Effects of temperature,solid content and pH on the stability of black carrot anthocyanins

Anthocyanin stability of black carrots was studied at various solid contents (11, 30, 45 and 64° Brix) and pHs (4.3 and 6.0) during both heating, at 70–90 °C, and storage at 4–37 °C. Monomeric anthocyanin degradation fitted a first-order reaction model. Degradation of monomeric anthocyanins increased with increasing solid content during heating, while it decreased during storage. For example, at pH 4.3, half-life periods for anthocyanins at 30, 45 and 64° Brix were, respectively, 8.4, 6.9 and 5.2 h during heating at 80 °C and 18.7, 30.8 and 35.9 weeks during storage at 20 °C. At 30–64° Brix, increasing pH from 4.3 to 6.0 enhanced the degradation of anthocyanins during heating. The effect of pH on thermal stability of anthocyanins was also studied at six different pHs (2.5–7.0) in citrate-phosphate buffer solutions and significant decrease in anthocyanin stability was observed at pHs above 5.0. Higher activation energies (E_a) were obtained during heating than during storage with increasing solid contents. At 30–64° Brix, E_a values ranged from 68.8 to 95.1 kJ mol⁻¹ during heating and from 62.1 to 86.2 kJ mol⁻¹ during storage. Q₁₀ values at 20–37 °C were as high as 3.1 at 45° Brix and 3.6 at 64° Brix.     

Characteristics and antioxidative activity of Maillard reaction products from a porcine plasma protein–glucose model system as influenced by pH

Maillard reaction products (MRPs) were prepared by heating the solution containing 2% porcine plasma protein (PPP) and 2% glucose adjusted to various pHs (8, 9, 10, 11 and 12) at 100 °C for different times (0, 2, 4, 6 and 8 h). The pH of all MRPs markedly decreased within 2 h of heating time. Browning and intermediate products, as monitored by absorbance at 420 nm and absorbance at 294 nm, sharply increased within 2 h (P < 0.05). Thereafter, slight increases were observed up to 8 h. Fluorescence intensity (Ex 347 and Em 415 nm) sharply increased within the first 2 h with a subsequent decrease when heating time increased (P < 0.05). Increases in browning and formation of intermediate products were concomitant with the decreases in free amino group and reducing sugar contents. Among all MRPs tested, those derived from the PPP–glucose system at pH 12 rendered the highest browning and intermediate products. However, no differences in reducing power or DPPH radical-scavenging activity of MRPs with initial pH ranges of 10–12 were noticeable. Electrophoretic study revealed that cross-linked proteins with high molecular weight were formed in the PPP–glucose model system to a greater extent at pHs 8 and 9, than at pHs 10–12. Nevertheless, heating times had no pronounced effect on protein pattern of glycated proteins.     

Effect of milk solids concentration on the gels formed by the acidification of heated pH-adjusted skim milk

Reconstituted skim milk of 10–25% total solids was adjusted to pH values between about 6.2 and 7.1 and heated at 80 °C for 30 min. Gels were formed from the heated milks by slow acidification to pH 4.2 and the gelation process and final gels were analyzed for their rheological properties. At each milk concentration, the final acid gel firmness (final G′) and breaking stress could be changed markedly by manipulation of the pH during heating. The final gel firmness and breaking stress could also be modified by changing the concentration of the milk solids prior to heating and acidification. The results indicated that similar gel firmness and breaking stress could be achieved over a range of milk concentrations by control of the pH of the milk during heating. When expressed as a percentage change in final G′ or breaking stress relative to that obtained at the natural pH, plots of the change in final G′ or breaking stress versus pH fell close to a single curve, indicating that the same mechanism may influence the gelation properties at all milk concentrations. The final G′ and breaking stress were related to the denaturation and interaction of the whey proteins with the casein micelles, and the formation of non-sedimentable casein when the milk was heated.     

Comparative study on acid-induced gelation of myosin from Atlantic cod (Gardus morhua) and burbot (Lota lota)

Physicochemical and rheological properties of myosin from Atlantic cod and burbot during acid-induced gelation at room temperature (22–23 °C) by d-gluconic acid-δ-lactone (GDL) were monitored. Turbidity and particle size of both myosins increased and salt soluble content decreased when pH decreased, suggesting the formation of protein aggregates caused by acidification. The formation of disulphide bonds in myosin gelation was induced by acid. Ca²⁺-ATPase activity of myosin decreased (p < 0.05), while surface hydrophobicity increased during acidification (p < 0.05). Furthermore, the decreases in maximum transition temperature (T_max) and the denaturation enthalpies (ΔH) were found in both myosins. During acidification, the increases in storage modulus (G′) and loss modulus (G″) of myosin were observed (p < 0.05), revealing the formation of elastic gel matrix. Thus, gelation of myosin from Atlantic cod and burbot could take place under acidic pH via denaturation and aggregation. However, myosin from Atlantic cod was generally more favourable to gelation than was burbot myosin.     

