Gelation pH Research Articles

Kaolin-based stable colloidal nano-silica: Peptization factors and stability assessments via designed experiments

This study aims to synthesize stable colloidal silica via the peptization method as a green and low-cost route. It is crucial to adopt a proper synthesis procedure and choose an appropriate raw material. To achieve this purpose, kaolin was employed as a silica rich source that occurs abundantly in nature. The process involves synthesis of the wet gel through the succession of calcination, acid leaching, alkaline treatment, sodium silicate precipitation, and then peptization of the wet gel. Effect of the acid type on acid leaching was evaluated. Effective factors affecting the gel purity such ad acid concentration, pH of gelation, and temperature of alkaline treatment, were studied and optimized via a statistical design of the experiments. Subsequently, the influential parameters on stability and particle size of the obtained colloidal silica, including the temperature of the gel formation, pH of sol medium, concentration of silica gel, and type of stabilizing base, were investigated via one-facto-at-a-time. The samples were characterized by X-ray fluorescence analysis (XRF), dynamic laser light scattering analysis (DLS), X-ray Diffraction (XRD), Fourier transform infrared (FTIR), Brunauer–Emmett–Teller (BET), and Field emission scanning electron microscopy (FESEM) analyses. Results showed that under optimum conditions, ultra-pure silica gel with a silica content of 99.34 % was obtained. The colloidal sample with the highest stability (zeta potential of −75.6 mV), had nanoparticles showing sizes in the range of 21–66 nm.

Effect of calcium-sequestering salts and heat treatment on the rheological and textural properties of acid gels from blends of skimmed buffalo and bovine milk

The influence of adding 5 mm trisodium citrate (TSC) or disodium hydrogen phosphate (DSHP) and heat treatment (85 °C or 95 °C for 5 min) on the acid gelation properties of blends of skim buffalo and bovine milk (0:100, 25:75, 50:50, 75:25, 100:0) was investigated. Significant increases in gelation pH, final G′ values, firmness, and water-holding capacity of gels were observed with increasing proportion of buffalo skim milk and with higher heating temperature. Differences in gel firmness were linked to gel microstructure, where milk blends containing higher proportion of buffalo skim milk formed gels with denser protein network clusters. The addition of TSC or DSHP reduced the gelation pH, final G′ values and gel firmness, but increased gel water-holding capacity. These results provide a better understanding of acid gelation of buffalo and bovine milk blends which will subsequently promote the potential of using milk mixtures in modulating the gel texture.

Pilot Formulation Study of Ph-sensitive Gels

Abstract Drugs remain for a short time on mucus membranes, such as oral, ocular, or nasal mucus, which are washed with physiological fluids. One of the possibilities to overcome this obstacle is the application of solutions that, due to the physiological environment or stimulus, turn into more viscous gels. These gels often also have mucoadhesive properties and the drug is released from them for a longer period. Carbomer 940 (C940), polycarbophil (PCP), and chitosan (CH) are gel-forming excipients, and the consistency of their solutions changes due to the concentration of protons (pH); therefore, they are referred to as pH-sensitive gelling agents. The aim of this study was to prepare pH-sensitive solutions that form gels in the pH of the oral cavity. We prepared water solutions with various concentrations of gel-forming excipients and evaluated the appearance, pH of the solution, injectability of the solution, and pH of gelation. By determining the pH of gelation, suitable concentrations (w/w) of the used polymers were found, namely, 0.1% C940, 0.225% PCP, and 2.5% CH with medium molecular weight (CHM). The 0.1% C940 and 0.225% PCP solutions were injectable through the syringe with the smallest 0.5 mm needle diameter. The 2.5% CHM solution was not injectable even through the syringe with the largest 0.8 mm needle diameter. Solgels prepared at the determined concentrations were evaluated by a dissolution test in a pH 6.8 phosphate buffer using methylene blue (MB) as a model substance. After 60 min of dissolution, 77.04% ± 5.94%, 48.85% ± 5.74%, and 77.35% ± 4.98% of MB were released from samples with C940, PCP, and CHM, respectively. The dissolution of the C940 and CHM samples took place according to the Korsmeyer–Peppas kinetic model (R2 0.999 ± 0.001, 0.978 ± 0.003) and of the PCP samples took place according to the first-order model (R2 0.994 ± 0.001). The 0.225% PCP pH-sensitive gel showed the most advantageous properties in terms of injectability, pH gelation, and prolonged release of MB.

