Physicochemical characterization and functional properties of galactomannans from mesquite seeds (Prosopis spp.)

In the present study, the physicochemical and functional characteristics of galactomannans (GM) from mesquite seeds were investigated and compared with the characteristics of a commercial GM. The mesquite gum was extracted with water at room temperature, and its physicochemical parameters, thermal constants and functional properties were determined. The results showed that mesquite GM had contents of 2.56% moisture, 4.54% protein and 0.06% ash; trace levels of fat; 95.40% total carbohydrate; +63.48 optical rotation; an intrinsic viscosity of 12.36 dL/g and a molecular weight of 1.2 × 10⁶ g/mol. The sugars detected were mannose (Man) and galactose (Gal), with a Man:Gal ratio of 1.50. The curves obtained by calorimetry indicated a transition temperature (Tg), melting temperature (Tm) and heat capacity (Cp) very similar to those of the guar GM. The evaluation of the functional properties of the mesquite GM revealed a solubility of 92.10%, an emulsion capacity of 95% and an emulsion stability of 92.24%. The polysaccharide extracted from the mesquite seeds is a GM with physicochemical and functional properties similar to those reported for other legume seed gums, allowing us to conclude that mesquite GM has the potential for use in the food industry.     

Comparison of molecular and emulsifying properties of gum arabic and mesquite gum using asymmetrical flow field-flow fractionation

The molecular and emulsifying properties of gum arabic (GA) and mesquite gum (MG) were characterized using asymmetrical flow field-flow fractionation connected to multi-angle light scattering and refractive index detection. Properties such as molar mass, root-mean-square radius (r_rms), hydrodynamic radius (r_h), conformation, apparent densities and distribution of proteinaceous matter over the whole molar mass range were determined. GA displayed a low molar mass (3.4 × 10⁵ g/mol), protein-poor component (population 1) and a high molar mass (1.9 × 10⁶ g/mol), protein-rich component (population 2). MG displayed one molar mass population with an average molar mass of 1.1 × 10⁶ g/mol. For both GA and MG, the conformation (r_rms/r_h) was increasingly spherical with increasing molar mass. However, MG had higher values of r_rms/r_h for a specific molar mass suggesting differences in structure between GA and MG. The protein content increased with increasing molar mass for both gums, although to a higher extent for GA. Selective adsorption, during emulsification experiments, could be observed of population 2 of GA which may be due to a combination of the higher protein content and a more flexible structure rendering it more surface active than population 1. Comparing GA and MG in terms of emulsion stability, it could be concluded that GA-stabilized emulsions have considerably higher stability against coalescence.     

Rheological behavior of aqueous dispersions of cashew gum and gum arabic: effect of concentration and blending

Rheological properties of cashew gum (CG) and gum arabic (AR), the exudate polysaccharides from Anacardium occidentale L. and Acacia, at different solutions (0.4–50% w/v) were studied. The intrinsic viscosity, [η], of CG in water at 20°C was ≈0.1 dl g⁻¹, while that of AR was ≈0.6 dl g⁻¹. The apparent viscosity of the unheated and the heated (at 80°C for 30 min) CG and AR solutions showed a progressive increase with increasing concentration. The flow curves of blends with equal viscosity solutions of AR/CG: 25/75, 50/50 and 75/25, showed no major interaction. The apparent viscosity (η_a) vs. shear rate data for both the AR and CG dispersions (4–50% w/v) exhibited shear-thinning characteristics at low shear rates (< about 10 s⁻¹) and Newtonian plateaus at shear rates >100 s⁻¹, and the Sisko model described well the η_a vs. data of all the dispersions.     

Application and evaluation of mesquite gum and its fractions as interfacial film formers and emulsifiers of orange peel-oil

Mesquite gum was fractionated using hydrophobic interaction chromatography, yielding three fractions (F₁, F₂, F₃) whose average molecular masses ranged from 1.81 × 10⁴ to 5.23 × 10⁵ Da; F₁ had 90% polysaccharide and 1% protein contents, while F₂ and F₃ contained 16 and 46% of protein, respectively. Fractions' ability to form oil–water interfacial films and to stabilize orange peel–oil emulsions was evaluated. The highest interfacial viscosity (321 m Nm⁻¹) and highest instantaneous elastic modulus (E₀) = 0.113 × 10⁻⁴ m Nm⁻¹ were exhibited by F₂ and these values were significantly higher than those exhibited by the whole mesquite gum. F₁ did not exhibit viscoelastic properties. Emulsions made with F₂, F₃, and the whole mesquite gum had coalescence rates of the order of 10⁻⁸ s⁻¹, indicating that these emulsions were very stable. Nevertheless, emulsions made with F₂ were significantly more stable than those made with F₃ and whole mesquite gum, and emulsions made with F₁ broke after 1 day aging. These results indicate that there is a close correlation between emulsion stability, interfacial rheological properties, and an adequate relatively high protein/high polysaccharide balance in the fractions.     

