Rheological Properties Of Gels Research Articles

Rheological, thermal, and structural properties of heat-induced gluten gel: Effects of starch with varying degrees of debranching

This study evaluated the effects of starch with varying degree of debranching on the rheological, thermal, and structural properties of heat-induced gluten gel. As the duration of starch debranching treatment increased from 0 to 8 h, the viscoelasticity of the gel containing debranched starch (DBS) improved. Compared with the gluten gel (G), the gel strength of the G + DBS (8 h) sample increased by 65.2 %. The degradation temperature of gluten was minimally affected by DBS, while the weight loss rate increased by 4.4 %. Furthermore, the α-helical structure of gluten decreased, concomitant with an increase in β-sheet content. Notably, DBS treated for 8 h exhibited more hydrogen bonds with the tyrosine of gluten and triggered disulfide bridge conformation to transition from g-g-g to t-g-g, thereby reducing the stability of the molecular conformation of gluten proteins, as evidenced by the decreased height and width of the molecular chains observed in atomic force microscopy images. Overall, the composite gel structure induced by DBS exhibited a more continuous and homogeneous owing to the improved compatibility between DBS and gluten proteins, favoring the formation of a robust gel. These findings provide valuable insights for utilizing DBS to enhance gluten gel properties.

Effect of Faba Bean Isolate and Microbial Transglutaminase on Rheological Properties of Pork Myofibrillar Protein Gel and Physicochemical and Textural Properties of Reduced-Salt, Low-Fat Pork Model Sausages.

The study was performed to determine the effect of faba bean protein isolate (FBPI) alone or in combination with microbial transglutaminase (MTG) on the rheological properties of pork myofibrillar protein gel (MPG), and physiochemical and textural properties of reduced-salt, low-fat pork model sausages (LFMSs). The cooking yields of MPGs with MTG or FBPI alone decreased and increased, respectively. However, the combination of FBPI and MTG was similar to the control (CTL) without FBPI or MTG. Gel strength values of MPG added with both FBPI and MTG were higher than treatments with FBPI or MTG alone. The hydrophobicity values of CTL were lower than those of MPG with FBPI alone, whereas the addition of MTG decreased the hydrophobicity of MPGs. The incorporation of FBPI alone or in combination with MTG decreased sulfhydryl groups (p<0.05). Shear stress values of MPGs with MTG tended to be higher than those of non-MTG treatments at all shear rates, and the addition of FBPI into MPGs increased shear stress values. Reduced-salt (1.0%) LFMSs with FBPI alone or combined with MTG had both lower cooking loss and expressible moisture values than those of CTL and similar values to the reference sample (REF, 1.5% salt). Textural properties of reduced-salt LFMSs with FBPI or MTG were similar to those of REF. These results demonstrated that the combination of FBPI and MTG could improve the water binding capacity and textural properties of pork MPGs and LFMSs and might be suitable for application in the development of healthier meat products.

Preparation of soy protein isolate-naringin-chitosan protein gel: Synergistic effect of ohmic heating pre-treatment and chitosan addition

Soybean protein isolate (SPI)-Naringin (Nar) complex pre-aggregates were prepared by ohmic heating (OH) and protein gels were formed by adding chitosan (CS). The properties of the pre-aggregate, gel rheological properties, texture, and water holding capacity (WHC) were evaluated. For the properties of the SPI-Nar pre-aggregate, under an OH treatment of 6 V/cm, the α-helix and β-turn structures of the SPI-Nar pre-aggregate were found to be 17.72% and 15.30%, respectively, with a uniform particle size distribution. The surface hydrophobicity, total free sulfhydryl, and turbidity were measured to be 794, 6.54 μmol SH/g, and 0.364, respectively. Atomic force microscopy images showed an Rq value of 3.63 and a height of 14.5 nm. Regarding the properties of the SPI-Nar-CS protein gel, when the CS addition level was 3%, the gel (SPI-Nar-CS 3) exhibited the best rheological properties, with hardness, springiness, and cohesiveness values of 10.17 g, 0.79 mm, and 0.31, respectively. The WHC and LF-NMR analysis of the protein gel revealed that SPI-Nar-CS 3 exhibited a WHC of 90.67% and optimal LF-NMR imaging and apparent state. SEM images showed the best microstructure at this CS addition level. In addition, the synergistic mechanism between the OH treatment and CS addition in protein gel formation was discussed, providing a theoretical foundation for future applications in the food industry.