Acid gelation functionality of casein micelles in concentrated state: Influence of calcium supplementation or chelation combined with enzymatic stabilization

The main structure-building component in gelled dairy products is the casein micelle (CM). It was previously shown that in concentrated state of CMs, the changes of their compositional and colloidal properties in response to the addition or chelation of calcium divers from the reactions at milk-like casein concentration. This study aimed to evaluate the relationship between these specifically induced properties of CMs and the acid gelation functionality of a micellar casein concentrate (MCC). A covalent stabilization of the structures of pre-modified and native CMs by treatment with transglutaminase (Tgase) prior to acidification with glucono-δ-lactone was additionally tested. During acidification, structure formation was monitored in a rheometer to gain insights on mechanistic changes in the course of structural changes during acidification compared to gelation of unmodified MCC. Gelation pH, gel firmness, and serum binding capacity were analyzed to characterize gel structures at a final pH of 4.6. The structure formation process was highly affected by prior changes in composition, integrity, and structural stabilization of CMs. Gelation pH and acid gel firmness were reduced by ionic strength. Thermal and Tgase treatment induced opposing effects, leading to compensation when combined with prior salt supplementation. A synergistic increasing effect on serum binding capacity was found for trisodium-citrate supplementation and subsequent Tgase treatment. New mechanistic insights on acid gel structure formation progression were gained. This study provides a better insight into the relationship between structural CM properties prior to acid gelation and the resulting acidification progress, as well as the final acid gel properties.

Oleogels from mesoporous whey and potato protein based aerogel microparticles: Influence of microstructural properties on oleogelation ability

Animal-based whey protein isolate (WPI) and plant-based potato protein isolate (PPI) aerogel microparticles (particle size ∼40–77 μm) were produced via top-down wet milling of alcogels followed by supercritical–CO2–drying and used as matrices for structuring of liquid sunflower oil. pH variation (pH 3.0, 7.0, 9.0) during heat-induced gelation was used to tune aerogel microstructural properties, resulting in high specific surface areas (347–480 m2/g) and mesopore volumes (2.3–5.6 m3/g) as well as different macro-to mesoporous ratios. Oleogels oil content (70–84 wt%) and firmness (0.55–1.25 N) were related to pH during gelation, yielding firmest oleogels for aerogel templates produced at pH 9. All oleogel samples showed high physical stability, as shown by oil holding capacity (OHC) up to 95%. Minimization of macropore volume, high mesopore fractions, and high specific surface areas were found to increase OHC. Results suggest that for WPI and PPI, different aerogels microstructures induced by different gelation pH rather than protein nature, to be the driving factor affecting aerogel oleogelation ability and demonstrate the versatility of the aerogel particle-template approach in terms of protein source, thus highlighting the importance of aerogel microstructure design to fine-tune oleogel properties.

Modular Design and Bonding Mechanism of Internal Boron–Nitrogen Coordinated Boronic Ester Hydrogels with Alkaline pH Responsiveness and Tunable Gelation pH

