Protein Foam Stability Research Articles

Effects of simultaneous water-enzyme separation on the physical and chemical properties of peanut oil and protein

Peanut (Arachis hypogaea L.) is widely cultivated as a valuable industrial oilseed. This study aimed to investigate the oil and protein that was extracted from peanuts by aqueous enzymatic method (AEM). Compared with freeze-thaw demulsification (FTD), n-hexane extraction (NHE) and protease demulsification (PD), the fatty acid composition of oil by combination of oleic and citric acids demulsification (COCAD) was similar. The acid value of the oil extracted by new AEM and various demulsification methods was between 0.12 and 0.59 mg KOH/g, the peroxide value was between 0.06 and 0.19 g/100 g, the free fatty acid content was between 0.32% and 0.71%, and the oxidation induction time was between 0.13 and 3.21 h. The content of tocopherol in oil: NHE>FTD>PD>COCAD. The amino acid and protein subunit compositions of peanut protein extracted by AEM (AEMPP), peanut protein isolate (PPI) and commercially available peanut protein (CAPP) were similar. Scanning electron microscope revealed that protein powders morphology of various extraction methods. Compared to CAPP and PPI, β-turns and random coil structure of AEMPP was increased. The solubility, water and oil holding capacity, emulsifying activity index, emulsification stability, foaming property and foam stability of protein: AEMPP > PPI > CAPP. This study provides a theoretical basis for the large-scale industrial application of AEM.

Improving the whey protein foam structures by using novel acetylated triglycerides: A response surface methodology (RSM) approach

AbstractProtein foams are common to foods, such as meringue, whipped cream and mousses. Stability is a challenging issue determined by fat and sugar content. We hypothesize that acetyl‐triacylglycerols (acetyl‐TAG) that possess sn‐3 acetate group with high oleic content can provide stability to the foam at reduced sugar concentrations by increasing the surface viscosity and minimizing serum drainage. A fractional factorial Box‐Wilson design was used to investigate the effects of whey protein concentration (WPI) (2–10 wt%), sucrose concentration (SC) (10–30 wt%) and acetyl‐TAG concentration (ATC) (0–1 wt%) on overrun (FO), stability against serum drainage (FD) and surface dilatational rheology. Each response was analyzed by linear regression model fitting and a backward elimination algorithm for significance (α = 0.01). FO was significantly affected (p < 0.01) by WPI and ATC, but not sucrose concentration. The optimum overrun (nearly 700%) was obtained at 9 wt% WPI and 0.6 wt% ATC. Drainage and viscoelastic properties were significantly (p < 0.01) affected by all process variables. Dynamic complex modulus (|E|) as measured using an optical tensiometer was around 30–40 mN/m when acetyl‐TAG was higher than 0.5 wt%. Our findings indicated that the acetyl‐TAG can be used to enhance the stability of protein foams in reduced sugar food products, however, not at high sugar concentrations (30 wt%).

Effects of short-term and long-term cold plasma treatment on the color, structure, and Pickering foaming properties of Grass pea protein particles

In this study, the effects of short-term (30 and 60 seconds) and long-term (300 and 600 seconds) cold plasma treatments at two voltages (9.4 and 18.6 kVpp) on the color, structure, and foaming properties of Grass pea protein isolate (GPPI) were investigated. The b* value of the protein particles (yellow color) increased with increasing treatment time and applied voltage. FTIR spectroscopy revealed a decrease in intramolecular aggregates of GPPI after short-term cold plasma treatment (S-CPT), which was accompanied by an increase in the α-helix to β-sheet transition with increasing treatment time and applied voltage. Long-term cold plasma treatment (L-CPT) increased the intermolecular aggregates, α-helix and β-sheet structures, with the exception of L-GPPIPT/60018.6 particles. The pH of the protein dispersion decreased as treatment time and applied voltage increased, with the exception of L-GPPIPT/60018.6 dispersion. Changes in the free amino groups and particle size distribution demonstrated that the S-CPT fabricated smaller particles with flexible conformations, whereas the L-CPT produced particles of different sizes with compact conformations due to protein aggregations and intermolecular interactions. S-CPT increased particle water binding capacity and the absorption rate of particles at the water-air interface, whereas L-CPT decreased these properties. The best foamability and foam stability were obtained with S-GPPIPT/6018.6 and L-GPPIPT/6009.4 particles, respectively. Microscopic observation indicated that cold plasma treatment altered the morphological properties of the protein-stabilized foam. Results of this study indicate that S-CPT is an effective solution for improving GPPI's foamability, while L-CPT has the potential to enhance protein foam stability through the Pickering mechanism.

