Starch and protein, two important nutritional components of foods, have a significant effect on their physicochemical properties and quality. Starch-protein mixed systems (complexes, gels and mixtures) have better physicochemical properties than either alone, and have attracted extensive attention from food, medicine and other industries. This review summarizes the preparation methods for starch-protein mixed systems and their effect on the physicochemical properties of foods, as well as recent progress in their application. This review may provide a theoretical basis for extending the applications of starch and protein in the food industry.

In this study, the nutrients and flavor substances of Fotiaoqiang cooked by the traditional and modern cooking processes were evaluated by analysis of physicochemical indicators and the contents of free amino acids and taste nucleotides as well as using an electronic tongue, gas chromatography-ion mobility chromatography (GC-IMS) and principal component analysis (PCA). The results showed that different cooking processes had a significant impact on the fat content of Fotiaoqiang (P < 0.05). Taste-active nucleotides in Fotiaoqiang cooked by the traditional process could better combine with umami amino acids, imparting a better umami taste to Fotiaoqiang. The electronic tongue results showed that Fotiaoqiang cooked by the two processes were different mainly in bitterness and astringency. The GC-IMS results showed that Fotiaoqiang cooked by the traditional process contained more volatile flavor substances than that cooked by the modern process. PCA showed that there were great differences in the composition of volatile compounds between the two cooking processes. The findings of this study can provide a theoretical reference for the development and application of Fotiaoqiang products.

In this study, coix seed starch nanoparticles were prepared by nano-precipitation method using three different systems (alkali solution, water-ethanol system and dimethyl sulfoxide (DMSO)-ethanol system). The structures and physicochemical properties of the three nanoparticles were investigated by analysis of their particle characteristics, molecular characteristics, crystallization characteristics and thermal characteristics. The results showed that the nanoparticles prepared using alkaline solution had the highest proportion of nanoparticles (85.65%). Both the nanoparticles prepared using alkaline solution and water-ethanol system had an A-type crystalline structure, while the crystalline structure of the nanoparticles prepared using DMSO-ethanol system changed from A-type to amorphous. The nanoparticles prepared using alkali solution at 45 ℃ had the smallest particle size (348 nm), the highest polydispersity, higher degree of order, relative crystallinity and thermal stability, indicating that alkali solution was the most suitable to prepare coix seed starch nanoparticles. This study may provide a theoretical basis for the preparation of starch nanoparticles and the study of their structural properties as well as the expansion of the application of coix seed starch.

Lotus seed protein isolate (LSPI) was used as emulsifier to prepare high internal phase (high load) β-carotene-loaded emulsion (LSPI-BC). The stability and β-carotene retention rate of LSPI-BC were measured, and the mechanism of the changes in LSPI-BC at different stages of in vitro digestion was investigated. The results showed that LSPI-BC had long-term stability at low temperature (4 ℃), and the retention rate of β-carotene was over 85%. However, the stability and β-carotene retention rate of LSPI-BC decreased significantly when the temperature was above 25 ℃. High temperature treatment caused LSPI to unfold and expose hydrophobic groups, forming a spatial network structure that imparts LSPI-BC with good thermal stability and protects the β-carotene from further degradation. In the in vitro digestion experiment, salivary mucin and high concentrations of ions in the oral digestive fluid decreased the magnitude of surface charge on the droplets and then affected the stability of the emulsion. In the gastric phase, flocculation or fusion occurred due to the effect of pH, the potential changed from negative to positive, and the protein aggregates dispersed. In the intestinal phase, the droplet size decreased obviously and the absolute value of potential increased. After hydrolysis, the 1,1-diphenyl-2-picylhydrazyl (DPPH) radical scavenging ability increased significantly. In addition, free fatty acids were released gradually during simulated digestion, and the amount of free fatty acids released increased obviously in the first 30 min of digestion, and then reached 61.94% at 60 min, indicating that LSPI was more suitable for encapsulating active substances. The encapsulated active substance remained stable in acidic medium, its release was delayed during in vitro digestion and its bioavailability was increased to 58.51%. This study may provide a theoretical basis for the development and utilization of LSPI for high loading and sustained release of lipid-soluble active substances.