Juan M Rodrı́guez Patino

Universidad de Sevilla, Hispalis, Andalusia, Spain

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Publications (8)31.92 Total impact

  • R Baeza · C Carrera Sanchez · A. M. R Pilosof · J. M Rodrı́guez Patino
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    ABSTRACT: In the present work we have studied the static (film structure and elasticity) and dynamic characteristics (surface dilatational properties) of β-lactoglobulin (βLG) monolayers spread at the air–water interface in the presence of polysaccharides in the aqueous phase, at 20 °C and at pH 7. The measurements were performed on a fully automated Wilhelmy-type film balance. As polysaccharides with interfacial activity we have used propylene glycol alginates (PGA). To evaluate the effect of the degree of PGA esterification and viscosity, different commercial samples were studied-kelcoloid O (KO), kelcoloid LVF (KLVF) and manucol ester (MAN). Xanthan gum (XG) and λ-carrageenan (λC) were studied as non-surface active polysaccharides. The results reveal a significant effect of surface active and non-surface active polysaccharides on static—when the polysaccharide was added in the subphase the π-A isotherms shifted to higher surface pressure values as the time increased-and dynamic—the presence of polysaccharide in the aqueous phase decreased the surface dilatational modulus of a pure β-lactoglobulin monolayer-characteristics of β-lactoglobulin monolayers. To explain the observed effects three phenomena were taken into account: (i) the ability of the polysaccharide to adsorb at the interface by it-self and to increase the surface pressure, (ii) the interfacial complexation of the polysaccharide with the adsorbed protein and (iii) the existence of a limited thermodynamic compatibility between the protein and polysaccharide, depending on the protein-polysaccharide system.
    No preview · Article · Nov 2004 · Food Hydrocolloids
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    ABSTRACT: Structural and topographical characteristics of two major fractions of soy globulin from a soy protein isolate, β-conglycinin (a 7S globulin) and glycinin (a 11S globulin)—including the effect of chemical reduction of glycinin with dithiothreitol (DTT)—spread at the air–water interface at pH 8 and at 20 °C were determined from π–A isotherms coupled with a microscopic, non-invasive technique—Brewster angle microscopy. The structural characteristics of 7S and 11S globulin spread monolayers depend on film ageing. We have observed a significant shift of the π–A isotherms towards higher molecular areas over time. The ageing effect was due to unfolding of the protein at the interface. A change in the monolayer structure was observed at surface pressure of 17–19 mN/m. At a microscopic level, the heterogeneous monolayer structures visualised near to the monolayer collapse and during the monolayer expansion proved the existence of large regions of protein aggregates. Relative reflectivity increases with surface pressure and was a maximum at the monolayer collapse. The monolayer structure was more expanded for 7S than for 11S, but the maximum of both surface pressure and reflectivity (at the minimum molecular area) was observed for 11S globulin. The chemical reduction of glycinin with DTT produced a significant expansion of the monolayer structure.
    No preview · Article · Mar 2004 · Food Hydrocolloids
  • Juan M Rodrı́guez Patino · Ma.Rosario Rodrı́guez Niño · Cecilio Carrera Sánchez
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    ABSTRACT: The main interfacial physico-chemical characteristics and the kinetics of the formation of protein and emulsifier mixed films at the air–water interface are reviewed. Recent advances include the development of new molecular resolution and spectroscopic techniques coupled with surface rheological instruments and the incipient development of computer simulation of the displacement of proteins by emulsifiers.
    No preview · Article · Nov 2003 · Current Opinion in Colloid & Interface Science
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    ABSTRACT: In this paper we studied the β-conglycinin (fraction 7S) and glycinin (fraction 11S) structural characterization, hydrophobicity, and solubility, and the surface activity at equilibrium of adsorbed and spread films at the air–water interface. These properties were analyzed as a function of the aqueous phase pH and the protein concentration in the bulk phase, including the chemical reduction of glycinin with dithiothreitol (DTT). The surface activity of 7S, 11S, and 11S+10 mM DTT in aqueous solutions has been investigated over a range of protein concentrations (5–1×10−6% wt/wt) at pH 2.0, 5.0, and 8.0. The temperature and the ionic strength were maintained constant at 20 °C and 0.05 M, respectively. The surface activity at equilibrium was quantified by the surface pressure, which was determined by the Wilhelmy plate method. The fractions 7S and 11S would be under native conditions at pH 8.0, and they would be progressively unfolded when the pH diminishes towards the acidic region. These fractions are found to be partially denatured at pH 5.0 near the isoelectric point. The conformational change at the highest acidic pH takes place together with a greater exposure of the hydrophilic residues in a more polar region. Reduction of glycinin resulted in molecular conformational changes, which enhanced molecular hydrophobicity and increase molecule flexibility. Surface pressure data at low protein concentration indicated a low surface activity that rises to a plateau as the monolayer is saturated at higher protein concentrations. The protein concentration and the surface pressure at the plateau depend on the pH, but not on the type of protein in the aqueous phase and on the chemical reduction of glycinin with DTT neither. Poor surface activity was observed for pH 5.0. However, the equilibrium spreading pressure depends on the protein and the aqueous phase pH. Some differences were observed between surface pressure at the plateau for adsorbed protein and equilibrium spreading pressure for 7S, 11S, and 11S+10 mM DTT.
