Effects of sucrose on egg white protein and whey protein isolate foams: Factors determining properties of wet and dry foams (cakes)

The effects of sucrose on the physical properties of foams (foam overrun and drainage ½ life), air/water interfaces (interfacial dilational elastic modulus and interfacial pressure) and angel food cakes (cake volume and cake structure) of egg white protein (EWP) and whey protein isolate (WPI) was investigated for solutions containing 10% (w/v) protein. Increasing sucrose concentration (0–63.6 g/100 mL) gradually increased solution viscosity and decreased foam overrun. Two negative linear relationships were established between foam overrun and solution viscosity on a log–log scale for EWP and WPI respectively; while the foam overrun of EWP decreased in a faster rate than WPI with increasing solution viscosity (altered by sucrose). Addition of sucrose enhanced the interfacial dilational elastic modulus (E′) of EWP but reduced E′ of WPI, possibly due to different interfacial pressures. The foam drainage ½ life was proportionally correlated to the bulk phase viscosity and the interfacial elasticity regardless of protein type, suggesting that the foam destabilization changes can be slowed by a viscous continuous phase and elastic interfaces. Incorporation of sucrose altered the volume of angel food cakes prepared from WPI foams but showed no improvement on the coarse structure. In conclusion, sucrose can modify bulk phase viscosity and interfacial rheology and therefore improve the stability of wet foams. However, the poor stability of whey proteins in the conversion from a wet to a dry foam (angel food cake) cannot be changed with addition of sucrose.     

Foams Prepared from Whey Protein Isolate and Egg White Protein: 1. Physical, Microstructural, and Interfacial Properties

ABSTRACT:  Foams were prepared from whey protein isolate (WPI), egg white protein (EWP), and combinations of the 2 (WPI/EWP), with physical properties of foams (overrun, drainage 1/2 life, and yield stress), air/water interfaces (interfacial tension and interfacial dilatational elasticity), and foam microstructure (bubble size and dynamic change of bubble count per area) investigated. Foams made from EWP had higher yield stress and stability (drainage 1/2 life) than those made from WPI. Foams made from mixtures of EWP and WPI had intermediate values. Foam stability could be explained based on solution viscosity, interfacial characteristics, and initial bubble size. Likewise, foam yield stress was associated with interfacial dilatational elastic moduli, mean bubble diameter, and air phase fraction. Foams made from WPI or WPI/EWP combinations formed master curves for stability and yield stress when normalized according to the above-mentioned properties. However, EWP foams were excluded from the common trends observed for WPI and WPI/EWP combination foams. Changes in interfacial tension showed that even the lowest level of WPI substitution (25% WPI) was enough to cause the temporal pattern of interfacial tension to mimic the pattern of WPI instead of EWP, suggesting that whey proteins dominated the interface. The higher foam yield stress and drainage stability of EWP foams appears to be due to forming smaller, more stable bubbles, that are packed together into structures that are more resistant to deformation than those of WPI foams.     

Foams Prepared from Whey Protein Isolate and Egg White Protein: 2. Changes Associated with Angel Food Cake Functionality

ABSTRACT:  The effects of sucrose on the physical properties and thermal stability of foams prepared from 10% (w/v) protein solutions of whey protein isolate (WPI), egg white protein (EWP), and their combinations (WPI/EWP) were investigated in wet foams and angel food cakes. Incorporation of 12.8 (w/v) sucrose increased EWP foam stability (drainage 1/2 life) but had little effect on the stability of WPI and WPI/EWP foams. Increased stability was not due to viscosity alone. Sucrose increased interfacial elasticity ( E  ') of EWP and decreased E' of WPI and WPI/EWP combinations, suggesting that altered interfacial properties increased stability in EWP foams. Although 25% WPI/75% EWP cakes had similar volumes as EWP cakes, cakes containing WPI had larger air cells. Changes during heating showed that EWP foams had network formation starting at 45 °C, which was not observed in WPI and WPI/EWP foams. Moreover, in batters, which are foams with additional sugar and flour, a stable foam network was observed from 25 to 85 °C for batters made from EWP foams. Batters containing WPI or WPI/EWP mixtures showed signs of destabilization starting at 25 °C. These results show that sucrose greatly improved the stability of wet EWP foams and that EWP foams form network structures that remain stable during heating. In contrast, sucrose had minimal effects on stability of WPI and WPI/EWP wet foams, and batters containing these foams showed destabilization prior to heating. Therefore, destabilization processes occurring in the wet foams and during baking account for differences in angel food cake quality.     