Boronic ester hydrogels have been widely used in biomedical fields for their stimuli responsiveness to multiple disease-related triggers. However, the restricted pH for gelation and the poor hydrolysis stability limit their application in variable physiological microenvironments. Here, we report a modular conjugation method for designing internal boron–nitrogen coordinated boronic ester (IBNCB) hydrogels by constructing polymers with phenylboronic acid or N,N-bis(2-hydroxyethyl) moieties based on amides. Eight distinct IBNCB hydrogel models composed of polymer/polymer or polymer/micromolecule were prepared, exhibiting a unique pH responsiveness in the alkaline environment, an enhanced hydrolysis stability, bidirectional pH-tunable mechanical properties, and a lowered and tunable pH for gelation. In addition, the IBNCB hydrogels maintained a sol–gel transitional responsiveness to reactive oxygen species (ROS), glucose, and temperature. Especially, we found that the pH required to form an ideal IBNCB hydrogel should be greater than the pKa of phenylboronic acid but lower than the pKa of N,N-bis(2-hydroxyethyl), and reducing the pKa of phenylboronic acid could lower the gelation pH. The pKa of the tertiary amine in N,N-bis(2-hydroxyethyl) was shown to be important in the creation of the B–N coordination bond, which influenced the formation of the IBNCB bond. Finally, we explored the effect of the main chain’s charge on gelability and proposed the dynamic equilibrium mechanism of IBNCB bonds in the hydrogel. We expect that the multi-stimuli-responsive IBNCB hydrogels will provide a new strategy for designing smart materials sensitive to physicochemical signals. Furthermore, the amide-based modular conjugation could be exploited to generate a theoretically limitless number of novel IBNCB materials including microgels, polymer vesicles, and micro–nano particles.

Effect of Coagulant and Treatment Conditions on the Gelation and Textural Properties of Acidic Whey Tofu.

This study aimed to investigate the properties of acidic whey tofu gelatin generated from two acidic whey coagulants by pure fermentation of Lactiplantibacillus paracasei and L. plantarum, as well as the characteristics of acidic whey tofu. The optimal holding temperature and the amount of coagulants added were determined based on the pH, water-holding capacity, texture, microstructure, and rheological properties of tofu gelation. Then, the differences in quality between tofu produced by pure bacterial fermentation and by natural fermentation were investigated under optimal tofu gelatin preparation conditions. The tofu gelatin presented the best texture at 37 °C with a 10% addition of coagulants fermented by both L. paracasei and L. plantarum. Under these conditions, the coagulant produced by the fermentation of L. plantarum resulted in a shorter formation time and stronger tofu gelatin compared with that produced from L. paracasei. Tofu produced by the fermentation of L. paracasei had higher pH, less hardness, and a rougher network structure, whereas tofu produced by the fermentation of L. plantarum was closer to tofu produced by natural fermentation in terms of pH, texture, rheology, and microstructure.

Acid and rennet gelation properties of sheep, goat, and cow milks: Effects of processing and seasonal variation

Gelation is an important functional property of milk that enables the manufacture of various dairy products. This study investigated the acid (with glucono-δ-lactone) and rennet gelation properties of differently processed sheep, goat, and cow milks using small-amplitude oscillatory rheological tests. The impacts of ruminant species, milk processing (homogenization and heat treatments), seasonality, and their interactions were studied. Acid gelation properties were improved (higher gelation pH, shorter gelation time, and higher storage modulus (G') by intense heat treatment (95°C for 5 min) to comparable extents for sheep and cow milks, both better than those for goat milk. Goat milk produced weak acid gels with low G' (<100 Pa) despite improvements induced by heat treatments. Seasonality had a marked impact on the acid gelation properties of sheep milk. The acid gels of late-season sheep milk had a lower gelation pH, no maximum in tan δ following gel formation, and 70% lower G' values than those from other seasons. We propose the potential key role of a critical acid gelation pH that induces structural rearrangements in determining the viscoelastic properties of the final gels. For rennet-induced gelation, compared with cow milk, the processing treatments of the goat and sheep milks had much smaller impacts on their gelation properties. Intense heat treatment (95°C for 5 min) prolonged the rennet gelation time of homogenized cow milk by 8.6 min (74% increase) and reduced the G' of the rennet gels by 81 Pa (85% decrease). For sheep and goat milks, the same treatment altered the rennet gelation time by only less than 3 min and the G' of the rennet gels by less than 14 Pa. This difference may have been caused by the different physicochemical properties of the milks, such as differences in their colloidal stability, proportion of serum-phase caseins, and ionic calcium concentration. The seasonal variations in the gelation properties (both acid and rennet induced) of goat milk could be explained by the minor variation in its protein and fat contents. This study provides new perspectives and understandings of milk gelation by demonstrating the interactive effects among ruminant species, processing, and seasonality.

