Optimization of Hydrocolloid Extraction From Wild Sage Seed (Salvia macrosiphon) Using Response Surface

The effect of temperature (25–80°C), water to seed ratio (25:1–85:1) and pH (3–9) on the yield, apparent viscosity and emulsion stability index of wild sage seed hydrocolloid was investigated. The generated quadratic model showed that the optimum conditions for maximizing the responses were when temperature was 25°C, water to seed ratio was 51:1 and pH was 5.5. All hydrocolloid solutions (1% w/v) showed shear thinning behavior in different extraction conditions, consistency coefficient and flow behavior index varied from 4.455 to 9.435 (Pa.sⁿ), and 0.317 to 0.374, respectively. Besides, the chemical compositions of the seed and extracted gum were determined at optimal conditions.     

Rheological Properties of Sonicated Guar,Xanthan and Pectin Dispersions

The influence of high intensity ultrasound on the rheological characteristics of guar, xanthan, and pectin dispersions was investigated. Guar 1%, xanthan 1% and pectin 2% (w/v) dispersions were sonicated at varying intensity levels of 3.7, 6.3, 8.1, and 10.1 W/cm² for 5 min at 25^oC. Significant differences were observed in the rheological characteristics of each sonicated hydrocolloid dispersion studied. Sonication affected the consistency index (k), flow behaviour index (n) and complex power law constants (a and b). No recovery was observed in the structure breakdown after a 24-h storage period. Changes in the rheological properties of guar and pectin dispersions were significantly higher than that of xanthan dispersions.     

Effect of ozonation on the rheological and colour characteristics of hydrocolloid dispersions

The effect of ozonation on the rheological and colour characteristics of guar, carboxyl methyl cellulose (CMC), and pectin dispersions was investigated. Guar 1%, CMC 1% and pectin 2% (w/v) dispersions were ozonated at varying ozone concentrations of 2.4%, 4.0%, 5.6% and 7.8% (w/w) for 3, 5, 7 and 10 min processing times at 20 ± 1.0 °C. Flow and dynamic rheological properties together with Hunter colour parameters (L^*, a^*, b^*) were measured for control and treated samples. Significant differences were observed in the rheological characteristics and colour of all ozonated hydrocolloid dispersion studied. No recovery was observed in the structure breakdown after a 24 h storage period. This study indicates that ozonation has a significant effect on both the rheology and colour of hydrocolloid dispersions and that due attention should be given before incorporating these hydrocolloids in food formulations which are subsequently ozonated in food processing and preservation processes.     

Viscoelastic behavior of reconstituted Aloe vera hydrogels as a function of concentration and temperature

Viscoelastic properties for reconstituted A. vera hydrogels were evaluated in different ranges of concentration (0.2–1.6%, w/v) and temperature (30–60°C). The storage (G′) and loss (G″) moduli were well described by power function of the frequency (R² > 0.92). The combined effect of concentration and temperature was optimized for reconstituted gel formation, targeting maximum viscoelastic moduli (G₀′ and G′′₀) and minimum slope (n′ and n″) values using response surface methodology. The optimum condition selected was 1.6%, w/v at 30°C having higher gel strength [G′₀ (47.8 Pa.s^n′) and G″₀ (27.4 Pa.s^n′)], as well as minimum slope values [n′ (0.24) and n″ (0.08)]. Further, the effect of initial aging time on the viscoelastic moduli of optimized sample (1.6%, w/v at 30 ± 1°C) was noticed by fitting the intermediate creep ringing data to rheological models. The viscoelastic moduli (G′_J and G′_K) increased with aging time (0–180 min) for optimized A. vera hydrogel, as confirmed by Jeffrey’s and Kelvin-Voigt models. The obtained results suggested that optimized conditions for reconstituted A. vera gel formation could be useful to improve the gel strength which could be useful for various food applications.     