Comparative effect of thermal treatment on the physicochemical properties of whey and egg white protein foams

The optimization of the functionalities of commercial protein ingredients still constitutes a key objective of the food industry. Our aim was therefore to compare the effect of thermal treatments applied in typical industrial conditions on the foaming properties of whey protein isolate (WPI) and egg white proteins (EWP): EWP was pasteurized in dry state from 1 to 5 days and from 60 °C to 80 °C, while WPI was heat-treated between 80 °C and 100 °C under dynamic conditions using a tubular heat exchanger. Typical protein concentrations of the food industry were also used, 2% (w/v) WPI and 10% (w/v) EWP at pH 7, which provided solutions of similar viscosity. Consequently, WPI exhibited a higher foamability than EWP. For WPI, heat treatment induced a slight decrease of overrun when temperature was above 90 °C, i.e. when aggregation reduced too considerably the amount of monomers that played the key role on foam formation; conversely, it increased foamability for EWP due to the lower aggregation degree resulting from dry heating compared to heat-treated WPI solutions. As expected, thermal treatments improved significantly the stability of WPI and EWP foams, but stability always passed through a maximum as a function of the intensity of heat treatment. In both cases, optimum conditions for foam stability that did not impair foamability corresponded to about 20% soluble protein aggregates. A key discrepancy was finally that the dry heat treatment of EWP provided softer foams, despite more rigid than the WPI-based foams, whereas dynamically heat-treated WPI gave firmer foams than native proteins.     

A Method for the Measurement of Foam Formation and Stability

A whipping method for the measurement of overrun and foam stability was developed. Using this method the characteristic foams formed by the following proteins were studied: sodium caseinate, milk protein isolate and whey protein. The method was able to detect differences between foams produced by different proteins. The effects of copper sulfate and proteose-peptone on egg white foams were studied to show the reliability of the method. It was demonstrated that the addition of ImM copper sulfate stabilized (p < 0.05) foams made from both fresh and powdered egg white. Addition of proteose-peptone (0.05% and 0.1%) reduced the overrun and destabilized egg white foams.     

The stability and physical properties of egg white and whey protein foams explained based on microstructure and interfacial properties

The goal of this investigation was to determine if physical models, based on micro-scale (bubbles) and nano-scale (interface) properties, can be used to explain the macroscopic foaming properties of egg white protein (EWP) and whey protein isolate (WPI). Foam properties were altered by adding different amounts of sucrose (4.27–63.6 g/100 mL) and microstructures were observed using confocal laser scanning microscopy and bubbles were quantitatively measured using image analysis. Addition of sucrose decreased the initial bubble size, corresponding to higher foam stability and lower air phase fraction. EWP foams were composed of smaller bubbles and lower air phase fractions than WPI foams. Increased sucrose concentration caused a decreased liquid drainage rate due to a higher continuous phase viscosity and smaller bubble sizes. WPI foams had faster rates for liquid drainage and bubble coarsening than EWP foams. The differences were attributed to faster bubble disproportionation in WPI foams, caused by lower interfacial elasticity and lower liquid phase fractions. The experimentally fitted parameters for foam yield stress did not follow universal trends and were protein type dependent. EWP foams had higher yield stress than WPI foams due to smaller bubble sizes and higher interfacial elasticity. The yield stress of WPI foams increased slightly with addition of sucrose and cannot be accounted for based solely on model parameters. It appears that changes in stability of EWP and WPI foams can be explained based on physical models while unaccounted for protein-specific effects remain regarding foam yield stress.     

Whipping Studies with Partially Deloctosed Cheese Whey

Whipping properties of various whey preparations were studied by measuring overrun and stability of foams produced in a Hobart mixer. Presence of heat-labile whey proteins resulted in poor whippability, poor foam stability, and low overruns. Removal of the heat-acid coagulated proteins greatly improved wh’ppability, and foams resembled whipped egg whites with overruns of more than 2,500%. Increasing total solids by evaporation of the acid supernatant or by addition of sucrose or soluble starch decreased the overrun but increased foam stability. Air uptake and overrun were negatively affected by calcium hydroxide. Foams from dialyzed supernatants with addition of sucrose were successfully baked into meringues.     

