Nanofibers from soybean hull insoluble polysaccharides as Pickering stabilizers in oil-in-water emulsions formulated under acidic conditions.

BACKGROUND: Pickering emulsions are a kind of emulsion stabilized by solid particles. These particles generate a physical or mechanical barrier that provides long-term stability to emulsion. Cellulose nanofibers are effective Pickering emulsifiers given their long length, high flexibility and entanglement capability. In this work, soybean hull insoluble polysaccharides (HIPS) were used as source of cellulose nanofibers by using a combination of chemical and mechanical treatment. The chemical composition, morphology, flow behavior, water holding capacity (WHC) and emulsifying properties of the nanofibers were studied. RESULTS: Nanofibers with diameters between 35 and 110 nm were obtained. The WHC increased significantly after the mechanical treatment, and the rheological behavior of the nanofibers was typical of cellulosic materials. Nanofibers were effective emulsifiers in oil-in-water (O/W) emulsions formulated under acidic conditions, without the need of using any additional surfactant. Emulsions were not affected by changes in the pH of the medium (3.00-5.00), and were stable to coalescence. CONCLUSION: It is possible that cellulose nanofibers form an entangled network which acts as a mechanical steric barrier, providing stability to coalescence. These results are important for the development of effective O/W Pickering emulsifiers/stabilizers, with large applications in the food industry. © 2023 Society of Chemical Industry.

Acid emulsions stabilized by soy whey concentrates and soluble soybean polysaccharides: Role of biopolymer interaction strategies on stability against environmental stresses.

This article focuses on the evaluation of different interaction strategies between soy whey concentrates (SWC) and soluble soybean polysaccharides (SSPS) at pH 3.0 on the emulsion stability against freeze-thawing and mechanical stirring. Emulsions were prepared from aqueous dispersions of both biopolymers (3.0% w/w SSPS and SWC, 1:1 mass ratio) and sunflower oil (10% w/w) by aqueous phase complexation (APC), interfacial complexation (IC) and interfacial complexation and sonication (ICS). SWC control emulsion was a poor emulsifying ability; SSPS addition, through the APC and ICS strategies, noticeably improved the SWC emulsifying properties. ICS emulsions showed the highest stability to environmental stresses, due a combination of low initial particle size, flocculation degree and steric hindrance promoted by the presence of SSPS chains at the interface. This study provides valuable information forthe utilization of whey soy proteins in acid dispersed systems stable to environmental stresses.

Impact of environmental stresses on the stability of acidic oil-in-water emulsions prepared with tofu whey concentrates.

The emulsifying properties of tofu-whey concentrates (TWCs) at pH 3.0, 4.0, and 5.0, and the stability of the resultant oil-in-water emulsions against freeze-thawing (24 h, -20 °C) and controlled or mechanical stress (orbital stirring at 275 rpm, 40 min) were addressed. TWCs were prepared from tofu-whey by heating at 50 °C (8.0 kPa) or 80 °C (24.0 kPa), dialysis (4 °C, 48 h), and freeze-drying, giving the samples TWC50 and TWC80, respectively. The particle size and interfacial properties at the oil/water interface were measured. Emulsions were prepared by mixing the TWC aqueous dispersions (1.0% protein w/w) and refined sunflower oil (25.0% w/w) by high-speed and ultrasound homogenization. The preparation of TWCs at higher temperatures (80 °C) promoted the formation of species of larger particle size, a slight decrease of interfacial activity, and the adsorption of more rigid biopolymer structures associated with an increase of film viscoelasticity in interfacial rheology measurements. The emulsifying properties of both concentrates were enhanced with decreasing pH (5.0-3.0), through a significant decrease of particle size (D4,3) and flocculation degree (FD), but only those prepared with TWC80 exhibited higher stability to freeze-thawing and mechanical stress at pH 3.0. This could be ascribed to a combination of low initial D4,3 and FD values, high protein load, and the presence of rigid species that impart high viscoelasticity to the oil/water interface. These results would be of great importance for the utilization of TWCs as food emulsifiers in acidic systems to impart high stability to environmental stresses.

