Molecular characteristics of tara galactomannans: Effect of degradation with hydrogen peroxide

Tara gum (M_w = 1519 × 10³ g/mol) was degraded by hydrogen peroxide in the presence/absence of ascorbic acid, and properties of the products were investigated using gel permeation chromatography, Fourier transform infrared spectroscopy, atomic force microscope, and rheometer methods. Results showed that molecular weight of tara gum decreased with increasing concentration of hydrogen peroxide. The addition of ascorbic acid could sharply increase the degradation rate and degree of tara gum by hydrogen peroxide, which is also confirmed by atomic force microscope. The degradation products kept the structure characteristics of galactomannan. However, they performed different rheological properties. At 1% (w/v) of concentration, DP1 (941 × 10³ g/mol) and DP2 (335 × 10³ g/mol) prepared by H₂O₂ exhibited non-Newtonian behavior, while DP3 (35.1 × 10³ g/mol) and DP4 (14.2 × 10³ g/mol) obtained by hydrogen peroxide plus ascorbic acid displayed Newtonian property. These results may promote the application of tara gum in diverse fields.     

Evaluation of extrusion-modified fenugreek gum

The present study was carried out to investigate the molecular mass distribution, hydration, and emulsifying properties of extrusion-modified fenugreek gum. Fenugreek gum was extruded in a twin-screw extruder with four different zone 5 barrel temperatures (105, 120, 135, and 150 °C). To minimize the reduction in molecular weight of fenugreek gum during the extrusion process, an exit die was not used. High performance size exclusion chromatography revealed that extrusion cooking slightly changed the molecular mass distribution of the gum. Hydration properties of the gum, such as water dispersibility, water solubility, water hydration viscosity, and water absorption rate, were significantly improved after extrusion cooking. The results suggested that extrusion processing of fenugreek gum could lead to some changes in the structure and functional groups, including disruption of the cell-wall structures and unfolding of the polysaccharide molecules, which could lead to the exposure of functional groups, such as hydrophilic groups, from inside, thereby improving the hydration properties. However, the extrusion process did not significantly affect the water holding capacity of the gum, nor significantly influence the emulsion capacity and stability of the gum. On the other hand, the extrusion process did noticeably remove the unpleasant flavor associated with the original fenugreek gum.     

Influence of guar gum addition on physicochemical,microbial, rheological and sensory properties of stirred yoghurt

This study investigated the effects of adding guar gum (0, 0.6 and 0.8 g/100 mL) on the physicochemical, microbial, rheological and sensory properties of stirred yoghurt. Incorporation of guar gum into the yoghurt significantly affected the pH and colour, but did not significantly influence the lactic acid bacteria counts. The magnitudes of apparent viscosity (η_a,100), consistency index (K), yield stress (σ_oc), storage modulus (G′) and loss modulus (G″) for yoghurt samples containing guar gum (0.6–0.8 g/100 mL) were significantly greater than those for the control (without guar gum), indicating that guar gum can improve the steady and dynamic shear rheological properties of yoghurt.     

香豆胶与玉米淀粉混合物流变特性的研究

为了研究不同质量分数（0%、2%、4%、6%、8%）的香豆胶对玉米淀粉糊化混合物剪切流变特性与动态黏弹性的影响,使用旋转流变仪,采用Herschel-Bulkley模型对剪切流变数据进行分析。测试结果为：香豆胶与玉米淀粉糊化混合物是假塑性流体。随着香豆胶质量分数的增加,混合物稠度系数K显著增加,下行线流体指数n显著降低,假塑性增强。动态黏弹性测定结果为：混合物贮能模量（G''）和损耗模量（G''）都随香豆胶质量分数增大而增大,损耗角正切tanδ＜1,说明香豆胶的添加增大了混合物的黏弹性。当香豆胶质量分数为8%时,混合物黏性最大,弹性最小,混合物具有更好的黏弹性。     

Covalent attachment of fenugreek gum to soy whey protein isolate through natural Maillard reaction for improved emulsion stability

