Impact of Sample Aging on Freeze-Thaw Stability of Oil-in-Water Emulsions Prepared with Soy Protein Isolates

The freeze-thaw stability of oil-in-water emulsions prepared with unheated and heated aqueous dispersions of fresh and stored soy protein isolates was evaluated in the absence and presence of glucose or sorbitol (0.75–15.0% w/w). Sample aging had a negative impact of freeze-thaw stability. The cryoprotectant addition enhanced the freeze-thaw stability, but at low concentrations emulsions prepared with unheated soy protein isolates showed better response to freeze-thawing. Nevertheless, at the highest cryoprotectant concentration, a total stabilization was evidenced for all emulsions. The results of this article indicated that the cryoprotectants act on proteins at interfacial level.Facultad de Ciencias ExactasCentro de Investigación y Desarrollo en Criotecnología de Alimento

Effects of pH, protein:polysaccharide ratio, and NaCl-added concentration on whey protein isolate and soluble soybean polysaccharides electrostatic-complexes formation

In the present work, the interaction between whey protein isolate (WPI) and soluble soybean polysaccharide (SSPS) was studied as a function of pH (7.0 to 2.0), WPI:SSPS mass ratio (1:1 to 10:1), and NaCl-added concentration (0 to 100 mM). The interaction was analyzed by ζ-potential, turbidity, and state diagrams. Then, WPI-SSPS complexes were obtained in the optimized conditions of pH (4.0 to 3.5), WPI:SSPS ratio (2:1 to 6:1), and NaCl-added concentration (0 to 100 mM). The complexes were characterized by ζ-potential, particle size, and physical stability in a factorial 3 × 3 design with analysis by response surface methodology. This methodology showed that the characteristics of the WPI-SSPS complexes are modulated by the modification of the studied parameters. By lowering the pH, the complexes showed a ζ-potential closer to 0 and higher physical stability. By decreasing the WPI:SSPS ratio, the complexes showed more negative ζ-potential. Finally, by increasing the NaCl concentration, the complexes showed negative ζ-potential but an increment of mean particle size and polydispersity index. Data obtained in this work is useful to design WPI-SSPS complexes with specific characteristics of size, charge, and physical stability. These complexes could then be applied in food, medicinal or cosmetic matrices for different purposes.Fil: Igartúa, Daniela. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Investigación en Funcionalidad y Tecnología de Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cabezas, Dario Marcelino. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Investigación en Funcionalidad y Tecnología de Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Palazolo, Gonzalo Gastón. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Investigación en Funcionalidad y Tecnología de Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

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 (Tp) 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.Fil: Sobral, Pablo Antonio. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Palazolo, Gonzalo Gastón. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Wagner, Jorge Ricardo. Universidad Nacional de Quilmes; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentin

Freeze-thaw stability of oil-in-water emulsions prepared with native and thermally denatured soybean isolates

Freeze-thaw stability of oil-in-water emulsions prepared with native or thermally-denatured soy isolates (NSI and DSI, respectively) as the sole emulsifier and sunflower oil (φ = 0.25) has been examined at various protein concentrations (0.5, 1.0 and 2.0%. w/v), comparatively with sodium caseinate (SC). The freeze-thaw stability was assessed by measurements of particle size, oiling off and gravitational separation after isothermal storage at -20°C for 24. h and further thawing. The oil phase remained in liquid state and the amount of ice formed was similar (>97%) whatever the sample type and protein concentration. At 0.5%, NSI and DSI emulsions where highly unstable, exhibiting a coagulated cream layer with appreciable oiling off (>25%), whereas those prepared with SC were more stable, due to their initial lower flocculation degree (FD %) and particle size. For all emulsions, the increase of protein concentration (0.5-2.0%. w/v) improves the freeze-thaw stability as a consequence of a decrease of initial FD %. At 2.0%, where is enough protein to cover the interface, a lower coalescence stability of NSI emulsion respect to those prepared with NSI was observed after freeze-thawing. This result can be attributed to the high tendency to aggregation of native soy globulins at subzero temperatures. Notwithstanding this, unlike the SC emulsions, the formation of new flocs in soy isolates-stabilized emulsions during freeze-thawing cannot be totally controlled.Fil: Palazolo, Gonzalo Gastón. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sobral, Pablo Antonio. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Wagner, Jorge Ricardo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Effect of isolation conditions on structural properties and surface behavior of soy-whey proteins

