RESUMO
The present work evaluated how a native pea protein isolate (PPI) affects the key roles carried out by bile salts (BS) in lipid digestion by means of the in vitro static INFOGEST protocol. Two gastric residence times were evaluated (10 and 60 min), and then the peptides obtained (GPPP) were mixed with BS at physiological concentration in simulated intestinal fluid to understand how they interact with BS both at the bulk and at the interface. Both GPPP give rise to a film with a predominant viscous character that does not constitute a barrier to the penetration of BS, but interact with BS in the bulk duodenal fluid. When the peptides flushing from the stomach after the different gastric residence times undergo duodenal digestion, it was found that for the longer gastric residence time the percentage of soluble fraction in the duodenal phase, that perform synergistically with BS micelles, was twice that of the lower residence time, leading to an increase in the solubilization of oleic acid. These results finally lead to a greater extent of lipolysis of olive oil emulsions. This work demonstrates the usefulness of in vitro models as a starting point to study the influence of gastric residence time of pea protein on its interaction with BS, affecting lipolysis. Pea proteins were shown to be effective emulsifiers that synergistically perform with BS improving the release and bioaccessibility of bioactive lipids as olive oil.
Assuntos
Ácidos e Sais Biliares , Digestão , Lipólise , Proteínas de Ervilha , Ácidos e Sais Biliares/metabolismo , Ácidos e Sais Biliares/química , Proteínas de Ervilha/química , Proteínas de Ervilha/metabolismo , Pisum sativum/química , Pisum sativum/metabolismo , Peptídeos/metabolismo , Peptídeos/química , Duodeno/metabolismo , HumanosRESUMO
In food formulations, lipids are normally incorporated as emulsions stabilized by different types of emulsifiers. The emulsifiers can affect fatty acid (FA) solubilization as they can interact with FA. The main purpose of the present work is the development of a methodology to evaluate the FA solubilization in an aqueous medium in the absence and presence of exogenous emulsifiers. To this end, a combination of turbidimetry, oiling off and dynamic light scattering (DLS) was used. The FA solubility, as well as its supramolecular assemblies, were determined by analyzing the changes in the turbidity profile and the corresponding size of particles obtained by DLS. Oleic acid (OA) was used as a model FA and a simulated intestinal fluid (SIF) as the aqueous phase. Emulsifiers of low (Tween 80) and high (protein and polysaccharide) molecular weight were tested. Tween 80 was the only emulsifier that improved OA solubilization, whereas the macromolecules only affected the supramolecular structure that OA adopted, being the structure of these assemblies governed by the emulsifier nature.
Assuntos
Emulsificantes , Ácidos Graxos , Emulsões , Polissorbatos , SolubilidadeRESUMO
During the last decade a special interest has been focused on studying the relationship between the composition and structure of emulsions and the extent of lipolysis, driven by the necessity of modulate lipid digestion to decrease or delay fats absorption or increase healthy fat nutrients bioavailability. Because bile salts (BS) play a crucial role in lipids metabolism, understanding how typical food emulsifiers affect the structures of BS under duodenal conditions, can aid to further understand how to control lipids digestion. In the present work the BS-binding capacity of three emulsifiers (Lecithin, Tween 80 and ß-lactoglobulin) was studied under duodenal conditions. The combination of several techniques (DLS, TEM, ζ-potential and conductivity) allowed the characterization of molecular assemblies resulting from the interactions, as modulated by the relative amounts of BS and emulsifiers in solution.
Assuntos
Ácidos e Sais Biliares/metabolismo , Emulsificantes/metabolismo , Secreções Intestinais/metabolismo , Intestinos/fisiologia , Lactoglobulinas/metabolismo , Lecitinas/metabolismo , Digestão , Alimentos , Humanos , Técnicas In VitroRESUMO
The behaviour of proteins (ß-lactoglobulin (ßlg) and soy protein isolate (SPI)) and a surface active polysaccharide (hydroxypropylmethylcellulose, HPMC) o/w interfacial films under simulated gastrointestinal conditions using the interfacial tensiometer Octopus were compared and related to the performance of the emulsions (using the same emulsifiers) under in vitro digestion. The evolution of interfacial tension (γ) was used to investigate the effect of gastrointestinal fluids on o/w interfacial films. Clear differences were observed among these emulsifiers. During the gastric phase, HPMC showed the lowest change in γ values as compared to protein films. The most important changes occurred during the intestinal stage where it was observed an important decrease of γ associated with the rapid penetration of BS, followed by a lower rate of decrease attributable to the accumulation of FFA at the interface. In the last stage, the subphase was exchanged by buffer alone, to remove the reversibly adsorbed digestion products. SPI formed the most resistant interface to the remotion of digestion products, followed by HPMC and finally by ßlg. The results agree with the degree of lipolysis reported for the emulsions stabilized by these emulsifiers, which suggest that lipid digestion could be modulated by the ability of emulsifiers to prevent the BS activity (to adsorb at the O/W interface or remove the inhibitory digestion products from the interface). Thus, emulsifiers-BS interactions appears as a key factor in controlling the lipolysis.