Comparison of micellar casein isolate and nonfat dry milk for use in the production of high-protein cultured milk products.

High protein levels in yogurt, as well as the presence of denatured whey proteins in the milk, lead to the development of firm gels that can make it difficult to formulate a fluid beverage. We wanted to prepare high-protein yogurts and explore the effects of using micellar casein isolate (MCI), which was significantly depleted in whey protein by microfiltration. Little is known about the use of whey protein-depleted milk protein powders for high-protein yogurt products. Microfiltration also depletes soluble ions, in addition to whey proteins, and so alterations to the ionic strength of rehydrated MCI dispersions were also explored, to understand their effects on a high-protein yogurt gel system. Yogurts were prepared at 8% protein (wt/wt) from MCI or nonfat dry milk (NDM). The NDM was dispersed in water, and MCI powders were dispersed in water (with either low levels of added lactose to allow fermentation to achieve the target pH, or a high level to match the lactose content of the NDM sample) or in ultrafiltered (UF) milk permeate to align its ionic strength with that of the NDM dispersion. Dispersions were then heated at 85°C for 30 min while stirring, cooled to 40°C in an ice bath, and fermented with yogurt cultures to a final pH of 4.3. The stiffness of set-style yogurt gels, as determined by the storage modulus, was lowest in whey protein-depleted milk (i.e., MCI) prepared with a high ionic strength (UF permeate). Confocal laser scanning microscopy and permeability measurements revealed no large differences in the gel microstructure of MCI samples prepared in various dispersants. Stirred yogurt made from MCI that was prepared with low ionic strength showed slow rates of elastic bond reformation after stirring, as well as slower increases in cluster particle size throughout the ambient storage period. Both the presence of denatured whey proteins and the ionic strength of milk dispersions significantly affected the properties of set and stirred-style yogurt gels. Results from this study showed that the ionic strength of the heated milk dispersion before fermentation had a large influence on the gelation pH and strength of acid milk gels, but only when prepared at high (8%) protein levels. Results also showed that depleting milk of whey proteins before fermentation led to the development of weak yogurt gels, which were slow to rebody and may be better suited for preparing cultured milk beverages where low viscosities are desirable.

How mass and heat transfers could affect chitosan membrane formation via an enzymatic gelation

Herein, a 1D numerical model was developed to simulate the enzymatic gelation of chitosan in thin film geometry, corresponding to a thin polymer solution cast onto a support. Mass and heat transfer phenomena were taken into account in the mathematical model and coupled to the chemical reactions involved during the chitosan gelation process (urea hydrolysis, equilibrium reactions, deprotonation of chitosan). External mass transfers involving water and ammonia evaporation as well as carbon dioxide intake and evaporation (depending on the gelation process stage) were integrated in the model. A comparison was done in deep cell geometry between the numerical results obtained with the 1D and a 0D model developed and validated in a previous work. The 1D model was then able to predict the influence of the external transfers on the chitosan gelation kinetics. More precisely the model developed herein exhibited that minimum initial concentrations of urease and urea are necessary to reach the advanced gelation pH during the process, which is a prerequisite for preparing thin chitosan membrane.

Controlling collagen gelation pH to enhance biochemical, structural, and biomechanical properties of tissue-engineered menisci.

