Study of emulsions stabilized with Phaseolus vulgaris or Phaseolus coccineus with the addition of Arabic gum, locust bean gum and xanthan gum

The properties of o/w emulsions stabilized with 1%w/v common bean (Phaseolus vulgaris L.), V or scarlet runner bean (P. coccineus L.), Coc extracted by isoelectric precipitation or ultrafiltration, at pH 7.0 and 5.5, with the addition of Arabic gum, locust bean gum, xanthan gum and a mixture of xanthan gum–locust bean gum (0.1 %w/v and 0.25 %w/v) are studied. The stability of emulsions was evaluated on the basis of oil droplet size, creaming, viscosity and protein adsorption measurements. The addition of Arabic gum, caused an increase in D[4,3] values and a decrease in the amount of protein adsorbed at the interface. The addition of locust bean gum in some emulsions reduced the amount of protein adsorbed. The addition of xanthan and to a less extend of the polysaccharide mixture, promoted a decrease in D[4,3]. So, emulsion stability was affected by the polysaccharide nature. Differences were also observed with respect to the protein nature, the method of its preparation and emulsion's pH. All polysaccharides enhanced the emulsions viscosity with xanthan and xanthan–locust bean gum exhibiting the higher values. V isolates and isoelectricaly precipitated isolates of both V, Coc showed higher viscosity values. The stability was enhanced by the increase of the viscosity of the continuous phase and the creation of a network, which prevents the oil droplets from coalescence.     

稳定剂对软冰淇淋品质的影响

对软冰淇淋浆料的粘度及软冰淇淋的硬度、膨胀率、抗融性等指标进行测试来观察黄原胶、刺槐豆胶和卡拉胶对软冰淇淋品质的影响.结果表明：在没有乳化剂存在的前提下,刺槐豆胶的抗融性最好,卡拉胶次之,黄原胶较差,但刺槐豆胶对软冰淇淋膨胀率的影响不稳定,当添加量为0.2%～0.4%时能显著提高软冰淇淋的膨胀率,其他用量时膨胀率则反而降低,黄原胶可提高产品的膨胀率,卡拉胶则降低膨胀率;在粘度方面,三者均有增稠作用,作用大小依次为黄原胶、刺槐豆胶和卡拉胶;三者均有降低产品硬度的趋势,刺槐豆胶的降低程度大于卡拉胶和黄原胶.     

黄原胶对大豆蛋白营养棒体系质地及微观结构的影响

通过质构仪、激光共聚焦显微镜、电子扫描显微镜和低场核磁共振技术等手段,研究了添加1%黄原胶对含有大豆蛋白的营养棒模型体系质构、微观结构、水分子及亲水小分子的迁移等的影响。结果表明:黄原胶的添加改变了体系微观网状结构,同时影响了体系内水及糖醇等小分子的分布,从而对大豆蛋白模型体系的质构有明显的软化效果,改善其质构和口感。     

Rheological and structural characterization of gels from whey protein hydrolysates/locust bean gum mixed systems

The gelling ability of whey proteins can be changed by limited hydrolysis and by the addition of other components such as polysaccharides. In this work the effect of the concentration of locust bean gum (LBG) on the heat-set gelation of aqueous whey protein hydrolysates (10% w/w) from pepsin and trypsin was assessed at pH 7.0. Whey protein concentrate (WPC) mild hydrolysis (up to 2.5% in the case of pepsin and 1.0% in the case of trypsin) ameliorates the gelling ability. The WPC synergism with LBG is affected by the protein hydrolysis. For a WPC concentration of 10% (w/w), no maximum value was found in the G′ dependence on LBG content in the case of the hydrolysates, unlike the intact WPC. However, for higher protein concentrations, the behaviour of gels from whey proteins or whey protein hydrolysates towards the presence of LBG becomes very similar. In this case, a small amount of LBG in the presence of salt leads to a big enhancement in the gel strength. Further increases in the LBG concentration led to a decrease in the gel strength.     

