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The effect of ultrasound (US) pretreatment (0, 200, 400, 600, and 800 W) on the physicochemical, emulsification, and gelatinization characteristics of citric acid (CA)-treated whey protein isolate (WPI) was investigated. Size exclusion chromatography demonstrated that when compared with untreated WPI, US pretreatment promoted production of more molecular polymers in the CA-treated WPI. There was a reduction in particle size of CA-treated WPI with the increase of US power (0–800 W), whereas its free sulfhydryl content, surface hydrophobicity, and intrinsic fluorescence strength increased. Furthermore, compared with untreated WPI, emulsifying ability index and emulsifying stability index of CA-treated WPI were increased by 14.04% and 10.10%, respectively, at 800 W. Accordingly, US pretreatment promoted the gel formation of CA-treated WPI, and its gel hardness was increased by 28.0% with US power ranging from 0 to 800 W. Therefore, US and CA treatment can be considered as an effective way to improve the emulsifying and gelatinization characteristics of WPI.

Impact of extrusion pretreatment (50, 70, 90, 110 and 130 °C) on physicochemical, emulsifying properties and water holding capacity (WHC) of transglutaminase (TGase) cross-linked whey protein isolate (WPI) were investigated in this study. The results of molecular size distribution and SDS-PAGE proved that there were more macromolecular polymers formed in TGase cross-linked WPI after extrusion pretreatment (E-WPI-TGase) and the consumption of free amino groups for E-WPI-TGase was the largest at the extrusion temperature of 50 °C and 70 °C. As the extrusion temperature increased from 90 °C to 130 °C, particle size of WPI after extrusion pretreatment (E-WPI) was not changed significantly, compared with that of E-WPI-TGase (p > 0.05). In addition, the emulsifying properties, surface hydrophobicity and WHC of E-WPI-TGase were higher than those of WPI cross-linked by TGase (WPI-TGase) (p

This work systematically researched the binding behavior mechanism and foaming properties of bovine α-lactalbumin (α-La) and glycyrrhizic acid (GA) or ginsenosides (GR) in bulk at pH 7.0 by using the methods of multi-spectroscopic, molecular docking and molecular dynamics (MD) simulation. The intrinsic fluorescence results showed that binding behavior mechanism of GA and GR bounded onto α-La was static quenching. Moreover, the Ka of α-La/GA (3.44 × 104) was larger than that of α-La/GR complex (9.57 × 102) at 298 K. The main driven forces of α-La/GA were hydrogen bonds, van der Waals and hydrophobic interaction forces, while only hydrophobic interaction force was involved in α-La/GR complex. Meanwhile, molecular docking result showed that the docking site of α-La/GA and α-La/GR was mainly located in sheet with S1, S2 or S3 and helix with H4 or h1. There were six hydrogen bonds in α-La/GA, whereas no hydrogen bond was present in α-La/GR. The MD results presented that the electrostatic interaction energy, the Van der Waals interaction energy and the nonpolar solvent energy were favorable for binding between α-La and GA or GR. Among them, the main contributed amino acid residues of α-La/GA complex were Thr33, Gln54, Tyr103, Trp104 and Leu110, while the main interacted residues of α-La/GR system were Trp60, Val99, Tyr103 and Trp104. Furthermore, GA and GR bonded onto α-La had insignificant impact on the secondary structure of α-La. Finally, the addition of GA and GR (1.0 mg/mL) induced a 155.57% and 111.11% increase in the foaming property of α-La. The obtained results provide some new insights to the interaction mechanism of α-La bounded with GA and GR. Additionally, it also indicates that α-La/saponin complex has the ability to apply in the protein-based foaming foods.

Conjugated linoleic acid contains unsaturated fatty acids with multiple bioactivities, but it has poor oxidative and physical stabilities. Its emulsion was fabricated with glycosylated whey protein isolate and hydrolysates of glycosylated whey protein isolate to enhance its stability. An obvious decrease in peroxide value, thiobarbituric acid-reactive substances, particle size and creaming index of emulsion loaded by hydrolysates of glycosylated protein isolate with the increase of hydrolysis time. However, the absolute value of zeta-potential and interfacial adsorption rate of emulsion stabilized by hydrolysates of glycosylated whey protein isolate, were increased by 10.99 and 16.94% at hydrolysis time of 120 min, compared with emulsion loaded by glycosylated whey protein isolate. Thus, limited hydrolysis of glycosylated whey protein isolate as an effective method, remarkably improved the oxidative and physical stability of emulsion.

High-protein nutrition bars (HPNBs) contain 20–50% protein and can effectively and quickly provide the energy needed by the body for performance. They are widely used as sustenance in sports, fitness, and the military as a means of replenishing vital nutrients after physical endurance. However, the hardening of HPNBs occurs quickly during storage due to the interaction of ingredients in the bar's matrix and effects of the external environment. This will lead to deleterious changes in the qualities of the HPNBs, such as taste, and it can seriously affect their market value. This review expounds the factors affecting the hardening of HPNBs during storage, such as sugar crystallization, water migration, protein self-aggregation, phase separation, and Maillard reactions. Research advances in the current anti-hardening methods are summarized, and the characteristics, advantages, and mechanisms of various methods employed in anti-hardening strategies are also expounded. The hardening of HPNBs is a complicated process involving physical changes during the early stage and chemical reactions during the middle and late stages of the storage period. Measures such as the selection of raw materials, substitution of protein with hydrolyzed protein, protein modification, addition of polyphenols, storage conditions, and other methods have achieved promising preliminary anti-hardening results. However, the development of anti-hardening HPNB methods that enable prolonged shelf lives and maintain or enhance taste and nutritional benefits represents a crucial focus for improving the processing and storage of HPNBs.