Formation Of Weak Gels Research Articles

Optimization of the stabilizers and cow milk levels for the production of camel milk-based yogurt using response surface methodology

The production of yoghurt from camel milk (CML) is limited due to weak gel formation. As a trial to produce CML-set-type yoghurt, sixteen treatments were prepared from CML, cow milk, and stabilizers (gelatin and gum-Arabic; 1:1) using a D-optimal design. A desirable hardness of set-type yoghurt was obtained from CML (56%), cow milk (42%), and stabilizers (2%). Another study was designed to choose the best combination of stabilizers (1, 1.5 or 2% of gelatin in combination with 1% of gum-Arabic). The increased levels of gelatin resulted in a significant increase (p < 0.05) in the viscosity and consistency index of yoghurt milk, an increase (p < 0.05) in yoghurt hardness and viscosity, and a reduction in syneresis (p < 0.05). In conclusion, an acceptable set-type yoghurt can be produced by using a combination of CML and cow milk (1.3:1) and a stabilizers' mixture of gelatin (1 or 1.5%) and gum-Arabic (1%).

Effect of Soy Protein Isolate on Pasting, Rheological, and Textural Attributes of Potato Starch

AbstractThe effects of different concentrations of soy protein isolate (SPI) on the functional, rheological, pasting, and structural properties of potato starch (PS) are investigated. The water and oil absorption capacity (OAC) of PS‐SPI mix increased significantly with the addition of SPI. Gel strength, peak, final, breakdown, and setback viscosity of PS decreases, whereas the pasting temperature increases with an increase in SPI fraction. Both the Herschel–Bulkley and power law model are found to equally fit in steady state rheology. The PS‐SPI blend exhibits pseudoplastic behavior. The addition of SPI decreases the storage (G′) and loss modulus (G″). SPI also lowers the flow stress values in the amplitude sweep test. Frequency sweep confirms the formation of weak gel formation in PS‐SPI blend by exhibiting a lower value of G′ and G″ than the pure starch. The microstructure of composite gel appears less dense with greater pore size than starch gel. The hardness of the SPI‐PS blend gel decreases from 6.76 to 0.85 N when the SPI content is increased from 0% to 50%. Fourier transform infrared (FTIR) confirms that no chemical groups are formed or destroyed during the composite gel‐making process.

Effect of hydrophilic and hydrophobic emulsifiers on physio-chemical, structural and water distribution properties of meat-based cookies

Meat-based products are highly susceptible to weak gel formation upon heating. In this study, the effect of different emulsifiers on the rheological, pasting and microstructural properties of meat-based sugar-snap cookies was investigated. Cookies were processed with the addition of freeze-dried fish meat (1% w/w) and emulsifiers (0.5% w/w of wheat flour). The addition of emulsifiers especially diacetyl tartaric acid ester of mono- and diglycerides (DATEM) increased storage modulus (G′), a viscous behavior, compared to control and other emulsifiers. Expansion and hardness were significantly (P < 0.05) improved in DATEM and sodium pyrophosphate (SPP) samples compared to the control indicating the compact structure of starch-protein and emulsifiers molecules. The gelatinization characteristics particularly peak and final viscosities were significantly (P < 0.05) increased in DATEM samples with high water holding capacity (WHC) suggesting the strong interaction among starch-protein and emulsifiers. Low-field magnetic resonance (LF-NMR) analysis exhibited that T21 relaxation time, an indication of tightly bound water, was also highest in DATEM sample while unbound water (T23) was highest in control and sodium dodecyl sulphate (SDS) samples. Scanning electron microscopy (SEM) analysis revealed that DATEM containing samples were dense and uniform whereas wide holes were found in control and SDS samples. It was concluded that DATEM could be an effective emulsifier with improved physio-chemical, structural and pasting properties of meat-based cookies. The study will open a new window for the best use of suitable emulsifiers for meat-based cookies, however, future studies are needed to check their storage stability.