Heat-induced gels from pea protein soluble colloidal aggregates: Effect of calcium addition or pH adjustment on gelation behavior and rheological properties

Heat-induced protein gels are appreciated due to their texture in a variety of food products. To support the shift to more sustainable protein consumption more knowledge is needed about plant protein gelation behavior and rheological properties of gels. In this study, the effect of calcium concentration (10 mM–100 mM) and pH (5.9–6.8) on heat-induced gelation behavior of 10 w/w% pea protein water-soluble extract separated from a commercial pea protein isolate (WSE-PPI) were for the first time investigated and compared. The rheological results show Gʹ values of around 3000 Pa for gels containing 20 mM calcium, and then a decrease in Gʹ by a factor ∼1.3 when the calcium concentration increased to 100 mM, whereas a continuous increase in gel strength was observed with the pH decrease of WSE-PPI dispersions. By comparison of calcium-addition and pH-adjusted heat-induced gels at the same pH, it was found that at low calcium concentrations (≤20 mM), the calcium-assisted gels exhibited higher gel strength. Contrariwise, at high calcium concentrations (≥50 mM), the pH-adjusted gels have higher gel stiffness and larger deformability before rupture. CLSM results verified this finding and show that the gel structure of pH-adjusted gels are more homogenous, containing significantly more compact structure. Overall, our findings show a systematic link between microstructure and rheological properties of heat-induced gels, which can be controlled by the calcium addition and pH adjustment. These results provide valuable information for the modulation, design, and customization of plant derived protein gels for specific food applications.

Rheological and physicochemical properties of heat-induced ovalbumin gels in presence of sodium carboxymethyl cellulose.

In this study, the effect of sodium carboxymethylcellulose (CMC-Na) on the rheological and physicochemical properties of heat-induced ovalbumin (OVA) gels was evaluated. The OVA/CMC-Na composite gels were prepared by heat-induced (85 °C, pH 7.0) a mixture of CMC-Na (0, 0.2, 0.4, 0.8 and 1%) and OVA. The results revealed that the addition of CMC-Na dramatically reduced the springiness and hardness of the composite gels, while slightly enhancing the intermolecular hydrogen bonding interactions, which facilitated the improvement of the softness of the gels. It can be observed by SEM that the added CMC-Na was stacked on the surface of the OVA, resulting in visible "linear bumps". All gel samples exhibited shear-thinning behavior. The apparent viscosity of the composite gels increased with the addition of CMC-Na, and the OVA gel with 1% CMC-Na showed the highest apparent viscosity and the lowest storage modulus (G'). Additionally, low field nuclear magnetic resonance (LF-NMR) measurements indicated that the increasing CMC-Na boosted the water mobility of the composite gel. This study offers a novel approach to the development of ovalbumin-based soft gel foods, especially for certain populations with swallowing difficulties.

Thermal, Rheological, Structural and Adhesive Properties of Wheat Starch Gels with Different Potassium Alum Contents.

Wheat starch (WS) is a common adhesive material used in mounting of calligraphy and paintings. Potassium alum (PA) has indeed been used for many centuries to modify the physicochemical properties of starch. Thermal analysis revealed that the presence of PA led to an increase in the gelatinization temperature and enthalpy of the starch gels. The leached amylose and the swelling power of the starch gels exhibited a maximum at the ratio of 100:6.0 (WS:PA, w/w). The rheological properties of starch gels were consistent with changes in the swelling power of starch granules. SEM observations confirmed that the gel structure became more regular, and the holes grew larger with the addition of PA below the ratio of 100:6.0 (WS:PA, w/w). The short-range molecular order in the starch gels was enhanced by the addition of PA, confirmed by FT-IR analysis. Mechanical experiments demonstrated that the binding strength of the starch gels increased with higher PA concentrations and decreased significantly after the aging process. TGA results revealed that PA promoted the acid degradation of starch molecules. This study provides a detailed guide for the preparation of starch-based adhesive and its applications in paper conservation.