Stability of whipped dairy creams containing locust bean gum/λ-carrageenan mixtures during freezing–thawing processes

The role of locust bean gum (LBG)-λ-carrageenan mixtures on the stability of whipped dairy creams in freezing-thawing processes was analysed as a function of the gum concentration (between 0 and 0.1% w/w). DSC analysis of ice crystallisation in the cream aqueous phase was carried out in order to know the influence of the hydrocolloid ratio on freezable water content. From this analysis, a potential cryostabiliser effect of whey proteins could be deduced since they provoked an increase in the T_m′ value. Changes in overrun, viscoelastic behaviour (creep compliance parameters) and stiffness (extrusion test) due to freezing–thawing and frozen storage (1 month at −18 °C) of the whipped cream were analysed in samples. Freezing provoked collapse of the foam structure, but samples containing λ-carrageenan at concentration greater than 0.085% showed a well preserved firmness, as deduced from the small changes observed in their viscoelastic parameters. The λ-carrageenan cryoprotection mechanism is not based on the freezable water content reduction since this value was similar for all gum mixtures.     

Rheology and breadmaking performance of rice-buckwheat batters supplemented with hydrocolloids

The aim of this work was to investigate the effects of hydrocolloid addition on rheological properties and breadmaking performance of rice-buckwheat batter at different water levels. Xanthan gum (XG) and propylene glycol alginate (PGA) were added to rice-buckwheat blend (60:40) at levels of 0.5–1.5%. Batter rheological properties were investigated using dynamic measurements in the linear viscoelastic range (frequency sweep and time cure tests). The addition of both hydrocolloids significantly enhanced the storage modulus (G′) of batter. XG exerted greater effect on G′ than PGA. Different effects on starch gelatinisation were observed for the two hydrocolloids. PGA breads showed higher improvement in terms of increased specific volume (V_s), decreased crumb firmness and crumb structure than XG breads. Different technological behaviours were explained on the basis of batter rheological properties.     

Rheological behaviour of pullulanase-treated guar galactomannan on co-gelation with xanthan

The present study involves the use of non-specific enzyme pullulanase (from Bacillus acidopullulyticus) to remove galactose residues from guar galactomannan to obtain modified guar galactomannan mimicking the functional properties of locust bean gum. The modified guar galactomannan blended with xanthan exhibited the rheological behaviour of elastic modulus (G′) greater than viscous modulus (G″) with a decrease in tan δ value similar to locust bean gum/xanthan blend. Also a twofold increase in the magnitude of elasticity compared to xanthan alone suggested the synergistic interaction with formation of three dimensional networks. The modified guar galactomannan with galactose content of 21% and M:G ratio 1:3.8, almost akin to locust bean gum, showed a better interaction with xanthan. Dynamic stress sweep study of modified guar galactomannan/xanthan blend with increased yield stress of 800 dynes/cm² also indicated the synergistic behaviour. Modified guar galactomannan also revealed the maximum synergistic interaction with xanthan at a mixing temperature of 60 °C than at 20 °C, 30 °C, 40 °C and 50 °C, respectively. Modification of guar galactomannan by pullulanase is an alternative route to produce galactose-depleted guar galactomannan with enhanced rheological functionalities on co-gelation with xanthan, as a cost effective replacement to locust bean gum.     

Microstructure and color of starch–gum films: Effect of gum deacetylation and additives. Part 2

Xanthan gum deacetylation, additives (sucrose, soybean oil, sodium phosphate and propylene glycol) and pH modifications influence on cassava starch-based films microstructure and color has been studied. X-ray diffraction and microscopic analysis have demonstrated that sucrose addition influenced (p<0.05) the film crystallinity during 60 days storage (75% RH, 23 °C). Although not enough to prevent sucrose crystallization, deacetylated xanthan gum addition delayed the crystallization process. Comparing to the control, only cassava starch concentration and the additives sucrose and sodium phosphate affected samples total color difference (ΔE). However, all samples presented high lightness and low color values for ‘a’ redness and ‘b’ yellowness, indicating that, independent of the additives or pH modifications, the materials were almost colorless, with a high brilliancy.     