Collagen-based hydrogels have been widely used in biomedical applications due to their biocompatibility. Enhancing mechanical properties of collagen gels remains challenging while maintaining biocompatibility. Here, we demonstrate that gelation pH has profound effects on cellular activity, collagen fibril structure, and mechanical properties of the fibrochondrocyte-seeded collagen gels in both short- and long-terms. Acidic and basic gelation pH, below pH7.0 and above 8.5, resulted in dramatic cell death. Gelation pH ranging from 7.0 to 8.5 showed a relatively high cell viability. Furthermore, physiologic gelation (pH7.5) showed the greatest collagen deposition while glycosaminoglycan deposition appeared independent of gelation pH. Scanning electron microscopy showed that neutral and physiologic gelation pH, 7.0 and 7.5, exhibited well-aligned collagen fibril structure on day 0 and enhanced collagen fibril structure with laterally joined fibrils on day 30. However, basic pH, 8.0 and 8.5, displayed a densely packed collagen fibril structure on day 0, which was also persistent on day 30. Initial equilibrium modulus increased with increasing gelation pH. Notably, after 30 days of culture, gelation pH of 7.5 and 8.0 showed the highest equilibrium modulus, reaching 150 -160 kPa. While controlling gelation pH is simply achieved compared with other strategies to improve mechanical properties, its influences on biochemical and biomechanical properties of the collagen gel are long-lasting. As such, gelation pH is a useful means to modulate both biochemical and biomechanical properties of the collagen-based hydrogels and can be utilized for diverse types of tissue engineering due to its simple application.

Effects of heating temperatures and pH of skim milk fortified with milk protein concentrate on the texture and microstructure of high-protein yoghurts

Texture and microstructure of high-protein yoghurts manufactured from milk protein concentrate (MPC) fortified skim milk heated at different temperatures (75, 80, 85, 95 °C for 10 min) and pH (6.5, 6.7, 6.9, 7.1) were studied. Whey protein (WP) denaturation increased from 16% to 89% with increasing heating temperatures, while WP binding to casein micelles decreased from 95% to 21% with increasing heating pH. Gelation pH during fermentation increased with increasing heating temperatures and pH. Gel network became denser when heating temperatures and pH increased. Firmness and coagulum particle size of yoghurts increased with increasing heating temperatures and pH. Water-holding capacity reached above 87%, and increased slightly with increasing heating temperatures and pH, followed by slight decreases during storage. Reducing heating temperatures and pH of milk base offers potential strategies to obtain a desirably smooth texture without excessive syneresis for high-protein yoghurts manufactured by concentration before fermentation.

Self-assembly of Fmoc-diphenylalanine in water above the critical pH for gelation

The dipeptide, fluorenylmethyloxycarbonyl- di- phenylalanine (FmocFF), has displayed the self-assembly characteristics of short peptides in a way to induce hydrogel formation. The biocompatibility of these hydrogels makes them an important material to study. The underlying fibrils of the gel phase are built of β-sheets stabilized by ππ stacking between respective aromatic side chains and end group of the peptide. Gel formation can be triggered by adding water to dimethysulfoxide or by dissolving the peptide at a pH greater than 10.0 and subsequently titrating with HCl.

Synthesis of silica powder with high pore volume by skeleton reinforcement

In this paper, a method composed of gelation of basic skeleton (first step) and skeleton reinforcement process (second step) was introduced to synthesize silica powder with high pore volume through the reaction between water glass and sulfuric acid. No organic solvents were involved in the entire preparation process and the final product was collected by spray drying. The effect of concentration of base solution, gelation point pH value and skeleton reinforcement time on the BET specific surface area and pore volume of the prepared silica powder were investigated intensively. The results show that, a basic skeleton with good dispersibility and high porosity was obtained when the concentration of base solution was 0.1 mol⋅L −1 and the gelation pH value reached 6.5. Then the basic skeleton grew into a more uniform porous structure after 30 min skeleton reinforcement. Under these optimum conditions, silica powder prepared by skeleton reinforcement method had a BET specific surface area of 358.0 m 2 ⋅g −1 , and its pore volume reached 2.18 cm 3 ⋅g −1 , which was much higher than that of prepared by skeleton-free method (1.62 cm 3 ⋅g −1 ) and by direct gelation method (0.31 cm 3 ⋅g −1 ).

