Temperature-dependent complexation between sodium caseinate and gum arabic

Complex formation between sodium caseinate and gum arabic as a function of temperature was investigated using dynamic light scattering, fluorescence and NMR. At neutral pH, the turbidity and the particle size increased when sodium caseinate and gum arabic mixtures were heated in situ at temperatures above a critical temperature. The increases in turbidity and particle size were reversible. This effect was considered to be due to hydrophobic interactions, leading to the formation of a complex between sodium caseinate and gum arabic. ¹H NMR spectroscopy showed that ANS, which bound to caseinate at low temperatures in caseinate solution or a caseinate-gum arabic mixture, was released at high temperatures upon formation of a caseinate or caseinate-gum arabic complex. This supported changes observed in the fluorescence of 8-anilino-1-naphthalene sulfonate upon binding to caseinate, which decreased at high temperatures for caseinate alone or when sodium caseinate was mixed with gum arabic. Light-scattering (turbidity) and dynamic light-scattering studies show that the temperature-dependent complexation between sodium caseinate and gum arabic was sensitive to the mass ratio of protein to gum arabic (greater complexation at a 1:5 ratio than a 1:1 ratio) and the pH (maximum complexation at pH 6.5).     

Emulsifying Effects of Food Macromolecules In Presence of Ethanol

The influence on droplet size of ethanol present during homogenization was investigated for emulsions stabilized by macromolecular emulsifiers: sodium caseinate, whey protein isolate, gelatin and gum arabic. Emulsions produced with polysaccharide gum arabic had increasing droplet size as ethanol concentration increased, in contrast to the protein-stabilized emulsions which had decreasing droplet size (up to 20 % ethanol for gelatin and 30 % ethanol for the milk proteins), followed by increasing droplet size with increasing ethanol concentration. Interfacial tension measurements indicated that the emulsifying property of the macromolecules depended on adsorption at the oil-water/alcohol interface during emulsification.     

Complex coacervates obtained from lactoferrin and gum arabic: Formation and characterization

Proteins and polysaccharides are the most frequently used hydrocolloids in the food industry, and their interaction can provide products such as complexes coacervates, which can be used as ingredients and biomaterials or in microencapsulation systems. In the present work, the interaction between lactoferrin (0.1, 0.2, 0.3, 0.5 and 1% w/w) and gum arabic (0.1% w/w) with various concentrations of NaCl (0, 0.01, 0.25, 0.3 and 0.5 mol/L) and at various pH values (from 1.0 to 12.0) was studied. The pH for the formation (higher turbidity) of the insoluble complex coacervates (pH_Ø1) varied according to the amount of NaCl used in the system (pH 3.5 to 5.3); these values are below the isoelectric point of lactoferrin (8.0), at which the protein is more positively charged, generating electrostatic binding. At a pH of approximately 2.0, this bond weakens, leading to the solubilization of precipitates, resulting in a sudden decrease in the turbidity (pH_Ø2). Samples containing a lower concentration of lactoferrin (0.1, 0.2 and 0.3% w/w) showed greater turbidity and consequently a higher formation of precipitates or aggregates. Even these samples, which contained a salt concentration of 0.3 mol/L, showed higher turbidity and displacement points of pH_Ø1 and pH_Ø2. The zeta potential and particle size values were used to study the influence of the pH, ionic strength and temperature on the interaction between the biopolymers. It was observed that the formation of macromolecules occurred between the isoelectric point of the protein (8.0) and the pKa of the polysaccharide (2.0), and a certain salt concentration (0.25 mol/L) led to larger particle sizes. It was observed that, at pH 7.0, a concentration of 0.1% gum arabic was able to stabilize the denaturation of the protein in solutions containing 0.1% lactoferrin, resulting in a constant particle size at all temperatures studied.     