Steady shear flow properties of wild sage (Salvia macrosiphon) seed gum as a function of concentration and temperature

The steady shear flow properties of dispersions of a new potential hydrocolloid, sage seed gum (SSG), were determined as a function of concentration (0.5–2% w/w), and temperature (20–50 °C). SSG dispersions exhibited strong shear-thinning behavior at all conditions tested, which was even more pronounced than commercial hydrocolloids like xanthan, guar gum and locust bean gum. Different time-independent rheological models were used to fit the experimental data, although the Herschel–Bulkley model (H–B) was found the best model to describe steady shear flow behavior of SSG. An increase in gum concentration led to a large increase in yield stress and consistency coefficient values, whereas there was no definite trend with an increase in temperature. On the other hand, the above-mentioned increases in concentration and temperature did not yield a clear evolution of the shear-thinning characteristics of SSG dispersions. An Arrhenius-type model was also used to describe the effect of temperature. The activation energy (E_a) appeared in the range of 3949–16384 J/mol, as concentration increased from 0.5 to 2%, at a shear rate of 100 s⁻¹. The yield stress values estimated by viscoplastic rheological models were much higher than the data determined by stress ramp method. Apparent viscosity of SSG surpassed many commercial hydrocolloids such as guar gum, locust bean gum, Tara gum, fenugreek gum and konjac gum at the same conditions, which suggest it as a very good stabilizer in food formulations.     

Viscoelastic characterization of solid foods from creep compliance data: application to potato tissues

 Two software systems were developed to simplify acquisition and analysis of data describing creep behavior of viscoelastic solid foods and to determine the magnitude of instantaneous elastic compliance, viscoelastic compliances and viscosity associated with Newtonian flow. The first of these systems was used to store information on the experiment, to collect the data generated during the experiment, to present these in real time and to create files containing the experimental data for subsequent analysis. The second system was used to fit data to discrete Kelvin-Voigt models with four, six or eight constants. The systems were tested in the calculation of rheological properties of fresh and cooked potato tissues. A six-element Burgers model containing two discrete Voigt units proved the most suitable for defining tissue creep behavior, suggesting that different structural components could be related to each unit. The instantaneous elastic modulus could be associated with internal cell pressure. Gelatinization of starch and viscoelastic units appeared to reflect the viscoelastic properties of pectic substances and hemicelluloses, respectively. Received: 5 March 1998     

Rheological Characterization of Binary Combination of Gleditsia triacanthos Gum and Tapioca Starch

In the current study, Gleditsia triacanthos gum and tapioca starch were combined and rheological characterization of the binary mixture was performed. Gleditsia triacanthos gum at four different concentrations (0.1, 0.4, 0.7, and 1.0%, w/v) was mixed with tapioca starch at a constant level (2.5%, w/v). Steady shear and dynamic shear rheological properties of samples were determined using a stress/strain controlled rheometer at a constant temperature (25ºC). Oswald de Waele model was used to describe the shear rate effect on apparent viscosity values of the samples. Increase in the Gleditsia triacanthos level increased the apparent viscosity and consistency coefficient of the samples. Similarly, dynamic shear rheological parameters of the samples increased with the increase of Gleditsia triacanthos gum. The concentration of 0.7% for Gleditsia triacanthos gum was determined to be cross point for the liquid–solid phase. From this level, the elastic behavior became more dominant compared to viscous behavior because tangent delta was equal to one in this concentration. To describe the effect of Gleditsia triacanthos level on the studied rheological parameters, the Power law and exponential type models were used.     

Effect of thermal treatments on functional properties of cress seed (Lepidium sativum) and xanthan gums: A comparative study

Foods are generally subjected to thermal treatments during processing operations, which affect on the functional properties of hydrocolloid solutions. In this paper, the effect of different thermal conditions (60 °C-30 min, 80 °C-23 min, 100 °C-18 min and 121 °C-15 min) on functional properties (rheological, emulsifying and foaming properties) of cress seed gum and xanthan gum were investigated. The results demonstrated that cress seed gum solutions had desirable rheological, emulsifying and foaming properties. When the hydrocolloid samples were heated, an irreversible increase in viscosity of cress seed gum solutions was observed and as a result, the emulsification and foaming properties improved. Whereas, xanthan gum would not have the ability to stand against heat treatment and its viscosity decreased. Nevertheless, the viscosity values of xanthan gum solutions were always higher than cress seed gum in all conditions.     