In this study, the impact of isolation conditions on structural and surface properties at the air/water interface of soy-whey proteins (SWP) was assessed. SWP were obtained by precipitation of soy-whey (at pH 4.5 or 8.0) with acetone or ammonium sulfate. Despite the fact that all SWP samples exhibited similar electrophoretic patterns, they showed different protein content (from 54.2 to 98.2% w/w). When precipitation was performed at pH 4.5, SWP samples evidenced a decrease of protein solubility (SP) and thermal stability, while the precipitation with acetone promoted the enrichment in polysaccharides and minerals. For all samples, intrinsic fluorescence, surface hydrophobicity and Fourier transform infrared (FTIR) studies revealed structural changes correlated to protein unfolding and aggregation processes. However, the surface behavior can be predicted from these studies mainly due to differences in surface hydrophobicity and the differential contribution of insoluble aggregates. The heating of SWP samples enhanced the surface activity, regardless of the pH of the raw material and the isolation method. These results can be useful as a reference research and as a starting point for industrial exploitation of proteins from soy wastewater.Fil: Ingrassia, Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Sobral, Pablo Antonio. Universidad Nacional de La Plata. Facultad de Ciencias Exactas; ArgentinaFil: Risso, Patricia Hilda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Palazolo, Gonzalo Gastón. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Investigación en Funcionalidad y Tecnología de Alimentos; ArgentinaFil: Wagner, Jorge Ricardo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Investigación en Funcionalidad y Tecnología de Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Quiescent stability of o/w emulsions prepared with soy whey, tofu whey and their isolated proteins

El objetivo del trabajo fue analizar la estabilidad de emulsiones aceite en agua (o/w) preparadas con suero de soja o de tofu y sus proteínas aisladas. El suero de soja (SS) fue obtenido en laboratorio como sobrenadante isoeléctrico de la preparación de aislado nativo de soja (ANS); el suero de tofu (ST), residual líquido industrial, fue cedido por una empresa local. Ambos sueros fueron liofilizados dando SSL y STL. A partir del SS y ST se aislaron las proteínas PSS y PST respectivamente, por precipitación con acetona en frío y liofilización. A todas las muestras se le determinó el contenido proteico (N´6,25) a fin de preparar dispersiones acuosas de igual concentración proteica. Se prepararon dispersiones de las muestras en buffer fosfato de sodio 10 mM, pH 7,0, con una concentración de proteína de 0,1-1 % p/v. Las emulsiones o/w fueron preparadas homogeneizando 10 ml de las dispersiones acuosas con 5 ml de aceite de girasol (Ultraturrax T-25, 20.000 rpm, 1 min., 20ºC). Las emulsiones iniciales resultantes se caracterizaron por difracción láser (distribución de tamaño de partícula) y por turbidimetría (área interfacial creada). La estabilidad de las emulsiones se evaluó por medida de la cinética de separación gravitacional (analizador óptico vertical) y del aceite separado (AS%) por el método de dilución del colorante. Todas las emulsiones iniciales, menos la SSL, mostraron distribuciones similares de tamaño de partícula del tipo bimodal con una población mayoritaria a 50-60 mm; cuando se analizaron sin y con SDS dieron valores D43 entre 30 y 40 mm. Las distribuciones correspondientes a la emulsión SSL, medidas sin y con SDS, fueron diferentes debido a la presencia de flóculos estables, lo cual se reflejó en valores de D43 sin y con SDS, 70,6 y 45,5 mm, respectivamente y en la baja estabilidad a la separación gravitacional. A una concentración de proteína equivalente, las emulsiones preparadas con sueros fueron siempre menos estables a la separación gravitacional que las elaboradas con sus respectivas proteínas aisladas. Por otra parte, las PST dieron emulsiones más estables a la separación gravitacional que las provenientes de suero de soja obtenido en laboratorio. Según las medidas de AS%, el orden de estabilidad en todas las concentraciones ensayadas fue PST > PSS > STL > SSL. Estos resultados permiten concluir que STL, en el cual las proteínas se encuentran desnaturalizadas, es un mejor agente estabilizante que SSL, del mismo modo que PST lo es respecto de PSS. Las emulsiones de PST fueron precisamente las que exhibieron los valores más altos de área interfacial creada y el menor tamaño de partícula. Las proteínas aisladas de ambos sueros dan emulsiones más estables que los sueros respectivos, indicando un efecto negativo de los componentes no proteicos del suero, como los oligosacáridos y las sales.This article focuses on the quiescent stability of emulsions oil in water (o/w) prepared with soybean whey or tofu whey and their isolated proteins. Soybean whey (SS) was obtained as isoelectric supernatant of the soy isolate preparation; the tofu whey (ST), industrial waste, was given by a local company. Both liquids were freeze-dried giving the samples SSL and STL. The proteins PSS and PST were isolated from SS and ST respectively, by precipitation with cold acetone and freeze-drying. The protein content of each sample was determined (N´6.25) in order to prepare aqueous dispersions of the same protein concentration. Aqueous dispersions of each sample were prepared in 10 mM sodium phosphate buffer, pH 7.0, at different protein concentrations (0.1-1% w/v). O/w emulsions were obtained by mixing 10 ml aqueous dispersions and 5 ml of sunflower oil (Ultraturrax T-25 high-speed homogenizer, 20,000 rpm, 1 min, 20°C). Fresh emulsions were characterized by laser diffraction (particle size distribution, PSD) and turbidimetry (interfacial created area). Emulsion stability was evaluated by measuring the creaming kinetic (vertical optical analyzer) and oiling-off (AS% w/w) by the dye dilution method. All emulsions, with exception of those prepared with SSL, showed similar PSD both in the absence and presence of SDS: a bimodal character, a main particle population at 50- 60 mm and D43 values in the range 30-40 mm. For SSL emulsions, the PSD measured with and without SDS exhibited noticeable differences (D43 = 70.6 and 45.5 mm respectively) due to the presence of stable flocs, which enhanced the creaming. At the same protein concentration, emulsions prepared with soy whey samples were always less stable that those prepared with their isolated proteins. Moreover, PST emulsions were more stable against creaming than those prepared with PSS. On the other hand, AS % decreased in the sequence: PST > PSS > STL > SSL. These results suggest that STL, in which proteins are thermally denatured, is a better stabilizing agent that SSL; similarly, PST is a better emulsifier that PSS. Precisely, PST emulsions exhibited the highest values of interfacial area and the smallest mean particle size. The isolated proteins showed better emulsifying properties than those exhibited by freeze-dried soy and whey. This indicates a negative effect of non-protein components present in the soy whey, as oligosaccharides and salts.Centro de Investigación y Desarrollo en Criotecnología de Alimento