Deep Eutectic Solvents for Enhancing the Rheological Behavior of Polymers and Clays in Polymeric Water-Based Drilling Fluids

Drilling fluids with high suspending capacity without high viscosity are required in drilling operations, such as horizontal wells and highly deviated wells, with the “cutting bed”. Non-viscosifying rheological modifiers that can enhance the rheological properties of polymer drilling fluids are urgently needed. This study reports the application of a choline-chloride-based deep eutectic solvent (Gly-DES) as a rheological modifier for polymeric water-based drilling fluids. The rheological effects of Gly-DES on bentonite/polymer fluids were evaluated by high-temperature rheological testing, rheological model fitting, and rheological parameter (yield point, fluidity index, gel strength, etc.) analysis. The results showed that 2–4 wt % Gly-DES can improve the rheological properties of polymer drilling fluid in the temperature range of 150 °C. The addition of Gly-DES significantly improved the rheological parameters of drilling fluids, such as the yield point, gel strength, low shear rate viscosity, etc. At the same time, the viscosity of drilling fluids was always stable at different temperatures, which means that Gly-DES can help improve the suspension and cutting carrying capacity of drilling fluids without significantly increasing the viscosity of drilling fluids. Mechanistic analysis revealed that Gly-DES was connected to the polymer and bentonite through hydrogen bonds and ionic bonds, which enhanced the cross-linked network structure of the polymer at high temperatures and promoted the formation of weak gels in Na bentonite suspensions. Gly-DES can simultaneously enhance rheology, inhibit clay hydration, and improve filter cake lubricity and has the potential to be a multifunctional drilling fluid treatment agent.

Muco-adhesion Evaluation of Polysaccharides in Simulated Physiological Fluids

Gellan gum is a microbial exopolysaccharide, water-soluble polymers secreted by microorganisms during fermentation. The biopolymer gellan gum is a relatively recent addition to the family of microbial polysaccharides that is gaining much importance in food, pharmaceutical and chemical industries due to its novel properties. The purpose of this work is to investigate the impact of physiological fluids on both the physical and chemical properties of gellan gum, and to understand the role of polymers gel in muco-adhesion and drug delivery to prolong the residence time of the drug inside the body. Muco-adhesion measurements of retention time were performed using bespoke retention apparatus to determine the retention of labelled gellan gum dose. The physiological fluids used in this work are artificial gastric juice, artificial saliva fluid, and artificial tears fluid. Results of this work show that in general the viscosity of gellan increased with high concentration and the gel formation is strong with artificial gastric juice (HCL) and weak gel formation with artificial saliva and tears but the retention time is longer with saliva and tears than with artificial gastric juice.

Impact of Low‐Pressure Argon Plasma on Structural, Thermal, and Rheological Properties of Corypha umbraculifera L. Starch: A Non‐Conventional Source of Stem Pith Starch

AbstractThe impact of low‐pressure argon plasma on structural, pasting, rheological, and thermal characteristics of starch from talipot palm (Corypha umbraculifera L.) is analyzed. Talipot palm is a non‐conventional source of starch. The starch is subjected to a different plasma power with different time duration. Exposure of talipot starch to plasma with different power (7.5 and 15 W) and time (30 min and 1 h) significantly affects the physicochemical and functional properties. SEM micrographs show that the plasma treatment causes severe damage to the granule surface. The pasting profile of talipot starch is considerably decreased by plasma treatment. The relative crystallinity and thermal properties are also decreased by plasma treatment. Plasma‐treated talipot starches exhibit a decreased storage and loss modulus indicating weak gel formation. However, the treatment considerably increases the paste clarity of the starch gel.

New Carbamates and Ureas: Comparative Ability to Gel Organic Solvents

Two series of novel amphiphilic compounds were synthesized based on carbamates and ureas structures, using a modification of the synthesis methods reported by bibliography. The compounds were tested for organic solvent removal in a model wastewater. The lipophilic group of all compounds was a hexadecyl chain, while the hydrophilic substituent was changed with the same modifications in both series. The structures were confirmed by FT-IR, NMR, molecular dynamic simulation and HR-MS and their ability to gel organic solvents were compared. The SEM images showed the ureas had a greater ability to gel organic solvents than the carbamates and formed robust supramolecular networks, with surfaces of highly interwoven fibrillar spheres. The carbamates produced corrugated and smooth surfaces. The determination of the minimum gelation concentration demonstrated that a smaller quantity of the ureas (compared to the carbamates, measured as the weight percentage) was required to gel each solvent. This advantage of the ureas was attributed to their additional N-H bond, which is the only structural difference between the two types of compounds, and their structures were corroborated by molecular dynamic simulation. The formation of weak gels was demonstrated by rheological characterization, and they demonstrated to be good candidates for the removal organic solvents.

