High-intensity ultrasound treatment on casein: Pea mixed systems: Effect on gelling properties

Ultrasound treatment on commercial pea protein isolates systems: Effect on structure, rheology and gelling properties

Pea protein has attracted great attention due to its capability to meet the growing requirements from consumers for desired nutrition and texture from plant protein. Hence, the current study aimed to investigate the effects of different ultrasonic treatment parameters (power and duration) on the gelling characteristics of commercial pea protein isolates (PPIc). The findings demonstrated that by manipulating the ultrasonic power and treatment duration, great enhancement of the solubility, adhesiveness and formation strength of PPIc gel can be realized. The reduction in particle size was positively correlated with higher power and longer treatment durations. Interestingly, no direct correlation between average particle size, solubility, turbidity, and ζ-potential was observed. Additionally, the ultrasound-modified PPIc in this study exhibited comparable characteristics to laboratory-prepared pea protein isolates, in terms of solubility, water-holding capacity, and gel strength. Overall, manipulating ultrasonic parameters presents a feasible method to customize the texture of pea-protein-based substitute.

Preparation and application of glucono-δ-lactone-induced gel of transglutaminase cross-linked black bean protein isolate-whey protein isolate: Effect of ultrasound pretreatment

A glucono-δ-lactone induced gel was prepared using transglutaminase cross-linked black bean protein-whey protein to deliver riboflavin. Ultrasound pretreatment was found to positively affected gels' hardness, water holding capacity and elasticity. The hardness and elasticity of protein gel pretreated by ultrasound at 360 W were the best, and the water holding capacity of protein gel pretreated by ultrasound at 480 W was the best. These improvements could be attributed to the enhanced hydrophobic interactions and disulfide bonds between proteins by ultrasound pretreatment, which could facilitate a dense network structure, as observed by scanning electron microscope. The dense network of ultrasound-pretreated protein gel effectively protected the riboflavin, and the riboflavin release was reduced by 52 % during gastric digestion for the gel produced at ultrasound power of 360 W, enabling a large amount of riboflavin for absorption and utilization in the intestine. These findings will guide the design of double protein complex gels, providing possible avenues for use as carriers of biologically active substances such as riboflavin.

Ultrasound-mediated soybean-egg white protein acid-induced emulsion gels: A multi-design approach integrating techno-functional properties, digestibility, and nutritional value

This study investigated the effects of formulation and ultrasound on the processing properties and nutrient digestion of soy protein isolate (SPI)-egg white protein (EWP) emulsion gels. The incorporation of EWP significantly improved the texture properties and freeze-thaw stability through disulfide bonds and homogeneous networks in comparison to SPI emulsion gels. However, swelling ratio of emulsion gels at SPI:EWP ratios of 3:1 and 2:1 decreased due to disruption of SPI network continuity. After ultrasound, SPI-EWP emulsion gels exhibited higher gel strength, freeze-thaw stability, and swelling ratio. Digestion kinetics showed an increased half-life time of SPI-EWP emulsion gels with no significant difference in PCmax. Flexible proteins could adsorb around small droplets, forming tight interfacial layers and a dense and uniform network according to particle size and Cryo-SEM. This work elucidated the mechanism of performance stabilization and digestion kinetics of SPI-EWP emulsion gels, supporting the design of animal and plant protein complex products.

Acid-induced pea protein gels pretreated with media milling: Gelling properties and the formation mechanism

This study explored the effect of stirred media mill (SMM) processing on the acid-induced gelling properties of pea protein. Results showed that SMM treatment enhanced the gel strength from 75.06 g to 183.89 g and increased the water holding capacity from 46.64 % to 73.50 %. The minimum gelation concentration achieved for SMM-treated pea protein was 4 %, significantly lower than that of heat-pretreated pea protein (9 %). SMM decreased protein aggregate size from 104 μm to 180 nm. Microscopy analysis revealed that the small aggregates facilitated the formation of uniform gel networks with tight connections. Linear rheology indicated that small protein aggregates resulted in slower gelation rates with a higher G' for the formed gels. The SMM-pretreated protein gel showed strain hardening, shear thinning behaviors, and satisfactory stability to withstand large-amplitude oscillatory shear. Overall, SMM emerges as a promising technology for producing protein gel products with strong mechanical attributes and customizable rheological properties.