Gel Rheological Properties and Storage Texture Kinetics of Starches Isolated from Anchote (Coccinia abyssinica (Lam.) Cogn.) Cultivars.

Anchote is a tuber crop indigenous to Ethiopia. Starch hydration properties and important gel characteristics which include: color, gel rheological properties (at 2, 4, 6, 8, and 10% starch:water w/w) and gel texture evolution (at 10% starch:water w/w), during 0 to 192 h storage (at 4 °C), of anchote starches isolated from four anchote cultivars (Desta 01, Desta 24, white and red) were evaluated and compared with potato and cassava starches (PS and CS). The lightness (L*) and whiteness scores of the anchote starch ranged up to >95, with slight differences among the cultivars, making them pure starches. Swelling power (SP) and water solubility index (WSI) of the anchote starches increased with increasing cooking temperature (40, 50, 60, 70, 80 and 90 °C), and their rate of increase varied significantly with the control starches, as follows: CS < anchote starches < PS. Anchote starch gels resisted higher stresses before breaking their structure and showed higher elasticity with lower (tan δ)1 values than PS and CS gels. They also had greater viscoelastic moduli even at lower concentrations than the PS and CS gels, and their stability increased with increasing concentration. The study of the gels' texture evolution during storage revealed that anchote starch gels had significantly higher (≥40%) initial and final (after 192 h) hardness and were less adhesive than the PS gel. Despite some significant differences in the studied starch gel quality parameters among the starches from the anchote cultivars, the results suggested their promising potential as additional new materials in the development of food products, specifically as a functional ingredient for the formulation of gel-like products.

Effect of Chitosan on Rheological, Mechanical, and Adhesive Properties of Pectin-Calcium Gel.

In the present study, chitosan was included in the pectin ionotropic gel to improve its mechanical and bioadhesive properties. Pectin-chitosan gels P-Ch0, P-Ch1, P-Ch2, and P-Ch3 of chitosan weight fractions of 0.00, 0.25, 0.50, and 0.75 were prepared and characterized by dynamic rheological tests, penetration tests, and serosal adhesion ex vivo assays. The storage modulus (G') and loss modulus (G″) values, gel hardness, and elasticity of P-Ch1 were significantly higher than those of P-Ch0 gel. However, a further increase in the content of chitosan in the gel significantly reduced these parameters. The inclusion of chitosan into the pectin gel led to a decrease in weight and an increase in hardness during incubation in Hanks' solution at pH 5.0, 7.4, and 8.0. The adhesion of P-Ch1 and P-Ch2 to rat intestinal serosa ex vivo was 1.3 and 1.7 times stronger, whereas that of P-Ch3 was similar to that of a P-Ch0 gel. Pre-incubation in Hanks' solution at pH 5.0 and 7.4 reduced the adhesivity of gels; however, the adhesivity of P-Ch1 and P-Ch2 exceeded that of P-Ch0 and P-Ch3. Thus, serosal adhesion combined with higher mechanical stability in a wide pH range appeared to be advantages of the inclusion of chitosan into pectin gel.

Impact of Starch Concentration on the Pasting and Rheological Properties of Gluten-Free Gels. Effects of Amylose Content and Thermal and Hydration Properties.

The pasting and rheological properties of starch gels from different botanical origins have been widely used to evaluate the application of these starches in pharmaceutical and food products. However, the ways in which these properties are modified by starch concentration and their dependence on amylose content and thermal and hydration properties have not been adequately established so far. An exhaustive study of the pasting and rheological properties of starch gels (maize and rice (normal and waxy in both cases), wheat, potato, and tapioca) at concentrations of 6.4, 7.8, 9.2, 10.6, and 11.9 g/100 g was performed. The results were evaluated in terms of a potential equation fit between each parameter and each gel concentration. The parameters determined for the gels at the studied concentrations were correlated with the hydration properties and thermal properties by applying principal component analysis (PCA). Wheat starch, followed by normal maize and normal rice starches, presented a greater capacity to modulate their gels' pasting and viscoelastic properties via their concentration in water. On the contrary, the characteristics of waxy rice and maize, potato, and tapioca starches were barely modified by concentration in pasting assays, but the gels of potato and tapioca showed noticeable changes in their viscoelastic properties as functions of concentration. In the PCA plot, the non-waxy cereal samples (wheat, normal maize, and normal rice) were located close to each other. Wheat starch gels were the most dispersed on the graph, which is consistent with the high dependence on the concentration of the gel shown in most of the studied parameters. The waxy starches had close positions not too distant from those of the tapioca and potato samples and with little influence from amylose concentration. The potato and tapioca samples were close to the vectors of the crossover point in rheology and peak viscosity in their pasting properties. The knowledge gained from this work allows a better understanding of the effects of starch concentration on food formulations.