Effect of Fat Substitution on the Rheological and Textural Properties of Raw Chicken Meat Emulsion and Cooked Patties

The present study was conducted to evaluate the rheological behaviour and textural properties of raw chicken meat emulsion and cooked patties respectively. Low fat chicken emulsions were prepared with the addition of pre-optimized levels of 1%lemon albedo, 2% mango peel powder, and 2% banana peel powder with the replacement of 50% vegetable oil in formulation The rheological behaviour of low fat emulsion and textural properties of these low fat emulsion based chicken patties were observed. The formulation of chicken meat emulsion was maintained by the addition of water with the replacement of fat. Dynamic oscillatory measurements revealed the weak gel formation of emulsions with addition of fat replacers, as storage modulus values (G΄) were higher than the loss modulus values (G˝). Chicken meat patties were prepared from these low fat chicken meat emulsions. Textual profile analysis of cooked patties showed a significant (P&lt;0.05) effect on hardness, fracturability, cohesiveness, gumminess, and chewiness values. Therefore, it was concluded that replacement of fat with optimum level natural fat replacers (lemon albedo, mango peel powder and banana peel powder) resulted in predominant visco-elastic behaviour of emulsions which in turn had a significant effect on textural properties of the emulsion. Hence, the visco elastic behaviour of emulsion and the effect of textural properties might improve the acceptability of cooked low fat chicken patties.

Influence of age on molecular characteristics and rheological behavior of nopal mucilage.

Nopal mucilages are of interest due to a variety of potential applications, which include their use as thickeners and rheological modifiers. In this work, changes in molecular characteristics of nopal mucilages with their age and its influence on the rheological behavior of their solutions were analyzed by light scattering, high performance liquid chromatography, a colorimetric method, and linear viscoelastic rheometrical measurements. For this, mucilages obtained from cladodes from Opuntia ficus‐indica with different ages, namely 20, 80, and 600 days, respectively, were extracted using water as solvent and then subjected to freeze‐drying. The weight‐average molecular weight (M w) of the mucilages was found to increase along with the age; meanwhile, the concentration of uronic acids increased and the galactose, rhamnose, and xylose contents decreased. Increasing M w with age resulted in enhanced viscoelastic behavior of solutions, namely, higher viscosity and elasticity at lower mucilage concentrations. Also, along with increasing M w, decrease in neutral sugar contents and increase of pectic compounds (uronic acids) and Ca+ cations in mucilages with age promoted formation of weak gels. Overall, the molecular weights and rheological behaviors reported in this work for nopal mucilages are comparable to those of widely used thickeners such as xanthan and guar gums, which suggest their use in similar applications regarding its age.

Physical and compositional characteristics of cheese and yogurt made from partially demineralized milk protein concentrate

The milk protein concentrate (MPC) has been extensively studied; however, the MPC partial demineralization through the diafiltration (DF) and its effect on MPC ability to produce milk coagulate products has not been fully explored; therefore, it was considered studying the MPC demineralization process with DF and evaluate the effect of this treatment on the compositional and textural characteristics of enzymatically and acid-coagulated products. The MPC of ultrafiltration was diafiltered by two cycles, later this MPC was used to make a fresh cheese, a set yogurt and stirred yogurt. The application of a single DF cycle removed 22.2% of the ashes and 8.12% of the MPC calcium, but no statistically significant differences were present (P&gt; 0.05) between the application of two DF cycles. The cheeses with MPC undergone to one cycle and two cycles of DF were less hard and presented less resistance to chewing, and the set yogurt showed lower springiness values due a total solids and calcium content, that was affected by DF. These phenomena increased the coagulation time and the formation of weaker gels. The DF achieved the maximum milk demineralization in a single cycle.

Phase behavior and rheological properties of basil seed gum/whey protein isolate mixed dispersions and gels.