Impact of Sample Aging on Freeze-Thaw Stability of Oil-in-Water Emulsions Prepared with Soy Protein Isolates

The freeze-thaw stability of oil-in-water emulsions prepared with unheated and heated aqueous dispersions of fresh and stored soy protein isolates was evaluated in the absence and presence of glucose or sorbitol (0.75–15.0% w/w). Sample aging had a negative impact of freeze-thaw stability. The cryoprotectant addition enhanced the freeze-thaw stability, but at low concentrations emulsions prepared with unheated soy protein isolates showed better response to freeze-thawing. Nevertheless, at the highest cryoprotectant concentration, a total stabilization was evidenced for all emulsions. The results of this article indicated that the cryoprotectants act on proteins at interfacial level.Facultad de Ciencias ExactasCentro de Investigación y Desarrollo en Criotecnología de Alimento

Cream-like emulsions prepared with soy milk 3: effect of temperature cycling

En este trabajo se analizó el efecto de ciclos calentamientoenfriamiento sobre cremas preparadas a 60ºC con leche de soja en polvo reconstituida, aceite de girasol y grasa láctea y almacenadas posteriormente a 4ºC durante 3 horas. Los ciclos consistieron en un calentamiento a 40ºC o 50ºC (30 min) seguido de un enfriamiento a 4ºC (2 horas). En los ensayos realizados sobre cremas formuladas con 40% de fase lipídica se observó un aumento de los valores de G’ y G’’ después del ciclo 40ºC-4ºC, a pesar de no haberse observado un aumento en el contenido de grasa sólida. Estos resultados se atribuyen a la formación de agregados de gotas inducida por la fusión parcial, reordenamiento y recristalización de la grasa láctea en las gotas. Estudios de resonancia magnética nuclear de pulsos, calorimetría diferencial de barrido y distribución de tamaño de partícula por difracción de luz permitieron corroborar que el principal mecanismo de formación de agregados es la coalescencia parcial. Frente al mismo ciclo térmico, la crema con 20% de fase lipídica no aumentó su consistencia, dada la ausencia o formación insuficiente de agregados por el bajo número de gotas. Ensayos similares sobre la nata a 40ºC o sobre las cremas de leche de soja a 50ºC, no mostraron cambios reológicos, debido a la fusión casi total de la grasa.In this work, the effect of temperature cycling on emulsions formulated with reconstituted soy milk, sunflower oil and high melting point milk fat was analysed. The emulsions were prepared at 60°C, stored at 4°C (3 h), warmed at 40°C or 50°C (30 min) and afterwards cooled at 4°C (2h). Although solid fat content of emulsions did not raised after tempering at 40°C, increase of G' and G″ was observed only in those formulated with 40% lipid phase. This phenomenon was attributed to droplet aggregation due to partial melting, recrystallization and reordering of fat crystals in oil droplets. The main droplet destabilization mechanism was the partial coalescence; it was corroborated by nuclear magnetic resonance, differential scanning calorimetry and droplet size distribution studies. On the other hand, the consistency of 20% of lipid phase emulsion did not increased. Low droplet concentration disfavoured the partial coalescence of droplets. Similar assays on cream at 40°C and cream-like soy milk emulsions at 50°C, did not show rheological modifications, due to almost total melting of milk fat during tempering.Facultad de Ciencias Exacta