Rheological and textural properties of heat-induced gels from pulse protein isolates: Lentil, mungbean and yellow pea

The molecular structure and conformation of the plant-based proteins dominate their gelation behaviour. These aspects have been mostly overlooked for underutilised pulse proteins such as lentils and mungbean that differ structurally with soy and pea proteins. Rheological and textural properties of heat-induced gels of lentils (LPIs) (green, red and black lentils), mungbean (MBPI) and yellow pea (YPPI) were compared with commercial soy (CSPI) and pea (CPPI) protein isolates. On investigation of the dynamic rheological parameters, the critical protein concentration (CPC) of MBPI was the lowest (14% w/v) followed by LPIs (18% w/v) and YPPI (22% w/v). Also, vicilin-rich MBPI showed a lower gelation temperature (Tgel 77 °C) and developed stronger gels compared to LPIs and YPPI. On the other hand, commercial isolates with larger particle size, water holding capacity and denatured state showed lower CPC (CPPI, 14% w/v) than their folded and more soluble counterparts (YPPI 22% w/v). Hence, the study of thermo-rheological properties of pulse proteins with distinct molecular and conformation characteristics has yielded a structure-gelation paradigm. These findings support the development of plant protein-gelled products not limited to meat and dairy analogues.

Effect of Ultrafiltered Milk on the Rheological and Microstructure Properties of Cream Cheese Acid Gels

The addition of ultrafiltered (UF) milk retentate is known to impact milk properties during mozzarella and cheddar cheese production, but the effect during cream cheese production is less well understood. Little is known about the impact of UF retentate on the intermediate stages of manufacture, such as protein assembly and the formation of hydrated acid gel structures. Here, milk prepared for cream cheese manufacture using a concentration factor of 2.5 or 5 had a similar particle size distribution to unconcentrated cheese milk after homogenization but increased viscosity and a slower rate of acidification, which could be altered by increasing starter culture concentration. The acid gels formed contained more protein and fat, resulting in a higher storage modulus, firmness, and viscosity. A denser microstructure was observed in acid gels formed with UF retentate addition, and quantitative two- or three-dimensional analysis of confocal images found a greater volume percentage of protein and fat, decreased porosity, and increased coalescence of fat. The mobility of water, as assessed by proton nuclear magnetic resonance, was reduced in the dense UF gel networks. Water movement was partially obstructed, although diffusion was possible between interconnected serum pores. These insights improve our understanding of acid gel formation. They can be used by manufacturers to further optimize the early and intermediate stages of cream cheese production when using concentrated milk to reduce acid whey production and lay the foundation for larger pilot scale studies of intermediate and final cream cheese structure.

Rheological properties and microstructure of rennet-induced casein micelle/κ-carrageenan composite gels

This study aimed to investigate effects of kappa-carrageenan (κ-carrageenan) concentration and storage temperature on the rheological and texture properties of casein micelle/κ-carrageenan composite gels. The particle size, zeta potential, Fourier transform infrared spectroscopy of the mixture, and microstructure of the composite gels were measured. The movement of κ-carrageenan characteristic bond showed that the casein micelle and κ-carrageenan formed a complex with larger particle size through electrostatic adsorption. The electrostatic repulsion between molecules increased with the increase of κ-carrageenan concentration, which stabilized the mixed system. It was found that both κ-carrageenan concentration and storage conditions affected the gel's rheological properties and microstructure. As the concentration of κ-carrageenan increased, the storage modulus (G′) of the composite gels increased, the rennet coagulation time (RCT) decreased, and the water holding capacity (WHC) increased at 25 °C. Microstructure results showed that a more uniform and denser gel network structure with smaller pore sizes was formed after the addition of κ-carrageenan compared with the control. G′ and RCT were reduced and microscopic phase separation occurred after storage at 4 °C, resulting in a porous structure with large pore sizes. Thus, the addition of κ-carrageenan could enrich the diversity of food gel structure to obtain an ideal gel.