Effect of pH on the properties of soy protein–pectin complexes

The interactions of a commercial soy protein isolate (SPI) and a 2:1 SPI:high methoxy pectin (PEC) complex were evaluated over a range of pH values (3-7). The SPI formed very large (> 50 ??m) and largely insoluble aggregates (< 10%) close to its isoelectric point (IEP, pH 4 and 5) and smaller, more soluble (> 80%) particles at higher and lower pH values. The addition of PEC increased the solubility of SPI close to its IEP (pH 4 and 5) and prevented the formation of very large aggregates. However, PEC reduced the solubility of SPI at higher and lower pH values presumably via a depletion mechanism. The ??-potential of diluted SPI dispersions decreased from positive to negative with increasing pH, passing through zero at pH 4.6, the isoelectric point (IEP) of the protein. At pH < 6, the addition of PEC reduced the charge of the protein suggesting the formation of a complex while at pH 6 or 7 there was no evidence of complex formation. The increased SPI solubility in the IEP in the presence of PEC is probably due to the formation of charged complex which do not aggregate while the decreased solubility of protein in the presence at high and low PEC is probably due to the formation of insoluble complexes and a depletion interaction respectively. Thermal treatment (30 min, 90 °C) enhanced the solubility of the SPI:PEC complexes close to the IEP (pH 4 and 5), but reduces it at low pH (pH 3). The SPI:PEC complexes could be manufactured in the form of a beverage at pilot scale where their solubility was enhanced by homogenization.     

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.     

Strand-like phase separation in mixtures of xanthan gum with anionic polyelectrolytes

Binary aqueous mixtures of xanthan gum with anionic polyelectrolytes (alginate, polyacrylate, carboxymethylcellulose, λ-carrageenan, and low methoxyl pectin) exhibited phase separation above threshold concentrations of added polyelectrolyte. Dynamic oscillatory rheology showed that separation was associated with a large decrease in storage modulus, and when viewed under plane-polarised light, the dispersed phase exhibited a birefringent, strand-like morphology indicative of a liquid crystalline phase. At constant xanthan concentration, the strand thickness was inversely related to the viscosity of the added polyelectrolyte solution. Phase diagrams obtained for xanthan:alginate, and xanthan:carboxymethylcellulose mixtures showed that whilst the strands contained both xanthan and polyelectrolyte, the continuous phase was xanthan-free. Mixtures of xanthan gum with neutral polysaccharides (maltodextrin, methylcellulose) did not show phase separation, and separation was not observed when xanthan was replaced by scleroglucan a neutral polysaccharide which, like xanthan, adopts a stiff, helical structure in solution. The alginate concentration required to initiate phase separation was inversely related to alginate molecular weight, and was independent of the alginate mannuronate/guluronate ratio. Higher concentrations of alginate were required to elicit phase separation when the salt content of the mixture was increased. The results suggest that segregative phase separation, driven by repulsive interactions between polyelectrolytes, promotes the formation of liquid crystalline structures in the xanthan-rich domain. The consequence is that the decreased viscosity reported when xanthan solutions undergo liquid crystal formation, occurs at much lower xanthan concentrations, when in the presence of an anionic polyelectrolyte.     

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 effects of the combined use of stabilizers containing locust bean gum and of the storage time on Kahramanmaraş-type ice creams

This study was aimed primarily at determining the suitability of locust bean gum and various stabilizers in the production of Kahramanmaraş-type ice creams, the physical, chemical and sensory properties of the ice creams produced, and the stabilizer combination that could produce the best quality ice cream. With a total amount of stabilizer of 1.0%, ice creams of four different combinations containing locust bean gum, carboxymethyl cellulose, guar gum and sodium alginate were produced and their properties during a 6-month storage period compared with the control sample produced using only salep extract ( Orchis orchida ).
  The ice cream produced using only the salep extract had significantly higher ( P  < 0.05) levels of titratable acidity, lower pH and viscosity values, and were harder and less resistant to melting compared to those produced with the stabilizer combinations. The stabilizer mixtures containing locust bean gum yielded better results than those with the salep extract. An analysis of the effect of storage time on the properties of the ice creams indicated that, of the physical properties examined, only the decrease in the penetrometer values was significant ( P  < 0.05). Apart from the difference observed in the third month during the storage of the ice creams produced with the salep extract, the differences during the storage time were not found to be significant ( P  > 0.05).     