Identification of 5,6-dihydro-6-propyl-2H-pyran-2-one as the major volatile constituent in mesquite (Prosopis) flour

Mesquite (Prosopisspp.) are woody leguminous plants that belong to the family Leguminosae and grow in arid and semiarid regions of America, Africa and Asia. Prosopis spp. produce indehiscent fruit (pods) that can be milled to yield flour that is sold commercially and is used in pastries and baked goods. The major volatile constituent of mesquite flour was identified as 5,6-dihydro-6-propyl-2H-pyran-2-one on the basis of its Kovats index and mass spectrum. Using δ-nonalactone as an internal standard its concentration was determined to be 59.75 ± 7.07 mg/kg (n = 3).     

A further amendment to the classical core structure of gum arabic (Acacia senegal)

Using the more recently available techniques such as methylation–GC–MS, 1D (¹H, ¹³C) and 2D (COSY, TOCSY, HMQC and HMBC) NMR spectral analysis, we have revisited the classical structure of gum arabic (Acacia senegal). Methylation and GC–MS analysis confirmed that gum arabic (A. senegal) is a highly branched polysaccharide with the backbone composed of 1,3-linked galactopyransyl (Galp) residues substituted at O-2, O-6 or O-4 positions. The terminal sugar residues are 59.5% of the total sugars. The residues of →2,3,6-β-d-Galp1→, →3,4-Galp1→, →3,4,6-Galp1→ and substitutions at O-2 and O-4 position were not identified in previous studies.     

Influence of CaCl2 on the water vapor permeability and the surface morphology of mesquite gum based edible films

Oil-in-water (O/W) emulsions with a dispersed phase mass fraction (φ_m) of 0.175 were prepared by dispersing a blend of candelilla wax/mineral oil (2:1 ratio) in 10 g of mesquite gum per 100 g of water containing either CaCl₂ (0.0, 0.1, 0.2, 0.3, 0.4 or 0.5 g) alone or combined with 1.5 g of glycerol. The mean volumetric droplet size (d_3,0), the rate of droplet coalescence (C) and the viscosity-shear rate behavior of the emulsions were affected by the addition of CaCl₂ alone or combined with glycerol. The Carreau-Yasuda model fitted best the viscosity-shear rate data of all the emulsions. The surface morphology of the edible films, analyzed by Atomic Force Microscopy (AFM), exhibited a strong dependence on the CaCl₂ concentration. Maximum roughness occurred with a CaCl₂ concentration of 0.3 g per 100 g. Films with glycerol showed significantly higher roughness than those with only CaCl₂. Water vapor permeability (WVP) was significantly lowered as the concentration of CaCl₂ increased from 0.1 to 0.3 g per 100 g in the coatings, but increased again at CaCl₂ concentrations of 0.4-0.5 g per 100 g. Coatings containing glycerol displayed significant higher WVP.     

New studies on gum ghatti (Anogeissus latifolia) part I. Fractionation,chemical and physical characterization of the gum

This paper describes the fractionation, chemical and physical characterization of processed gum Ghatti (Gatifolia SD), and identifies the source of its surface activity. Four fractions were separated using the gradual ethanol precipitation method. With the increase of alcohol concentration, the chemical composition of the fractions exhibited a pattern: arabinose content increased, but the galactose, protein and uronic acid contents decreased in the order of: F50 (50% ethanol precipitate), F65 (65% ethanol precipitate), F80 (80% ethanol precipitate) and FS (the supernatant after 80% ethanol precipitation). Rheologically gum ghatti and its fractions exhibited Newtonian flow behavior until gum concentrations reached to 20% (w/v), at which point gum ghatti showed some shear thinning. At the same shear rate and concentration, the apparent viscosities of these fractions decreased in the order: F50 > F65 > F80 > FS. When compared at same concentration, the FS fraction had the highest surface activity relative to the Gatifolia SD, the other fractions and even gum Arabic. Monosaccharide composition and preliminary structural analysis showed that the branching of the polymer increased in the order of F50, F65 and F80. The degree of branching levels, protein and uronic acid content could be responsible for the different solubility of the fractions in alcohol. However, the molecular structure of FS is significantly different from the other fractions. FT-IR spectroscopy revealed no esterified carboxyl group in gum ghatti. Detailed structural elucidation of each fraction will follow.     