Observation of dissipating solvated protons upon hydrogel formation.

Aqueous hyaluronan solutions form an elastic hydrogel within a narrow pH range, around pH 2.4, making this a model system to study the conformational changes of the hydrogen bond network upon gelation. This pH-dependent behavior allows us to probe water surrounding a biologically relevant molecule in different environments (liquid versus elastic state) which change due to an environmental stimulus. Here, we use Terahertz (THz) reflection absorption spectroscopy in attenuated total reflection (ATR) geometry as a tool to study gelation. THz spectroscopy is sensitive to changes in the hydrogen-bonded water network, and here we show that we can correlate changes in macroscopic properties to changes in the solvation of hyaluronan. Above and below the gelation pH, solvated protons are present in the solutions, however, this spectral signature is completely absent between pH 2.4-2.8, which is the pH at which hyaluronan forms a hydrogel. We propose that solvated protons are forming ion pairs with hyaluronan in this pH range. Adding urea or glucose to hyaluronan solutions changes their elasticity, in which an increase or decrease in elasticity can be linked to the formation and destruction of these ion pairs, respectively.

Iron Encapsulation by Deacetylated Glucomannan as an Excipient Using the Gelation Method: Characteristics and Controlled Release.

SUMMARYResearch backgroundDeacetylation and the use of CaCl2 as a gelation agent improve the performance of glucomannan as iron encapsulant. This study was conducted to investigate the effects of deacetylation degree and pH of gelation on the characteristics of encapsulated iron using gelation in CaCl2 solution.Experimental approachGlucomannan was deacetylated at various NaOH concentrations and was subsequently utilized as an iron excipient using the pipette-dropped gelation method in CaCl2 solution to directly investigate the process of encapsulation by gelation. The pH of the gelation solution was also changed. The beads were subsequently vacuum-dried.Results and conclusionsDeacetylation led to lower endothermic peak of the glucomannan than that of the native one. The deacetylation degree and pH of gelation did not significantly affect the diameter of the beads but influenced their appearance and physical characteristics. The backbone of glucomannan was not changed by either the deacetylation degree or the pH of the gelation. The highest encapsulation efficiency (73.27%) was observed in the encapsulated iron using the glucomannan matrix of the highest deacetylation degree (82.56%) and gelated in the solution at pH=10. The highest deacetylation degree of glucomannan caused the highest swelling of the beads, which led to the release of a higher amount of iron. Glucomannan deacetylation improves the iron encapsulation and enables higher iron release at pH=6.8 than at pH=1.2. The Weibull model was the best-fitting model to represent the profile of iron release from the deacetylated glucomannan matrix using the gelation method (R2>0.93) at pH=6.8 and pH=1.2.Novelty and scientific contributionThis result supports the application of deacetylated glucomannan using NaOH as a pH-sensitive matrix for iron encapsulation and CaCl2 solution as gelation agent. A higher deacetylation degree leads to the release of a higher amount of iron from the matrix. The encapsulation does not only protect the iron but also delivers it to the absorption site and controls its release, which is useful in supplement formulation or food fortification. The results show that the deacetylated glucomannan as the matrix holds more iron in encapsulation process.

Acid gelation of heat-treated recombined milk: Fat globule membrane composition and gelation functionality

Recombined whole milk was prepared by heating skim milk before homogenising with milkfat (HEHO milk) or by homogenising milkfat with unheated skim milk and heating the recombined milk (HOHE milk). Heat treatment caused whey protein denaturation, more at higher temperatures and slightly more in HEHO milk than in HOHE milk. Less protein was adsorbed to the fat globules of the HEHO milk than the HOHE milk; the former had a higher proportion of αS-casein and β-casein and a lower proportion of κ-casein and denatured whey proteins at the interface, indicating a different interaction mechanism. Gelation pH and gelation time were similar for acidified HEHO and HOHE samples and correlated to the denaturation of whey proteins. The final G’ and yield stresses were lower for the HEHO than the HOHE milk. The differences in gelation behaviour were related to the compositions and interactions of the proteins adsorbed to the fat globules.