High pressure induced changes on sarcoplasmic protein fraction and quality indicators

The combined effect of pressure and mild temperature treatments on bovine sarcoplasmic proteins and quality parameters was assessed. M. longissimus dorsi samples were pressurised in a range of 200–600 MPa and 10–30 °C. High Pressure Processing (HPP) induced a reduction of protein solubility (p < 0.001) compared to non-treated controls (NT), more pronounced above 200 MPa. HPP at pressures higher than 200 MPa induced a strong modification (p < 0.001) of meat colour and a reduction of water holding capacity (WHC). SDS–PAGE analysis demonstrated that HPP significantly modified the composition of the sarcoplasmic protein fraction. The pressurisation temperature mainly affected protein solubility and colour; a smaller effect was observed on protein profiles. Significant correlations (p < 0.001) between sarcoplasmic protein solubility and both expressible moisture (r = −0.78) and colour parameters (r = −0.81 to −0.91) suggest that pressure induced denaturation of sarcoplasmic proteins could influence to some extent WHC and colour modifications of beef. Changes in protein band intensities were also significantly correlated with protein solubility, meat lightness and expressible moisture. These results describe the changes induced by HPP on sarcoplasmic proteins and confirm a relationship between modification of the sarcoplasmic protein fraction and alteration of meat quality characteristics.     

Rheological,thermal and structural behavior of poly(ε-caprolactone) and nanoclay blended films

Poly(ε-caprolactone)/nanoclay composite (PCLNC) films were prepared by solvent casting method using a wide range of layered silicate (2.5–10%) and were characterized by different techniques. Nanofiller dispersions in PCL matrix were studied by wide-angle X-ray diffraction (XRD) and transmission electron microscopy (TEM), and results indicated the formation of some intercalated nanostructure of PCLNC. Rheological and thermal properties of PCLNC were measured by parallel-plate oscillatory rheometry and differential scanning calorimetry (DSC), respectively. Rheological study indicated that the predominating liquid-like properties (viscous modulus, G″ > elastic modulus, G′) of neat PCL gradually transformed to solid-like (G′ > G″) behavior after incorporation of clay in the temperature range of 90–120 °C. A plot of G′ vs. G″ provide information on intercalation and microstructure of nanocomposite. Applicability of time–temperature superposition (TTS) principle and van Gurp–Palmen plot (phase angle vs. absolute complex modulus) on rheological data of clay incorporated PCL were employed and found that the results failed to follow the rules. Incorporation of the nanoclay into PCL matrix increased the crystallization temperature (T_c) and melting temperature (T_m) of neat PCL from 28.7 to 32.3 °C and 56.3 to 59.2 °C, respectively due to the nucleating effect, but the glass transition temperature (T_g) (≈−65 °C) was remained unaffected. The decrease in crystallinity with increase in clay concentration was confirmed by both XRD and DSC data.     

Sweetness and texture perception in mixed pectin gels with 30% sugar and a designed rheology

Pure low-methoxyl (LM) pectin and mixtures of LM and high-methoxyl (HM) pectin in different ratios were used to produce gels with control over the rheological parameter storage modulus (G′). The gels either had similar pectin concentrations and different G′ values, or different pectin concentrations and similar G′ values. All gels were prepared with 30 g/100 g sugar, in the presence of 0.1 g/100 g CaCl₂, at pH 3.5; these are conditions that favour gel formation of both LM and HM pectin.The gels were compared for their sensory characteristics; specifically sweetness, sourness, thickness, and glueyness. Sweetness was found to increase with increasing storage modulus (G′) in pectin gels of similar pectin concentration, but different G′ values. Gels with higher proportions of LM pectin were perceived as sweeter than those with low LM pectin ratios. These gels also had increasing loss modulus (G″), and increasing differences between G′ and G″, which indicates that diffusion has a bearing on the perception of sweetness in pectin gels. Thickness and glueyness were mostly determined by total pectin concentration. Thickness also increased with increasing LM pectin concentration while glueyness increased with increasing HM pectin concentration.     

