Purification and partial physicochemical characteristics of protein free fenugreek gums

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

Microstructure and rheology of β-lactoglobulin–galactomannan aqueous mixtures

The effect of the addition of a galactomannan (locust bean gum, LBG, or tara gum, TG) on the microstructure and rheological properties of a globular protein (β-lactoglobulin, β-Lg) solution was studied at pH 7.0, when the protein bears a net negative charge. Confocal laser scanning microscopy was used to explore the microstructure. Steady shear and dynamic oscillatory measurements were performed with a controlled stress rheometer AR2000 (TA Instruments) fitted with a cone-and-plate geometry. Mixtures were prepared with 6.5 wt% β-lactoglobulin concentration and 0.31–0.82 wt% LBG or 0.23–0.71 wt% TG concentration. All mixed systems were two-phase. The microstructure was clearly dependent on the concentration of the galactomannan in the mixture: the systems evolved from a continuous matrix of β-lactoglobulin enriched phase containing some small inclusions of the galactomannan, to a matrix of galactomannan-enriched continuous phase containing aggregates of β-lactoglobulin. Modifications of the flow and viscoelastic properties with respect to the individual components were clearly evidenced for the mixed systems. Phase inversion detected by microscopy could also be detected by rheology as a modification in the flow/viscoelastic behaviour.     

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.     

Viscosity of galactomannans during high temperature processing: influence of degradation and solubilisation

The rheological properties of guar gum (GG) and locust bean gum (LBG), in response to high temperature treatments, were measured using a rheometer equipped with a high pressure cell. This has allowed the viscosity to be assessed at temperatures above 100°C and as the polymer suspension is heated from 20 to 121°C and then cooled back to ambient temperature to simulate a food sterilisation cycle. Activation energies for depolymerisation estimated from viscosity changes with time at a series of constant temperatures were estimated as 63 kJ/mol for GG and 98, 104, 110 kJ/mol for three different samples of LBG. A model was developed to interpret the viscosity change through the simulated sterilisation cycle. This took into account the degradation of the polysaccharide and the change in viscosity due to thermal motion. Estimations of molecular weight changes during the heating process suggest that GG is more susceptible to thermal degradation than LBG. It is suggested that this is due to the greater ability of the latter to associate in solution.     

衍生化气相色谱法测定亚麻胶的单糖组成

目的采用衍生化气相色谱法(GC)测定亚麻胶的单糖组成。方法从亚麻粕中提取纯化得亚麻胶,经酸水解、衍生化后,用气相色谱分析。结果亚麻胶样品中鼠李糖、阿拉伯糖、岩藻糖、木糖、甘露糖、葡萄糖和半乳糖的质量分数分别为12.13%,6.83%,4.30%,12.70%,3.75%,10.15%,15.30%。结论亚麻胶主要由鼠李糖、阿拉伯糖、岩藻糖、木糖、甘露糖、葡萄糖和半乳糖7种单糖组成,以半乳糖含量最高。     

Linear viscoelasticity of carob protein isolate/locust bean gum blends

Linear viscoelastic properties of locust bean gum (LBG), carob protein isolate (CPI) and LBG–CPI aqueous dispersions were studied at different concentration and pH values. LBG and CPI dispersions show marked different linear viscoelasticity behaviour. The former system exhibits a fluid-like behaviour for all the concentrations considered (2–4 wt.%), whereas the later shows gel-like mechanical spectra. An increase in linear viscoelastic functions, G′ and G″, takes place as protein concentration becomes higher, as a consequence of a strengthening of the gel network. CPI dispersions were affected by the pH value, in agreement with the CPI solubility profile. The behaviour observed for CPI–LBG dispersions shows an apparent evolution with time, suggesting occurrence of thermodynamic incompatibility between both biopolymers that finally leads to a segregative separation of LBG-rich and CPI-rich phases. Both microstructure and viscoelastic properties of the final LBG–CPI systems are highly dependent on pH value.     

胡芦巴胶的降血糖疗效

为研究胡芦巴胶对体内血糖水平的影响,进行了动物疗程实验,对于患阿脲糖尿病鼠,每天每千克体重分别添加０．１８,０．９和４．５ｇ的补充胡芦巴胶膳食;而对于正常鼠,添加量为每天每千克体重４．５ｇ,实验期为３２ｄ．对于这两类鼠,胡芦巴胶有显著的降血糖功效（Ｐ＜０．０５和Ｐ＜０．０１）,尤其对于病鼠,０．９ｇ／（ｋｇ·ｄ）和４．５ｇ／（ｋｇ·ｄ）的剂量,降血糖作用显著,并且降血糖效果取决于剂量的大小。     

