Rheological behaviour of uncross-linked and cross-linked gelatinised waxy maize starch with pectin gels

Rheological characterisation of uncross-linked (UPS) and cross-linked (CPS) waxy maize starch with pectin was conducted to determine the influence of pectin on the properties of the starch. The viscoelastic behaviour of 5% (w/v) gel systems containing UPS and CPS polysaccharides at 25 °C was evaluated by small angle deformation oscillation rheometry. Viscoelasticity measurements of the cross-linked polysaccharides indicated that the elastic component increased after cross-linking. Among all gels studied, the properties of the CPS mixtures (ratios 2:3 and 3:2) showed quite high storage (G′) and loss (G″) moduli (compared with gels of other ratios), indicating that gels of these two particular ratios had the greatest degree of elasticity and were very well structured. The results suggest that cross-linking between starch and pectin molecules can give rise to novel rheological properties.     

Gelling properties of kefiran, a food-grade polysaccharide obtained from kefir grain

The physicochemical and gelling properties of kefiran, a water-soluble glucogalactan with probed health-promoting properties, were investigated. Gel permeation chromatograms revealed a single distribution of molecular weight corresponding to 10⁷ Da. Intrinsic viscosity of kefiran determined using Huggins extrapolations was 6.0 dl/g and using Kramer approximations was 5.95 dl/g.Kefiran has a Newtonian behaviour in diluted solutions, which becomes pseudoplastic at higher concentrations. Rheological behaviour of the solution before and after freeze drying was evaluated by small deformation oscillatory rheological measurements. The mechanical spectrum of solution corresponded to an entangled network behaviour. After freeze–thaw treatment of the solution, a rheological behaviour transition from a liquid-like system to a gel was observed. The storage modulus (G′) in cryogels was 35 times higher than the value obtained for the solution. Rheological characteristics of the cryogel were influenced by kefiran concentration. As the polymer concentration increased, higher number of interactions was evident for the increment in both moduli (G′ and G″). The behaviour of kefiran cryogels about 37 °C determines its ability to melt at mouth temperature. These results suggest that kefiran cryogels could be an interesting alternative for its application in food formulations.     

On solid-like rheological behaviors of globular protein solutions

Dynamic viscoelastic and steady flow properties of β-lactoglobulin, bovine serum albumin, ovalbumin, and α-lactalbumin aqueous solutions were investigated at 20°C. When a sinusoidal strain in the linear viscoelastic region was applied, the solutions of the globular proteins except for α-lactalbumin showed typical solid-like rheological behavior: the storage modulus G′ was always larger than the loss modulus G″ in the entire frequency range examined (0.1–100 rad/s). Under a steady shear flow, strong shear thinning behavior was observed with increasing shear rate from 0.001 to 800 s⁻¹, for the globular proteins except for α-lactalbumin. The values of the steady shear viscosity η were lower than those of the dynamic shear viscosity η* at a comparable time scale of observation, violating the Cox–Merz rule, and thus suggesting that a solid-like structure in a globular protein solution was susceptible to a steady shear strain. During isothermal gelation of the protein colloids at 70°C, no crossover between G′ and G″ was observed so that the gelation point was judged by an abrupt increase in the modulus or a sudden decrease in tanδ.     

Associative and segregative interactions between gelatin and low-methoxy pectin: Part 2—co-gelation in the presence of Ca

The effect of segregative interactions with gelatin (type B; pI=4.9; 0–10 wt%) on the networks formed by low-methoxy pectin on cooling in the presence of stoichiometric Ca²⁺ at pH 3.9 has been investigated by rheological measurements under low-amplitude oscillatory shear. Samples were prepared and loaded at 85 °C, cooled (1 °C/min) to 5 °C, held for 100 min, and re-heated (1 °C/min) to 85 °C, with measurement of storage and loss moduli (G′ and G″) at 10 rad s⁻¹ and 2% strain. The final values of G′ at 5 °C for mixtures prepared at the same pH without Ca²⁺ were virtually identical to those observed for the same concentrations (0.5–10.0 wt%) of gelatin alone, consistent with the conclusion from the preceding paper that electrostatic (associative) interactions between the two polymers become significant only at pH values below 3.9. Increases in moduli on cooling in the presence of Ca²⁺ occurred in two discrete steps, the first coincident with gelation of calcium pectinate alone and the second with gelation of gelatin. Both processes were fully reversible on heating, but displaced to higher temperature (by 10 °C), as was also observed for the individual components. The magnitude of the changes occurring over the temperature range of the gelatin sol–gel and gel–sol transitions demonstrates that the gelatin component forms a continuous network; survival of gel structure after completion of gelatin melting shows that the calcium pectinate network is also continuous (i.e. that the co-gel is bicontinuous). On progressive incorporation of NaCl (to induce phase separation before, or during, pectin gelation) the second melting process, coincident with loss of calcium pectinate gel structure, was progressively abolished, indicating conversion to a gelatin-continuous network with dispersed particles of calcium pectinate. These qualitative conclusions are supported by quantitative analyses reported in the following paper.     