Effects of Lysozyme, Clupeine, and Sucrose on the Foaming Properties of Whey Protein Isolate and β-Lactoglobulin

Lysozyme and clupeine interacted with β-lactoglobulin to form aggregates. Sucrose reduced the aggregation. The addition of lysozyme (0.5%) to β-lactoglobulin (2.5%) reduced the time required to reach an overrun maximum and increased foam stability and heat stability by 124% and 377%, respectively. Lysozyme (0.5%) also improved overrun (98%), foam stability (114%) and heat stability of the foams (12%) made with whey protein isolate (WPI, 5%). Lysozyme and sucrose further improved the foaming properties of β-lactoglobulin and WPI. The addition of clupeine and sucrose gave similar results. The foaming properties of β-lactoglobulin and WPI with the inclusion of sucrose and lysozyme were superior to those of egg white.     

Interfacial and foaming properties of soy protein and their hydrolysates

The objective of the work was to study the impact of soy protein hydrolysis on foaming and interfacial properties and to analyze the relationship between them. As starting material a sample of commercial soy protein isolate was used (SP) and hydrolysates were produced by an enzymatic reaction, giving hydrolysates from 0.4% to 5.35% degree of hydrolysis (DH).In this contribution we have determined foam overrun (FO), stability against liquid drainage and foam collapse, and the apparent viscosity of foams produced by a whipping method. The surface properties determined were the adsorption isotherm and surface dilatational properties of two hydrolysates (2 and 5.35% DH, H1 and H2 respectively).The hydrolysis of soy proteins increased the surface activity at bulk concentrations where SP adopts a condensed conformation at the monolayer. At concentrations where it adopts a more expanded conformation a very low degree of hydrolysis (H1) also promoted the enhancement of surface activity. However, at 5.35% degree of hydrolysis (H2) the surface activity decreased. Moreover, H2 presented lower surface activity than H1 at every bulk concentration.The hydrolysis increased the elastic component of the dilatational modulus and decreased phase angle of films at bulk concentrations below that corresponding to the collapse of SP monolayer (2% bulk protein).SP hydrolysis increased foam overrun and the stability against drainage that could be related to increased surface activity of protein hydrolysates. However, the collapse of foams was promoted by hydrolysis and could be ascribed to a decrease of the relative viscoelasticity (higher phase angle) of surface films.The results point out that a low degree of hydrolysis (2–5%) would be enough to improve the surface activity of SP, decrease foam drainage and maintaining a considerable viscoelasticity of the surface films to retard foam collapse.     

Measurement of the Yield Stress of Protein Foams by Vane Rheometry

The yield stresses of protein foams made from varying protein types (spray dried egg white and whey protein isolate), protein concentrations, whip times, and mixer models were evaluated using vane rheometry. Two methods of analysis (point and slope methods) were investigated. Yield stress values determined by slope and point methods were similar for egg white protein foams but did not agree in the analysis of whey protein foams. Point method values were very reproducible in all foams tested. Egg white protein solutions formed stiffer foams more rapidly and at lower protein concentrations than foams made from whey protein isolate. Vane rheometry was shown to be a reliable method of determining yield stress in protein foams.     

Use of Mucor miehei lipase to improve functional properties of yolk-contaminated egg whites

Egg yolk contamination of egg whites continues to be a serious problem in the egg industry. The ability of egg whites to form stable and voluminous foams is greatly inhibited by yolk contamination, even at very low levels, between 0.01% and 0.2% w/w yolk in white. Experiments were conducted to determine if Mucor miehei lipase could regenerate the functional properties of yolk-contaminated egg whites. Lipase from M. miehei and colipase from porcine pancreas were added to yolk-contaminated (0.2%, w/w) egg white samples to hydrolyze triglycerides originating from egg yolk. Enzymatic hydrolysis of triacylglycerols was confirmed using thin-layer chromatography. Treatment of yolk-contaminated samples with lipase and colipase yielded significant (P < 0.05) improvements in a number of the functional properties, including the final foam volume, foam capacity, and foaming power. These functional properties showed complete restoration to control levels. However, foam stability and foam drainage levels were not statistically different from yolk-contaminated samples that had not been enzymatically treated. Enzyme-treated yolk-contaminated egg whites were also tested in angel food cakes. Enzyme-treated, yolk-contaminated egg whites performed similarly to non-yolk-contaminated control, and much better than yolk-contaminated sample in angel food cakes. The results show that most negative effects of yolk contamination can be reversed by treatment with Mucor miehei lipase and colipase.     

