Search

This study was performed to examine the effect of two soy peptides addition with hydrolysis degrees of 90% and 30% (hydrolysis degree (DH)90, DH30) at various concentrations (1–10 mg/mL) on soy protein isolate (SPI) gel behavior and pure SPI gel was set as control. SPI gels with adding peptides were prepared, and their rheological, textural, and tribological properties, as well as water‐holding capacity, zeta potential, and particle size, were determined. During the rheological measurement, adding peptides reduced storage modulus (G′) compared to the control, with larger particles formed. However, peptide addition could significantly reduce gelation time, showing a more significant effect with DH30. The gels' firmness, adhesiveness, and water‐holding capacity decreased as peptide concentration increased. Syneresis was observed in gels with peptides, whereas the control sample showed no syneresis. Based on the rheological results, the shear stress in the control sample was higher than in the gels containing peptides indicating more resistance to shear. The gels with DH30 showed greater G′ and G″ than DH90 at all studied concentrations. Nevertheless, there was an improvement in the lubrication behavior of SPI gels with peptide addition. DH30 showed a relatively more significant friction reduction than DH90, indicating their slightly better lubrication properties. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effects of incorporating different concentrations of flaxseed gum (FG) into acid-induced soy protein isolate (SPI) gels. The investigation focused on assessing the effects of FG on the textural, rheological, and tribological properties of the resultant SPI gels. The results showed that adding a small amount of FG (0.05%) to the SPI gel system increased the storage modulus (G′) and enhanced gelation while improving textural properties including hardness, viscosity, elasticity, and adhesion. Moreover, these gels exhibited strong water-holding capacity, a desirable property in various food products. However, when the concentration was increased to 0.3%, the WHC of the gel decreased, as did the hardness and cohesiveness. The particle size of the gel also increased with increasing concentration. Tribological investigations revealed that at 0.05–0.2% FG addition, the coefficient of friction (μ) of the composite gel was decreased compared to the pure SPI gel. In the sliding speed range of 1–100 mm/s, the coefficient of friction gradually increased with increasing concentration. When the FG concentration was 0.05%, the μ of the gel system was the lowest. In summary, low concentration of FG (0.05%) was found to play an important role in improving the properties of SPI gel, including enhancing textural, rheological, and lubricating properties. [ABSTRACT FROM AUTHOR]

Rice starch (RS) and soy protein (SP) were mixed at various ratios and the physicochemical, rheological and tribological properties of the resulted pastes were analyzed. Microscopy and spectral techniques were applied to follow the structural changes during cooling and heating processes. Higher proportion of SP resulted in lower swelling power. According to DSC and RVA results, SP inhibited the gelatinization of starch, leading to higher pasting temperature; the peak, trough, final viscosities, set back and enthalpy changes were decreased with increasing SP concentration. All the samples presented a shear thinning behavior and the mixtures with soy proteins showed lower viscosity, yield stress and consistency coefficient than pure starch paste. The creep-recovery test showed that the addition of soy proteins resulted in more liquid-like mixtures, causing weakening of instantaneous elastic recovery. The combination of rice starch and soy proteins increased the friction, compared with their individual components, except RS/SP 9/1 at sliding speed >20 mm/s. According to the microstructure and spectra analysis, the soy protein adhered on the surface of starch granules, which might have hindered the leaching of amylopectin; and the association between starch and soy proteins mainly occurred when the starch granules were gelatinized, which could be reinforced during starch retrogradation. • Rice starch (RS)/ soy protein (SP) mixtures were studied at a wide range of ratio. • SP inhibited the gelatinization and reduced viscosity of RS paste. • Prominent association between RS and SP occurred during retrogradation. • Friction of mixtures were generally higher than individual components. [ABSTRACT FROM AUTHOR]

To understand the heat treatment and flaxseed gum (FG) on the properties of commercial spray dried soy protein isolate (SPI), SPI dispersions were prepared with mass ratio of 6 %, 9 %, and 12 % in water and the corresponding protein concentrations of 2.2 %, 3.61 % and 5.23 % were reached after centrifugation. The solutions were treated at different temperatures (25, 75 and 100 °C) and the particle characteristics and physical properties of the resulted samples were determined. The influence of different concentrations (0.05 % to 0.3 %) of FG addition was evaluated in the SPI solution at 5 % protein concentration. The results showed that heating caused decrease of particle size of the SPI proteins and 100 °C heat treatment caused decrease of hydrophobicity and viscosity of the protein dispersions, and increase of their physical stability, and the effect was more marked at high protein concentration; while heat treatment at 75 °C caused substantial increase in protein hydrophobicity and viscosity, and decrease of stability. Addition of FG resulted in increase of particle size, absolute value of zeta potential and hydrophobicity of the protein solutions. The viscosity of the solution was decreased with addition of FG, but higher FG concentration could lead to higher viscosity. The physical stability of the mixed system was improved at low FG concentrations, but decreased at concentration higher than 0.2 %, which was more significant after 100 °C heat treatment. FG incorporation could improve the boundary lubrication of the protein solutions. [ABSTRACT FROM AUTHOR]