Soy whey protein isolate (SWPI)–fenugreek gum (hydrolyzed and unhydrolyzed) conjugates were prepared by Maillard-type reaction in a controlled dry state condition (60 °C, 75% relative humidity for 3 days) to improve emulsification properties. Fenugreek gum was partially hydrolyzed using 0.05 M HCl at 90 °C for 10 min (HD10), 30 min (HD30) and 50 min (HD50) to examine if molecular weight had an effect on the emulsifying properties. The formation of SWPI–fenugreek gum conjugates was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Measurements of particle size distribution and average particle size have shown that conjugation of SWPI–fenugreek gum at 60 °C for 3 days was enough to produce relatively small droplet sizes in oil-in-water (o/w) emulsions. A ratio of 1:3 and 1:5 of SWPI:fenugreek gum was more effective in stabilizing emulsion compared to 1:1 ratio. Unhydrolyzed fenugreek gum conjugates exhibited better emulsifying properties compared to partially hydrolyzed fenugreek gum conjugates. The order of the conjugates in lowering the particle size of emulsions was as follows: SWPI–unhydrolzed fenugreek gum > SWPI–HD10 > SWPI–HD30 > SWPI–HD50.     

Sensory,functional characteristics and in vitro digestibility of snacks supplemented with non-traditional ingredient raw and processed fenugreek

Fenugreek seeds were germinated, soaked and roasted and were evaluated for nutritional properties. Raw and processed fenugreek seeds were used to develop snack product. Snacks were examined for the sensorial, functional, antinutritional properties and in vitro digestibility. Using sensory analysis, 5% level of substitution of raw and processed fenugreek was accepted for the development of extruded snacks. Lateral expansion was highest for snacks prepared from processed fenugreek (163.0% to 206.1%) than raw fenugreek (162.5 to 168.7%), and vice versa for bulk density. The antioxidant activity and total phenolic content were highest for snacks prepared from germinated fenugreek (7.30% to 9.87% and 1.352 to 3.561 mg GAE g⁻¹ of sample) and lowest for snacks prepared from raw fenugreek (6.68% to 7.03% and 1.29 to 2.76 mg GAE g⁻¹ of sample). Not only extrusion but also processing such as soaking, roasting and germination reduced the antinutritional content of the snack product. Both in vitro digestibilities increased with extrusion cooking. In vitro digestibility was also found to be higher in snacks prepared from processed fenugreek than raw fenugreek. Therefore, development of such functional foods using processed fenugreek would raise the consumer demand and benefit the population by increasing the health status.     

Antioxidant and free radical-scavenging activities of chickpea protein hydrolysate (CPH)

Chickpea protein hydrolysate (CPH) was fractionated by gel filtration on Sephadex G-25. The antioxidant and free radical-scavenging activities of four CPH fractions (Fra.I, Fra.II, Fra.III, and Fra.IV) were measured using reducing power, inhibition of linoleic acid autoxidation, and 1,1-diphenyl-2- pycrylhydrazyl (DPPH)/superoxide/hydroxyl radical-scavenging assay. The antioxidant activity of Fra.IV (81.13%) was closer to that of α-tocopherol (83.66%) but lower than that of BHT (99.71%) in the linoleic acid oxidation system. Amino acid analyses showed that Fra.IV with the strongest antioxidant activity also had the highest total hydrophobic amino acids content (38.94% THAA) and hydrophobicity (125.62 kcal/mol amino acid residue) compared with the other three fractions. The molecular weight distribution of Fra.IV was found to vary from 200 to 3000 Da.     

Functional properties of fenugreek (Trigonella foenum graecum) protein concentrate

Proximate composition and physicochemical properties of a protein concentrate prepared from fenugreek seed were determined. The effects of pH and/or NaCl concentration on these properties were investigated. The protein content of fenugreek was found to be 28.4%. The crude fibre content was 9.3% and crude fat was 7.1%. The minimum protein solubility was observed at pH 4.5, which was 18.5%, while maximum protein solubility was observed at pH 11, which was 91.3%.     