Supercritical fluid extraction and microencapsulation of bioactive compounds from red pepper (Capsicum annum L.) by-products

The objective of this work was to obtain and stabilize natural vitamins from red pepper by-products. The method of obtainment was supercritical carbon dioxide extraction, studying different parameters that affect the yield. The highest extraction yield was found at 60 °C, 24 MPa extraction, with no modifier added and 0.2–0.5 mm particle size. The recovered extract was a red-coloured oil. The extract was subsequently microencapsulated by spray-drying using gum arabic as wall material to avoid the degradation of vitamin over the storage time. The thermal stability of microcapsules was analysed by thermal gravimetric analysis (TGA), while size, shape and morphology of microcapsules were studied by scanning electron microscopy (SEM). The microcapsules containing pepper extract were particles of spherical shape with dents on the surface, the average size of these particles was 5.46 μm.     

Fractionation and physicochemical characterization of peach gum polysaccharides

One kind of Chinese peach gum was fractionated by different solvent extraction (water followed by alkaline solutions). Chemical analysis showed peach gum polysaccharides were acidic arabinogalactans, mainly composed of arabinose (∼50%), galactose (∼37%) and uronic acid (13–14%), with the molecular weight of ∼4.60 × 10⁶ g/mol according to high performance size exclusion chromatography (HPSEC) analysis. Peach gum solution exhibited typical shear thinning flow behavior properties, K (consistency index) values increased while n (flow index) values decreased with the increasing of concentration. Dynamic sweep tests showed that moduli of peach gum solutions were highly dependent on frequency, concentration and temperature. Water extractable fraction was able to form gel network when concentration was higher than 4%. Alkaline extracted peach gum gave weaker rheological responses, such as lower viscosity at same concentration when compared to the water extractable fraction. Two alkaline extractable fractions exhibited similar intrinsic viscosities of 21.18 dl/g (0.1 M NaOH extractable, AE01) and 21.76 dl/g (0.5 M NaOH extractable, AE05), respectively, while water extractable fraction (WE) formed aggregate in water at low concentration. All fractions extracted from peach gum exudates showed better emulsion capacity and stability than gum arabic and fenugreek, which could be used in food industry to replace or partially replace gum arabic.     

Extraction and physicochemical characterisation of polysaccharide gum from Yanang (Tiliacora triandra) leaves

Yanang (Tiliacora triandra) is a vegetable used in many cuisines of the northeast of Thailand and Lao People’s Democratic Republic. This paper reports the optimised extraction and some physicochemical characteristics of polysaccharide gum from Yanang leaves. The optimised extraction condition was at the leaf:water ratio of 1:6.6, 85 °C, and 100 min extraction time. The major monosaccharide constituent of Yanang gum was xylose, together with substantial amounts of other neutral sugars. The FT-IR spectra of Yanang gum were similar to that of xylan. Yanang gum exhibited shear-thinning flow behaviour and the extent of shear-thinning was concentration dependent. The mechanical spectra of Yanang gum at low concentration (0.5%) were typical of semi-diluted to concentrated solutions. However, with increasing concentration, the solution behaved like a weak gel.     

Effect of high-hydrostatic pressure and pH on the rheological properties of gum arabic

The effect on the viscoelastic behaviour, of pressure-treating hydrated gum arabic samples (800 MPa) at different pH values (2.8, 4.2 and 8.0) was investigated, using controlled stress rheometry. The treated samples were analysed for their complex (G∗), storage (G′) and loss (G″) moduli as a function of frequency, using dynamic oscillatory testing. Significant changes in the rheological properties were observed in both the pressurised gum solutions and in those previously buffered at pH 2.8. The gum, at its natural pH (4.25) and at alkaline pH (8.0), was enhanced by pressure treatment, but only for the already “good” quality gum samples. High-pressure treatment had substantial effects on the frequency-dependence of the moduli of both the pressurised and the pressurised/pH-treated solutions, with the latter being more pronounced, suggesting differing structures or changes in the overall degree of interaction of the gum systems after pressure treatment.     

Characterisation of interactions between fish gelatin and gum arabic in aqueous solutions

The interactions between fish gelatin (FG) and gum arabic (GA) in aqueous solutions were investigated by turbidimetry, methylene blue spectrophotometry, zeta potentiometry, dynamic light scattering, protein assay, and state diagram at 40 °C and a total biopolymer concentration (C(T)) of 0.05%. FG underwent complex coacervation with GA, possibly via its conformational change, depending on pH and FG to GA ratio (FG:GA). The formation of FG-GA complexes was the most intense when pH 3.55 and FG:GA=50:50 (6.6:1 M ratio), however, the coacervate phase was found to be composed of a much higher FG fraction. The pH range of complex formation shifted to a higher pH region with increasing FG:GA. Soluble and insoluble FG-GA complexes were formed even in a pH region where both biopolymers were net-negatively charged. Varying C(T) significantly influenced not only the formation of FG-GA complexes but also the development and composition of coacervate phase.     