Effect of Aqueous Phase Composition on Stability of Sodium Caseinate/Sunflower oil Emulsions

The aim of the present work was to investigate the effect of aqueous phase composition on the stability of emulsions formulated with 10 wt% sunflower oil as fat phase. Aqueous phase was formulated with 0.5, 2, or 5 wt% sodium caseinate, or sodium caseinate with the addition of two different hydrocolloids, xanthan gum or locust bean gum, both at 0.3 or 0.5 wt% level or sodium caseinate or with addition of 20 wt% sucrose. Emulsions were processed by Ultra-Turrax and then further homogenized by ultrasound. Creaming and flocculation kinetics were quantified by analyzing the samples with a Turbiscan MA 2000. Emulsions were also analyzed for particle size distribution, microstructure, viscosity, and dynamic surface properties. The most stable systems of all selected in the present work were the 0.3 or 0.5 wt% XG or 0.5 wt% LBG/0.5 wt% NaCas coarse emulsion and the 20 wt% sucrose/5 wt% NaCas fine emulsion. Surprisingly, coarse emulsions with the lower concentration of NaCas, which had greater D _4,3, were more stable than fine emulsions when the aqueous phase contained XG or LBG. In these conditions, the overall effect was less negative bulk interactions between hydrocolloids and sodium caseinate, which led to stability. Sugar interacted in a positive way, both in bulk and at the interface sites, producing more stable systems for small-droplet high-protein-concentration emulsions. This study shows the relevance of components interactions in microstructure and stability of caseinate emulsions.     

Light stability of spray-dried bixin encapsulated with different edible polysaccharide preparations

Bixin was encapsulated by spray-drying with gum arabic or maltodextrin, and the stability was evaluated in aqueous solution both under illumination or in the dark at 21 °C. The microcapsules containing emulsifier, such as gum arabic or maltodextrin + Tween 80, showed the highest encapsulation efficiency, respectively 86% and 75%, less superficial imperfections and higher stability than bixin encapsulated with maltodextrin alone or blended with sucrose. The kinetic behavior of bixin photodegradation in all encapsulated systems was composed by two first-order decays, due to the presence of bixin outside and inside the microcapsules. Bixin encapsulated with gum arabic was 3 to 4 times more stable than that encapsulated with maltodextrin. In all systems, greater bixin stability (<two orders of magnitude) was observed in the dark than under illuminated conditions. In addition, 10 times greater bixin stability was observed for encapsulated solutions as compared to the non-encapsulated systems in the absence of light.     

Viscoelastic characterization of fluid and gel like food emulsions stabilized with hydrocolloids

Food emulsions exhibit a great diversity of rheological characteristics; hydrocolloids are usually added to deal with creaming instability. Viscoelastic measurements provide information about the microstructure of the system. The objectives of this work were: a) to determine the viscoelastic behavior of two different low in fat oil-in-water food emulsions: a gel like and a fluid type emulsions stabilized with hydrocolloids (gellan gum and xanthan-guar mixtures respectively) b) to model and predict the mechanical relaxation spectrum for both emulsions and continuous aqueous phases. Low-in-fat oil-in-water emulsions (20 g/100 g) were prepared using sunflower oil and Tween 80 (1 wt.%). Fluid emulsions containing xanthan and guar gums were formulated using a synergistic ratio 7:3, with total hydrocolloid concentration ranging between 0.5 to 2 wt%. The aqueous phases contained NaCl (2 wt.%) and acetic acid (2 wt.%). The effect of hydrocolloids was studied using oscillatory measurements (G’ and G” vs. frequency) within the linear viscoelastic range previously determined by stress-sweeps. Time-Concentration Superposition principle was applied to find the master curves that describe the mechanical spectra of the viscoelastic materials. Superposition allows to obtain a wide spectrum of nearly ten decades of frequencies in emulsions containing xanthan–guar mixtures, whereas gellan gum systems did not show a significant frequency displacement. Viscoelastic behavior of the systems was satisfactorily modeled using Baumgaertel-Schausberger-Winter (BSW) equation. This empirical model was used to predict the mechanical relaxation spectrum for both emulsions and continuous aqueous phases. Validation of the predicted spectra was carried out through creep compliance data for emulsion-filled gels and steady-state flow curves for emulsions containing xanthan–guar mixtures.     