Assuntos
Lactoglobulinas/metabolismo , Óleos/metabolismo , Polissacarídeos/metabolismo , Proteínas de Soja/metabolismo , Água/metabolismo , Digestão , Emulsões/metabolismo , Trato Gastrointestinal/metabolismo , Derivados da Hipromelose/metabolismo , Absorção Intestinal , Mucosa Intestinal/metabolismo , Lipólise , Manometria/métodos , Tensão SuperficialRESUMO
Casein glycomacropeptide (CMP) is a 64- amino acid peptide found in cheese whey, which is released after κ-casein specific cleavage by chymosin. CMP lacks aromatic amino acids, a characteristic that makes it usable as a nutritional supplement for people with phenylketonuria. CMP consists of two nonglycosylated isoforms (aCMP A and aCMP B) and its different glycosylated forms (gCMP A and gCMP B). The most predominant carbohydrate of gCMP is N-acetylneuraminic acid (sialic acid). Here, we developed a CMP purification process based on the affinity of sialic acid for wheat germ agglutinin (WGA). After formation of chitosan beads and adsorption of WGA, the agglutinin was covalently attached with glutaraldehyde. Two matrices with different WGA density were assayed for CMP adsorption. Maximum adsorption capacities were calculated according to the Langmuir model from adsorption isotherms developed at pH 7.0, being 137.0 mg/g for the matrix with the best performance. In CMP reduction from whey, maximum removal percentage was 79% (specifically 33.7% of gCMP A and B, 75.8% of aCMP A, and 93.9% of aCMP B). The CMP was recovered as an aggregate with an overall yield of 64%. Therefore, the matrices developed are promising for CMP purification from cheese whey. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:171-180, 2017.
Assuntos
Aminoácidos/química , Caseínas/isolamento & purificação , Ácido N-Acetilneuramínico/química , Fragmentos de Peptídeos/isolamento & purificação , Proteínas do Soro do Leite/isolamento & purificação , Adsorção , Aminoácidos/metabolismo , Animais , Caseínas/química , Bovinos , Quitosana/química , Cromatografia de Afinidade , Glicosilação , Leite/química , Fragmentos de Peptídeos/química , Soro do Leite/química , Proteínas do Soro do Leite/químicaRESUMO
The effect of high intensity ultrasound (HIUS) may produce structural modifications on proteins through a friendly environmental process. Thus, it can be possible to obtain aggregates with a determined particle size, and altering a defined functional property at the same time. The objective of this work was to explore the impact of HIUS on the functionality of a denatured soy protein isolate (SPI) on foaming and interfacial properties. SPI solutions at pH 6.9 were treated with HIUS for 20 min, in an ultrasonic processor at room temperature, at 75, 80 and 85°C. The operating conditions were: 20 kHz, 4.27 ± 0.71 W and 20% of amplitude. It was determined the size of the protein particles, before and after the HIUS treatment, by dynamic light scattering. It was also analyzed the interfacial behavior of the different systems as well as their foaming properties, by applying the whipping method. The HIUS treatment and HIUS with temperature improved the foaming capacity by alteration of particle size whereas stability was not modified significantly. The temperature of HIUS treatment (80 and 85°C) showed a synergistic effect on foaming capacity. It was found that the reduction of particle size was related to the increase of foaming capacity of SPI. On the other hand, the invariable elasticity of the interfacial films could explain the stability of foams over time.