Effect of food matrix and heat treatment on the rheological properties of salmon-based baby food

Shelf stable baby foods from Alaskan salmon were developed from red and pink salmon with and without bones. The effect of salmon type, presence of bones and thermal treatment (121 °C for 55 min) on the dynamic (viscoelastic) and flow models were evaluated. Rheological behaviors of all samples were also tested over a temperature range of 25–55 °C. All samples had a higher viscoelastic behavior with consistently higher storage modulus (G′) than loss modulus (G″) over the entire frequency range used (0.5–100 rads/s at 25 °C). Thermal treatment had a significant effect (p < 0.0001) on viscoelastic behavior of baby foods when the exponential model (G′ or G″ = A(ω)^b) was used. A values were higher for the processed food for G′ and G″, and b values. The Casson model was found to be the best for the shear rate – shear stress for all types of tested samples. Retorted samples exhibited lower yield stress than their unretorted counterparts. Retorted samples were susceptible to temperature change more than unretorted samples as shown by energy of activation values (E_a) when the effect of temperature (25–55 °C) was studied with an Arrhenius type model. Red salmon without bone had higher E_a values among all samples and with pink salmon with bone recording a lowest among all of them.     

Maturation effects in fish gelatin and HPMC composite gels

This study assessed the effectiveness of using hydroxylpropylmethylcellulose (HPMC) to enhance mechanical strength and thermal stability in fish skin gelatin (FG). The significant increase in absorbance (A₄₀₀) observed after HPMC had been added to FG and then matured indicated successful formation of a composite gel. Increased gel strength and storage modulus (G′) indicated the enhanced gelation ability of the matured composite gel, while increased melting temperature (T_m) and enthalpy (ΔH) indicated its improved thermal stability. Maturation-related rheological property improvements were more noticeable at 4 °C than 10 °C, but no apparent differences in T_m improvement were observed between 4 °C and 10 °C maturation. Nevertheless, the composite gel exhibited reversible cold and thermal gelation properties.     

Characterization and improvement of rheological properties of sodium caseinate glycated with galactose, lactose and dextran

The aim of this work was to investigate the effect of non-enzymatic glycosylation with galactose, lactose, and 10 kDa dextran on the rheological properties of sodium caseinate. To promote the formation of covalent complexes, the reaction was done in solid state (a_w = 0.67), pH 7.0 (0.1 M sodium phosphate buffer), and temperature set at 50 and 60 °C. The progress of Maillard reaction was indirectly traced by measuring the formation of the Amadori compound, through furosine (2-furoylmethyl-lysine) analysis, and brown polymers, and the resulting glycoconjugates were characterized by LC/ESI-MS and SEC. Results showed a higher reactivity of galactose than lactose and dextran to form the glycoconjugates, due to its smaller molecular weight. Glycation with galactose and lactose increased the viscosity of caseinate and also altered its flow characteristics from Newtonian to shear-thinning. Oscillatory testing showed a higher elastic modulus (G′) in glycoconjugates when compared to non-glycated caseinate, especially with galactose, where a gel-like behaviour was observed after long incubation times. Glycation with dextran did not produce substantial improvements in the rheological properties of caseinate, probably due to the limited extent of the reaction. Our results show that by controlling the rate and extent of the Maillard reaction is a technologically feasible operation to improve the viscosity and gelling properties of sodium caseinate-based ingredients.     

Effect of sulfation on the physicochemical and biological properties of citrus pectins

Citrus pectins were subjected to chemical modification, specifically sulfation, and the antimicrobial and anticoagulant activities of the derivative were investigated. Compared to native pectin, the FT-IR spectra of the derivative showed two new absorption bands at 1250 cm⁻¹ (SO) and 810 cm⁻¹ (C–O–S), implying that the pectin was successfully sulfated. The degree of substitution was also determined to be 0.15 by elemental analysis. In rheological measurements, sulfation gave rise to significant reduction of viscosity of pectin. Moreover, the pectin derivative exhibited improved antimicrobial effects against Bacillus cereus and Vibrio fischeri and the anticoagulant activity, which increased in a concentration-dependent manner. These results demonstrated that the incorporation of sulfate groups into the pectin structure appeared to play an important role in improving its biological activities.     