THE EFFECT OF PLANT PROTEINS ON THE FORMATION OF STRUCTURAL AND RHEOLOGICAL PROPERTIES OF NOUGAT

This paper considers the problem of increasing the nutritional value of whipped confectionery such as nougat by using hemp- based and soya-based protein-containing ingredients. The main tendencies of obtaining new types of food based on plant proteins with complete amino acid composition are described. The paper presents information on cultivating and using hemp and soya both in Ukraine and in the world, and suggests how products of their processing can be applied to improve the quality and increase the biological value of confectionery. It has been investigated what effect protein-containing ingredients obtained from hemp and soya have on the structural properties of foam in the technology of whipped confectionery such as nougat. It has been established that increasing the amount of plant protein additives leads to a decrease in the foaming ability, but the stability of protein foams increases. Adding 10% of protein-containing hemp additives increases the foam stability by 6%, while protein-containing soya additives increase it by 5%. The paper presents the results of studying the structural and rheological properties of nougat mass with protein-containing plant additives in the amount 2.5–10% of the weight of sugar. It has been determined that adding protein-containing hemp and soya ingredients increases the viscosity and plastic strength of the products and stabilises their structure. The effect of different amounts of nuts on the kinetics of nougat crystallisation has been studied. It is recommended to add 5% of hemp and 7.5% of soya protein-containing additives instead of sugar during the whipping of nougat mass, because it reduces the whipping time and has a positive effect on structure formation. The recommended amount of roasted pistachio kernels in the samples suggested is 25–35% of the total weight of nougat, with the resting time 30–60 minutes and the moulding temperature 50–55°C. The nutritional value of the new products with protein-containing hemp and soya ingredients and nuts has been calculated. It has been noted that nougat has been enriched with protein, unsaturated fatty acids, and minerals (potassium, calcium, magnesium, phosphorus).

Enhancing protein self-association at the gas–liquid interface for foam fractionation of bovine serum albumin from its highly diluted solution

Improving foam stability is an important issue in foam fractionation of proteins from their aqueous solutions with low foam properties. In this work, enhancing protein self-association at the gas–liquid interface by sodium citrate (Na-citrate), instead of adding surfactants, was used to improve the stability of protein foams. Using bovine serum albumin (BSA) as a model protein, the role of Na-citrate in enhancing self-association of BSA at the gas–liquid interface was studied at the molecular level. Then, the role of the enhanced protein self-association in intensifying foam fractionation of BSA was studied. The results show that by weakening electrostatic repulsion between the BSA molecules and unfolding their structures, Na-citrate induced the formation of 12 and 18 BSA aggregates at the gas–liquid interface. The enhanced protein self-association effectively increased the interfacial adsorption of BSA and improved the foam stability. At BSA concentration 50mg/L, the recovery percentage of BSA with 30mmol/L Na-citrate increased by 4 folds while its enrichment ratio just decreased by 11.5%, compared to those without Na-citrate. The results give a clear understanding of the role of protein self-association in foam fractionation of proteins.