Conformational and rheological changes in catfish myosin during alkali-induced unfolding and refolding

Changes in the conformation of catfish (Ictalurus punctatus) myosin due to (i) cations (ii) alkaline pH and (iii) salt addition were determined using circular dichroism, tryptophan fluorescence, differential scanning calorimetry and hydrophobicity studies. The relation between conformation and storage modulus (G′) of alkali treated myosin was studied. Two types of bases, NaOH and KOH were used for unfolding myosin under three alkaline conditions, pH 11.0, 11.5 and 12.0. Myosin, unfolded under alkali conditions was immediately refolded by adjusting pH back to 7.3. Subjecting myosin to alkaline conditions and subsequent readjustment to pH 7.3 increased the G′ of thermally treated myosin. G′ was affected by the presence or absence of salt during alkali treatments. When salt was present during alkali unfolding of myosin, the added salt stabilized the conformation of myosin against alkali unfolding and denaturation. In the absence of salt or when salt was added after refolding, myosin showed significantly higher denaturation and high G′ on heating and cooling. Among the different alkaline pH values, myosin treated at pH 11.0 showed higher G′. The type of anions influenced the conformation of myosin and the strength of gels. Treatment of myosin with KOH resulted in greater denaturation and higher gelling ability (G′) compared to NaOH.     

Yeast leavened banana-bread: Formulation,processing, colour and texture analysis

Banana powder (BP) was added to hard-red spring wheat (HRSW) flour intended for yeast-leavened bread formulation. Five different formulations containing 10%, 15%, 20%, 25%, and 30% BP were prepared with varying amounts of base flour, while vital gluten was maintained at 25% in all blends. Based on the added BP amounts only, the prepared bread could deliver 42.87–128.6 mg potassium/30 g of bread (one regular slice) and 0.33–1.00 g of fibre. Although the dough water absorption was increased, due to BP addition, the dough mixing tolerance (MTI) decreased. The bread loaf volume was significantly higher than the control except for the 30% blend, where the loaf volume was similar to the control. Bread staling increased with BP levels due to the high sugar content but, this effect was limited to the first two days of storage. Blends exhibited darker colour due to the high sugar and protein, while the 25% and 30% blends had the lowest percent of freezable water. The amounts of acetic acid extractable proteins from the dry blends and the dough decreased with increase in BP. The linear rheological properties of the control, 10%, and 30% blends exhibited similar viscoelastic solid behaviour, where both G′ and G′′ had plateaus (G′ > G′′) and they were parallel to each other over three decades of the frequency. Blends showed higher moduli values than the control.     

Heat-induced gel formation of plasma proteins: New insights by FTIR 2D correlation spectroscopy

Generalized 2D correlation spectroscopy (COS) has been applied to FTIR spectra of porcine plasma proteins to elucidate the sequence of events leading to pH- and/or thermal-induced protein unfolding and aggregation. Changes in the amide I′ region of the infrared spectra (in the pH range between 7.5 and 4.5, at 0.5 pH intervals) at 30 °C were especially evident as the pH approached the pI of serum albumin (4.8), with the globulin fraction in the plasma proteins undergoing denaturation prior to serum albumin. The effect of increasing temperature (from 30 to 90 °C, in increments of 5 °C) on the secondary structure of the plasma proteins at pHs in the range of 7.5–6.0 revealed that a decrease in alpha-helical structures is taken place previously to diminish native beta-sheets. So, the overall results of this study demonstrate that serum albumin and the globulin fraction differ in their sensitivity to pH and temperature.     

Influence of muscle type on rheological properties of porcine myofibrillar protein during heat-induced gelation