Effects of guar gum and arabic gum on the physicochemical,sensory and flow behaviour characteristics of frozen yoghurt

This study investigated the effect of guar gum and arabic gum on physicochemical, sensory and flow behaviour properties of frozen yoghurt. The results indicated that gums significantly affected the viscosity, overrun and melting rate of frozen yoghurt. The highest overrun value was observed in sample containing 0.5% arabic gum. Frozen yoghurt containing 0.3% guar gum had the highest viscosity. The longest first dripping time was observed in sample containing 0.5% arabic gum. Flow behaviour of samples showed that all frozen yoghurts exhibited shear thinning behaviour. Guar gum at a concentration of 0.2% and arabic gum at a concentration of 0.5% presented the best total acceptability. The results of this study revealed that the frozen yoghurt produced with arabic gum had the better overall sensory and physicochemical characteristics.     

Effect of carboxymethylcellulose and locust bean gums on some of physicochemical,mechanical, and textural properties of extruded rice

Extrusion is a composite process consisting of many different unit operations such as mixing, cooking, pasting, and molding. In this process, the raw material is forced through a tiny opening to be transformed into a product with a desired and unique shape, texture, color, and taste. In combination with different amounts and types of additives, this technique can result in functional food products for a broad range of people suffering from micronutrient deficiency. The hydrocolloid compounds are now employed to improve the texture and performance properties of many food products. Therefore, this study scrutinized the effects of carboxymethylcellulose and locust bean gums at different levels (0.5, 0.75, and 1%) alone or in combination with each other on chemical, physical, mechanical, and textural properties of extruded rice in comparison with the qualitative properties of the control rice. A completely random design was used along with three replications to analyze the test results. Then the means were compared through Duncan's multiple range test at (α = 5%). According to the results, addition of gums increased moisture, ash, total color difference, water absorption capacity, solubility, failure force, rupture energy, elasticity module, and toughness when reduced lateral expansion was compared to the control. Moreover, the addition of gums after the cooking process increased cooking loss, texture hardness, chewability, and elasticity of the specimens in comparison with the control. According to the results of pre‐ and post‐cooking tests, the specimens containing locust (0.75%) and carboxymethylcellulose (0.75%) gums were the best treatments.     

Hydrothermal modifications of tropical tuber starches – Effect of ANN on the physicochemical,rheological and gelatinization characteristics

Cassava, sweet potato and arrowroot starches were hydrothermally modified by ANN under different conditions of temperature, moisture and time duration of treatment and the properties are compared. ANN brought about changes in swelling volume, solubility, gelatinization and rheological properties. The three starches behaved differently after the treatment. All the three tuber starches showed decrease in swelling volume after ANN treatment. The solubility decreased for cassava starch, whereas it slightly increased for majority of annealed sweet potato starches and significantly increased for arrowroot starch. For cassava starch, there was a decrease in peak viscosity, but for the other two starches, it increased after ANN. Differential scanning calorimetric studies showed that ANN resulted in a narrowing of DSC patterns for all the starches. The effect of ANN on the dynamic rheological properties was found to depend up on the source of starch. The modification resulted in increased gel hardness, gumminess, adhesiveness and decreased springiness for the starch gels. Tuber starches became less susceptible to enzyme action after ANN.     

Rheological properties of a soluble self-assembled complex from starch, protein and free fatty acids

Controlled interaction among amylose, protein and free fatty acids was performed using a pasting cell installed in a rheometer resulting in the formation of a soluble high molecular weight complex. Rheological characterization of solutions of the formed complex as well as during its formation in a range of temperatures of 25-95 °C and shear conditions ranging from 2.5 to 16.7 rad/s were performed. Different fatty acids (oleic acid, linoleic, palmitic, and conjugated linoleic acids), corn starch and whey protein, in a range of protein concentrations from 3.75% to 10% were used to produce the complex. By using rheological techniques and size exclusion chromatography was found that concentration of protein, type of free fatty acid, temperature, time and shear rates, all, had a significant effect on the formation of the complex and its rheological properties. Rheological results proved that the formation of the complex starts at 75 °C but its structure set during cooling at 55 °C. Increases in the shear rates applied during the complex formation significantly reduced its viscosity. Increases in the amount of protein increased the order of the complex. Conjugated linoleic acid, a bioactive compound, was able to be incorporated in the complex but using a slower heating rate than that used for the other fatty acids.     