Many food formulations comprise proteins and polysaccharides simultaneously, contributing in the functional properties in food systems. In this study, the effects of basil seed gum (BSG) addition to whey protein isolate (WPI) dispersions were investigated through phase behavior, steady shear flow, and small amplitude oscillatory shear tests (SAOS). The phase behavior of WPI‐BSG mixed solutions was dependent on the initial concentration of biopolymers, while the effect of BSG was predominant. Herschel–Bulkley model characterized the flow behavior of ternary mixtures, very well. Furthermore, apparent viscosity, the extent of thixotropy and viscoelastic behavior enhanced with increase in BSG concentration, significantly (p ˂ .05). Temperature sweep measurements showed a reduction in WPI gelling temperature by increase in BSG concentration. SEM results depending on BSG concentration revealed the protein continuous, bicontinuous, and polysaccharide continuous networks. Phase separation may be attributed to depletion flocculation and thermodynamic incompatibility of WPI and BSG molecules. The results confirmed the occurrence of phase separation and weak‐gel formation through mixtures, but the rate of gelation was more than the phase separation. In consequence, these results may open up new horizons in developing novel food products and delivery systems as well as utilizing as emulsifying, thickening and gelling agents in food and pharmaceutical industry.

Actividad sinbiótica in vitro de Lactobacillus plantarum encapsulado con mezclas de mucílago de Aloe vera, fructanos de agave y aditivos alimenticios como materiales de pared

In recent years, the development of functional and synbiotic food products has been focused on the study of synbiotic matrices, were a prebiotic and a probiotic are combined to increase the health benefits to the host. In this work the in vitro synbiotic activities of Lactobacillus plantarum microcapsules with Aloe vera mucilage, high degree of polymerization agave fructans and food additives as wall materials were evaluated. The synbiotic behavior was assessed by rheological mucoadhesion, simulation of gastrointestinal digestion, growth inhibition of pathogens, antibiotic activity of extracellular metabolites and viability of the probiotic during storage at room and refrigeration temperatures. Rheological studies demonstrated that the biopolymer mixture interact with intestinal adhesion proteins (mucin) by the formation of weak gels with hydrogen bonds. During the simulated gastrointestinal digestion, the viability of the microorganism released from mixtures with arabic gum increases after two hours, which evidence microorganism release from the capsule. The extracellular metabolites extract (e.g. butyric, lactic and acetic acids) proved to be significantly more effective in the growth inhibition of pathogens and the storage viability reduction is lower than 0.5 log CFU/g after 70 days. To our knowledge, these results show for the first time, that microcapsules of a known probiotic encapsulated with Aloe vera mucilage, agave fructans of high degree of polymerization and arabic gum, do behave as a synbiotic matrix, guaranteeing that the probiotic will produce potential health benefits and could be used in the formulation of functional foods and products.

Aggregation and weak gel formation by pectic polysaccharide homogalacturonan

This study presents a novel model of homogalacturonan (HG) based on the dissipative particle dynamics (DPD). The model was applied to investigate the mechanism of self-aggregation of low-methoxylated homogalacturonan in aqueous solutions in the absence of cations. The coarse-grained model provided new insights into the structural features of HG aggregates and networks in aqueous solutions. Depending on the properties and concentration of polysaccharides, two major patterns of self-assembly were observed for HG - ellipsoidal aggregates and a continuous three-dimensional network. Simulations showed that a decrease in the degree of dissociation of HG results in a higher rate of self-aggregation, as well as facilitating the formation of larger assemblies or thicker nanofilaments depending on the type of final self-assembly. Simulations of polysaccharides of different chain lengths suggested the existence of a structural threshold for the formation of a spatial network for HG consisting of less than 35 GalA units.

