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.

As the most common type of anemia, iron-deficiency anemia has attracted more and more attention. With the change of nutrition and health needs and the enhancement of safety awareness, there has been increasing interest in the research and development of oral iron supplements with good iron supplementation effect, easy absorption, small side effects and high safety. This paper reviews recent progress in the development and research of iron supplements. In this paper, the raw material source, structure, action mechanism, preparation, application, and digestion and absorption mechanism of iron protein succinate are reviewed, and future prospects of polypeptide-iron complexes and iron protein succinate are discussed. We anticipate that this review will provide a theoretical basis for the research and development of iron supplements.

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.

The impact of adding polysaccharides extracted from liquid-cultured mycelia of Inonotus obliquus into yak yogurt on its sensory evaluation score and titratable acidity was investigated to determine the optimal addition amount of the polysaccharides. The process parameters for producing yak yogurt with added Inonotus obliquus polysaccharides were optimized, and the quality of the yogurt prepared under optimized conditions was evaluated and compared with that of yogurt without added Inonotus obliquus polysaccharides as a control. The results showed that addition of 0.4% Inonotus obliquus polysaccharides to yak yogurt led to the highest sensory score together with a moderate acidity. Using orthogonal array design, the optimal process conditions were determined as follows: ratio of Streptococcus thermophilus G2 to Lactobacillus paracasei L9, 1:1; fermentation time, 14 h; temperature, 38 ℃; and sucrose concentration, 8 g/100 mL. Compared with the control, the as-prepared yogurt increased the number of viable lactic acid bacteria, titratable acidity and water-holding capacity by 34.1%, 11.0% and 16.8% respectively, and the pH value decreased accordingly. Addition of Inonotus obliquus polysaccharides into yak yogurt improved its firmness and viscosity as well as flavor.

Molecular biology studies have confirmed that bioactive polysaccharides are naturally occurring polymers that have a variety of physiological and biochemical functions. The water-complexing ability, high viscosity, antioxidant and anti-aging properties of bioactive polysaccharides lay the foundation for their application in the fields of food, and the use of bioactive polysaccharides as a bioactive ingredient in functional foods has become a current research focus. Fermented milk has good flavor and probiotic properties, but it also has the disadvantages of short shelf life, poor curd quality, and general probiotic performance. How to improve the quality of fermented milk is a current major challenge. This article focuses on recent progress in the application of different types of bioactive polysaccharides in fermented milk, and reviews the effects and mechanisms of action of bioactive polysaccharides on the physicochemical, gel and probiotic properties of fermented milk. Furthermore, it discusses future prospects for the application of bioactive polysaccharides in fermented milk. This review is expected to provide a reference for exploring the functions of bioactive polysaccharides and improving the quality of fermented 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.