Effect of polysaccharides with different ionic charge on the rheological,microstructural and textural properties of acid milk gels

The effects of addition of polysaccharides with different ionic charge on rheology, microstructure, texture and water holding capacity (WHC) of acid milk gels were studied and compared to that of gelatin addition. Similar to gelatin, starch (neutral) and xanthan gum (anionic) did not prevent milk gelation in the first 30 min of the acidification stage, even at high concentrations, and the typical casein network in acid milk gels could still be seen from electron micrographs; gelling and melting of these hydrocolloids were observed during the cooling and heating stages at specific concentrations. On the other hand, two neutral polysaccharides, guar gum (≥ 0.05%) and locust bean gum [LBG] (≥ 0.1%) inhibited milk gelation from the beginning of the acidification stage; the microstructure of the gel was modified greatly and no gelling/melting was observed during the cooling or heating stages. Another anionic polysaccharide, carrageenan, induced earlier milk gelation at low concentration (≤ 0.05%), but inhibited gelation entirely at high concentration (0.2%); inflections at ~ 27 °C and 21 °C were also observed during the cooling and heating stages at 0.05% concentration. The gel microstructure was not changed greatly, but showed smaller particle size at a carrageenan concentration of 0.05% than control sample. None of the polysaccharides showed as much improvement in WHC of the milk gels as gelatin did. Hence, xanthan and starch were found to be closer to gelatin in their effect on acid milk gels compared to guar gum, LBG and carrageenan.     

Small and large deformation rheology and microstructure of κ-carrageenan gels containing commercial milk protein products

The rheological behaviour of commercial milk protein/κ-carrageenan mixtures in aqueous solutions was studied at neutral pH. Four milk protein ingredients; skim milk powder, milk protein concentrate, sodium caseinate, and whey protein isolate were considered. As seen by confocal laser microscopy, mixtures of κ-carrageenan with skim milk powder, milk protein concentrate, and sodium caseinate showed phase separation, but no phase separation was observed in mixtures containing whey protein isolate. For κ-carrageenan concentrations up to 0.5 wt%, the viscosity of the mixtures at low shear rates increased markedly in the case of skim milk powder and milk protein concentrate addition, but did not change by the addition of sodium caseinate or whey protein isolate. For κ-carrageenan concentrations from 1 to 2.5 wt%, small and large deformation rheological measurements, performed on the milk protein/κ-carrageenan gels, showed that skim milk powder, milk protein concentrate or sodium caseinate markedly improved the strength of the resulting gels, but whey protein isolate had no effect on the gel stength.     

Surface dilatational properties of whey protein and hydroxypropyl-methyl-cellulose mixed systems at the air–water interface

In this work we have studied the impact of the competitive adsorption of a whey protein concentrate (WPC) and three well characterized hydroxypropyl-methyl-cellulose (HPMCs), commercially known as E4 M, E50LV and F4 M, on the surface dilatational properties (surface dilatational modulus, E, surface dilatational elasticity, E_d, and loss angle tangent, tan δ) of mixed films adsorbed at the air–water interface. The increase in E_d values with adsorption time could be associated with biopolymer adsorption at the interface. The surface dilatational properties depend on the WPC and HPMC concentrations in the aqueous phase and on the WPC/HPMC ratio. Although the values of E_d were mainly determined by HPMC at short adsorption times, for mixed systems with the lowest protein concentration (1 × 10⁻⁴ wt%) the E_d values were close to those of HPMCs, even at long term adsorption. The values of tan δ indicate the formation of adsorbed mixed films with high viscoelasticity, with a gel structure, which in turn should be attributed to the association of biopolymer molecules occurring at the interface. Only one biopolymer is the dominant one in the solid character of these mixed systems. HPMC at high concentrations slightly reduced the long-term solid character of the films confirming the existence of competition for the air–water interface as expected with two surface-active biopolymers with high molecular weight.     

Influence of different hydrocolloids on major wheat dough components (gluten and starch)

The aim of this study was to determine the effect of three hydrocolloids from different sources (arabic gum, pectin and hydroxypropylmethylcellulose) on wheat dough major components (gluten and starch) using hydrated model systems. Gluten characteristics were evaluated concerning hydration properties (swelling, water retention capacity, water binding capacity), gluten quality (gluten index, the amount of wet and dry gluten), protein sodium dodecyl sulphate extractability, and rheological properties (elastic and viscous moduli); whereas the effect of hydrocolloids on wheat starch was assessed by recording the viscometric profile. Results showed that hydrocolloids tested affected in different extent to starch and gluten properties, being their effect dependent on the hydrocolloid type and also its concentration. All the hydrocolloids, with the exception of arabic gum, decreased the viscoelastic moduli during heating and cooling, yielding a weakening effect on gluten. Pectin mainly acted on gluten properties, varying gluten hydration, and also the quantity and quality of gluten. In addition, arabic gum acted primarily on the viscometric properties of starch. Therefore, hydrocolloid effect was greatly dependent on the hydrocolloid type, which defines its interaction with other components of the system.     