Comparing foam and interfacial properties of similarly charged protein–surfactant mixtures

The foam stability of protein–surfactant mixtures strongly depends on the charge of the protein and the surfactant, as well as on their mixing ratio. Depending on the conditions, the mixtures will contain free proteins, free surfactants and/or protein–surfactant complexes. To be able to compare different protein–surfactant mixtures, generic knowledge about the occurrence of each of these states and their relative contribution to foam stability is essential. In this work, the foam stability and interfacial properties of bovine serum albumin (BSA) mixed with sodium dodecyl sulphate (SDS) as well the binding of SDS to BSA as are studied at different molar ratios (MR). A comparison is made with β-lactoglobulin (BLG) mixed with SDS. Both proteins and SDS are negatively charged at pH 7. The foam stability in the presence of small amounts (up to MR 1) of SDS is half the value of the pure protein solutions. The foam stability for both protein surfactant mixtures reaches a minimum at MR 20. A further increase of the MR leads to an increase of foam stability. The foam stability of BLG–SDS at MR >20 follows the foam stability of pure SDS solutions at equivalent concentrations, while BSA–SDS mixtures have an offset and begin to increase from MR >50. This behaviour was also reflected in the surface pressure and complex dilatational elastic moduli, and could be linked to the binding of the surfactant to the proteins. Both proteins bind SDS at high and low affinity binding sites. BSA's high affinity binding sites have a binding stoichiometry of 5.5 molSDS/molprotein, and BLG's high affinity binding site has a stoichiometry of 0.8 molSDS/molprotein (determined by isothermal titration calorimetry). Binding to the low affinity binding sites, occurs with a binding ratio, leading to an accumulation of free surfactants. While the basic mechanisms underlying the foam properties of mixed systems are not explained in detail by this approach, the foam stability plots of both protein surfactant mixtures could be superimposed using the concentration of free SDS.

Protein Adsorption at the Electrified Air–Water Interface: Implications on Foam Stability

The surface chemistry of ions, water molecules, and proteins as well as their ability to form stable networks in foams can influence and control macroscopic properties such as taste and texture of dairy products considerably. Despite the significant relevance of protein adsorption at liquid interfaces, a molecular level understanding on the arrangement of proteins at interfaces and their interactions has been elusive. Therefore, we have addressed the adsorption of the model protein bovine serum albumin (BSA) at the air-water interface with vibrational sum-frequency generation (SFG) and ellipsometry. SFG provides specific information on the composition and average orientation of molecules at interfaces, while complementary information on the thickness of the adsorbed layer can be obtained with ellipsometry. Adsorption of charged BSA proteins at the water surface leads to an electrified interface, pH dependent charging, and electric field-induced polar ordering of interfacial H(2)O and BSA. Varying the bulk pH of protein solutions changes the intensities of the protein related vibrational bands substantially, while dramatic changes in vibrational bands of interfacial H(2)O are simultaneously observed. These observations have allowed us to determine the isoelectric point of BSA directly at the electrolyte-air interface for the first time. BSA covered air-water interfaces with a pH near the isoelectric point form an amorphous network of possibly agglomerated BSA proteins. Finally, we provide a direct correlation of the molecular structure of BSA interfaces with foam stability and new information on the link between microscopic properties of BSA at water surfaces and macroscopic properties such as the stability of protein foams.

Competitive Destabilization/Stabilization of β‐Lactoglobulin Foam by PEO‐PPO‐PEO Polymeric Surfactants

The effect on β‐lactoglobulin foamability and foam stability of the poly(ethylene oxide)‐poly(propylene oxide) block copolymers F127 (PEO99‐PPO65‐PEO99), molecular weight 12500 g/mol, and P85 (PEO26‐PPO39‐PEO26), molecular weight 4600 g/mol, has been investigated at constant protein concentration, 10 µM (0.2 mg/L), and varying block copolymer concentrations, ranging from 0.02 to 1600 µM. Foam was generated by means of air sparging and the foam volume and liquid volume of the foam were measured for one hour. It was found that foam stabilized by F127 or P85 in the concentration range 20–1600 µM contained a larger liquid volume initially than pure β‐lactoglobulin foam. Furthermore, β‐lactoglobulin foamability was only marginally affected by the presence of F127, while it was reduced in an interval of low P85 concentrations. The protein foam stability was retained in the presence of the larger polymer F127, whereas P85 largely reduced the stability, indicating that the size of the polymeric surfactant is important. The results are discussed in relation to surface rheological properties and forces acting across foam films. Steric repulsion generated between the surfaces of foam films is suggested to be the main stabilizing factor in dry foam containing F127. The instability of the mixed β‐lactoglobulin/P85 system is suggested to be caused by two effects. First, there are incompatible stabilization mechanisms of block copolymer and protein, as supported by previous surface rheological data. Second, there is a reduced importance of long‐range steric repulsion when P85 is added, compared to the case where F127 and β‐lactoglobulin are mixed.