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。     

Rheological properties of gluten-free bread formulations

In this study, the rheological properties of rice bread dough containing different gums with or without emulsifiers were determined. In addition, the quality of rice breads (volume, firmness and sensory analysis) was evaluated. Different gums (xanthan gum, guar gum, locust bean gum (LBG), hydroxyl propyl methyl cellulose (HPMC), pectin, xanthan–guar, and xanthan–LBG blend) and emulsifiers (Purawave^™ and DATEM) were used to find the best formulation for gluten-free breads. Rice dough and wheat dough containing no gum and emulsifier were used as control formulations. The rice dough containing different gums with or without emulsifiers at 25 °C showed shear-thinning behavior with a flow behavior index (n) ranging from 0.33–0.68 (except pectin containing samples) and consistency index (K) ranging from 2.75–61.7 Pa sⁿ. The highest elastic (G′) and loss (G″) module were obtained for rice dough samples containing xanthan gum, xanthan–guar and xanthan–LBG blend with DATEM. When Purawave^™ was used as an emulsifier, dough samples had relatively smaller consistency index and viscoelastic moduli values compared to DATEM. The viscoelastic parameters of rice dough were found to be related to bread firmness. Addition of DATEM improved bread quality in terms of specific volume and sensory values.     

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.     

Influence of type,concentration and flow behaviour of hydrocolloid solutions on aroma perception

The effects of the addition of two hydrocolloids—locust bean (LBG) and xanthan gums—at two concentrations (0.2 and 0.5%, w/v) on the intensity of the aroma of limonene and of isopentyl acetate solutions was studied using the pairwise ranking test. Previously, the rheological behaviour of the studied gums was analysed, finding that while LBG solutions were slightly pseudoplastic at the lower concentration and more so at the higher one, the xanthan solutions were clearly pseudoplastic at both concentrations. Addition of 0.2% LBG did not alter the limonene aroma intensity perceived, but on adding 0.5% LBG, above the coil overlap concentration (c*), the decrease in aroma intensity was significant. Addition of xanthan gum at any concentration did not modify the limonene aroma intensity perceived by judges, which can be attributed to the low value of c* for solutions of this gum. No difference in isopentyl acetate aroma was found among samples.     

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

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

The chemical composition and some physical properties of a water-soluble gum from Prosopis africana seeds

A water‐soluble gum was extracted from the endocarp capsule of the seed coat of Prosopis africana. The gum yield varied substantially with the method of dehulling. Maximum yield was obtained after boiling in 0.1 m Na₂CO₃ for 4 h. The effects of two different gum concentrations on the rheological properties of gum solutions were examined. The gum formed viscous solutions at low concentrations and exhibited stable viscosity in the pH range 6.0–8.0. Chemical analyses showed that the purified gum had a composition of 2.4% fat, 1.04% protein, 21.5% crude fibre and a gelation concentration of at least 10%. Galactose and mannose were the major polysaccharides identified. Large reductions in viscosity were observed with the addition of various concentrations of Na⁺ salts. The activation energies of flow for 2 and 3% gum solutions were in the range of 19.2–22.8 kJ mol^?1 and were characteristic of systems with little intra‐ and intermolecular interactions.     

魔芋胶的复配研究

本文研究了与魔芋胶复配的单体胶的种类及最佳配比区域。研究发现 :卡拉胶和刺槐豆胶与魔芋胶复配效果最好 ;通过通用旋转组合设计实验 ,建立了凝胶强度、脱液收缩率与三种胶配比之间的动态模型 ,通过计算机分析得出了三种胶的最佳配比区域。复配后的魔芋胶的凝胶特性优于卡拉胶。     

Isolation and chemical evaluation of carob (Ceratonia siliqua L.) seed germ

The present investigation was undertaken in order to study the influence of the dehusking procedure on the germ meal composition of carob (Ceratonia siliqua L.) seeds and also to investigate its detailed composition and nutritive value. Meals of carob seed germ were obtained by acid treatment or boiling water treatment of the whole seeds. These procedures allowed to separation of the tight-fitting brown coat of the seed and the removal of the endosperm. Results indicated that the carob germ meal composition could be affected by the isolation procedures. Small reductions were observed in protein and lipid contents in germ meals from acid extraction. The analysis of the carob germ meal (containing fine fragments of husk and endosperm), which could be really obtained industrially, showed the following composition: moisture 8.3%, ash 6.5%, lipids (neutral and polar) 6.6% containing ∼21% of polar lipids, crude proteins 54.7% and energy value 17.5 kJ/g.     

Determination of galactomannan (gum) in guar (Cyamopsis tetragonolobus) by high performance liquid chromatography

A method is described for analysis by HPLC of galactomannan (gum) in seed of guar (Cyamopsis tetragonolobus (L) Taub). The dry seed is ground in 950 ml litre^?1 ethanol, and free sugars are removed by ethanol extract; the seed residue is hydrolysed with 2 M trifluoracetic acid in a pressure cooker (1 h at ? 105 kPa). Hydrolysing the gum in situ avoids the problems common with other techniques of extracting different fractions of gum, each having different mannose: galactose ratios. The method serves as a simple measure of gum contents in guar, and up to 20 samples per day can be processed.     