Role of cosolutes in gelation of high-methoxy pectin. Part 2. Anomalous behaviour of fructose: calorimetric evidence of site-binding

Gels of high-methoxy pectin (DE 70; 1.0 wt%; pH 3.0) in the presence of fructose at concentrations of 50, 55, 60 and 65 wt% showed an intense endotherm followed immediately by an intense exotherm on heating. These transitions occurred over approximately the same temperature-range as initial gelation on cooling (characterised by low-amplitude oscillatory measurements of G′ and G″) and increased in magnitude with increasing concentration of fructose. The displacement of both transitions, and particularly the exotherm, to progressively higher temperature as the rate of heating was increased was much greater than anticipated from simple thermal lag, indicating that the underlying structural changes are slow. The proposed interpretation is that fructose is capable of site-binding to pectin in both the ordered (threefold helix) and disordered state; the endotherm is attributed to helix melting and displacement of fructose; the subsequent exotherm is attributed to re-attachment of fructose to disordered chains, and the slow kinetics of this process to the conformational mobility of disordered pectin. On cooling over the same temperature range, a single exotherm was observed; the absence of detectable splitting is attributed to rapid re-attachment of fructose to conformationally-rigid helices. The magnitude of this endotherm (ΔH≈20 J/g) is close to the value found for cosolutes that show no evidence of site-binding, and to the net change in enthalpy for the endothermic and exothermic processes observed on heating, suggesting that the values of ΔH for displacement and re-attachment of fructose are essentially equal and opposite, with the net change coming from formation or melting of threefold helices. A smaller thermal process at higher temperature (endothermic on heating and exothermic on cooling) is attributed to hydrophobic association, which was also seen as an increase in G′ and G″ on heating in two consecutive cycles of temperature change.     

Studies of ovalbumin gelation in the presence of carrageenans and after manothermosonication treatments

Ovalbumin is a key ingredient in many food products due to its ability to form a three-dimensional network after heat denaturation, that is, to form gels. We have explored two ways of modifying gels based on ovalbumin: (1) the addition of carrageenans, and (2) manothermosonication (MTS) treatments of ovalbumin suspensions prior to gelation. Ovalbumin gels showed elastic modulus (G′) values of 1216 Pa after a heating and a cooling period. The addition of kappa, lambda, and iota carrageenan enhanced G′ values by 6, 1.7, and 1.7 fold, respectively. Kappa carrageenan was not only the most effective carrageenan in the improvement of ovalbumin gelation but changed also the gelation process at the end of the cooling phase. MTS treatments reduced G′ values of ovalbumin gels by about 50% measured immediately after MTS treatments but only by ca. 25% after 24 h, which reveals that ovalbumin modifications introduced by ultrasound, whatever they are, are reversible. This reduction does not preclude the use of manothermosonicated liquid egg as gelling agent.     

Purification and partial physicochemical characteristics of protein free fenugreek gums

Crude fenugreek gum (3.74% protein) was purified by dissolving in aqueous solvent and centrifugation to remove impurities which yielded a purified gum fraction containing 1.10% protein residue. Further purification of the gum was achieved by treating the gum solution with phenol to obtain protein free fenugreek gum (0.16% protein residue). The three types of fenugreek gums were evaluated for: molecular weight, surface activity and rheological performance. Surface and interfacial tension, measured by a Du Nouy ring, indicated that the removal of protein in the gum significantly reduced its surface activity. However, the crude fenugreek gum exhibited lower intrinsic viscosity and radius of gyration compared to the purified and protein free fenugreek gums. It was found that both protein residue and gum concentration affected the elastic modulus (G′), viscous modulus (G″), and complex viscosity (η^*).     