Moisture barrier properties and morphology of mesquite gum–candelilla wax based edible emulsion coatings

Composite edible coatings were formulated with candelilla wax alone, and candelilla wax blended with beeswax, white mineral oil and oleic acid (2:1 ratios) as the lipid phase, and mesquite gum as the structural material and their corrected water vapor permeability (WVPc) were determined. The coatings were applied to Persian limes and their effect upon physiological weight loss, color and chemical composition changes were evaluated. Addition of the blend of candelilla wax–mineral oil improved the WVPc (P<0.05) of the candelilla wax–mesquite gum coating formulation, and provided the lowest physiological weight loss, best dark shade green colour retention and unaltered physicochemical parameters to Persian limes, in comparison to the rest of the coating formulations tested. There was a close relationship between the performance and the microstructure of coatings. Coatings showing more uniform and less defects (fissures, fractures, pinholes) in the surface morphology were those exhibiting the lowest WVP values.     

Isolation, purification and characterization of a new gum from Acanthophyllum bracteatum roots

A new gum was isolated from the roots of Acanthophyllum bracteatum (ABG) by warm-water extraction. Purification was carried out by barium complexing to give a yield of 12.4% of pure air-dried or 5.8% of freeze-dried gum. The ABG contained 13.2% moisture, 84.3% carbohydrate, 0.9% protein and 1.5% ash. Its mineral content was comparable to commercial hydrocolloids. Monosaccharide analysis by HPLC showed the presence of galactose, glucose, arabinose, rhamnose and uronic acids in the ratio 16.0:7.2:3.0:1.0:3.1 respectively. The viscosity and pH value of 1% ABG solution at 25 °C were 51.5 mPa s and 6.85 respectively. ABG solutions (5-30 wt%) showed shear-thinning flow behavior at shear rates < 10 s⁻¹. The viscosity decreased as temperature increased, and was highest at the neutral state. ABG had low surface and emulsification properties but moderate foaming capacity and relatively high foaming stability, which suggests that ABG could potentially be used in food systems to improve foaming properties.     

NMR study of galactomannans from the seeds of mesquite tree (Prosopis juliflora (Sw) DC)

The seed gum from Prosopis juliflora is a galactomannan polysaccharide, which is located in the endosperm. Regarding P. juliflora galactomannan structural studies, there are reports on galactose substitutional pattern, but supporting data by NMR correlation studies are scarce. In this work, a procedure to obtain P. juliflora gum without contamination was employed and the gum was studied by NMR spectroscopy. Overall, results show that mesquite seed has a 1.1:1 Man/Gal ratio.     

Compositional analysis and rheological characterization of gum tragacanth exudates from six species of Iranian Astragalus

The sugar composition and viscoelastic behaviour of Iranian gum tragacanth exuded by six species of Astragalus was investigated at a concentration of 1.3% and varying ionic strength using a controlled shear-rate rheometer. Compositional analysis of the six species of gum tragacanth by high-performance anion-exchange chromatography with pulsed amperometric detection suggested the occurrence of arabinose, xylose, glucose, galactose, fucose, rhamnose and galacturonic acid residues in the gum structure; however, the proportions of each sugar varied significantly among the gums from the different species of Astragalus, and this variation led to interesting differences in functional properties. Rheological measurements performed on dispersions of the six species of gum tragacanth demonstrated viscoelastic properties. The mechanical spectra derived from strain sweep and frequency sweep measurements indicated that the different gum tragacanth dispersions had distinctive viscoelastic behaviours. Investigation of the viscoelastic properties of the different gum dispersions in the presence of NaCl revealed that the addition of NaCl could lead to slight to drastic decreases in the G′, G″ or η^∗ values of the various gums. In general, the results indicated that the six varieties of gum tragacanth studied exhibited significantly different rheological properties; therefore, these different gums may find use in a variety of applications as stabilisers, thickeners, emulsifiers and suspending agents depending on their rheological behaviour.     

Effect of gum arabic on the surface tension and surface dilational rheology of trisiloxane surfactant

The surface tension and surface dilational properties of trisiloxane surfactant silwet408, gum arabic, and their mixed solutions are reported. The dilational rheological properties are measured by means of oscillating drop method. The influences of dilational frequency, bulk concentration and aging time on dilational rheology properties have been investigated. The adsorption films of silwet408 behave elastic in nature at low bulk concentration. With increasing concentration, the dilational modulus becomes more frequency dependent and reaches a maximum value. The addition of 1 wt% gum arabic has no remarkable influence on the silwet408 films since the adsorption ability of silwet408 is much better than that of gum arabic. However, the maximum of dilational modulus and dilational elasticity are shifted toward a higher concentration, which has been correlated with the decreased molecular exchange in the presence of 1 wt% gum arabic.