PHYSIOCHEMICAL PROPERTIES AND ACE INHIBITORY CAPACITY OF HAZELNUT PROTEIN ISOLATE AND HYDROLYSATES

Protein solubility, water holding capacity, fat absorption capacity, emulsion activity index, emulsion stability index, gel formation capacity and Angiotensin-Converting Enzyme (ACE) inhibitory capacity of hazelnut protein isolate (HPI) and its hydrolysate were determined. The results showed that protein solubility had U shape solubility profile with an isoelectric point at pH 4.5-5 and highest value at pH 2 and pH 10. Water holding capacity and fat absorption capacity of HPI was found as 1.95 mL water/g protein and 2.1 g fat/g protein, respectively. Emulsion activity index and emulsion stability index values were found as 44 m2/g and 46 min at pH 7.0, respectively. Weak gel formation of HPI was seen at 8% and firm gel (LGC) was observed at 12% protein concentration. The concentration of pepsin hydrolysates needed to inhibit 50% of the ACE activity values (IC50) at 0, 30, 60 and 120 min of hydrolysis were 1.47 mg protein/mL, 0.27 mg protein/mL, 0.27 mg protein/mL and 0.26 mg protein/mL respectively. Whereas, IC50 of trypsin hydrolysates at 0, 30, 60 and 120 min were 5.51 mg protein/mL, 0.61 mg protein/mL, 0.56 mg protein/mL and 0.54 mg protein/mL. These results showed that isolates and hydrolysates of hazelnut has valuable functional properties and noted as good candidates for effectively reducing hypertension.

High‐pressure processing of pea protein–starch mixed systems: Effect of starch on structure formation

AbstractThis work explores the structural effects of high‐pressure processing (HPP) on starch in mixed pea protein–starch systems of varying concentrations. Reconstituted pea protein concentrate containing 9, 12, and 15% (w/w) protein, without added starch or in combination with 4 or 8% (w/w) pea starch, respectively, were subjected to HPP at 600 MPa for 4 min, at 5°C. Structural changes were investigated using dynamic rheology, scanning electron microscopy, and differential scanning calorimetry (DSC). The addition of starch enabled the formation of weak gels, at protein concentrations below the minimum required for gelation. Above the minimum protein concentration for gelation, starch addition resulted in stronger gels. Starch acted mainly as a filler in the pressure‐induced protein gel matrix, and starch granules remained intact after HPP. DSC analyses confirmed that starch remained ungelatinized after HPP, likely due to the limited availability of water in the mixed systems during HPP.Practical ApplicationsThe structure of pressure‐induced protein gels can be enhanced by adding starch. Besides being a low‐cost ingredient, starch remains ungelatinized after high‐pressure treatment, and thus can act like a fiber. Therefore, pressure‐treated protein–starch mixtures may lead to the development of low‐glycemic index, high‐protein products.

Impact of energetic neutral nitrogen atoms created by glow discharge air plasma on the physico-chemical and rheological properties of kithul starch

The changes in physico-chemical and rheological properties of kithul starch by the impact of energetic neutral nitrogen atoms produced by the glow discharge air plasma with novel technique were analysed. Here, treatment was carried out at different power levels (5 W & 15 W) and treatment time (30 min & 60 min). Decrease in amylose and moisture content and increase in swelling index and solubility of plasma treated kithul starch were observed. Fourier transform infrared spectra of plasma treated starch showed variation in the peaks corresponding to CH2 and OH groups. Relative crystallinity significantly (p ≤ 0.05) decreased after plasma treatment. Scanning electron microscopy showed severe damages on the starch granular surface by the effect of energetic neutral nitrogen atoms. Pasting properties increased and thermal properties showed significant (p ≤ 0.05) changes after plasma treatment. Storage modulus (G′) and loss modulus (G″) reduced at higher levels of plasma power and it indicated to its weak gel formation.

Impact of [formula omitted] irradiation on the physico-chemical, rheological properties and in vitro digestibility of kithul (Caryota urens) starch; a new source of nonconventional stem starch

Kithul (Caryota urense) starch was exposed to gamma irradiation at different doses (0.5 kGy, 1 kGy, 2.5 kGy, 5 kGy, 10 kGy). Its impact on physico-chemical, morphological, rheological properties and in vitro digestibility of kithul starch was studied. Irradiation decreased the pH, swelling index, amylose and moisture content of kithul starch and increased the carboxyl content, acidity, solubility. Free radical-mediated damage developed cracks and fissures on the granular surface of starch. Fourier transform infrared spectra (FT-IR) showed a marked reduction in the hydroxyl (OH) groups after irradiation. Irradiation did not affected to the crystalline pattern of native starch (Type-A pattern) but it decreased the relative crystallinity of kithul starch. Irradiation increased the light transmittance and freeze-thaw stability, but it reduced the syneresis. Pasting viscosity decreased after irradiation treatment. Irradiation made significant changes in the gelatinization properties of kithul starch. In vitro digestibility of kithul starch improved after irradiation and resistant starch followed decreasing trend. Lower value of storage modulus and loss modulus of irradiated kithul starches indicated to its weak gel formation.