The effect of soy protein components on acid soymilk gels was investigated by replacing 10%, 20% or 40% protein from soymilk powder with equivalent amount of protein from 7S or 11S, according to three stages (acidification, cooling and annealing) by dynamic oscillatory rheology. The final gels after cold storage were evaluated in terms of rheology, particle size, texture, water holding capacity (WHC), microstructure and tribology. Both 7S and 11S could effectively and almost equivalently improve the gel strength at incorporation ratio ≥20%, seen from the rheological and texture results, and enhance the WHC. Particle size (D[4,3]) of the gel was also increased by incorporation of high ratio of 7S or 11S. On the other hand, 20% and 40% 11S reduced the gelation time significantly during acidification and 40% 11S induced coarser microstructure than control; while 7S showed no significant effect on gelation time and 40% 7S incorporated gel showed well organized gel structure. Introducing 7S or 11S as low as 10% could effectively improve the gel lubrication; while high concentration (40%) could induce the opposite effect. Also, 40% 7S postponed the transition from mixed regime to hydrodynamic regime; while 40% 11S brought it forward. Overall, 20% could be a reasonable ratio of 7S or 11S incorporation to improve the gel properties. Image 1 • 7S and 11S both caused positive effect on rheology and texture properties of gel. • 11S incorporation caused coarser microstructure of gel than 7S at 40% ratio. • Low proportion (10% & 20%) of 7S or 11S incorporation improved the gel lubrication. • 20% was a reasonable ratio of 7S or 11S incorporation to improve the gel properties. [ABSTRACT FROM AUTHOR]

Different types of hydrocolloids (gelatin [0.25, 0.5 and 1%], polysaccharides [ionic and neutral, 0.01, 0.05 and 0.1%] [w/w]) were applied in acid soymilk gels to investigate their effectiveness in improving the physical properties of gels. The function was found to vary considerably with the hydrocolloid types. Gelatin was found to have the best compatibility with soy proteins. The dynamic oscillatory rheology measurement indicated that no severe interruption to the soymilk gelation was caused and the microstructure of the final gels was not changed much even at 1% concentration. In the meantime, gelatin effectively enhanced the water holding capacity of the gels; gelatin (≥0.5%) dramatically decreased the particle size (D4, 3), increased the uniformity of the gel particles, and effectively improved the lubrication property of the gel. Neutral gums (locust bean gum and guar gum) caused severe interruption of soy protein gelation, showing negligible gelation during acidification and large amount of water separation at 0.1% concentration. Better compatibility with soy proteins was observed with ionic gums (ι-carrageenan and xanthan) than neutral ones, especially ι-carrageenan, showing enhanced yield stress, viscosity, storage modulus, gel firmness and water holding capacity at 0.05% concentration. Low concentration of any type of polysaccharide (0.01%) caused reduction of D4, 3 and decrease of friction coefficient in the mixed regime. The results suggested that gel particle characteristics, instead of viscosity, dominated the gel lubrication in this system. Three types of hydrocolloids showed dramatically different effect on the microstructure of the gels, which accorded well with the physical properties. Image 1 • Gelatin caused no severe interference of soymilk gelation even at 1% concentration. • Neutral gums inhibited the gelation, causing water separation at high concentration. • ι-carrageenan could improve the flow behavior and water holding capacity of the gel. • Gels with gelatin (≥0.5%) showed extremely uniform particle size and low friction. • Gel particle characteristics, instead of viscosity, dominated the gel lubrication. [ABSTRACT FROM AUTHOR]

Novel complexed microgels with enhanced pH and ion stability were constructed using heat-denatured soy protein isolate (SPI) and Chitosan (CS). Their characteristics and their effects on the textural, rheological, and tribological properties of soy yogurt were investigated. The complexed microgels showed larger particle sizes, lower surface hydrophobicity, and higher turbidity than pure SPI microgels. Incorporating the SPI-CS complexed microgels into the yogurts increased their protein content from 3.94% to 5.07% and reduced their fat content from 2.17% to 1.99%. Additionally, incorporating the microgels enhanced the texture of the yogurts, including increased firmness, elasticity, and viscosity, alongside improved water holding capacity (WHC). The incorporation of 0.8% SPI-CS microgels led to the optimum physicochemical characteristics. Rheological analyses demonstrated that incorporating SPI-CS microgels led to an increase in apparent viscosity and shear modulus. Furthermore, the presence of the SPI-CS microgels significantly improved the lubrication properties. Microstructural analysis showed subtle differences in the gel structure of the yogurts after microgel addition. The three-dimensional network structure within the microgel-fortified yogurts was more compact than that in the control. Thus, SPI-CS microgels potentially improve the nutritional profile and quality attributes of plant-based yogurt products. • Soy protein isolate (SPI)-chitosan (CS) microgels were prepared and characterized. • Properties of soy yogurt after incorporation of SPI-CS microgels were investigated. • SPI-CS microgels can make up for the textural and structural deficiencies of soy yogurt. • SPI-CS microgels significantly improved the lubrication properties of soy yogurt. [ABSTRACT FROM AUTHOR]