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.

This study was conducted to reveal the effect of milk-clotting enzyme (MCE) produced by Bacillus licheniformis on the texture of Cheddar cheese during ripening. Cheddar cheese and Cheddar cheese analogue were prepared with the MCE and designated as CDF and CD3, respectively, and commercial chymosin was used as a control (CCF).The changes in the texture, rheology and microstructure of cheese during ripening were analyzed. The results were as follows: The hardness of the three cheeses increased with maturation time, while the elasticity and chewiness presented a downward trend. The hardness, springiness and chewiness of CDF were the lowest. The scanning electron microscope (SEM) results showed that the compactness of the protein structure decreased with increasing maturity, and the structure of CDF was looser than that of CCF. The rheological results showed that the storage modulus and loss modulus decreased with increasing ripening time up to six months and increasing sweep temperature. The tan δ value decreased during the ripening process, indicating that the fluidity of cheese decreased with increasing ripening time. The fluidity and fusibility of CDF were better than those of the other groups. The above results indicated that the mechanical properties of cheese made with Bacillus licheniformis MCE were better than those made with commercial rennet, while the latter had harder texture and denser protein network structure.