The gelation characteristics of myofibrillar proteins are indicative of meat product texture. Defining the performance of myofibrillar proteins during gelation is beneficial in maintaining quality and developing processed meat products and processes. This study investigates the impact of pH on viscoelastic properties of porcine myofibrillar proteins prepared from different muscles (semimembranosus (SM), longissimus dorsi (LD) and psoas major (PM)) during heat-induced gelation. Dynamic rheological properties were measured while heating at 1 °C/min from 20 to 85 °C, followed by a holding phase at 85 °C for 3 min and a cooling phase from 85 to 5 °C at a rate of 5 °C/min. Storage modulus (G′, the elastic response of the gelling material) increased as gel formation occurred, but decreased after reaching the temperature of myosin denaturation (52 °C) until approximately 60 °C when the gel strength increased again. This resulted in a peak and depression in the thermogram. Following 60 °C, the treatments maintained observed trends in gel strength, showing SM myofibrils produced the strongest gels. Myofibrillar protein from SM and PM formed stronger gels at pH 6.0 than at pH 6.5. Differences may be attributed to subtle variations in their protein profile related to muscle type or postmortem metabolism. Significant correlations were determined between G′ at 57, 72, 85 and 5 °C, indicating that changes affecting gel strength took effect prior to 57 °C. Muscle type was found to influence water-holding capacity to a greater degree than pH.     

Effects of supercritical carbon dioxide treatment for sterilization purpose on meat quality of porcine longissimus dorsi muscle

The objective of this study was to investigate the effect of supercritical carbon dioxide (SC-CO₂) treatment for the sterilization purpose on meat quality and protein denaturation of the porcine longissimus dorsi muscle. The conditions of SC-CO₂ treatment were 7.4 and 15.2 MPa at 31.1 °C for 10 min. SC-CO₂ treatment had no effect on muscle pH, tenderness, and water-holding capacity (WHC). However, the samples treated at 7.4 MPa had a higher lightness value (52.97 vs. 46.94, P<0.001) and a more pronounced extent of sarcoplasmic protein denaturation (73.80 vs. 80.73, P<0.01) than the control samples. These results suggest that the paler color of samples treated with SC-CO₂ was associated with the sarcoplasmic protein denaturation, and the major denaturated proteins were determined to be phosphorylase b (PH), creatine kinase (CK), triosephophate isomerase (TPI), and one unknown protein. On the other hand, other quality traits were generally unaffected by the SC-CO₂ treatments at 7.4 or 15.2 MPa.     

Colour and sarcoplasmic protein evaluation of pork following water bath and ohmic cooking

The objective of this study was to investigate the effects of ohmic (OH) and waterbath (WB) cooking on colour attributes and sarcoplasmic changes of porcine longissimus dorsi muscle at the same endpoint temperatures (EPTs; range 10 °C–80 °C). The OH treatment was carried out at 10 V cm^− 1, and the WB temperature at 85 °C. The colour parameters, deoxymyoglobin% (DeoMb) and metmyoglobin% (MetMb) of the OH-cooked meat were significantly lower (P < 0.05) than those obtained by WB-cooking at the same EPTs (range 60 °C–80 °C). SDS-PAGE analysis showed that the meat treated with WB-cooking had a lower sarcoplasmic protein solubility (5.97 mg/g vs.14.89 mg/g, P < 0.05) and fainter protein bands than that of OH-cooking thus, indicating paler colour, and lower water-holding capacity especially in WB-cooked meat at EPTs above 40 °C. Strong correlations among lightness, browness, metmyoglobin% and soluble proteins were observed in meat following OH-cooking.     

Starch–cassia gum interactions: A microstructure – Rheology study

We present for the first time the interactions of starch and cassia gum – a novel galactomannan recently approved for use in food processing. Viscoelastic, pasting and microstructural characterization of various starches (waxy; high amylose; normal; cross-linked waxy corn starch; potato starch) containing different levels of the cassia gum was carried out. Significant changes were observed in the morphology of granule remnants formed during gelatinization in the starch pastes prepared with and without the addition of cassia gum. The freeze-dried starch–cassia gum pastes presented a shrunken and tight arrangement of the starch granule remnants, when studied by scanning electron microscopy. A significant reduction in the granule remnant size was also calculated using laser diffraction particle size analysis. The extent of interaction with cassia gum differed significantly among the various starch types. All the unmodified corn starches recorded an increase in peak viscosity at all levels of the cassia gum addition. An increase in the final viscosity of these starches was also observed by the addition of cassia gum, with high amylose and normal corn starch showing the maximum. Similarly, the extent of breakdown and setback viscosity also differed among the different starch types. Ranges of dynamic rheological measurements (temperature, time and frequency sweeps) were performed within the viscoelastic zones. Rheological parameters, such as storage modulus (G′), loss modulus (G″) and the gelatinization temperature (T_gel), of the corn starches during the heating cycle were observed to increase, when cassia gum was present at lower levels. The starch–gum systems also exhibited higher tan δ values during both the heating and the cooling cycles, indicating the dominance of the viscous modulus. The G′ and G″ of all the corn starch gels containing cassia gum showed higher values throughout the frequency sweep range. However, the increase in G′ and G″ of different starches was not always consistent with the increase in cassia gum levels. The changes in rheological behaviour during storage of the starch gels, aged on the plate of the rheometer and then studied through time sweeps at 5 °C and frequency sweeps at 25 °C, suggested that the starch gels containing cassia gum had less pronounced changes in the rheological parameters than had their control counterparts.     