Role of initial apparent viscosity and moisture content on post irradiation rheological properties of guar gum

Guar gum is a polygalactomannan used in various industries. Previous studies on radiation processing of guar gum showed a decrease in its viscosity during irradiation. Present work reports rheological properties and magnitude of depolymerization as affected by initial apparent viscosity (AV) and moisture contents of guar gum during irradiation processing. Rate of degradation was found to be dependent on the initial moisture content of guar gum during irradiation. D₅₀ values for oven dried gum was 490 Gy and it increased to 1250, 2600 and 2420 Gy in samples having 10%, 25% and 30% initial moisture respectively. EPR spectroscopy showed disappearance of anisotropic signals with increasing moisture content indicating crosslinking of polymer. FTIR spectroscopy results suggested that there were no major chemical functional group transformations during irradiation.     

Investigation of molecular weight distribution of LBG galactomannan for flours prepared from individual seeds, mixtures, and commercial samples

The molecular weight distribution has been determined for the galactomannan solubilized from three types of locust bean gum (LBG) flours: single carob seeds, mixtures, and a range of commercial products. To prepare crude endosperm flours from carob seeds with minimal galactomannan degradation, a new extraction and milling method was developed. The method consists of applying a brief thermal shock to the seeds, followed by an extended 3-day swelling period, and manual separation of endosperms; particle size reduction to a flour is accomplished on hydrated endosperms using a centrifugal mill. This method was optimized so that redissolved LBG flours produced solutions with the highest possible viscosity and the least amount of galactomannan degradation as determined by SEC. For the three samples types, the molecular weight distribution, w(M), was found to be unimodal, appearing as a sharply defined main peak (M_p≈1.1×10⁶ g/mol) with a small high molecular weight tail (up to 2.0×10⁶ g/mol) and broad low molecular weight tail (down to 0.01×10⁶ g/mol); polydispersities (M_w/M_n) were estimated to be 1.5–1.8. Variations in M_w and [η] for galactomannans extracted from individual seeds originating from the same carob tree were minimal and nearly indistinguishable from a bulk mixture (6 seeds, M_w=0.96–1.1×10⁶ g/mol, [η]=14.2–15.1 dl/g). There was a higher variability in these molecular parameters for galactomannans solubilized from commercial LBG flours, which generally exhibited lower M_w and [η], broader distributions, and reduced solubilities (M_w=0.86–1.0×10⁶ g/mol, [η]=12.4–13.6 dl/g). These side-effects were attributed to damage caused by industrial scale seed processing. The near constancy of M_p for the three sample types suggests that the average molecular size of LBG galactomannan varies only slightly due to natural or biological causes.     

Partial purification and comparison of precipitation techniques of proteolytic enzymes from trout (Salmo gairdnerii) heads

Proteolytic enzymes have been detected and partially purified from trout (Salmo gairdnerii) heads, which were preserved at −20 °C. Proteolytic enzymes, either in crude extract or in partial purified samples, were stable for 15 days with an optimum temperature of 55 °C. Proteolytic activity was very high in either alkaline or acidic pH regions. A particular ratio of cold acetone to crude extract (1.25:1) was found to be best for the partial purification of proteases, with a 99% recovery, compared with the partial purifications achieved using different cold acetone ratios or ammonium sulphate. This recovery was also confirmed via measurement of the particles (particle size analyser) contained either in crude extract or in the precipitated samples. The existence of mainly Zn–serine and possibly some Zn-acidic proteases was observed.     

Viscosity of solutions of xanthan/locust bean gum mixtures

Xanthan and locust bean gums are polysaccharides able to produce aqueous solutions with high viscosity and non‐Newtonian behaviour. When these solutions are mixed a dramatic increase on viscosity is observed, much greater than the combined viscosity of the separated polysaccharide solutions. In this work the influences of different variables on the viscosity of solutions of mixtures of xanthan/locust bean gum have been studied. Total polysaccharide concentration, xanthan and locust bean ratio on mixture and temperature at which the gum was dissolved (dissolution temperature) for both xanthan and locust bean gums have been considered. Under these different operational mixture conditions shear rate and time have also been considered to describe the rheological behaviour of the solutions studied. The high viscosity increase observed in these mixtures is due to the interaction between xanthan gum and locust bean gum molecules. This interaction takes place between the side chains of xanthan and the backbone of the locust bean gum. Both xanthan molecule conformation in solution – tertiary structure – and locust bean gum structure show great influence on the final viscosity of the solution mixtures. Xanthan conformation changes with temperature, going from ordered structures to disordered or chaotic ones. Locust bean gum composition changes with dissolution temperature, showing a dissolved galactose/mannose ratio reduction when temperature increases, ie the smooth regions – zones without galactose radicals – are predominantly dissolved. The highest viscosity was obtained for the solution mixture with a total polysaccharide concentration of 1.5 kg m⁻³ and a xanthan/locust ratio of 2:4 (w/w) and when xanthan gum and locust bean gum were dissolved at 40°C and 80°C, respectively. © 1999 Society of Chemical Industry