Steady and Dynamic Shear Rheological Properties,and Stability of Non-Flocculated and Flocculated Beverage Cloud Emulsions

Rheological properties of single-phase, and emulsions containing modified starch and gum arabic as surface active hydrocolloids, as well as xanthan and tragacanth gums as stabilizers were evaluated under steady and dynamic shear testing conditions using a control stress rheometer. Emulsions were formed by 9% and 14% gum concentrations with oil concentration maintained at 9% thus giving a 1:1 and 1.5:1 surface active agent to oil ratio, respectively. The rates of droplet coalescence and creaming, for a total of 8 emulsions, as a function storage time before and after dilution in a simulated fruit beverage were then investigated. Steady shear (flow curve) were well described by the Carreau model at shear stress ranging from 0.01 to 100 Pa. All prepared water phases indicated a zero-shear viscosity plateau followed by shear thinning behavior with flow behavior index (n) ranging from 0.51 to 0.79 for 14% starch-0.3% xanthan and 14% gum arabic-0.8% tragacanth stabilized emulsions, respectively. The water phase flow property data were well fitted by the Einstein equation and its expansions. The dynamic rheological properties of water phase and emulsions were also evaluated for G′(ω) and G″(ω) from 1 to 50 rad/s. Similar curves were obtained with varying degrees of deviations (G′ from G″) for different emulsions. Starch-xanthan emulsion and associated water phase at 1.5/1 agent to oil ratio demonstrated viscoelastic behavior (G′ ≥ G″) with lower droplet coalescence and creaming rates. On the other hand, gum arabic-xanthan emulsion at 1:1 agent to oil ratio showed the highest rate of droplet coalescence and a greater degree of creaming. It was speculated that the lower stability of gum arabic-xanthan emulsion could be related to the denaturation of proteinaceous part in the gum and loss of emulsification capacity due to lower pH and pasteurization.     

The effect of selected hydrocolloids on the rheological properties of processed cheese analogues made with vegetable fats during the cooling phase

The aim of this work was to observe the influence of different hydrocolloids on changes in the rheological properties of processed cheese and their analogues within the process of cooling depending on the type of the fat used (butter, coconut fat and palm oil). κ‐carrageenan, ι‐carrageenan, λ‐carrageenan, arabic gum and locust bean gum were used at a concentration of 1.0% w/w. With the decreasing temperature during the cooling period, an increase in the complex modulus (G*) was observed in all samples tested. Within the cooling period, the sample with the addition of κ‐carrageenan showed both the most significant increase in G* in comparison with the control and the highest values of hardness after a 7‐day storage period regardless of the type of the fat used. The samples with coconut fat were assessed as the hardest. On the other hand, the samples with palm oil showed the lowest hardness (with the same hydrocolloid used). In the gelling hydrocolloids (κ‐ and ι‐carrageenan), only small changes in temperature of coil‐to‐helix transition were observed (in range of 2–7 °C) as a result of the addition of different types of fat.     

Modification and Characterization of Leucaena glauca Seed Gum by Graft Copolymerization with Acrylonitrile

The suitable conditions for graft copolymerization of acrylonitrile on to Leucaena glauca seed gum in aqueous system were investigated using hydrogen peroxide as initiator. For the purpose, a series of reactions have been carried out at different reaction conditions which cover the range of hydrogen peroxide concentration (5–20 mmole/l), acrylonitrile concentration (0.05–0.25 mole/l), backbone concentration (0.00617–0.03086 mole AGU) and polymerization time (30–180 min). The grafting temperature was kept at 85°C for all reactions. The products have been characterized by various methods including viscometry, spectrophotometry and thermometry.     