Impact of cosolvents on formation and properties of biopolymer nanoparticles formed by heat treatment of β-lactoglobulin–Pectin complexes

The purpose of this study was to determine the influence of neutral cosolvents on the formation and properties of biopolymer nanoparticles formed by thermal treatment of protein–polysaccharide electrostatic complexes. Biopolymer particles were formed by heating (85 °C, 20 min) an aqueous solution containing a globular protein (β-lactoglobulin) and an anionic polysaccharide (beet pectin) above the thermal denaturation temperature (T_m) of the protein under pH conditions where the biopolymers formed electrostatic complexes (pH 5). The impact of two neutral cosolvents (glycerol and sorbitol) on the self-association of β-lactoglobulin and on the formation of β-lactoglobulin–pectin complexes was examined as a function of solution pH (3–7) and temperature (30–95 °C). Glycerol had little impact on the pH-induced self-association or aggregation of the biopolymers, but it did increase the thermal aggregation temperature (T_a) of the protein–polysaccharide complexes, which was attributed to its ability to increase aqueous phase viscosity. Sorbitol decreased the pH where insoluble protein–polysaccharide complexes were formed, and greatly increased their T_a, which was attributed to its ability to increase T_m, alter biopolymer–biopolymer interactions, and increase aqueous phase viscosity. This study shows that neutral cosolvents can be used to modulate the properties of biopolymer nanoparticles prepared by thermal treatment of protein–polysaccharide electrostatic complexes.     

Effects of xanthan gum on physicochemical properties and stability of corn oil-in-water emulsions stabilized by polyoxyethylene (20) sorbitan monooleate

The influence of added xanthan gum on rheological and dispersion characteristics and stability of concentrated (50% w/w) corn oil-in-water emulsions, stabilized with 5% (percentage on oil amount) polyoxyethylene (20) sorbitan monooleate (Tween 80), have been investigated. Emulsion with no xanthan indicated coalescence and poor creaming stability. All emulsions, with and without xanthan, showed shear-thinning flow behavior. Addition of xanthan protected emulsions from coalescence during 15 days of storage. Increase in xanthan concentration led to decrease in droplet average radius and creaming index, and increase in elastic properties of emulsions. Decrease in the emulsions flow behavior indexes, which suggested the extent of non-Newtonian behavior of emulsions, was influenced by increase in xanthan concentration. Above 0.04% of xanthan concentration, G′ and G″ values indicated formation of weak gels. Gel structure existence arises from droplet network association, due to depletion flocculation. Standard deviation of emulsions droplet size mean diameter decreased while concentration of added xanthan increased.     

Rheological properties of whey protein isolate stabilized emulsions with pectin and guar gum

Dynamic oscillatory and steady-shear rheological tests were carried out to evaluate the rheological properties of whey protein isolate (WPI) stabilized emulsions with and without hydrocolloids (pectin and guar gum) at pH 7.0. Viscosity and also consistency index of emulsions increased with hydrocolloid concentration. At γ = 20 s⁻¹, the value of viscosity of the emulsion with 0.5% (w/v) pectin was about fivefold higher than that of the emulsion without pectin. Flow curves were analyzed using power law model through a fitting procedure. Flow behaviour index of all emulsions except for containing 0.5% (w/v) guar gum was approximately in the range of 0.9–1.0, which corresponds to near-Newtonian behaviour. The shear thinning behaviour of emulsions containing 0.5% (w/w) guar gum was confirmed by flow behaviour index, n, of 0.396. Both storage (G′) and loss modulus (G″) increased with an increase in frequency. Emulsions behaved like a liquid with G″ > G′ at lower frequencies; and like an elastic solid with G′ > G″ at higher frequencies. Effect of guar gum was more pronounced on dynamic properties. Phase angle values decreased from 89 to <10° with increasing frequency and indicated the viscoelasticity of WPI-stabilized emulsions with and without pectin/guar gum.     

Role of cosolutes in gelation of high-methoxy pectin. Part 1. Comparison of sugars and polyols