Cream-like emulsions prepared with soybean milk: Effect of controlled stirring on rheological behaviour

La coalescencia parcial de las emulsiones o/w puede inducirse por agitación, debido a la presencia de cristales de grasa en las gotas. En este trabajo se estudió el efecto de la agitación sobre el comportamiento reológico de emulsiones tipo crema preparadas con leche de soja reconstituida (5% y 10%), aceite de girasol y grasa láctea de alto punto de fusión comparativamente con una nata comercial. Las cremas, inicialmente líquidas, aumentaron progresivamente la consistencia durante la agitación cuando el contenido de fase lipídica fue del 40%. Aunque se requirió un mayor tiempo de agitación en cremas con leche más concentrada (a igual proporción de fase lipídica) se registró un aumento más pronunciado de la viscoelasticidad. Por otra parte, al aumentar la concentración de grasa láctea en la fase lipídica se requirió un tiempo de agitación menor por verse favorecida la coalescencia parcial. Independientemente del contenido en grasa láctea, las emulsiones con fases lipídicas relativamente bajas (20%) no aumentaron su consistencia por agitación.In o/w emulsions, partial coalescence can be induced by stirring, due to the presence of fat crystals in oil droplets. In this work, effect of stirring on rheological behaviour of cream-like emulsions prepared with reconstituted soybean milk, sunflower oil and milk fat (high melting fraction) was analysed. Commercial milk cream sample was used as control. During stirring, progressive increase of consistency of 40% lipid phase emulsions was observed. Although a high stirring time was required in emulsions prepared with more concentrated soybean milk, a pronounced enhance of its viscoelasticity was observed. On the other hand, when milk fat concentration was increased in lipid phase, it was required a low stirring time value as consequence of promoted partial coalescence. Independently of the milk fat content, in emulsions with relatively low lipid phase content (20%) an increase of consistency was not observed.Facultad de Ciencias Exacta

Heat treatments of defatted soy flour: impact on protein structure, aggregation, and cold-set gelation properties

This study reveals that mild heat treatments of defatted soy flour promote Maillard reaction and modify its protein techno-functional properties such as solubility, aggregation, and cold-set gelation. Glycation was promoted by treatments of defatted soy flour (DSF) at 60 °C for 12, 24, and 48 h, with and without relative humidity control (RHC and WRHC, respectively) at 79%. All samples presented a significant increase of glycation extent (GE), reaching the highest value after 48 h at RHC. Despite all samples presented a similar protein denaturation degree, the increase in GE was accompanied by a decrease of antitryptic activity. Protein solubility (PS) of DSF remained constant for treated samples WRHC. However, PS decreased progressively with the treatment time at RHC. SDS-PAGE of soluble proteins revealed a positive relation between band intensities and PS. Despite sample dispersions showed a protein particle size increment with treatment time, further aggregation after heat-treatments at 100 °C produced a similar protein size distribution among samples. Rheological and microstructural studies of cold-set gels of samples obtained WRHC revealed no changes in the maximum elastic modulus (G’max) and a slight increase of its pore sizes. However, samples obtained with RHC showed cold-set gels with a progressive G’max decrease with the treatment time, which could be related to a coarser gel microstructure. In the more extreme condition, the sample obtained after 48 h at RHC showed a total loss of gelation capability. These results can be used to address the development of new tofu-like food products with different rheological properties.Fil: Ingrassia, Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Veterinarias; ArgentinaFil: Palazolo, Gonzalo Gastón. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Investigación en Funcionalidad y Tecnología de Alimentos; ArgentinaFil: Wagner, Jorge Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Investigación en Funcionalidad y Tecnología de Alimentos; ArgentinaFil: Risso, Patricia Hilda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Veterinarias; Argentin