The effect of viscous substances on the transit time of barley digesta in rats

The influence of a number of hydrocolloids on the transit time of digesta, stool weight and colour of stools was investigated in rats. All hydrocolloids tested gave the stools a lighter colour and increased their size and water content. The hydrocolloids could be divided into two groups according to their action on digesta passage: pectin, gum arabic, oxidised starch and barley β-glucan retarded it, while guar gum, carrageenan, tragacanth gum, carob bean gum, sodium alginate and sodium carboxymethyl cellulose accelerated it. After feeding carrageenan for 1 week it took several weeks before water content and transit time returned to normal. Gum arabic was found to cause caecal distension.     

Cross-linking proteins by laccase: Effects on the droplet size and rheology of emulsions stabilized by sodium caseinate

The aim of this work was to evaluate the influence of laccase and ferulic acid on the characteristics of oil-in-water emulsions stabilized by sodium caseinate at different pH (3, 5 and 7). Emulsions were prepared by high pressure homogenization of soybean oil with sodium caseinate solution containing varied concentrations of laccase (0, 1 and 5 mg/mL) and ferulic acid (5 and 10 mM). Laccase treatment and pH exerted a strong influence on the properties with a consequent effect on stability, structure and rheology of emulsions stabilized by Na-caseinate. At pH 7, O/W emulsions were kinetically stable due to the negative protein charge which enabled electrostatic repulsion between oil droplets resulting in an emulsion with small droplet size, low viscosity, pseudoplasticity and viscoelastic properties. The laccase treatment led to emulsions showing shear-thinning behavior as a result of a more structured system. O/W emulsions at pH 5 and 3 showed phase separation due to the proximity to protein pI, but the laccase treatment improved their stability of emulsions especially at pH 3. At pH 3, the addition of ferulic acid and laccase produced emulsions with larger droplet size but with narrower droplet size distribution, increased viscosity, pseudoplasticity and viscoelastic properties (gel-like behavior). Comparing laccase treatments, the combined addition of laccase and ferulic acid generally produced emulsions with lower stability (pH 5), larger droplet size (pH 3, 5 and 7) and higher pseudoplasticity (pH 5 and 7) than emulsion with only ferulic acid. The results suggested that the cross-linking of proteins by laccase and ferulic acid improved protein emulsifying properties by changing functional mechanisms of the protein on emulsion structure and rheology, showing that sodium caseinate can be successfully used in acid products when treated with laccase.     

Influence of pH and hydrocolloids addition on yam (Dioscorea alata) starch pastes stability

Yam tubers (Dioscorea alata) are a non-traditional starch source that could be used as food ingredient. The stability of yam starch pastes (6/100 g suspension) submitted to different pH conditions during gelatinization and the effect of hydrocolloids addition (guar and xanthan gums) on starch syneresis under refrigeration were analyzed. Changes in pH (3, 5, 6) or the addition of gums (0.1–0.5/100 g suspension) did not affect the starch gelatinization temperature nor the gelatinization enthalpy as determined by differential scanning calorimetry. Rheological behavior was characterized by amylograph profiles and oscillatory rheometry. Amylograms showed that yam starch pastes maintained a high viscosity under heat treatment and mechanical stirring in neutral to slightly acidic conditions. Brabender viscosity increased when gums were added; the effect of guar gum on viscosity was more marked than that of xanthan gum. During refrigerated storage exudate production was observed of pastes without gums. Xanthan gum, at a concentration of 0.5/100 g suspension, showed higher effectiveness than guar gum to reduce exudate production during refrigerated storage. The addition of hydrocolloids could allow yam starch to be used in foods requiring low temperatures.     