    No preview · Article · Oct 2003 · Colloids and surfaces B: Biointerfaces
  • J. J. Minones · J.M Rodrı́guez Patino · O Conde · C Carrera · R Seoane
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    ABSTRACT: Structural characteristics (structure, morphology, and relative film thickness) of dipalmitoyl phosphatidylcholine (DPPC), dipalmitoyl phosphatidylglycerol (DPPG) and dipalmitoyl phosphatidylserine (DPPS) monolayers were determined at the air–water interface at 20 °C and at pH 6 by means of surface pressure (π)–area (A) isotherms coupled with Brewster angle microscopy (BAM). At lower surface pressures, phospholipid monolayers adopted an expanded-homogeneous structure at the air–water interface. As the surface pressure increases, in the liquid-condensed phase (LC), phospholipid monolayers showed film anisotropy and domains with heterogeneous structures. The homogeneous structures observed at higher surface pressures proved the existence of parallel oriented aliphatic chains when the close-packed film molecules were in the solid state. The relative monolayer thickness increased with the surface pressure and was at a maximum at the collapse point. The phospholipid head-group has an important role on the structural characteristics of the monolayer at the air–water interface.
    No preview · Article · Apr 2002 · Colloids and Surfaces A Physicochemical and Engineering Aspects
  • Juan M Rodrı́guez Patino · Manuela Ruiz Domı́nguez
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    ABSTRACT: The effect of temperature and subphase composition (water and aqueous solutions of ethanol and glucose) on structural characteristics of some diglycerides (distearin, dipalmitin, and diolein) at the air/water interface, were studied. Monolayers of 1,2-distearin were found to be condensed, while 1,3-distearin monolayers were more expanded and unstable. Distearin monolayers (mixture of both isomers at 50% wt/wt) basically showed a liquid-condensed structure until the collapse point. The additivity rule was not fulfilled and the collapse pressure changed with 1,2-distearin molar fraction, which is indicative of the existence of interactions between molecules of both lipids, the mixture being non-ideal. Addition of glucose stabilized the liquid-condensed structure, while ethanol reduced the interval of existence of this phase. Dipalmitin showed solid, liquid-condensed or liquid-expanded structures, as a function of temperature and surface pressure, but the solid phase is predominant. For diolein films, only the liquid-expanded structure was observed.
    No preview · Article · Jul 2000 · Colloids and Surfaces A Physicochemical and Engineering Aspects
  • J. M. Rodrı́guez Patino · C.C. Sánchez · M. R. Rodrı́guez Niño
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    ABSTRACT: Brewster angle microscopy (BAM) coupled with surface pressure (π)–area (A) isotherms was used to visualize and determine structural characteristics of β-casein monolayers at the air–water interface as a function of subphase pH. The measurements were performed at 20°C. From the results of π–A isotherms, it can be concluded that β-casein monolayers at the air–water interface adopt two different structures. The monolayer structure was more condensed on acidic aqueous solutions. From BAM images, the domains that the residues of β-casein molecules adopt at the air–water interface appeared to be of uniform reflectivity, suggesting homogeneity in thickness and film isotropy. A method was applied to measure the relative reflectivity and relative film thickness. The relative reflectivity versus surface pressure plots reflects the surface equation of state for the spread β-casein monolayer, and is particularly sensitive of the existence of transitions in β-casein monolayers with compression. The relative film thickness increased with the film compression and was a maximum at the collapse point. At the same surface pressure, the relative film thickness is independent of the pH, but the surface density is higher at pH 5 than at pH 7, as a consequence of the more compact packing of β-casein residues on acidic subphases.
    No preview · Article · Sep 1999 · Food Hydrocolloids
  • Cecilio Carrera Sánchez · MaRosario Rodrı́guez Niño · Juan M. Rodrı́guez Patino
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    ABSTRACT: Monoglycerides are the most commonly used surfactants in the food industry in traditional food, low-fat products and instant foods. In this work we are essentially concerned with the study of the stability in monoglyceride monolayers (monopalmitin, monoolein and monolaurin) as a function of surface pressure (10 and 20 mN.m−1) and aqueous phase pH (pH 5 and 7). Monolayer stability was determined in an automated Langmuir-type film balance at constant temperature (20 and 40°C). The rate of monolayer molecular loss increases with surface pressure, and is pH dependent. Molecular loss at the interface also depends on the lipid. In the discussion, special attention will be given to the effect of the hydrocarbon chain length and the presence of a double bond in the hydrocarbon chain. Monopalmitin monolayers are more stable than those of monoolein and monolaurin. Maximum instability was observed with monolaurin monolayers. Two kinds of experiment have been performed to analyse relaxation mechanisms. In one, the surface pressure is kept constant, and the area is measured as a function of time. In the second, the area is kept constant at monolayer collapse and the surface pressure decreases. This decrease is measured as a function of time. Various relaxation mechanisms, including monolayer molecular loss by dissolution and/or collapse, can be fitted to the results derived from these experiments.
    No preview · Article · Jan 1999 · Colloids and surfaces B: Biointerfaces