Impact of the film-forming dispersion pH on the properties of yeast biomass films.

BACKGROUND: Yeast biomass, mainly composed of proteins and polysaccharides (mannans and ß-glucans), has been proposed to develop films. pH can affect the solubility of polysaccharides, the structure of the cell wall, and the interactions between proteins. Considering the potential impact of these effects, the pH of yeast film-forming dispersions was studied from 4 to 11. RESULTS: In tensile tests, samples increased their elongation by increasing pH, from 7 ± 2% (pH 4) to 29 ± 5% (pH 11), but Young's modulus was not significantly modified. Regarding thermal degradation, the maximum degradation rate temperature was shifted 46 °C from pH 4 to 11. Differences in water vapour permeability, colour, opacity, and roughness of films were also found. According to the results of differential protein solubility assay, hydrophobic interactions and hydrogen bonding were promoted at pH 4, but disulfide bonds were benefited at pH 11, in addition to partial ß-glucan dissolution and break-up of the alkali-sensitive linkage in molecules from the cell wall. CONCLUSION: The results lead to the conclusion that film-functional characteristics were greatly benefited at pH 11 in comparison with the regular pH of dispersion (pH 6). These results could help in understanding and selecting the pH conditions to enhance the desired properties of yeast biomass films. © 2021 Society of Chemical Industry.

Influence of chemical composition and structural properties on the surface behavior and foam properties of tofu-whey concentrates in acid medium.

This article focuses on the impact of chemical composition and structural properties of tofu-whey concentrates on their surface behavior at the air/water interface and foaming properties in acid medium. Liquid tofu-whey (pH 5.6 ±â€¯0.1) was concentrated at three combinations of temperature and pressure (50 °C-8.0 kPa, 65 °C-16.0 kPa and 80 °C-24.0 kPa), with further dialysis (4 °C, 48 h) and freeze-drying, giving the samples TWC50, TWC65 and TWC80, respectively. The increase of temperature during the concentration step promoted the enrichment of the concentrates in crude protein and calcium, without appreciable changes in the yield, the carbohydrate content and the polypeptide composition. For TWC80, the increase the degree of glycosylation and the intensity of the hydrophobic effect promoted the decrease of molecular flexibility and the formation of compact aggregates mediated by disulfide bridges as was evidenced by tricine-SDS-PAGE, TGA and FTIR assays. These structural differences have a pronounced impact of the pH-dependence of turbidity and solubility of protein and polysaccharides. At pH 4.0 all concentrates evidenced a ζ-potential close to zero, which enhanced their foam ability (overrun >1500%). Nevertheless, at this pH, TWC80 showed both the highest carbohydrate-to-protein mass ratio in the soluble fraction (>1.8) and foam stability (FS). Thus, the improvement of FS at pH 4.0 would be associated to the effective adsorption of compact rich-in-protein aggregates at the air/water interface and the higher content of soluble polysaccharides in the bulk phase. These findings are relevant for the application of tofu-whey concentrates in acidic dispersed systems, such as foams and aerated food emulsions.

Emulsifying properties of defatted rice bran concentrates enriched in fiber and proteins.

BACKGROUND: Rice bran (RB), a by-product of the rice milling industry, constitutes around 10% of the total weight of rough rice. The interest in the use of RB is centered on its nutritional quality, its low cost, and its extensive worldwide production. As RB is commonly used for oil extraction, the defatted rice bran (DRB) is obtained as a second by-product. The aim of this work was to obtain a defatted rice bran concentrate (DRBC), enriched in protein and fiber, from defatted rice bran flour (DRBF) and to determine its physicochemical and emulsifying properties. RESULTS: To obtain the DRBC, the starch was efficiently hydrolyzed (> 98%) with α-amylase and amyloglucosidase, with a concomitant increase in the proportions of crude protein (from 154.7 to 274.3 g kg-1 ) and total dietary fiber (from 276.1 to 492.3 g kg-1 ). Defatted rice bran concentrate exhibited a loss of protein solubility and increased surface hydrophobicity compared with DRBF. Defatted rice-bran concentrate dispersions with and without previous ultrasound treatment were prepared. The sonication led to an increase in the apparent viscosity. Emulsions were prepared with dispersions with and without previous ultrasound treatment and showed high stability in quiescent conditions over 28 days. However, the emulsions prepared with dispersions treated with ultrasound resulted in lower D4,3 values and higher elastic and viscous moduli. CONCLUSION: The rice bran concentrate can be used to obtain stable oil-in-water (O/W) emulsions, including both soluble and insoluble fractions, in acidic and neutral conditions. These innovative findings thus contribute to increasing the added value of this important by-product of the rice-milling industry. © 2019 Society of Chemical Industry.