Acid gelation of native and heat‐denatured soy proteins and locust bean gum

The effects of protein concentration and locust bean gum (LBG) addition on the mechanical properties, microstructure and water holding capacity of acidified soy protein (SPI) gels were studied. The protein was employed in two different states: (i) native and (ii) heat denatured. A slow acidification rate was induced in both systems by applying glucono‐δ‐lactone (GDL). The results indicated that the gels of native SPI were weaker, less deformable and showed lower water holding capacity than the gels of heat‐denatured SPI. The LBG addition led to an increase in the strength and water holding capacity of SPI gels, independent of the protein state (native or denatured). These results indicated that the properties of texture and water holding capacity of the SPI acid gels can be modulated by the process conditions or by the addition of other ingredients, such as polysaccharides.     

Characterization of gelation time and texture of gelatin and gelatin–polysaccharide mixed gels

The effects of cooling rate, holding temperature, pH and polysaccharide concentration on gelation characteristics of gelatin and gelatin–polysaccharide mixtures were investigated using a mechanical rheometer which monitored the evolution of G′ and G″. At low holding temperatures of 0 and 4 °C, elastic gelatin gels were formed whereas a higher holding temperature of 10 °C produced less elastic gels. At slow cooling rates of 1 and 2 °C/min, gelling was observed during the cooling phase in which the temperature was decreased from room temperature to the holding temperature. On the other hand, at higher cooling rates of 4 and 8 °C/min, no gelation was observed during the cooling phase. Good gelling behavior similar to that of commercial Strawberry Jell-O^® Gelatin Dessert was observed for mixtures of 1.5 and 15 g sucrose in 100 ml 0.01 M citrate buffer containing 0.0029–0.0066 g low-acyl gellan. Also, these mixed gels were stronger than Strawberry Jell-O^® Gelatin Desserts as evidenced by higher G′ and gel strength values. At a very low gellan content of 0.0029 g, increasing pH from 4.2 to 4.4 led to a decrease in the temperature at the onset of gelation, G′ at the end of cooling, holding and melting as well as an increase in gel strength. The gelation time was found to decrease to about 40 min for gelatin/sucrose dispersions in the presence of 0.0029 g gellan at pH 4.2 whereas the corresponding time at pH 4.4 was higher (79 min). In general, the gelation time of gelatin/sucrose dispersions decreased by a factor of 2 to 3 in the presence of low-acyl gellan. The addition of low-acyl gellan resulted in an increase in the gelation rate constant from 157.4 to 291 Pa. There was an optimum low-acyl gellan content for minimum gelation time, this optimum being pH dependent. Addition of guar gum also led to a decrease in gelation time to 73 min with a corresponding increase in the gelation rate constant to 211 Pa/min though these values were not sensitive to guar gum content in the range of 0.008–0.05 g. The melting temperature of gelatin/sucrose/gellan as well as gelatin/sucrose/guar mixtures did not differ significantly from that of pure gelatin or Strawberry Jell-O^® Gelatin Desserts. At pH 4.2, the melting rate constant was highest at a low-acyl gellan content of 0.0029 g whereas the rate constant was insensitive to low-acyl gellan content at pH 4.4. Addition of guar did not seem to affect the melting temperature or the melting rate constant.     

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.     

Chemical and sensory characteristics of low molecular weight fractions obtained from three types of Japanese soy sauce (shoyu) – Koikuchi, tamari and shiro shoyu

Three typical forms of Japanese soy sauce (shoyu), koikuchi, tamari and shiro shoyu, can be differentiated, primarily due to their different compositions of soybeans and wheat used for their productions. To evaluate and compare the chemical characteristics of the low molecular weight (MW) fractions of three types of shoyu with their sensory data, gel filtration fractions of ultrafiltration products with MW less than 500 Da (F-500) were subjected to chemical and sensory analyses. The results showed that salty and umami tastes were characteristic of all F-500 fractions, however, the umami taste intensities of those of koikuchi and tamari shoyu were found to be twice as large as that of shiro shoyu. After separation by gel filtration, it was found that the tastiest fractions of the three types of shoyu were those containing sodium salt, free l-glutamic acid and most other free amino acids, especially sweet taste-eliciting amino acids, at concentrations above their thresholds. In some umami fractions of koikuchi and shiro shoyu, that predominantly contained salt and phenylalanine but had a relatively low free l-glutamic acid content, a potential synergistic effect among free l-glutamic acid, salt and phenylalanine was obvious. This first report offers new insights into soy sauce research.