Rheological properties of cereal starch gels and Mesona Blumes gum mixtures

The effect of Mesona Blumes gum (MBG) was examined on steady and dynamic shear of MBG/rice starch and MBG/wheat starch gels. In addition, stress relaxation and creep tests were performed for two types of cereal starch gels. The flow curves of both MBG/starch gels exhibited pseudoplastic behavior at shear rates between 0.01 and 10 s⁻¹, and the data were fitted into the power law model (R² = 0.91–0.98). Dynamic mechanical spectrum showed that all gels were strong gels in frequency between 0.1 and 10 Hz. Stress relaxation data at different strains indicated a strain‐softening phenomenon for both gels. Data were fitted into Maxwell model (R² = 0.91–0.98). Creep curves were conducted at the shear stress 6.4 Pa within linear viscoelastic region of both MBG/starch gels. Data were fitted into Burgers model (R² = 0.91–0.98). Apparent viscosity η, storage moduli G′, equilibrium stress relaxation modulus G_e and zero apparent viscosity η₀ of MBG/rice starch gels decreased in the following order: 6/0>6/0.5>6/0.35>6/0.1 (starch/gum w/w). Whereas η, G′, G_e, and η₀ of MBG/wheat starch gels increased gradually along side the increase of MBG contents. The stress relaxation time λ of MBG/rice starch gels increased in the following order: 6/0<6/0.5<6/0.35<6/0.1 (starch/gum w/w) while λ of MBG/wheat starch gels decreased gradually with the increase of MBG level. The influence of MBG on two examined cereal starch is totally opposite.     

Extraction and physicochemical properties of low free fatty acid crude palm oil

Response surface methodology was applied to optimize the pre-treatment of oil palm (Elaeis guineensis) fruit spikelets before oil extraction. The treatment applied was drying at different times and temperatures. The dried spikelets were then subjected to mechanical processes and crude oil was extracted. A central composite design was employed to study the responses, namely percentage of free fatty acids (FFA) and oil yield, and the optimum conditions for minimum FFA and maximum oil yield were identified from their respective contour plots. It was concluded that the pre-treatment should be carried out for 12.8 h at 66.8 °C. Under the optimum conditions, the corresponding response values for FFA and oil yield were 1% and 33.6%, respectively. Some of the physicochemical properties of the extracted oil were then determined. The low free fatty acid crude palm oil exhibited good physicochemical properties and could be useful for industrial applications.     

Effects of pulsed electric fields on physicochemical properties of soybean protein isolates

Effects of pulsed electric fields (PEF) treatment (0-547 μs and 0-40 kV/cm) on physicochemical properties of soybean protein isolates (SPI) were studied. Solubility, surface free sulfhydryls (SH_F) and hydrophobicity of SPI dispersions (20 mg/ml) increased with the increment of the PEF strength and treatment time at constant pulse width 2 μs, pulse frequency 500 pulse per second (pps) and sample flow rate (1 ml/s). When the PEF strength and treatment time were above 30 kV/cm and 288 μs, solubility, surface SH_F, and hydrophobicity of SPI decreased due to denaturation and aggregation of SPI by hydrophobic interactions and disulfide bonds. Size-exclusion chromatography and laser light scattering analyses demonstrated further that stronger PEF treatment-induced dissociation, denaturation and reaggregation of SPI. Circular dichroism analysis showed that PEF treatment did not produce significant secondary structure changes of SPI. These results suggested that controlled PEF could be applied to process liquid food including soybean protein ingredient and to modify their structure and function in order to get desired products.     