Release of Tretinoin Solubilized in Microemulsion from Carbopol and Xanthan Gel: In Vitro versus Ex Vivo Permeation Study

Tretinoin (TRE) is, for its anti-comedogenic and comedolytic activity, widely used in the topical treatment of acne vulgaris. The effect lies in the regulation of sebum production and collagen synthesis. The study is devoted to the formulation of dermal gels containing TRE using microemulsion as the drug solubilizer. The aim was to evaluate the effect of the reference microemulsion (ME) and lecithin-containing microemulsion (MEL) on the release of TRE through the synthetic membrane (in vitro) and the pig's ear skin (ex vivo) through the Franz cell diffusion method. Subsequently, after an ex vivo study, the amount of the drug in the skin influenced by the applied formulation was determined. In addition, the impact of ME on the microscopic structure, texture, and rheological properties of gels was evaluated. On the basis of the analysis of texture, rheological properties, and drug release studies, Carbopol formulations appear to be more appropriate and stable. Considering the synthetic membrane as a stratum corneum, the Carbopol gel penetrated about 2.5-higher amounts of TRE compared to the Xanthan gel. In turn, ex vivo studies suggest that MEL slows the drug transfer to the dissolution medium, simulating absorption into the blood, which is a desirable effect in local treatment. The drug retention study proved the highest amounts of TRE in the skin to which microemulsion-Carbopol formulations were applied. The results confirm the benefit of TRE solubilization in ME due to its bioavailability from the tested dermal formulations.

Effect of molecular structure changes during starch gelatinization on its rheological and 3D printing properties

Although the changes in molecular structure during starch gelatinization has been intensively investigated, how a relationship between starch rheological properties, printability, and starch molecular structure changes during starch gelatinization remains unclear. This research is focused on the molecular structure changes of corn starch (CS) gels caused by different treatment temperatures and their effects on CS gel rheological and 3D printing properties. With increasing treatment temperature, the leached amylose content and short linear chains (DP 6–12) of CS increase, whereas the contents of long linear chains (DP > 12) decrease, which influences the rheological and 3D printing properties of starch. Due to the presence of the original granules and crystalline structure, the CS-65 starch gel presented a poor storage modulus (G′), indicating poor 3D printing performance. The leaching of amylose induced the formation of new crystal and cross-linked network structures, which is beneficial for increasing its G′. However, the increase in short amylopectin linear chains (DP 6–12) reduced the degree of short-range order and hydrogen bonding interactions, which was detrimental to its G′ and yield stress (τf). CS-80 starch gel exhibited the largest G′ and shear recovery rate, showing the highest self-supporting properties and printing precision. Extremely high temperatures contributed to the densification of the starch gel structure, which led to an increase in τf and difficult extrusion. Overall, molecular structural changes caused by starch gelatinization are critical to its ideal rheological properties for 3D printing.

Synthesis and evaluation of delayed anti-high temperature gel plugging agent

The malignant leakage of complex formations seriously restricts the drilling time and has become a major drilling technical problem that needs to be solved urgently at this stage. In particular, the malignant leakage of large fractures and fractured formations is difficult to construct, and the success rate of plugging is low. In this paper, according to the above formation conditions, by analyzing the leakage mechanism of the malignant leakage formation, the method of plugging the large fractures and broken fractured formations is summarized. The adiabatic copolymerization co-hydrolysis method was used as the gel synthesis method, 2-methacrylic acid amide and acrylamide (AM) were used as the main raw materials, and the redox initiation system composed of sodium sulfate and sodium bisulfite was used as the initiator. Using its redox initiation characteristics, high-strength bonding between organic polymer covalent bonds was achieved by a self-made cross-linking agent; using the thermoplasticity of hot-melt adhesive, the initiator is wrapped in hot-melt adhesive particles to achieve high-temperature slow-release initiation, and finally, a gel plugging agent with good compatibility with drilling fluid, controllable gel formation time, stable gel formation, and good gel breaking performance was synthesized, which is suitable for severe lost circulation under high-temperature and high-pressure conditions. A compatibility study of gel and common drilling fluid systems, the effect of temperature on gel formation, gel rheological properties under high temperature and high pressure, gel start-up pressure, and gel breakability tests were evaluated under laboratory conditions. The experimental results show that the gel has good compatibility with common drilling fluid systems; with the increase of temperature, the gel time of the gel plugging agent gradually decreases, and the gel time can be adjusted from 1 to 3 h at a high temperature of 150°C; when the concentration of the gel in the experimental slurry exceeds 2%, its rheological properties change abruptly; under certain conditions, the starting pressure of the gel can reach up to 6.5 MPa; and under the condition of 150°C, the gel breaking rate was over 98% after 24 h. Various experiments show that the gel’s performance meets the requirements for plugging malignant leakage formations, and the effect is good. Compared with traditional gel materials, the gel plugging agent synthesized in this paper has the characteristics of a simple configuration process and superior performance with drilling fluid, which provides a new idea for malignant leakage plugging.