Rheological properties of angel food cake made with pH unfolded and refolded egg albumen

Angel food cake was made using egg albumen subjected to the pH-induced unfolded and refolded treatment. The effect of treatment on the rheological properties of angel food cake was investigated. Egg albumen solutions were prepared and pH was adjusted to 1.5, 4.5, 8.5 or 12.5 and then held 60 min to unfold the proteins. After holding, the solutions were readjusted to pH 4.5 or 8.5, and held for 45 min to partially refold the proteins. Egg white foam with sucrose was whipped and flour and the rest of sucrose were folded into the foam. The foam batter was heated in a TA Instrument AR 2000 controlled stress rheometer equipped in a parallel geometry. Samples were heated from 21 °C to 150 °C at a rate of 8.5 °C per min and then cooled down to 21 °C to bake the angel food cake. At 21 °C, oscillatory stress sweep was performed. There was no relationship between the G′ value of angel cake batter and its G′ value at 150 °C. Changes in rheological properties of batters and angel food cakes using different combinations of ingredients were studied. The pH unfolding and refolding procedure led to more rigid final products compared to the controls with egg albumen samples not subjected to pH treatment. Adding sucrose to the flour increased the starch gelation temperature up to 82 °C. Higher protein concentrations resulted in better foams in the cake batter, but the batter made with an intermediate protein concentration produced the most rigid angel food cake. Adding egg albumin did not change gelation temperature of the starch. It appears that incorporation of flour with the egg white foam, leads to about a ten times decrease in the strength of the foam, and a decrease in the gelatinization process of starch after adding sugar, are crucial in forming of an angel food cake texture.     

Pendant drop tensiometry for the evaluation of the foaming properties of milk-derived proteins

Aim of the present study was to investigate the relationship between parameters derived from pendant drop tensiometry and foaming properties of milk-derived proteins. Foaming time and foam stability of solutions of whey protein isolate and two different whey protein hydrolysates with varying protein content were analysed. Pendant drop tensiometry was used to determine the surface elasticity and different parameters from a modified dynamic surface tension measurement to characterise protein adsorption to the air-water interface. A modified pendant drop technique allowed the characterisation of the surface occupation of proteins for very fast processes like air bubble stabilisation during foaming. Principal component analysis revealed a close relation between foaming time and parameters from dynamic surface tension measurement (lag time for protein adsorption to the interface, slope of the regression line for the change in surface tension) as well as foam stability with parameters derived from interfacial rheology (surface dilatational modulus as well as elastic and viscous components, phase angle). Therefore pendant drop tensiometry proved to be a valuable tool for the characterisation and prediction of the foaming properties and foam stability of protein solutions.     

Heat-induced Changes in Angel Food Cakes Containing Egg-white Protein or Whey Protein Isolate

ABSTRACT: Angel food cakes made from egg white or whey protein foams were compared. Cakes were evaluated based on final volume, dynamic volume change, and rheological transitions during baking. Cake expansion during baking was a function of protein concentration regardless of protein type. Cakes containing whey proteins had a lower ability to prevent collapse once starch gelatinization started during baking. Heat-treating whey proteins or adding xanthan gum increases cake volume, but not to the extent of egg-white proteins. Cakes containing egg-white proteins became more elastic at 60 to 85 °C than those containing whey proteins, indicating physical differences in the heat-set protein foam network associated with protein type.     