Utilization of Rice Husk Ash in the Preparation of Graphene-Oxide-Based Mesoporous Nanocomposites with Excellent Adsorption Performance.

Rice husk is an agricultural biomass waste. Burning rice husks in an oxygenic atmosphere releases thermal energy and produces ash that is rich in silica. Rice husk ash (RHA) can be used as a sustainable source of silica for producing high-value-added products. In this study, mesostructural graphene oxide (GO)/SBA-15, a graphene-based hybrid material, was synthesized from RHA. The materials are inspected by Fourier transform infrared spectrometer, Raman spectrometer, field-emission scanning electron microscopy, transmission electron microscopy, surface area analyzer, and X-ray diffraction analyzer. Studies have revealed that GO/SBA-15 possesses various oxygen functional groups that are helpful for dye adsorption. The material consisted of high pore volume of 0.901 cm3/g, wide pores of diameter 11.67 nm, and high surface area of 499 m2/g. Analysis of the methylene blue (MB) adsorption behavior of GO/SBA-15 composites revealed that their adsorption capacity depended on the gelation pH, GO content, adsorbent dosage, and initial dye (MB) concentration. The highest adsorption capacity of GO/SBA-15 was 632.9 mg/g. Furthermore, the adsorption isotherms and kinetics of GO/SBA-15 were investigated. This study demonstrated the great advantage of treated RHA and the potential of this material for use in organic dye adsorption.

Interaction between added whey protein ingredients and native milk components in non-fat acidified model systems

Non-fat acidified milk model systems were constructed from frozen casein and whey protein concentrates produced from skim milk using membrane filtration, and combined with commercial whey protein ingredients, i.e. nano-particulated whey protein (NWP), micro-particulated whey protein (MWP), and whey protein concentrate (WPC). Model systems were characterised in terms of particle size distribution and fractionation, surface hydrophobicity and accessible thiol groups, rheological behaviour, water holding capacity and graininess. Samples containing NWP exhibited higher surface hydrophobicity and increase in accessible thiol groups, shorter gelation time, higher gelation pH and G′, but increasing particle size and number of grains, when compared with addition of MWP and WPC. Addition of MWP resulted in weak gels with a less connected protein network and decreased number of grains. Mixtures of NWP and MWP (1:1) had rheological properties closer to those seen for MWP. Systems with WPC differentiated themselves with a large quantity of small aggregates.

Functional properties of three native starches and their modified derivatives

Starches were isolated from cocoyam (Xanthosoma sagittifollium), white yam (Dioscorea rotundata) and bitter yam (Dioscorea dumentorum). Starch modification was carried out using acetic anhydride and phthalic anhydride. The native and modified starches were characterized using Fourier Transformed Infra-red Spectroscopy (FTIR) for identification of the functional groups. Functional properties such as water absorption capacities, oil absorption capacity, swelling power, solubility, gelation temperature, least gelation capacity, amylose content and pH were determined using standard procedures. Acetylation increased the water absorption capacity, oil absorption capacity, swelling power, amylose content, and solubility of the starches while phthalation decreased water absorption capacity, oil absorption capacity, swelling power, and solubility of the starches. Native cocoyam starch has the highest gelation temperature (85 °C) while Acetylated bitter yam has the lowest gelation temperature (74 °C). The pH of the native and modified starches was within the range of 4.14 − 6.55. Phthalation and acetylation increased the bulk density of the starches. Native cocoyam, white yam, and bitter yam starches had the lowest gelation concentration (6%). Modification of native starches will improve the usage of starch in food and non-food applications.