Studies on rheological behavior of native and octenyl succinic anhydride modified buckwheat (Fagopyrum esculentum) starch gel and improved flow properties thereof

AbstractThe effect of octenyl succinic anhydride (OSA) esterification (1%–3% of dry starch) on powder flowability, functionality, pasting, and gel rheological properties of buckwheat starch (BS) was examined. The physical and flow properties like bulk density, tapped density, Hausner's ratio, Carr's index, cohesion index, and caking strength of starch improved significantly after esterification, indicating better flow behavior and storage stability. The solubility and swelling power were significantly increased, leading to a significant increase in peak viscosity and breakdown, while pasting temperature, setback, and final viscosity decreased. The esterification also restricted the retrogradation, which appeared as a lower hardness of retrograded gel. Starch gel prepared at 5%, 10%, and 15% concentrations showed shear thinning behavior. The dynamic shear properties obtained within the linear viscoelastic region showed weak gel behavior with a more elastic nature and were also demonstrated by the Power law.Practical applicationThe OSA modifies the structure and surface of starch granules to change the physical properties which help in better powder flowability of the dried starch. The findings on powder flowability of BS may help powder manufacturers to control and design powder handling and transportation equipment by preparing non‐cohesive, non‐sticky, and flowable dried starch powder. The findings of the rheological characteristics of BS gels can be exploited in the preparation and optimization of soup premix, thickening agents, food additives, and gravies. Moreover, the OSA modified gel has a low retrogradation rate, which could be used in a product like bread and cakes.

Rheological and structural properties of acid-induced milk gels as a function of β-casein phenotype

This study aimed to investigate if differences in β-casein polymorphic structure would affect the acid-induced (glucono-δ-lactone) gelation behaviour of corresponding skim milks. Gels obtained from skim milk containing A2/A2 β-casein had significantly lower elastic modulus, water holding capacity, and gel permeability compared to A1/A1 and A1/A2 gels. Microscopy images also showed a denser microstructure and smaller pore size in acid-induced gels prepared with A1/A1 and A1/A2 milks compared to A2/A2 milk. A number of reasons may account for these differences in gelation, specifically, gels with A1 β-casein contained greater amounts of α-helixes and aggregated β-sheets in their secondary structure compared to A2/A2 gel that was comprised mainly of random coils or polyproline II helixes. In addition, compositional differences such as greater total and micellar calcium and higher levels of total κ-casein existed in A1/A1 and A1/A2 milks compared to A2/A2 milk and may have contributed to the difference in gelation and gel structure. Although the role of β-CN phenotype on skim milk gelation may need further investigation, findings from this study clearly indicate that A2/A2 milk was associated with poor acid gelation properties. • Effects of acidification on milks with various β-caseins were studied. • Gels carrying A1 β-casein possessed greater water retention and lower permeability. • Increased β-sheets in gels carrying A1 β-casein related to higher storage modulus. • A2/A2 gel possessed a high amount of polyproline II structures. • Gels prepared of A1/A1 and A1/A2 milks possessed a denser microstructure.