Steady and Dynamic Shear Rheology of Rice Starch‐Galactomannan Mixtures

Rheological properties of rice starch‐galactomannan mixtures (5%, w/w) at different concentrations (0, 0.2, 0.4, 0.6 and 0.8%, w/w) of guar gum and locust bean gum (LBG) were investigated in steady and dynamic shear. Rice starch‐galactomannan mixtures showed high shear‐thinning flow behaviors with high Casson yield stress. Consistency index (K), apparent viscosity (η_a,100) and yield stress (σ_oc) increased with the increase in gum concentration. Over the temperature range of 20–65°C, the effect of temperature on apparent viscosity (η_a,100) was described by the Arrhenius equation. The activation energy values (E_a = 4.82–9.48 kJ/mol) of rice starch‐galactomannan mixtures (0.2–0.8% gum concentration) were much lower than that (E_a = 12.8 kJ/mol) of rice starch dispersion with no added gum. E_a values of rice starch‐LBG mixtures were lower in comparison to rice starch‐guar gum mixtures. Storage (G′) and loss (G′′) moduli of rice starch‐galactomannan mixtures increased with the increase in frequency (ω), while complex viscosity (η*) decreased. The magnitudes of G′ and G′′ increased with the increase in gum concentration. Dynamic rheological data of ln (G′, G′′) versus ln frequency (ω) of rice starch‐galactomannan mixtures have positive slopes with G′ greater than G′′ over most of the frequency range, indicating that their dynamic rheological behavior seems to be a weak gel‐like behavior.     

Relationship between structural changes and functional properties of soy protein isolates–carrageenan systems

The aim of this work was to study the change in the structural and functional properties of a native soy protein isolate (I) induced by the incorporation of carrageenan (C). Two types of samples were used: samples lyophilized from mixtures of I and C dispersions (IC ratio: 20:1 to 8:1), and samples prepared in situ with I and C powders (IC ratio: 5:1 to 1:1). In both kinds of I:C samples a new endotherm (DSC), which may be attributed to the IC-complex, and an increase in the thermal stability of 7S and 11S soy globulins was observed. In in situ samples, at a high ionic strength and C content, an increase in the temperature of this new endotherm was observed. 7S fraction was thought to be further involved in the formation of the complex; result confirmed through experiments carried out with 7S-C and 11S-C mixtures. The complex formation modified the pH-solubility profile of soy proteins. As the amount of C increased, a decrease in solubility—to a greater extent in the acidic zone—was observed. The loss of solubility was accompanied by a decrease in the surface hydrophobicity of soluble fractions. Electrostatic as well as hydrophobic interactions would be involved in the complex formation, depending on environmental conditions.Concerning the rheological behavior of such systems, the addition of C allowed the formation of gels of a greater gelation velocity and higher viscoelasticity compared to I dispersions. Results showed that lyophilized I:C mixtures can be employed as gelling agents with improved properties regarding independent ingredients. On the other hand, gelation of I dispersions of very low protein concentration can be performed through the addition of carrageenan in appropriate proportions.     

Influence of prior acid treatment on physicochemical and structural properties of acetylated sorghum starch

Influence of prior acid treatment on acetylation of starch isolated from an Indian sorghum cultivar was investigated. The starch was acid thinned (AT) using 0.1, 0.5, and 1 M HCl for 1.5 h and then acetylated (Ac) with acetic anhydride (8% w/w). The acid thinning and subsequent acetylation appeared to reduce the percentage acetylation as indicated by degree of substitution. Ac‐AT starches exhibited significantly different physicochemical, thermal, pasting, and gel textural properties from those of AT and Ac starches. Starches after dual modification showed higher solubility, lower AM content, gelatinization temperatures, retrogradation, peak viscosity, and gel hardness than native starch. Enthalpy and range of gelatinization were observed to be higher in dual modified starches than native starch. However, no significant changes in granule morphology or crystalline pattern of Ac‐AT starches were observed compared with native starch.     

香豆胶流变性的研究

研究了香豆胶的流变特性。胶中甘露糖：半乳糖大约为1：1,分子量约为3．12×105。较低浓度时剪切速率范围内剪切速率与粘度无相关性。较高浓度时香豆胶表现剪切变稀现象。由于聚合物水解,粘度随pH的降低而下降。在较高的pH范围,中性聚合物转变为聚电解质,使粘度增加。温度下降,粘度也降低。香豆胶的粘弹性较其它半乳甘露聚糖低,可能是由于较高的半乳糖含量使得内部交联降低,粘度下降。