Synergistic effect of tannic acid and modified atmospheric packaging on the prevention of lipid oxidation and quality losses of refrigerated striped catfish slices

Chemical, microbiological and sensorial changes of striped catfish (Pangasius hypophthalmus) slices treated without and with tannic acid (100 and 200 mg/kg) were determined during 15 days of storage at 4 °C in air and under modified atmospheric packaging (MAP, 60% N₂/35% CO₂/5% O₂). The slices consisted of 9.2 g lipid/100 g and the lipid contained 64.55% unsaturated fatty acids and 33.87% saturated fatty acids. During the storage, the sample treated with 200 mg/kg tannic acid and stored under MAP (M₂) had the lowest peroxide value (PV) and thiobarbituric acid-reactive substances (TBARS) with the coincidental lowest non-haem iron content, indicating the retarded lipid oxidation. Fourier transform infrared (FTIR) spectra indicated the formation of primary oxidation products and free fatty acids in M₂ sample after 15 days. Conversely, these compounds were found at lower contents in the control samples kept in air without tannic acid treatment (A₀), suggesting that the deterioration was more advanced. Myosin heavy chain of A₀ was degraded by 17.85% after 15 days of storage, whereas no change was noticeable in M_2, compared with the fresh sample (F). Based on microbiological acceptability limit (10⁷ cfu/g), the shelf-life of A₀ and M₂ was estimated to be 3 and 15 days, respectively. M₂ had the acceptable scores for all sensory attributes up to 15 days, while A₀ was acceptable when stored for 9 days. Therefore, tannic acid exhibited a synergistic effect with MAP on retarding lipid oxidation and microbial growth, thereby increasing the shelf-life of striped catfish slices during refrigerated storage.     

Acid-induced gelation of natural actomyosin from Atlantic cod (Gadus morhua) and burbot (Lota lota)

The acid-induced gelation of natural actomyosin (NAM) from burbot (Lota lota) and Atlantic cod (Gardus morhua) added with d-gluconic acid-δ-lactone (GDL) during incubation at room temperature (22–23 °C) for 48 h was investigated. During acidification, pH values of both NAMs reached 4.6 within 48 h. Both NAMs underwent aggregation during acidification as evidenced by increases in turbidity and particle size, especially after 6 h of incubation. The decreases in Ca²⁺-ATPase activity and salt solubility of both NAMs were observed during incubation. Decreases in total sulphydryl content with the concomitant increases in disulphide bond content of NAM from both species were also noticeable. Additionally, surface hydrophobicity of NAM increased, suggesting the conformational changes in NAM induced by acidification. The storage modulus (G′) values increased with increasing incubation time and G′ development was greater in Atlantic cod NAM, compared with burbot NAM. Differential scanning calorimetry (DSC) revealed that T_max and enthalpy of myosin peak shifted to the lower values and endothermic peak of actin completely disappeared. In general, gel development was more pronounced in Atlantic cod NAM, compared with the burbot counterpart. As visualised by transmission electron microscopy, network strands of aggregates from Atlantic cod were finer and more uniform than those of the burbot counterpart. Acid-induced gelation of NAM from both fish species therefore involved both denaturation and aggregation processes. However, gelation varied with fish species and had an impact on the resulting gels.     

Influence of the particle size on the rheological behaviour of chestnut flour doughs

The rheological properties of chestnut flour (CF) doughs with different particle size were studied using a controlled stress rheometer. The mixing curves and heating–cooling cycle responses were previously obtained from the Mixolab® apparatus. Shear measurements (0.1–10 s⁻¹), oscillation measurements (1–100 rad s⁻¹ at 0.1% strain), temperature sweep (30–100 °C) to achieve the gelatinization temperatures and creep-recovery tests (loading of 50 Pa for 60 s) were conducted in the rheometer. Mixolab® showed that CF samples with smaller particle size needed more water absorption to reach a consistency of 1.1 Nm. Shear viscosities of CF doughs exhibited a Newtonian plateau at low shear rate and shear thinning behaviour at higher shear rate. Apparent viscosity increased with increasing average particle size and steady-flow curves were fitted using Cross model. Oscillatory measurements of CF dough showed that the storage modulus, G′, was greater than loss modulus, G″, for all samples in the tested angular frequency range. CF samples with smaller particle size presented lower G′ and G″ values. Creep-recovery tests of these flours showed that elasticity was limited and unrecoverable proportion was very high. Gelatinization temperatures measured using Mixolab® and rheometer were practically coincident.     

