不同打发状态蛋清泡沫及其凝胶特性的比较

蛋清具有良好的起泡性和凝胶性,其在充气食品中具有难以取代的地位。为研究不同状态蛋清泡沫凝胶的理化性质,该文在室温条件下以恒定搅拌速率（980 r/min）制备了不同打发状态（打发时间为0、50、70和90 s）的蛋清泡沫,并测定了蛋清泡沫的理化特性。随后将不同打发时间的蛋清泡沫加热固化,制备了蛋清泡沫凝胶,通过显微观察、色度、质构和流变分析考察了蛋清泡沫凝胶的特性。实验结果表明,在恒定的搅拌速率下蛋清泡沫的气泡状态会随打发时间的变化而变化。适当延长打发时间,有利于形成比重较低的（0.16～0.17）、具有高起泡性和泡沫稳定性的固态泡沫。打发70 s的蛋清泡沫（蛋清泡沫呈小弯钩状,比重为0.165）稳定性最佳,且经加热固化后,该蛋清泡沫凝胶的亮度（L*=90.28）显著升高,硬度（27.69 g）和弹性（0.78 mm）显著降低（P<0.05）,凝胶性质优良。结果揭示了蛋清泡沫的流变学性质能显著影响蛋清泡沫及其凝胶的性能,为蛋清泡沫在充气食品中的应用提供了理论参考。     

Improvement of Foaming Property of Egg White Protein by Phosphorylation through Dry-Heating in the Presence of Pyrophosphate

ABSTRACT:  Egg white protein (EWP) was phosphorylated by dry-heating in the presence of pyrophosphate at pH 4 and 85 °C for 1 d, and the foaming properties of phosphorylated EWP (PP-EWP) were investigated. The phosphorus content of EWP increased to 0.71% as a result of phosphorylation. To estimate the foaming properties of EWP, the foams were prepared by 2 methods: bubbling of the 0.1% (w/v) protein solution and whipping of the 10% (w/w) protein solution with an electric mixer. The foaming power, which was defined as an initial conductivity of foam from 0.1% (w/v) protein solution, was a little higher in PP-EWP than in native EWP (N-EWP), and the foaming stability of PP-EWP was much higher than that of dry-heated EWP (DH-EWP) and N-EWP. The microscopic observation of foams from the 10% (w/w) solution showed that the foams of PP-EWP were finer and more uniform than those of N- and DH-EWP. Although there were no significant differences in the specific gravity and overrun of the foams between PP- and DH-EWP ( P  < 0.05), the specific gravity and overrun of the foams from PP-EWP were smaller and higher, respectively, than that of the foams from N-EWP. The drainage volume was smaller in the foams from PP-EWP than in those from N- and DH-EWP. These results demonstrated that phosphorylation of EWP by dry-heating in the presence of pyrophosphate improved the foaming properties, and that it was more effective for the foam stability than for the foam formation.     

Foam-mat drying of cowpea (<Emphasis Type="Italic">Vigna unguiculata</Emphasis>) using glyceryl monostearate and egg albumin as foaming agents

Foam-mat drying of cowpea using glyceryl monostearate (GMS) and egg albumin (EG) as foaming agents was investigated. GMS and EG were incorporated into cowpea paste (22%, 25% and 28% total solids) at 2.5, 5.0, 7.5, 10.0, 12.5 and 15% (w/w), and whipped for 3, 6, 9, 12, 15, 18 and 21 min, maintaining 15, 25 and 35 °C foaming temperatures. Foam density was measured and expressed in g/cm³. Cowpea foams were dried at 60 °C (Twb, wet bulb temperature 35 °C) for 48 min. Sensory attributes of akara produced from fresh and reconstituted pastes were evaluated.Generally, foam density decreased with increased concentrations of GMS and EG in cowpea paste. Foam density decreased with decrease in total solids of cowpea paste. Minimum foam densities were obtained in cowpea foams with GMS and EG after 9 and 21 min of whipping, respectively. EG-stabilized foams were unstable for drying. Sensory evaluation showed no significant difference (P>0.05, 0.01) in the quality attributes of akara produced from fresh and reconstituted GMS-stabilized cowpea powders.     

FOAM-MAT FREEZE-DRYING OF APPLE JUICEPART 1: EXPERIMENTAL DATA AND ANN SIMULATIONS

Freeze-drying of foamed and nonfoamed apple juice was studied in order to assess if there is a reduction in process time due to foaming. Foams were prepared by whipping apple juice with methylcellulose or egg albumin at different concentrations. Foamed and nonfoamed juice samples having different thickness and different initial weight were frozen at −40C and then freeze-dried at 20C during 48 h under vacuum. Sample weight loss and temperature were followed at different process times. A mathematical model based on artificial neural networks was developed to represent foam kinetics and temperature curves during freeze-drying. Foaming reduced process time if the comparison was done at equal sample thickness. However, lower density of foamed materials decreases weight load to the dryer. Unfortunately, the optimization of the process did not permit the determination of a practical minimal foam sample thickness to enhance both drying rate and dryer throughput.

PRACTICAL APPLICATIONS

Fruit juice powders have a large application in the food and nutraceutical industries. These powders are used as instant beverages, ingredients for bakery or extruded products and to incorporate in pharmaceutical tablets. Freeze-drying is an excellent process to obtain a high-quality fruit juice powder because it offers extraordinary nutritional, structure and sensorial qualities when compared with products of alternative drying process: air, vacuum, microwave and osmotic drying. However, the process cost is expensive due to the long drying times under vacuum. Process acceleration through optimization is therefore necessary in order to obtain high quality in the final products but at lower costs. This study aims to decrease the cost of the freeze-drying process by using foaming prior to processing to increase the drying rate.     