The Influence of Pectin from Apple and Gum Arabic from Acacia Tree on the Quality of Pizza

The aim of this work was to determine the effect of apple pectin and arabic gum on the organoleptic characteristics of pizza flans. Significant differences in the sensory characteristics, such as flavour and change during chewing as well as the quality between the pizza flan with the addition of hydrocolloids and the pizza flan without them were found out. The additions of hydrocolloids improve the quality and flavour of pizza flans. On the other hand, higher amounts of gum arabic from the acacia tree caused worse tenderness of the bakery product.      

Viscoelastic properties of high pressure and heat induced tofu gels

Tofu gels were rheologically examined to determine their storage or elastic (G′) and loss or viscous (G″) moduli as a function of frequency within their linear viscoelastic limits. The tofu gels were made using either glucono-δ-lactone (GDL) or calcium sulphate (CaSO₄·2H₂O), followed by either heat treatment (heated soymilk at ?97 °C prior to coagulation and subsequently held at 70 °C for 60 min, HT) or high pressure treatment (400 MPa at 20 °C for 10 min, HP). The overall moduli values of the GDL gels and CaSO₄·2H₂O gels of both physical treatments were similar, each gave frequency profiles expected for weak viscoelastic materials. However, although both temperature and high pressure treatments could be used to produce tofu gels, the final products were not the same. Pressure formed gels, despite having a higher overall “consistency” (increasing values of their moduli), had a proportionately higher contribution from the loss modulus (increased tan δ). Differences could also be observed using confocal scanning laser microscopy. While such treatment may give rise to differing systems/structures, with new or modified organoleptic properties, the more “open” structures obtained by pressure treatment may well cause processing difficulties if subsequent reworking or moulding is required.     

Viscoelastic properties of oat β-glucan-rich aqueous dispersions

C-trim is a healthy food product containing soluble dietary fibre β-glucan. The dispersion of C-trim in water is a hydrocolloid biopolymer. The linear and non-linear rheological properties of dispersions of C-trim biopolymers were investigated. The linear viscoelastic behaviours for C-trim dispersions were dependent on the β-glucan that C-trim contained. The C-trim20 and C-trim30, which have about 20% and 30% β-glucan, respectively, exhibited more fluid-like behaviours. The C-trim50 and C-trim95, which contain about 50% and 95% β-glucan, respectively, showed solid viscoelastic properties. The power law model fitting, as well as spectra, for the linear dynamic frequency sweep and stress relaxation of C-trim dispersions, suggested that the C-trim dispersions were composed of physical entanglement networks instead of chemical cross ones. The non-linear steady shearing studies for C-trim dispersions indicated that all four of the C-trim dispersions exhibited shear-thinning behaviours, which could be best described by the power law model.     

Viscoelastic properties of wheat gliadin and glutenin suspensions

Linear and non-linear rheological properties of wheat gliadin and glutenin suspensions were investigated at various concentrations. Linear dynamic viscoelastic properties for both gliadin and glutenin were strongly dependent on concentration. For gliadins, the storage moduli (G′), loss moduli (G″), and phase shifts dramatically changed within a narrow concentration range, indicating that gliadin suspension properties changed from viscous to viscoelastic. Glutenins exhibited viscoelastic solid behaviour at all measured concentrations. The non-linear shear viscoelastic properties of gliadin and glutenin also depended on concentration. Viscosities of gliadins displayed shear-thinning behaviour; viscosities for glutenins showed shear-thickening behaviour at low shear rates, and shear-thinning behaviour at higher shear rates. Our results indicate that gliadin’s structure in suspension changes over a small concentration range, and suggest that gliadin is important in adjusting and controlling gluten’s viscoelastic behaviour, and not only as a diluent of gluten’s functional properties.     