Ultrasound-assisted isolation of mucilaginous hydrocolloids from Salvia macrosiphon seeds and studying their functional properties

Time and energy consuming centrifugation and purification steps have been reported as the main challenges for isolation of high quality hydrocolloids from mucilaginous seeds in commercial production. Ultrasound-assisted isolation of mucilaginous hydrocolloids from Salvia macrosiphon seeds as an innovative technology was performed successfully. After determination of optimum swelling condition, mucilaginous hydrocolloids samples were isolated using ultrasonic system under different ultrasound conditions (i.e., time, 1–20 min, temperature, 5–60 °C and ultrasound power (30–150 W)) and their physicochemical characteristics were studied in terms of yield, lightness, chemical composition, rheological properties and intrinsic viscosity in comparison with the conventional method. Ultrasound method increased yield, lightness and purity, in particular protein content, of the isolated hydrocolloids. Rheological measurements showed that increase of the intensity of ultrasound causes a decrease in consistency coefficient and an increase in the flow behavior index and thus hydrocolloid solutions tend to show more Newtonian behavior. The critical concentrations of S. macrosiphon seed gum isolated with the conventional method and the strongest ultrasonic treatment were 0.06 and 0.2 g/dl, respectively. Ultrasound showed to be a suitable method to isolate hydrocolloids from S. macrosiphon seeds.Industrial relevanceIsolation of mucilaginous hydrocolloids from seeds is a major challenge for commercializing these promising hydrocolloids. Using power ultrasound, isolation of hydrocolloid from S. macrosiphon mucilaginous seeds was performed, successfully. Ultrasound is able to scrape swelled mucilage layers of the seeds layer by layer. In the conventional method during high shear application some parts of the seed cores are crushed that would require extra separation steps such as high speed centrifugation. However, with ultrasound method seed cores are not broken down, therefore no centrifugation step is needed.     

The interplay between diverse oil body extracts and exogenous biopolymers or surfactants

Hazelnuts, sesame seeds and soybeans were selected as three diverse sources of oil bodies. Application of aqueous extraction and centrifugation steps resulted in concentrated oil body creams that were studied for their physical stability after dilution to a series of 5.0 wt.% oil-in-water emulsions incorporating sodium caseinate (1.0 wt.%), Tween 80 (1.0 wt.%) or xanthan gum (0.1 wt.%). In terms of aggregation/coalescence and creaming, the stability of the oil body based emulsions was ruled to a large extent by the initial natural oil droplet size and the presence of co-extracted exogenous proteins and secondarily by the added biopolymers and the surfactant. More specifically, soybean oil bodies exhibited the highest physical stability, even though incorporation of Tween 80 into all three oil body emulsions improved the stability against aggregation/coalescence, while xanthan gum was an effective stabilizer against creaming.     

Effect of composition and antioxidants on the oxidative stability of fluid milk supplemented with an algae oil emulsion

The oxidative stability of an algal oil emulsion dispersed in water, or fluid milk of varying fat contents, was assessed from measurements of lipid hydroperoxide and propanal concentration. All of the milk samples, independent of their milk fat content, were stable compared to the aqueous samples. The extent of oxidation was unaffected when sodium azide (200 ppm) was added to inhibit microbial growth. Added iron (100 ppm) accelerated the oxidation rate in the aqueous samples, but had no effect on the milk samples. The antioxidant properties of milk were ascribed to the iron binding of casein. Added protein antioxidants (0.8 wt%) [i.e. sodium caseinate, whey protein isolate (WPI) and thermally denatured WPI] had minimal effects whereas EDTA and ascorbic acid (160 ppm) were effective antioxidants.     

不同乳化剂对油酸和亚油酸乳状液稳定性的影响

本文以粒径、稳定性和流变为考察指标,利用激光粒度仪、食品稳定性分析仪、流变仪等研究不同种类和添加量的食品乳化剂(阿拉伯胶、酪蛋白酸钠、吐温20)对不饱和脂肪酸(油酸和亚油酸)乳状液的制备及其稳定性的影响。结果表明,三种乳化剂均可制备出稳定性较好的乳状液,不同乳化剂的质量分数不同得到乳状液的稳定性不同。较高质量分数的阿拉伯胶(4%,w/v)乳状液,具有最低的澄清指数并且具有最大粘度(0.30~0.40 Pa·s)。当酪蛋白酸钠的质量分数为2%时,制备出的乳状液较稳定,但粒径较大,贮藏稳定性较差。较低质量分数的吐温20(1%,w/v)的乳状液具有最小粒径(0.20~0.21 μm),经过贮藏后变化程度也最小。本文研究了不同食品乳化剂制备的不饱和脂肪酸乳状液及其稳定性,可为不饱和脂肪酸乳状液的制备和应用提供参考。     