Mixtures of high-methoxy pectin (DE 70; 1.0 wt%; pH 3.0) with ethan-1,2-diol, glycerol, xylitol, sorbitol, glucose, fructose or sucrose at concentrations of 50, 55, 60 and 65 wt% were prepared at 95 °C and changes in storage modulus (G′) and loss modulus (G″) during cooling to 5 °C, heating to 90 °C and re-cooling to 5 °C (at 1 °C/min) were measured at 1 rad s⁻¹ and 0.5% strain. In all cases, the onset temperature for gelation during cooling and the moduli recorded at 5 °C increased with increasing concentration of cosolute. Both values, however, were substantially lower for the liquid cosolutes (ethan-1,2-diol and glycerol) than for mixtures incorporating the same concentrations of the solid cosolutes. The difference is attributed to inhibition of pectin–pectin interactions by pectin–cosolute interactions, which in turn are inhibited by cosolute–cosolute interactions, these being weaker for the liquid cosolutes than for the solids (as indicated by lower melting points). On heating, there was an initial reduction in modulus, with the same temperature-course as the increase on cooling; for the solid cosolutes, this was followed by an increase attributable to hydrophobic association of methyl ester substituents. No such increase was seen with the liquid cosolutes, but differential scanning calorimetry studies showed two (reversible) thermal transitions in all cases, one over the temperature-range of the initial gelation process on cooling and the other coincident with the increase in modulus on heating in the presence of the solid cosolutes. The absence of any detectable increase in modulus on heating with the liquid cosolutes is attributed to accumulation of cosolute around the polymer chains (i.e. pectin–cosolute interactions) promoting hydrophobic association between methyl ester groups on the same chain, or within small clusters of chains, with, therefore, no contribution to network structure. At high concentrations of the solid cosolutes, the increase in modulus on heating was followed by a decrease at higher temperature; this is attributed to excessive aggregation, and was reflected in lower moduli on subsequent re-cooling to 5 °C, in contrast to the enhancement in gel strength after heating and cooling that was observed at lower concentrations of the same cosolutes.     

Structure and rheology of the κ-carrageenan/locust bean gum gels

The structure and interaction of κ-carrageenan and locust bean gum (LBG) has been studied using rheology, cryo-SEM, conductivity and syneresis characterization. The rheological behaviour of the binary system has been characterized using both compression and shear measurements. Elimination of slip in the shear measurements yields G′ values of the order 10,000–30,000 Pa for a 1% κ-carrageenan gel in 0–0.2 M added KCl. These values are higher than previously reported. No synergistic peak was found with the addition of LBG as has been previously reported. The measured modulii for these gels yields a Poisson's ratio of 0.5. Compression rupture stress and strain were also monitored. The rupture measurements do show a synergistic peak indicating that the interaction does occur and is important at high strain amplitudes. The gel points as determined by conductivity for these systems show a decrease in temperature with increasing LBG concentration, which is consistent with rheological measurements. Syneresis results are reported for the range of κ-carrageenan/LBG ratios. The syneresis shown by the mixtures is the same as that shown by the same concentration of κ-carrageenan. Structures of the gels as determined by cryo-SEM are also reported. Characteristic length scales in these systems are of the order of tens of microns and show little change with LBG concentration. The reduction in the characteristic length scale with increasing LBG concentration is discussed in terms of the rheological behaviour.     

Effect of high-methoxy pectin on properties of casein-stabilized emulsions

We report on the effect of high-methoxy pectin on the stability and rheological properties of fine sunflower oil-in-water emulsions prepared with α_s1-casein, β-casein or sodium caseinate. The aqueous phase was buffered at pH 7.0 or 5.5 and the ionic strength was adjusted with sodium chloride in the range 0.01–0.2 M. Average emulsion droplet sizes were found to be slightly larger at the lower pH and/or with pectin present during emulsification. Analysis of the serum phase after centrifugation indicated that some pectin becomes incorporated into the interfacial layer at pH 5.5 but not at pH 7.0. This was also supported by electrophoretic mobility measurements on protein-coated emulsion droplets and surface shear viscometry of adsorbed layers at the planar oil–water interface. A low pectin concentration (0.1 wt%) was found to give rapid serum separation of moderately dilute emulsions (11 vol% oil, 0.6 wt% protein) and highly pseudoplastic rheological behaviour of concentrated emulsions (40 vol% oil, 2 wt% protein). We attribute this to reversible depletion flocculation of protein-coated droplets by non-adsorbed pectin. At ionic strength below 0.1 M, the initial average droplet sizes, the creaming behaviour, and the rheology were found to be similar for emulsions made with either of the individual caseins (α_s1 and β) or with sodium caseinate. At higher ionic strength, however, whereas emulsions containing β-casein or sodium caseinate were stable, the corresponding α_s1-casein emulsions exhibited irreversible salt-induced flocculation which was not inhibited by the presence of the pectin.     