Molecular structural properties of a polysaccharide isolated and purified from Sophora japonica pods and its relationship to their rheology

A water-soluble polysaccharide SJ-A presenting a relatively narrow molecular weight distribution was prepared by ethanol precipitation and purified from the pods of S. japonica. Chemical composition, molecular weight distribution, and glycosidic configurations of SJ-A were elucidated by sugar analysis, molecular determination, Fourier-transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR) analyses. The impacts of the concentration (0.5–2.0%) of SJ-A on the rheological parameters were investigated to clarify the molecular crosslinking features of SJ-A in relation to its rheological properties. The experimental results indicated that the microstructural coupling of the gel induced at higher concentrations of SJ-A required a higher frequency of the rheometer.     

Effect of Freezing on Functional and Textural Attributes of Cress Seed Gum and Xanthan Gum

Consumer habits have undergone great changes, motivated by the new social lifestyle. These changes have promoted the increase in the production of frozen foods; and as a result, many food applications of some hydrocolloids are limited due to functional loss during freezing. In this study, the effect of freezing treatments (?18 °C for 24 h and ?30 °C for 15 h) on rheological, emulsifying, foaming, and textural characteristics of cress seed gum as a new source of hydrocolloid in comparison with xanthan gum as a commercial gum were investigated. The results demonstrated that cress seed gum had significantly lower viscosity than xanthan gum solution, and the freezing treatments did not have significant impact on rheological properties of both products. Conversion of water to ice leads to an increment in molecular association and improved textural characteristics. The high tendency of cress seed gum chains to associate is attributed to its high mannose to galactose ratio. High stability of cress seed gum and similarity with xanthan gum make it attractive for use in frozen foods as a novel gum to provide specific functionality, minimize the negative effect of freezing, and reduce production costs.     

植物种籽胶SO型印花糊料的研制和应用

介绍植物种籽胶化学改性的工艺过程和反应原理,并就糊料研制中的重要环节、影响因素和应用性能进行了分析讨论。     

沙蒿胶多糖提取工艺条件研究

沙蒿胶多糖作为食品添加剂在食品加工领域中展现了广阔的应用前景。另外在医药、日用化工、沙漠治理等领域中也有广泛的应用。本文主要阐述了利用乙酸作为提取剂从沙蒿籽中提取沙蒿胶多糖的工艺，并采用正交试验的方法确定了提取沙蒿胶多糖的最佳工艺条件：提取温度50℃，提取时间：90min，提取液浓度85％，料液比1：5，在此工艺条件下沙蒿胶提取率为18％～19％。与目前国内干法生产工艺相比，本文提出的工艺生产的沙蒿胶在得率和纯度上都有了显著的提高。     

High viscosity of hydrocolloid from leaves of Corchorus olitorius L.

Viscous hydrocolloid from leaves of Corchorus olitorius L. was fractionated with ammonium sulfate solution (50%, w/v) followed by the stepwise extraction with distilled water. The yield of the hydrocolloid was 4.5% (w/w) based on dry material. Ash, protein, moisture and total sugars were 3.4, 5.3, 12.3 and 83.8% based on dry-material, respectively. The hydrocolloid consisted of mainly uronic acid and the weight ratio was approximately 90% of total sugars. When the molecular weight distribution was checked by size-exclusion chromatography, the hydrocolloid showed a wide uronic acid peak with a molecular weight of 940 kDa. The viscoelastic properties of the hydrocolloid were examined by low-amplitude oscillatory measurements and the hydrocolloid exhibited gel-like character at the concentration higher than 0.5% (w/w). Viscosity of the hydrocolloid surpassed other food hydrocolloids such as guar gum and locust bean gum at the same condition (0.25∼1.0% [w/w], 25 °C). When the hydrocolloid was heated over 60 °C (∼100 °C), an irreversible increase in viscosity was observed, suggesting the conformational change of the polysaccharide molecule.