties, and bioavailability. In this review, we summarize the application of multispectral methods, including ultraviolet-visible (UV-vis) absorption, fluorescence, Fourier transform infrared (FTIR), circular dichroism (CD) spectra, and molecular simulation techniques (molecular docking and molecular dynamics simulation) in the study of protein-active ingredient interaction. The principles, features, and examples of these techniques in the study of the interaction between protein and active ingredients are briefly described. This review also focuses on the application of molecular simulation in delivering active ingredients, regulating food flavor, and monitoring food quality based on protein-active ingredient systems, hoping to provide scientific reference for further study of the interaction between protein and active ingredients.

A liquid chromatographic (LC) method was established for the determination of α-casein, β-casein, κ-casein, α-lactalbumin and β-lactoglobulin in ultra high temperature (UHT) milk. The proteins in milk were denatured by adding a buffer solution containing bis[tris(hydroxymethyl)aminomethane (BisTris), guanidine hydrochloride, sodium citrate, dithiothreitol, etc. The analytes were detected by an ultraviolet (UV) detector and quantified by the external standard method. The results showed that the calibration curve of each protein had good linearity with a correlation coefficient above 0.995. The recoveries of spiked samples were between 95.2% and 105.0%, the detection limit was 0.01–0.02 g/100 mL, and the relative standard deviation was 0.78%–2.70%. The method is characterized by good separation effect, good repeatability and simple operation, and is suitable for quantitative analysis of α-casein, β-casein, κ-casein, α-lactalbumin and β-lactoglobulin in UHT milk.

Tea polyphenols, secondary metabolites found in green tea, are widely used in the food and medicinal industries because of their antioxidant and anti-cancer activity and preventive effect against cardiovascular diseases. The interaction of tea polyphenols with milk proteins can alter the structure of milk proteins and further affect the functional properties and bioavailability of dairy products. There have been widespread concerns about the binding of phenolic compounds to milk proteins due to the special structures of milk proteins. This review describes the mechanism of polyphenol-milk protein interaction, the factors influencing this interaction, the characteristics of reaction products, the methods used to analyze the mechanism, and the effects of this interaction on the functional properties and bioavailability of dairy products. Through this review, we aim to lay a theoretical basis for the development of new products based on the combination of tea polyphenols and milk proteins.