Characterization of gelation time and texture of gelatin and gelatin–polysaccharide mixed gels

The effects of cooling rate, holding temperature, pH and polysaccharide concentration on gelation characteristics of gelatin and gelatin–polysaccharide mixtures were investigated using a mechanical rheometer which monitored the evolution of G′ and G″. At low holding temperatures of 0 and 4 °C, elastic gelatin gels were formed whereas a higher holding temperature of 10 °C produced less elastic gels. At slow cooling rates of 1 and 2 °C/min, gelling was observed during the cooling phase in which the temperature was decreased from room temperature to the holding temperature. On the other hand, at higher cooling rates of 4 and 8 °C/min, no gelation was observed during the cooling phase. Good gelling behavior similar to that of commercial Strawberry Jell-O^® Gelatin Dessert was observed for mixtures of 1.5 and 15 g sucrose in 100 ml 0.01 M citrate buffer containing 0.0029–0.0066 g low-acyl gellan. Also, these mixed gels were stronger than Strawberry Jell-O^® Gelatin Desserts as evidenced by higher G′ and gel strength values. At a very low gellan content of 0.0029 g, increasing pH from 4.2 to 4.4 led to a decrease in the temperature at the onset of gelation, G′ at the end of cooling, holding and melting as well as an increase in gel strength. The gelation time was found to decrease to about 40 min for gelatin/sucrose dispersions in the presence of 0.0029 g gellan at pH 4.2 whereas the corresponding time at pH 4.4 was higher (79 min). In general, the gelation time of gelatin/sucrose dispersions decreased by a factor of 2 to 3 in the presence of low-acyl gellan. The addition of low-acyl gellan resulted in an increase in the gelation rate constant from 157.4 to 291 Pa. There was an optimum low-acyl gellan content for minimum gelation time, this optimum being pH dependent. Addition of guar gum also led to a decrease in gelation time to 73 min with a corresponding increase in the gelation rate constant to 211 Pa/min though these values were not sensitive to guar gum content in the range of 0.008–0.05 g. The melting temperature of gelatin/sucrose/gellan as well as gelatin/sucrose/guar mixtures did not differ significantly from that of pure gelatin or Strawberry Jell-O^® Gelatin Desserts. At pH 4.2, the melting rate constant was highest at a low-acyl gellan content of 0.0029 g whereas the rate constant was insensitive to low-acyl gellan content at pH 4.4. Addition of guar did not seem to affect the melting temperature or the melting rate constant.     

Effect of inulin on the rheological properties of silken tofu coagulated with glucono-δ-lactone

This study investigated the rheological properties of inulin-containing silken tofu coagulated with glucono-δ-lactone (GDL) upon heating. Inulin (Raftiline^® HP-gel) was added to a soy protein isolate-enriched cooked soymilk at 0%, 1%, 2%, 3% and 4% (w/v) levels along with 0.4% (w/v) GDL to prepare acid-induced silken tofu. Gelation was induced by heating the soymilk mixture from 20 to 90 °C at a constant rate (1 °C/min) or isothermally at 90 °C for 30 min. The gelling properties were measured with dynamic small-deformation mechanical analysis and static large-deformation compression tests. The rheological changes in soymilk during gelation were dependent upon both the pH decline (hydrolysis of GDL) and the specific temperature of heating. Control samples heated to 50 °C, with the pH lowered to 5.95, started to gel, showing a rapid increase in storage (G′) and loss (G″) moduli afterwards. The addition of 2% inulin lowered the on-set gelling temperature by 2.8 °C and improved (P < 0.05) both rheological parameters of the tofu gel as well as hardness and rupture force (textural profile analysis) of the formed silken tofu. The results indicated that inulin enhances the viscoelastic properties of GDL-coagulated silken tofu, and the textural effect of inulin is an added benefit to its current application mainly as a prebiotical ingredient in food.     

Clustering of instrumental methods to characterize the texture and the rheology of slimy okra (Abelmoschus esculentus) suspensions

Okra (Abelmoschus esculentus) is one of the ingredients widely used in African gastronomy because of the unique slimy texture it gives to sauces. However, processing and formulation can affect the textural and rheological properties of these sauces, leading to unacceptable quality for the African consumer. The aim of this study was to select the instrumental measurements best enabling (a) characterization of the rheology and texture of slimy sauces prepared from okra and (b) monitoring its evolution during the preservation process. Thirty-seven slimy suspensions (sauces and purées) were measured with 16 rheological and textural parameters. A principal component analysis revealed that flow consistency index K and flow behavior index n were well correlated with visco-elastic, adhesive, and shear thinning properties, and that stringiness was well correlated with elongational, cohesive, and ductile properties. These two sets of measurement methods are sufficient to characterize their rheological and textural properties, and necessary to discriminate them according to their process and formulation.