Assuntos
Tamanho da Partícula , Proteínas de Soja/química , Proteínas de Soja/isolamento & purificação , Ondas Ultrassônicas , Ar , Desnaturação Proteica , Água/químicaRESUMO
Proteins and polysaccharides are widely used in food formulation. While most of the proteins are surface active, only few polysaccharides can adsorb at the air-water interface; this is the case of propylene glycol alginates (PGA). It is known that casein glycomacropeptide (CMP), a bioactive polypeptide derived from κ-casein by the action of chymosin, presents a great foaming capacity but provides unstable foams. So, the objective of this work was to analyze the impact of mixing CMP and a commercial variety of PGA, Kelcoloid O (KO), on the interfacial and foaming properties at pH 7.0. It was determined the surface pressure isotherm, the dynamics of adsorption and the foaming properties for CMP, KO and the mixed system CMP-KO. CMP dominated the surface pressure of CMP-KO mixed system. The presence of KO synergistically improved the viscoelastic properties of surface film. The foaming capacity of CMP was altered by KO. KO foam presented a higher stability than CMP foam and it controlled the stability against drainage and the initial collapse in the mixed foam.
Assuntos
Alginatos/química , Caseínas/química , Fragmentos de Peptídeos/química , Adsorção , Membranas Artificiais , Pressão , Propriedades de SuperfícieRESUMO
The aim of this work was to study the effect of interactions between casein glycomacropeptide (CMP) and ß-lactoglobulin (ß-lg) at pH 6.5 and 3.5 on the foaming properties of the mixed systems with different CMP:ß-lg ratios. The foaming properties were determined by the bubbling method with a Foamscan instrument. A highest overall foam capacity (OFC), foaming capacity (FC) and mainly stability of mixed foams at pH 3.5, as compared to the mixed foams at pH 6.5 or the foams of CMP and ß-lg was observed. At pH 6.5, the stability of mixed foams decreased with increasing the CMP content, while OFC and FC values were similar to ß-lg foam. The performance of the mixed systems was discussed in relation with the interactions between CMP and ß-lg in the aqueous phase (as observed by dynamic light scattering and differential scanning calorimetry in previous works).
Assuntos
Caseínas/química , Glicopeptídeos/química , Lactoglobulinas/química , Fragmentos de Peptídeos/química , Concentração de Íons de HidrogênioRESUMO
The aim of this research is to quantify the competitive adsorption of a whey protein concentrate (WPC) and hydroxypropyl-methyl-cellulose (HPMC so called E4M, E50LV and F4M) at the air-water interface by means of dynamic surface tensiometry and Brewster angle microscopy (BAM). These biopolymers are often used together in many food applications. The concentration of both protein and HPMC, and the WPC/HPMC ratio in the aqueous bulk phase were variables, while pH (7), the ionic strength (0.05 M) and temperature (20 degrees C) were kept constant. The differences observed between mixed systems were in accordance with the relative bulk concentration of these biopolymers (C(HPMC) and C(WPC)) and the molecular structure of HPMC. At short adsorption times, the results show that under conditions where both WPC and HPMC could saturate the air-water interface on their own or when C(HPMC) > or = C(WPC), the polysaccharide dominates the surface. At concentrations where none of the biopolymers was able to saturate the interface, a synergistic behavior was observed for HPMC with lower surface activity (E50LV and F4M), while a competitive adsorption was observed for E4M (the HPMC with the highest surface activity). At long-term adsorption the rate of penetration controls the adsorption of mixed components. The results reflect complex competitive/synergistic phenomena under conditions of thermodynamic compatibility or in the presence of a "depletion mechanism". Finally, the order in which the different components reach the interface will influence the surface composition and the film properties.
Assuntos
Metilcelulose/análogos & derivados , Proteínas do Leite/química , Adsorção , Ar , Derivados da Hipromelose , Cinética , Metilcelulose/química , Propriedades de Superfície , Água , Proteínas do Soro do LeiteRESUMO
Caseinoglycomacropeptide (GMP) is a hydrophilic glycopeptide released from milk kappa-casein by chymosin hydrolysis during cheese making. GMP is thought to be a potential ingredient for specific dietary applications with several health benefits. In this study GMP was characterized at the air-water interface and its behaviour was related with the self-assembly of GMP in solution as affected by pH. This GMP self-assembly was investigated by dynamic light scattering and the interfacial properties were determined by tensiometry and surface dilatational measurements at pH 4, 5 and 7. At pH 5 GMP exhibited higher surface pressure at equilibrium than at pH 7. At pH 4 the behaviour was more complex due to self-assembly close to GMP pI. Dynamic measurement showed that the adsorption/penetration rate constant (K(ads)) is facilitated at higher GMP bulk concentrations, while the rate constant of rearrangement (K(r)) decreased at higher GMP concentrations which could be attributed to the existence of a steric restriction due to the higher GMP load at the interface. K(r) was higher at pH 5 because of lower electrostatic interactions close to the pI. The viscoelastic properties showed a complex behaviour due to the existence of protein-protein interactions depending on the GMP concentration, on the pH of the bulk and on the rates of diffusion, adsorption and rearrangement of GMP at the air-water interface.