十二种常见亲水胶体对馒头品质影响的研究

本文研究了12种亲水胶体不同添加量(0.2%、0.6%、1.0%)对馒头质构、比容、水分含量及持水力的影响。结果表明:适宜浓度的瓜尔豆胶,高甲氧基柑橘果胶在降低馒头硬度及咀嚼性的同时提高了馒头弹性(p<0.05),总体上有效地改善了馒头的质构特性。0.2%的瓜尔豆胶及魔芋胶,0.2%~1.0%的高甲氧基柑橘果胶、阿拉伯胶及乳清水解蛋白,0.6%~1.0%的低甲氧基柑橘果胶及酪蛋白钠使馒头比容显著增加(p<0.05)。在室温及-4 ℃条件下,与空白比较,除阿拉伯胶对馒头持水力无显著影响外,其他亲水胶体均能不同程度的提高显著馒头的持水力。由此可知,添加适宜浓度的瓜尔豆胶、高甲氧基柑橘果胶对馒头综合品质具有较好的改良效果。     

Compression resistance,sweetener's diffusion and sweetness of hydrocolloids gels

The effects of the type and concentration of two hydrocolloids—κ-carrageenan and gellan gum—and of the type and concentration of two sweeteners—sucrose and aspartame—on the gel resistance to compression, on the sweetener diffusion and on the intensity of the gel sweetness and the relationships between the gel physical properties and their perceived sweetness were studied. The gels true rupture stress increased with hydrocolloid concentration, this increase being higher for gellan gels. Gellan gels showed lower true rupture strain values, which in contrast with carrageenan gels, decreased on increasing hydrocolloid concentration. The addition of sucrose produced a bigger increase in gel strength at the higher hydrocolloid concentration. The main effect detected on the sweeteners’ diffusion constant was the higher value observed in low concentration (3 g L⁻¹) κ-carrageenan gels. Gellan gels were perceived as sweeter than κ-carrageenan gels. The decrease in sweetness due to an increase in hydrocolloid concentration was greater in gellan than in carrageenan gels. Variations in sweetener concentration, true rupture strain, and deformability modulus values explained 93% of the variability in sweetness for gels with sucrose and 94% for gels with aspartame.     

Adsorption dynamics and surface activity at equilibrium of whey proteins and hydroxypropyl–methyl–cellulose mixtures at the air-water interface

In this work the competitive behaviour of whey protein concentrate (WPC) and three well-characterized hydroxypropyl–methyl–celluloses (HPMCs), so-called E4M, E50LV and F4M, with different interfacial properties, were studied by measurement of the dynamics of adsorption and surface pressure isotherms. Such differences may be attributed to differences in the molecular weight and degree and molar substitution among the HPMCs. Thus, E4M having the highest molecular weight showed the highest surface activity among the HPMCs. The lower surface activity of F4M, in comparison to E50LV, may be attributed to its lower degree of total substitution. The experiments were performed at constant temperature (20 °C), pH 7, ionic strength 0.05 M and variable concentrations of the components.The differences observed between mixed systems were according to the relative bulk concentration of biopolymers and molecular structure of HPMC. In the presence of E4M a strong competence for the interface can be observed at short adsorption time. As E4M is more surface active than WPC, the replacement of E4M at the interface by WPC resulted in lower surface pressure. The mixture approached E4M behaviour at longer adsorption time. An additive or synergistic behaviour was observed for celluloses with lower surface activity (E50LV and F4M) at the lowest WPC and HPMC concentrations in the aqueous phase. A depletion mechanism in the vicinity of the interface would predominate in the presence of E50LV and F4M over the competence for the interface, giving rise to a cooperative behaviour. When WPC saturated the interface and the HPMC concentration in the aqueous phase was low enough, WPC dominated the surface pressure at long-term adsorption.