Standardized Procedure for Measuring Foaming Properties of Three Proteins, A Collaborative Study

A collaborative study involving nine laboratories was conducted over four years to evaluate a rapid, simple and reliable whipping method for measuring overrun and foam stability. Effectiveness of the method was assessed by measuring the characteristics of foams formed by three protein solutions (5%): sodium caseinate, milk protein isolate, and egg white protein; identifying and systematically eliminating sources of variability. Major sources of variability were protein dispersing technique, the mixer, and the care exercised by the operator during sampling and weighing. The method detected differences in foam stability between egg white, casein and milk protein isolate (pooled SD = 4.5) using different mixers.     

Egg Albumen Proteins Interactions in an Angel Food Cake System

The foaming properties of six albumen proteins were tested singly and in combinations in an angel food cake system. Physicochemical characteristics and foamability of the protein solutions and volume of cakes were determined. Solutions containing only globulins had good foaming properties and produced a large cake with excellent texture. Solutions of ovalbumin incorporated air after a long whip time and produced a large, coarse textured cake. Ovomucin, lysozyme, ovomucoid, and conalbumin had little or no foaming capacity. Association of ovomucin with globulins favored foam formation; however, cake volume was drastically reduced. Lysozyme, by complexing with ovomucin, depressed foaminess of the protein solutions but considerably larger cakes were produced. Lack of heat coagulative properties of the protein film was primarily responsible for low cake volumes.     

Partial Replacement of Egg White Proteins with Whey Proteins in Angel Food Cakes

This study was conducted to investigate the effects of partial replacement of egg white proteins (EWP) with whey protein isolate (WPI) on the appearance, structure, texture, and sensory properties of angel food cakes baked in conventional and microwave/conventional ovens. Factors studied were: 1) replacement of 25% or 50% of EWP with WPI; 2) added xanthan gum (XG), methyl cellulose (MC), cupric sulfate (Cu⁺²) or sodium phosphate (PHOS); and 3) conventional vs microwave/conventional oven baking. EWP replacement cakes without additives were generally inferior to 100% EWP control cakes, whereas EWP replacement cakes with added XG were most similar to 100% EWP control cakes with respect to appearance, texture, and sensory properties and those with added MC exhibited air cell size distributions that most closely resembled control cakes. The other additives and microwave/ conventional vs conventional baking had minor effects on the quality of EWP replacement cakes.     

Quality characteristics of angel food cake and muffin using lentil protein as egg/milk replacer

Replacement of animal proteins could be interesting for the food industry because it allows long‐term cost savings, among other reasons. Replacing egg/milk protein (50–100 wt%) by lentil protein (LP) was evaluated on angel cake/muffin quality. The replacement did not significantly affect final product volume, neither the muffins nor the angel food cakes. LP did not affect dough formation and contributed to hold crumb structure building an entangled network in both cake products. In addition, angel cakes and muffins containing LP had significantly lower baking loss than the control. Inferior quality for angel cakes and muffins containing LP was observed regarding hardness and chewiness that increased upon storage, compared to the control. For sensory evaluation in angel cakes, appearance of LP formulations showed lower scores than the control, likely due to the change of crumb colour. Other attributes were not significantly impacted by LP presence. For muffins, M‐100‐LPC formulation showed significant differences with the control for most of the attributes, except appearance and flavour. Indeed, consumers preferred muffins with 100% egg/milk protein replacement, which received higher acceptability scores than control. They also appreciated the ‘nutty’ flavour and moisture of angel cake with 50% egg protein replacement. This research suggests that lentil protein can totally or partially substitute egg/milk protein as foam and emulsion stabiliser in cakes, producing products with satisfactory quality.     

Factors Determining Yield Stress and Overrun of Whey Protein Foams

ABSTRACT: Foams were formed by whipping whey protein solutions (15% w/v protein) containing NaCl, CaCl₂, lactose, or glycine. Foam overrun and yield stress were determined. Foams made from whey protein ingredients have greater overrun and yield stress if the concentration of β-lactoglobulin is high relative to a-lactalbumin. The presence of 0.4 M CaCl₂ in the foaming solution increases overrun and yield stress for β-lactoglobulin and a-lactalbumin. The high yield stress of β-lactoglobulin and a-lactalbumin foams made from solutions containing CaCl₂ suggests that CaCl₂ is altering rheological properties of the interfacial protein film and/or contributing to protein aggregation or network formation in the lamellae.