Effect of salt content and type on emulsifying properties of hull soy soluble polysaccharides at acidic pH.

Hull soluble polysaccharide (HSPS) is a novel product consisting in a mixture of polysaccharides and proteins extracted from soy hulls by using a methodology based on the extraction of citric pectins. In this work we studied the effect of the addition of two different salts (NaCl and CaCl2) on the emulsifying properties of HSPS at acidic conditions. Low and high homogenization energies were used, obtaining coarse and fine emulsions, respectively. Mean droplet size, the stability against destabilizing processes (creaming, flocculation and coalescence) and the rheological properties of the emulsions were analyzed. Also, the rheology of the O/W interface was studied by using du Noüy ring geometry. Coarse HSPS emulsions were unstable to creaming, being more stable in the presence of salts. In contrast, fine HSPS emulsions showed long-term creaming stability similar to those performed with commercial citric pectin (CCP), although they differ in particle size distribution and flocculation degree. The presence of CaCl2 reduced the mean size of droplets in fine HSPS emulsions and improved their stability to flocculation and coalescence. Significant differences were observed in the rheological behavior of O/W emulsions and interfaces of HSPS and CCP with respect to the salt addition. Our results indicate that HSPS can be used in the formulation and stabilization of acidic O/W emulsions. Besides, HSPS generates emulsions with different characteristics than those obtained with citric pectins. The use of HSPS provides a suitable alternative in food engineering contributing to the exploitation and valorization of soy hulls, which represents an important waste material in soybean processing.

Effect of Xanthan Gum on the Rheological Behavior and Microstructure of Sodium Caseinate Acid Gels.

The aim of this work was to study the effect of xanthan gum (XG) on the gelation process of bovine sodium caseinate (NaCAS) induced by acidification with glucono-δ-lactone (GDL) and on the mixed acid gel microstructure. Before GDL addition, segregative phase separation was observed in all the NaCAS-XG mixtures evaluated. The gelation process was analyzed by using a fractional factorial experimental design. The images of the microstructure of the mixed acid gels were obtained by conventional optical microscopy and the mean diameter of the interstices was determined. Both the elastic character and the microstructure of the gels depended on the concentrations of XG added. As XG concentration increased, the kinetics of the gelation process was modified and the degree of compactness and elasticity component of the gel network increased. The microstructure of gels depends on the balance among thermodynamic incompatibility, protein gelation and NaCAS-XG interactions.

Indigenous filamentous fungi on the surface of Argentinean dry fermented sausages produced in Colonia Caroya (Córdoba).

Some producers of dry fermented sausages use fungal starter cultures with the aim to achieve a desirable surface appearance and avoid the growth of mycotoxigenic fungi. These commercial cultures are mainly composed of Penicillium nalgiovense biotype 6. In contrast, in the case of producers who do not use starters, sausages are spontaneously colonized by the house mycobiota, which generally consists of heterogeneous molds corresponding to different genera and species. In this work, the surface mycobiota of dry fermented sausages produced in Colonia Caroya (Córdoba, Argentina) was determined in both summer and winter seasons. All the sausages sampled had been made without the use of surface fungal starters. In the 57 sausages analyzed in the two winter seasons studied (2010 and 2012), we found a total of 95 isolates of filamentous fungi belonging to six genera (Penicillium, Aspergillus, Mucor, Cladosporium, Scopulariopsis and Eurotium) and ten fungal species, whereas in the 36 sausages analyzed in the two summer seasons studied (2011 and 2012), we found 89 isolates belonging to five genera (Penicillium, Aspergillus, Mucor, Cladosporium and Geotrichum) and ten fungal species. Although 16 different species were found in both winter and summer seasons, only 2 of them predominated completely. P. nalgiovense was found in almost 100% of the sausages analyzed, where biotype 4 was the most frequent. This species gives a whitish gray coloration to the sausages. Considering that the factories sampled do not use fungal starter cultures, this predominance is very interesting since mycotoxin production by this fungus has not been reported. Aspergillus ochraceus was isolated with a frequency of 80-90% in the summer seasons, but in none of the winter samples. The presence of this fungus in sausages produced in the summer was attributed to the high environmental temperatures and the uncontrolled temperature in the ripening rooms during the night. In all cases, A. ochraceus was responsible for the undesirable yellowish gold color of the casing. This fungus thus causes significant economic losses to the producers of Colonia Caroya during the months of high temperatures.