Assuntos
Caseínas/química , Glicopeptídeos/química , Adsorção , Ar , Difusão , Elasticidade , Concentração de Íons de Hidrogênio , Cinética , Proteínas do Leite/química , Tamanho da Partícula , Pressão , Soluções , Propriedades de Superfície , Temperatura , Fatores de Tempo , Substâncias Viscoelásticas/química , Viscosidade , Água/químicaRESUMO
The aim of this work was to study the interactions and adsorption of caseinoglycomacropeptide (GMP) and GMP:beta-lactoglobulin (beta-lg) mixed system in the aqueous phase and at the air-water interface. The existence of associative interactions between GMP and beta-lg in the aqueous phase was investigated by dynamic light scattering, differential scanning calorimetry (DSC), fluorometry and native PAGE-electrophoresis. The surface pressure isotherm and the static and dynamic surface pressure were determined by tensiometry and surface dilatational properties. The results showed that GMP presented higher surface activity than beta-lg at a concentration of 4%wt but beta-lg showed higher film forming ability. In the mixed systems beta-lg dominated the static and dynamic surface pressure and the rheological properties of interfacial films suggesting that beta-lg hinders GMP adsorption because, in simple competition, GMP should dominate because of its higher surface activity. The surface predominance of beta-lg can be attributed to binding of GMP to beta-lg in the aqueous phase that prevents GMP adsorption on its own.
Assuntos
Ar , Lactoglobulinas/química , Fragmentos de Peptídeos/química , Água , Adsorção , Varredura Diferencial de Calorimetria , Eletroforese em Gel de Poliacrilamida , Fluorometria , Propriedades de SuperfícieRESUMO
Surface pressure isotherms and structural and surface dilatational properties of three hydroxypropylmethycelluloses (HPMCs, called E4M, E50LV, and F4M) adsorbed films at the air-water interface were determined. In this work we present evidence that HPMC molecules are able to diffuse and saturate the air-water interface at very low concentrations in the bulk phase. As bulk concentration increased, structural changes at a molecular level occurred at the interface. These changes corresponded to transition from an expanded structure (structure I) to a condensed one (structure II). When the surface concentration of HPMC was high enough, the collapse of the monolayer was observed. The three HPMCs formed very elastic films at the air-water interface, even at low surface pressures. E4M showed features that make it unique. For instance it showed the highest surface activity, mainly at low bulk concentrations (<10(-4) wt %). The differences observed in surface activity may be attributed to differences in the hydroxypropyl molar substitution and molecular weight of HPMC. All three HPMCs formed films of similar viscoelasticity and elastic dilatational modulus, which can be accounted for by their similar degree of methyl substitution.
Assuntos
Ar , Metilcelulose/análogos & derivados , Água/química , Elasticidade , Derivados da Hipromelose , Metilcelulose/química , Transição de Fase , TermodinâmicaRESUMO
In the present work we have studied the characteristics of propylene glycol alginates (PGA) adsorption at the air-water interface and the viscoelastic properties of the films in relation to its foaming properties. 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). The temperature (20 degrees C) and pH (7.0) were maintained constant. For time-dependent surface pressure measurements and surface dilatational properties of adsorbed PGA at the air-water interface an automatic drop tensiometer was used. The foam was generated by whipping and then the foam capacity and stability was determined. The results reveal a significant interfacial activity for PGA due to the hydrophobic character of the propylene glycol groups. The kinetics of adsorption at the air-water interface can be monitored by the diffusion and penetration of PGA at the interface. The adsorbed PGA film showed a high viscoelasticity. The surface dilatational modulus depends on the PGA and its concentration in the aqueous phase. Foam capacity of PGA solutions increased in the order KO > MAN > KLVF, which followed the increase in surface pressure and the decrease in the viscosities of PGA solutions. The stability of PGA foams monitored by the drainage rate and collapse time follows the order MAN > KLVF > KO. The foam stability depends on the combined effect of molecular weight/degree of esterification of PGA, solution viscosity and viscoelasticity of the adsorbed PGA film.