Mechanism of ultrasound-induced soybean/egg white composite gelation: Gel properties, morphological structure and co-aggregation kinetics

This study aims to develop ultrasound-assisted acid-induced egg white protein (EWP)-soy protein isolate (SPI) composite gels and to investigate the mechanistic relationship between the co-aggregation behavior of composite proteins and gel properties through aggregation kinetics monitored continuously by turbidity. The results showed that the inclusion of EWP caused the attenuation of gel properties and maximum aggregation (Amax) because EWP could aggregate with SPI at a higher rate (Kapp), which impeded the interaction between SPI and the formation of a continuous gelling network. In the EWP-dominated system, SPI with higher molecular weights also increased the fractal dimension of gels. Ultrasound improved properties of composite gels, especially the SPI-dominated system. After ultrasound treatment, the small, uniform size of co-aggregates and the decrease in potential led to an increase in the aggregation rate and formation of dense particles, consistent with an increase in gelation rate and texture properties. Excessively fast aggregation generated coarse chains and more pores. Still, the exposure of free sulfhydryl groups assisted the gel structure units to form a compact network through disulfide bonding. On the whole, the study could provide theoretical support for a deeper understanding on the interaction mechanism and gelation of composite proteins.

Characterizations of emulsion gel formed with the mixture of whey and soy protein and its protein digestion under in vitro gastric conditions

Partially replacing animal proteins with plant proteins to develop new products has much attention. To get knowledge of their application in emulsion gels, heat-induced composite protein emulsion gels were fabricated using the mixtures of whey protein isolate (WPI) and soy protein isolate (SPI) with the final total protein concentration of 10% (w/w). The water holding capacity (WHC), mechanical and rheological properties and microstructure of mixed protein emulsion gels prepared at different WPI to SPI ratios (100:0, 90:10, 70:30, 50:50, 30:70, 10:90, 0:100, w/w) were investigated. The ratios of WPI to SPI showed little effect on the WHC of the mixed protein emulsion gels (p > 0.05). Increasing the ratio of SPI decreased the hardness and storage modulus (G') of mixed protein emulsion gels, whereas the porosity of mixed protein emulsion gels in the microstructure increased, as shown by CLSM. Both β-lactoglobulin and α-lactalbumin from WPI and 7 S and 11 S from SPI participated in forming the gel matrix of mixed protein emulsion gels. More protein aggregates existed as the gel matrix filler at the high soy protein levels. Interestingly, the G' of mixed protein emulsion gels at the WPI to SPI ratio of 50:50 was higher than the sum of G' of individual WPI and SPI emulsion gels. The whey protein network predominated the gel matrix, while soy protein predominated in the active filling effect. When subjected to an in vitro dynamic gastric digestion model, soy protein in the gels (WPI:SPI = 50:50) degraded faster than whey protein during gastric digestion. This study provided new information on the characteristics of composite protein emulsion gel fabricated with the WPI and SPI mixture.

Mechanical Properties, Microstructure, and In Vitro Digestion of Transglutaminase-Crosslinked Whey Protein and Potato Protein Hydrolysate Composite Gels

The production of animal protein usually leads to higher carbon emissions than that of plant protein. To reduce carbon emissions, the partial replacement of animal protein with plant protein has attracted extensive attention; however, little is known about using plant protein hydrolysates as a substitute. The potential application of 2 h-alcalase hydrolyzed potato protein hydrolysate (PPH) to displace whey protein isolate (WPI) during gel formation was demonstrated in this study. The effect of the ratios (8/5, 9/4, 10/3, 11/2, 12/1, and 13/0) of WPI to PPH on the mechanical properties, microstructure, and digestibility of composite WPI/PPH gels was investigated. Increasing the WPI ratio could improve the storage modulus (G') and loss modulus (G″) of composite gels. The springiness of gels with the WPH/PPH ratio of 10/3 and 8/5 was 0.82 and 0.36 times higher than that of the control (WPH/PPH ratio of 13/0) (p < 0.05). In contrast, the hardness of the control samples was 1.82 and 2.38 times higher than that of gels with the WPH/PPH ratio of 10/3 and 8/5 (p < 0.05). According to the International Organization for Standardization of Dysphagia Diet (IDDSI) testing, the composite gels belonged to food level 4 in the IDDSI framework. This suggested that composite gels could be acceptable to people with swallowing difficulties. Confocal laser scanning microscopy and scanning electron microscopy images illustrated that composite gels with a higher ratio of PPH displayed thicker gel skeletons and porous networks in the matrix. The water-holding capacity and swelling ratio of gels with the WPH/PPH ratio of 8/5 decreased by 12.4% and 40.8% when compared with the control (p < 0.05). Analysis of the swelling rate with the power law model indicated that water diffusion in composite gels belonged to non-Fickian transport. The results of amino acid release suggested that PPH improved the digestion of composite gels during the intestinal stage. The free amino group content of gels with the WPH/PPH ratio of 8/5 increased by 29.5% compared with the control (p < 0.05). Our results suggested that replacing WPI with PPH at the ratio of 8/5 could be the optimal selection for composite gels. The findings indicated that PPH could be used as a substitute for whey protein to develop new products for different consumers. Composite gels could deliver nutrients such as vitamins and minerals to develop snack foods for elders and children.