Effect of water content on thermal behavior of freeze-dried soy whey and their isolated proteins.

Thermal behavior of lyophilized soy whey (LSW) and whey soy proteins (WSP) at different water contents (WC) was studied by DSC. In anhydrous condition, Kunitz trypsin inhibitor (KTI) and lectin (L) were more heat stable for WSP with respect to LSW sample. The increase of WC destabilized both proteins but differently depending on the sample analyzed. Thermal stability inversion of KTI and L was observed for WSP and LSW at 50.0% and 17.0% WC, respectively, which correspond to the same water-protein content mass ratio (W/P ≈ 1.9). At W/P < 1.9, KTI was more heat stable than L. Before the inversion point, WC strongly modified the peak temperatures (T(p)) of KTI and L for WSP, whereas this behavior was not observed for LSW. The high sugar content was responsible for the thermal behavior of KTI and L in LSW under anhydrous condition and low WC. These results have important implications for the soy whey processing and inactivation of antinutritional factors.

Thermal behavior of soy protein fractions depending on their preparation methods, individual interactions, and storage conditions.

Different soy protein isolates (SPI) and whey soy protein (WSP) samples were obtained from fresh and stored soybean flour. Some samples were subjected to a long, cold storage. DSC thermograms of SPI showed the two characteristic endotherms, corresponding to denaturation of ß-conglycinin and glycinin. Low value of denaturation enthalpy and high glycinin denaturation temperature were related to a reduction of protein solubility of SPI. DSC thermograms of WSP also showed two characteristic endotherms, corresponding to Kunitz trypsin inhibitor and lectin. The methods and conditions of preparation and storage of WSP samples were factors that modified their thermal behavior. Some SPI-WSP mixtures (1:1) exhibited more complex thermograms and higher denaturation temperatures. Thermograms of SPI-denatured WSP mixtures showed that the thermal stabilization of soybean storage proteins was attributed to protein-protein interactions. The differences in the thermal behavior of single or mixed SPI and WSP could not be explained on the basis of mineral content.

Effect of calcium salts and surfactant concentration on the stability of water-in-oil (w/o) emulsions prepared with polyglycerol polyricinoleate.

The objective of this work was to obtain water-in-oil (w/o) emulsions with polyglycerol polyricinoleate (PGPR) as emulsifier and to study the effect of the addition of calcium in the dispersed aqueous phase on the stability of these systems. Emulsions were formulated with 0.2, 0.5 and 1.0% w/w PGPR and 10% w/w water containing calcium chloride at varied concentrations or other salts (calcium lactate or carbonate; sodium, magnesium or potassium chloride). The stability of these systems was studied with a vertical scan analyzer during 15 days; coalescence and sedimentation were observed as simultaneous destabilization processes. The increase of PGPR concentration and/or calcium chloride content gave more stable emulsions. The stabilizing effect of calcium salt was attributed to the diminution of the water droplets size, the decrease of the attractive force between water droplets and the increase of the adsorption density of the emulsifier. The viscoelastic parameters of the interfacial film were decreased with increasing calcium and PGPR concentrations. Calcium chloride produced a higher increase of stability than calcium salts with lower dissociation degree. The presence of any assayed salt in the aqueous phase also allowed the stabilization of w/o emulsions with higher water contents.