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ABSTRACT: The empirical model q = Q t/B + t, where q is the amount of water taken up at time t was useful to describe water uptake of several food powders determined either by the Baumann or the sorption isotherm method at 75.6 and 100% RH. The equilibrium values (Q) and the specific rate constant (K) derived from this model as (QB)-1 could be used to characterize food materials for hydration capacity and rate. Large differences were observed in Q values between methods and between food powders. The Baumann Q values and sorption isotherm Q values at 100% RH ranked similarly water takeup of food powders (R = 0.97, p < 0.001). Baumann K values and sorption isotherm K values at 100% RH also correlated highly. However, little differences were observed among the K and Q values of different food powders determined by the sorption isotherm method at 75.6% RH.
Journal of Food Science 08/2006; 61(2):407 - 409. · 1.66 Impact Factor
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ABSTRACT: The emulsion stabilizing properties of a variety of food protein products in relation to their water (WAC) and oil (OAC) uptakes and the viscosity of the external phase were investigated. Protein products were treated as two entities for regression analysis. Emulsion instability of protein products with a lipophilic water-oil absorption index could be explained and accurately predicted on the basis of the WAC, OAC, and viscosity. Emulsion instability of protein products with a hydrophilic water-oil absorption index could be predicted using WAC and viscosity. High WAC, OAC, and viscosity of protein products were associated with optimum stabilizing properties.
Journal of Food Science 08/2006; 53(3):845 - 848. · 1.66 Impact Factor
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ABSTRACT: An index for describing the relative hydrophilic-lipophilic character of proteins was proposed based on the measurement of the “spontanoeous water and oil uptake”. The water-oil absorption index (WOAI) showed a defined correlation with emulsifying capacity (EC) for most proteins making it possible to predict EC in a simple way. Maximum emulsion capacity was achieved when the WOAI was nearly two, that is when the protein absorbed twofold more water than oil. Proteins with WAOI greater than two had increasingly hydrophilic characteristics and concomitantly increasingly low EC. Proteins with WOAI lower than two showed increasingly lipophilic characteristics and concomitantly increasing low emulsifying capacity. The finding of this study supports the concept that emulsifying capacity of proteins depends on the suitable balance between the hydrophilic and lipophilic characteristics, rather than merely high values for each one.
Journal of Food Science 08/2006; 52(5):1381 - 1383. · 1.66 Impact Factor
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ABSTRACT: Emulsion instability at 37, 45 and 60°C of soy protein-stabilized emulsions of variable protein-oil concentration were systematically investigated. A regression model for prediction of emulsion instability was derived. The variables were functions of the relationship between the water and oil absorbed by the protein and total water and oil in the emulsion. The regression model derived for soy protein stabilized emulsions was suitable for predicting emulsion instability of many other protein stabilized emulsions. Knowledge of water-and-oil-absorption capacity of the protein and composition of the emulsion would allow a rapid prediction of emulsion instability.
Journal of Food Science 08/2006; 56(1):116 - 120. · 1.66 Impact Factor
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ABSTRACT: Drainage of 14 protein-stabilized foams was determined as a function of time. Drainage conformed to the empirical equation v = Vt/(B + t), where v is the volume of drained liquid at time t, V is the maximum drained volume, and B is the time needed to drain V/2. Rate constants and initial rates of drainage could be calculated from parameters V and B. However, B would be the preferred index of foam stability as it was not influenced by the initial volume of liquid in the foam.
Journal of Food Science 08/2006; 56(1):24 - 26. · 1.66 Impact Factor
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ABSTRACT: The relationship between surface and interfacial tension of 14 food proteins and their hydrophilic/lipophilic characteristics was studied. Maximum lowering of surface and interfacial tension was achieved when the water-oil absorption index (WOAI), calculated by measuring the spontaneous water and oil uptake was nearly two; the protein absorbed twice as much water as oil. The ability of a protein to decrease interfacial tension between oil and water was related to its ability to emulsify oil, being determined by the WOAI. However, stability of emulsions was not ensured by a large decrease in interfacial tension.
Journal of Food Science 08/2006; 56(1):253 - 254. · 1.66 Impact Factor
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ABSTRACT: Hydrophilic characteristics of four soybean protein isolates, determined through measurement of spontaneous water absorption capacity (WAC), were greatly affected by pH in the range of 2 to 7. While minimum WAC was apparent near the isoelectric region and increased away from the pI (isoelectric point) for most isolates, a partially hydrolysed soy protein isolate behaved the opposite way. Lipophilic characteristics, determined as the spontaneous oil absorption capacity (OAC), varied up to 120% as pH changed. The balance between hydrophile and lipophile (WOAI), calculated as the ratio between WAC and OAC, showed a response to pH similar to WAC, with a minimum value near the pI, except for the hydrolysed isolate. Emulsifying capacity (EC) was maximum near the pI. However, the hydrolysed isolate showed a greater EC, reaching a maximum at pH 3, which could be attributed to peptides of different size and net charge with no single pI. As the hydrophilic/lipophilic balance reached lower values as a result of the effect of pH, EC increased, suggesting that a relatively high hydrophobicity is needed to enhance the EC of soy proteins. The effect of pH on emulsion stability was opposite to that shown on EC, except for the hydrolysed isolate, as maximum instability was apparent near the pI, where electrostatic and steric repulsions between oil droplets are highly decreased. The effect of pH on emulsion stability was closely related to WAC and indicated that a high hydration of the interfacial film is necessary for increasing stability against creaming and flocculation.
LWT - Food Science and Technology. 29(4):334-339.