Restoration of protein foam stability through electrostatic propylene glycol alginate-mediated protein–protein interactions

The action of propylene glycol alginate in the enhancement of foam stability of a destabilised Tween 20/bovine serum albumin mixed system was evaluated. A significant increase in the foam stability was observed in the presence of low concentrations of propylene glycol alginate. A pseudo-plateau level of foam stability was obtained in the presence of approximately 0.8 μg/ml propylene glycol alginate in the solution used to form the foam. Foam stability enhancement due to bulk viscosity changes and surface effects were elucidated. The increase in foam stability was investigated by reference to the properties of thin liquid films and the macroscopic interface of test solutions. Propylene glycol alginate was found to slow the rate of thin film drainage, increase the equilibrium thickness of the films, slow the lateral diffusion of a fluorescent probe molecule located in the adsorbed layer and increase the elasticity of the interface. Data are consistent with propylene glycol alginate-induced crosslinking of protein in the adsorbed layer. This polysaccharide presents a means for controlling protein foam stability.

Enhancement of Protein Foam Stability by Formation of Wheat Arabinoxylan‐Protein Crosslinks

ABSTRACTThe foam stability properties of a defined mixed solution of Tween 20 and bovine serum albumin was evaluated as a function of arabinoxylan concentration. A marked increase in the foam stability was observed with low concentrations of arabinoxylan. Maximum improvement in the foam stability was obtained with 0.2–0.3 mg/mL of arabinoxylan. Enhancement of foam stability due to a combination of bulk viscosity changes and surface effects was identified. The relative contribution of arabinoxylan to bulk viscosity and adsorbed layer structure was studied by examination of the properties of thin liquid films and the macroscopic air‐water interface. Arabinoxylan reduced the rate of thin film drainage, increased the equilibrium thickness of the films, slowed the lateral diffusion of a fluorescent probe molecule located in the adsorbed layer, and increased the surface elasticity. These data are congruent with arabinoxylan‐mediated crosslinking of adsorbed protein. These observations may be of significance in gas retention during breadmaking. In addition, this naturally occurring polysaccharide offers potential for use in the control of protein foam stability.

Control of Surfactant-Induced Destabilization of Foams through Polyphenol-Mediated Protein-Protein Interactions

The effectiveness of (+)-catechin in the control of foam stability of a deliberately destabilized Tween 20//3-lactoglobulin mixed system was investigated. Significant improvement in the foamability and foam stability was obtained in the presence of low concentrations of (+)-catechin. The maximum improvement was observed at a molar ratio of (+)-catechin to protein of approximately 0.1. The mechanism of action of (+)-catechin was investigated by careful study of the properties of thin liquid films (isolated foam lamellae). This polyphenolic compound was found to increase the equilibrium thickness was located in the adsorbed layer. The data are consistent with (+)-catechin-induced cross-linking of proteins in the adsorbed layer. Such molecules offer considerable potential protein foam stability.

Determination of protein foam stability from time-dependent pressure monitoring

An apparatus is described for the determination of protein foam stability from time-dependent measurements of the small pressure changes above the collapsing foam in a closed chamber. Experimental data are reported for foams made with a fixed concentration (0.1% wt) of bovine serum albumin (BSA) and various concentrations of the nonionic polysaccharide dextran at neutral pH. The results show a loss of foam stability at low dextran contents, an increase in stability at high contents, and a minimum level of stability at a dextran:bovine serum albumin (BSA) molar ratio of ~2. The trends in the data obtained with the new pressure monitoring apparatus are consistent with those obtained by visual observations of the rate of foam volume decay.