Rheological, micro-structural and sensorial properties of camel milk yogurt as influenced by gelatin

Production of camel milk yogurt faces serious limitations of no or weak gel formation because of several possible factors. This study was undertaken to overcome this limitation with addition of gelatin (0–1.25%) to camel milk and comparison was made with commercial and prepared bovine milk yogurt. Chemical composition, acidity, syneresis, textural, rheological, micro-structure and organoleptic properties were studied. Syneresis was reduced significantly by gelatin addition especially at 1 and 1.25% level. Textural and rheological properties of camel milk yogurt were enhanced and were almost similar to commercial and bovine milk yogurt and a clear shift from watery to gel like phase was noticed. Structural (FTIR) analysis demonstrated a peak at 1516 cm−1 was observed to be more intense in 1.25% followed by 0.75% gelatin added yogurt. Micro-structural features were also influenced by gelatin incorporation especially in the sample added with 1.25% gelatin which appeared to be similar to bovine milk yogurt. However, sensory analysis revealed that except texture all other parameters received lower score for camel milk yogurt compared to the bovine.

Effects of heating and calcium and phosphate mineral supplementation on the physical properties of rennet-induced coagulation of camel and cow milk gels.

The physical properties of rennet-induced coagulation of preheated camel and cow milk gels (50 and 70 °C for 10 min) enriched with calcium chloride (CaCl2) and hydrogen phosphate dihydrate (Na2HPO42H2O) were evaluated using the dynamic low amplitude oscillatory shear analysis. The storage modulus (G') and loss modulus (G") of camel milk gels showed significant (P < 0·05) lower values than those of cow milk gels. The preheating of camel milk at 50 °C affected negatively the gelation properties, while the preheating at 70 °C prevented the formation of rennet-induced milk gels. No effect was observed on the gelation properties of cow milk gels. The CaCl2 added at 10 and 20 mM to preheated camel and cow milk reduced significantly (P < 0·05) the gelation time and increased the gel firmness. In contrast, Na2HPO42H2O added at 10 and 20 mM induced the formation of weak gels for preheated camel and cow milk at 50 °C, and even no gelation for preheated camel milk at 70 °C.

Gellan gum methacrylate and laponite as an innovative nanocomposite hydrogel for biomedical applications

Successful treatment of infected wounds still represents an open challenge in the biomedical field. Nanocomposite hydrogels (NC) are a valid solution to this problem as they can be used as wound dressing materials for the delivery of therapeutic agents at the site of the injury. In addition, their improved mechanical properties make possible a sterile treatment, which is not generally possible using conventional hydrogels. Here in this work, gellan gum methacrylate (GG-MA), a biocompatible polymer recently proposed for the fabrication of injectable and photocrosslinkable hydrogels, was combined with laponite® XLG to form novel NC hydrogels as innovative wound dressing material. Clay concentration was varied in the range of 0.1 up to 1% w/v to study the possible clay–polymer interactions prior and after UV irradiation, showing the formation of weak gels having storage modulus G′ varying from 1 up to 100Pa, even prior photocrosslinking. As expected, the highest value of G′ (over 1000Pa) was found for the NC hydrogel containing 1% w/v of laponite after UV irradiation. The same system showed unaltered mechanical properties after steam sterilization compared to the one composed of 0.5% of clay, which showed a decrease in the stress failure after steam treatment. Moreover, the effect of laponite on the swelling and release capability was studied to test these new nanocomposite systems as a carrier of the model drug ofloxacin. Laponite was able to decrease the amount of antibiotic released over the first eight hours compared to the GG-MA hydrogels, although the amount of clay did not influence the diffusion coefficient of ofloxacin. Finally, preliminary cytotoxicity tests on human fibroblasts were carried out to evaluate the NC hydrogel biocompatibility. Overall, we anticipate the possible use of this novel NC hydrogel as wound dressing material for the treatment of burn wounds, which are subjected to chronic infections.