Effects of washing with oxidising agents on the gel-forming ability and physicochemical properties of surimi produced from bigeye snapper (Priacanthus tayenus)

The effects of washing with hydrogen peroxide (H₂O₂) and sodium hypochlorite (NaOCl) solutions on the gel-forming ability and physicochemical properties of surimi produced from bigeye snapper (Priacanthus tayenus), stored in ice for up to 14 days, were investigated. Generally, pH and the trichloroacetic acid (TCA)-soluble peptide content of washed mince varied, depending on the type of oxidizing agent and storage time of the fish. With increasing time of storage, the pHs of water- and H₂O₂-washed mince were lower than that of NaOCl-washed mince (P < 0.05). However, no differences in the TCA-soluble peptide contents of the resulting mince washed with any media were observed (P > 0.05). Washing with 20 ppm NaOCl resulted in the highest increase in both the breaking force and the deformation of mince from fish stored in ice for all the times studied (P < 0.05). Natural actomyosin (NAM) extracted from NaOCl-washed mince had higher surface hydrophobicity and disulfide bond (SS) content than that of water-washed mince (P < 0.05). With no effect on Ca²⁺-, Mg²⁺-, or Mg²⁺–Ca²⁺-ATPase activities, NaOCl washing resulted in an increase in Mg²⁺–EGTA-ATPase activity of NAM (P < 0.05). The results suggested that washing mince with the appropriate type and concentration of oxidizing agent can improve the gelling ability of surimi, particularly from low quality fish.     

Effects of variation in the palm stearin: Palm olein ratio on the crystallisation of a low-trans shortening

Changes in the rheological properties during crystallisation and in the crystal size and morphology of blends containing rapeseed oil with varying percentages of palm stearin (POs) and palm olein (POf) have been studied. The crystals formed from all three blends were studied by confocal laser scanning microscopy, light microscopy and environmental scanning electron microscopy, which revealed the development of clusters of 3–5 individual elementary “spherulites” in the early stages of crystallisation. The saturated triacylglycerol content of the solid crystals separated at the onset of crystallisation was much greater than that in the total fat. Fat blends with a higher content of palm stearin had a more rapid nucleation rate when observed by light microscopy, and this caused an earlier change in the rheological properties of the fat during crystallisation. Using a low torque amplitude (0.005 Pa, which was within the linear viscoelastic region of all samples studied) and a frequency of 1 Hz, the viscoelastic properties of melted fat during cooling were studied. All samples, prior to crystallisation, showed weak viscoelastic liquid behaviour (G″, loss modulus >G′, storage modulus). After crystallisation, a more “solid like” behaviour was observed (G′ similar to or greater than G″). The blend having the highest concentration of POs was found to have the earliest onset of crystallisation (27% w/w POs; 12 mins, 22% w/w POs; 13.5 mins, 17% w/w POs, 15 mins, respectively). However, there were no significant differences in the time to the point when G′ became greater than G′ among the three blends.     

The impact of concentration,temperature and pH on dynamic rheology of psyllium gels

Structural aspects of the psyllium gum prepared from the seed husk of the plant of Plantago ovata Forsk was characterized by dynamic rheology and microscopy. Dynamic rheological properties of psyllium gel in the linear viscoelastic region, as a function of concentration (2, 2.5 and 3% w/w), temperature (5–95 °C) and pH (2.5–10) were investigated. Mechanical spectra of the psyllium gels were obtained by frequency sweep measurement classified into that of weak gels because G′ was larger than G″ throughout the tested frequency range and the separation of the two moduli (tan δ) was greater than 0.1. The phase angle increased with temperature and a peak associated with gel melting appeared at about 40 °C. All gels at different pH presented a typical weak gel spectrum. Scanning electron microscopy showed porous structures with different pore-size distribution for psyllium gels under different conditions in terms of concentration, pH and temperature.