A Polyanionic Tartrate‐containing Temperature‐responsive Hydrogel

Thermogels, a class of hydrogels which show spontaneous sol-gel phase transition when warmed, are an important class of soft biomaterials. To date, however, most amphiphilic polymers that are able to form thermogels in aqueous solution are uncharged, and the influence of ionisable groups on thermogelation are largely unknown. Herein, we report the first example of a polyanionic amphiphilic multi-block copolymer, containing multiple pendant carboxylate groups, that can form transparent thermogels spontaneously when warmed up to physiological temperature. We demonstrate that introducing negative charges onto thermogelling polymers could significantly alter the properties of the micelles and thermogels formed. Furthermore, the polymer's polyanionic character provides new options for modulating the gel rheological properties, such as stiffness and gelation temperatures, through electrostatic interactions with different cations. We also demonstrated that the polyanionic thermogel allowed slower sustained release of a cationic model drug compound compared to an anionic one over 2 weeks. The findings from our study demonstrate exciting new possibilities for advanced biomedical applications using charged polyelectrolyte thermogel materials.

Rheological properties of enzymatic milk gel: Effect of ion partitioning in casein micelles

Casein micelles (CMs) are colloids of ∼150 nm diameter formed by the association of milk proteins and minerals. Divalent milk cations, i.e. Ca 2+ and Mg 2+ , exist in two forms in CMs: either directly bound to casein residues (C-bound) without inorganic phosphate, or in a precipitated form called micellar calcium phosphate (MCP). The composition and properties of CMs vary with changes of the physicochemical conditions of milk; e.g. after the addition of salt or a change of pH. Moreover, the rheological properties of enzymatic milk gels are known to be strongly influenced by variations of mineral equilibria. We report in this study on the effect of cation partitioning in CMs on the rheology of enzymatic milk gel. Firstly, salts and acid (CaCl 2 , MgCl 2 , Na 2 HPO 4 , Na 3 Cit and HCl) were added to produce a set of 19 milk samples containing different proportions of C-bound and MCP in order to identify correlations with rheological parameters (G′, G″, tanδ) of the resulting gels. Three milks were then selected according to the mineral content of CMs and the resulting gels were further characterized in order to propose mechanisms that might explain the dependence of gel macroscopic properties on those of CMs. We showed that the rheological properties of gel were well correlated with the two types of cations present in CMs: an increase in C-bound cations raised the values of G′ and G″ while an increase in the MCP content lowered the tanδ. To explain these inter-dependencies, CMs were viewed as soft colloids whose modulus could be tuned by their MCP content. Consequently, CMs with different mineral contents would have differing abilities to fuse after aggregation, which appeared to link the rheological and microscopic attributes of the gels in a consistent manner. These results will be useful to understand the complex variations in the rheological properties of milk gels produced in the dairy industry. • Micellar cations exist as directly bound to casein (C-bound) or as MCP. • G′ and G″ of enzymatic milk gel are positively correlated to C-bound. • tanδ is negatively correlated to MCP. • Kinetics of gel aging depends on the MCP and on the rate of fusion of para-micelles.

Comparative Preclinical Study of Lidocaine and Mepivacaine in Resilient Hyaluronic Acid Fillers

Background: Hyaluronic acid-based filler injections are now well-established aesthetic procedures for the correction of skin tissue defects and volume loss. Filler injections are becoming increasingly popular, with a growing number of injections performed each year. Although classified as a minimally invasive procedure, the introduction of a needle or a canula may remain painful for the patient. A major improvement was achieved with the incorporation of local anesthetics into the formulation for pain relief. Methods: In this study, two well-known anesthetics, lidocaine and mepivacaine, were systematically compared to assess their influence on filler mechanical and biological features. The impact of each anesthetic was monitored in terms of gel rheological properties, stability, durability, and degradation. The release profiles of each anesthetic were also recorded. Finally, the pharmacokinetics of each anesthetic in rats were assessed. Results: For all the rheological and biological experiments performed, lidocaine and mepivacaine influences were comparable. The addition of either anesthetic into a soft-tissue filler showed no significant modifications of the stability, durability, and degradability of the gel, with similar release profiles and pharmacokinetics at an equivalent concentration. Conclusions: Substituting lidocaine with mepivacaine does not impact the properties of the gels, and thus both can be equally incorporated as anesthetics in soft-tissue fillers.