Instrumental Method for Characterizing Protein Foams

A whipping machine for cream analysis (Cream Tester CTII) was used to foam egg white, milk proteins and soy protein isolate. Foam formation and final rigidity were characterized by the current input to the beating motor. In addition, specific volume, rigidity (compressive strength by Instron) and stability (drainage) of the foams were determined by methods that minimized foam damage during handling. Current input during whipping distinguished fresh vs pasteurized egg white and positively correlated with compressive strength of final egg white foams. Such correlation was not found for milk protein and soy protein isolate foams of lower strength and stability.     

The effect of instant green tea on the foaming and rheological properties of egg albumen proteins

The effects of three varieties of instant green tea (from China, Japan and Kenya) on the foaming and thermal properties of 1% (w/v) egg albumen and the gelation properties of 5 and 15% (w/v) egg albumen were investigated. All varieties produced similar effects on the foaming and gelation properties of egg albumen, but to different extents depending on the tea constituents. Mixtures of 1% (w/v) egg albumen and 0.25–0.4% (w/v) instant green teas in distilled water showed the greatest foam expansion (800–1140%) and foam stability (97–100%) at 10 min after whipping compared with 1% (w/v) egg albumen alone (226% for foam expansion and 34% for foam stability). Addition of instant green teas at levels above 0.5% (w/v) decreased foam expansion and stability. Small‐deformation rheology of mixtures of 5% (w/v) egg albumen and 1 or 2% (w/v) instant green teas showed an initial increase in elastic modulus (G′) and viscous modulus (G″) followed by a small, broad peak, indicating that the binding of tea constituents (polyphenols) with proteins may be reversible between 20 and 54 °C; this peak was not seen for 5% (w/v) egg albumen on its own. Large‐deformation rheological tests also indicated increased strength of mixed egg albumen/green tea gels with increasing levels of instant green teas. Differential scanning calorimetry thermograms showed that for the same instant green tea a higher concentration decreased the onset and peak (T_m) temperatures and enthalpy change values of all egg albumen protein peaks. Copyright © 2007 Society of Chemical Industry     

Influence of pasteurisation,freezing and storage on properties of egg products made from eggs stored for 7 and for 28 days

The influence of the age of eggs before breaking, pasteurisation, freezing and storage at —17°c and the method of whipping on the foaming power, foam stability and viscosity of liquid egg albumen and liquid whole egg were studied. The foaming power (relative volume of foam) and the foam stability were determined with the aid of a Hobart whipping machine N 50. The viscosity was measured with a Brookfield viscometer type LV. Liquid egg albumen from 28-day-old eggs had a better foaming power with better stability than that from 7-day-old eggs. The viscosity of the liquid egg albumen from 7-day-old eggs was higher than that from 28-day-old eggs. When pasteurised with aluminium sulphate, the foaming power and the foam stability of all liquid egg albumens increased. When pasteurised without aluminium sulphate, both properties increased for liquid egg albumen from 7-day-old eggs and decreased for that from 28-day-old eggs. During the first weeks of storage of the egg white at −17°C, the foaming power, foam stability and viscosity gradually increased. Whipping for 1 min at setting 2 and 2 mill at setting 3 yielded a higher foaming power and a higher stability of the foam than whipping for 1 min at setting 2 and then a few minutes at position 3 until visually the optimum had been reached. These differences were significant (P < 0·01) for the foaming power and foam stability. There was no significant difference between the foaming power and stability of the foam for liquid whole egg prepared from 7-day-old eggs and that from 28-day-old eggs. Pasteurisation (3 min at 65°c) gave a decrease in foaming power and foam stability and an increase in viscosity. These differences were significant (P < 0·07) for the foaming power and viscosity. Storage resulted in lower foaming power and higher foam stability. In this case, higher viscosity values were also obtained. The whipping method did not give any significant differences.     

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.     

Effects of sucrose and sodium chloride on foaming properties of egg white proteins

Egg white proteins are extensively utilised in the food industry as foaming agents. A number of factors, singly or in combination, can affect the foaming characteristics of egg albumen. In this study, egg white protein solutions heated at various temperatures in the presence of variable concentrations of sucrose and NaCl were whipped for different periods of time. All factors had a significant impact on the foaming properties of egg albumen. Increasing NaCl content and whipping time enhanced protein adsorption at the air–water interface. The presence of sucrose delayed foam formation but contributed to the stability of the aerated system. Controlled denaturation of the protein solutions induced by mild heat treatment enhanced the foaming properties of egg white proteins. This data indicates that the foaming properties of egg white proteins can be manipulated by altering the effect of extrinsic factors in order to achieve optimal formulations for food industrial applications.     

月桂酸型甘油二酯-大豆油基油泡沫的制备及其在蛋黄酱中的应用

旨在构建健康、低脂、高稳定性的新型蛋黄酱产品,以甘油和月桂酸为原料经过Novozyme 435脂肪酶催化,制备月桂酸型甘油二酯(DAG)粗产物,采用分子蒸馏和硅胶柱层析技术对粗产物进行纯化得到高纯度月桂酸型DAG(纯度>92%),以此为原料制备油泡沫,探究了搅打时间对油泡沫起泡能力、气泡粒径分布、微观结构及稳定性的影响,并将油泡沫50%部分替代或完全替代大豆油用于蛋黄酱制备,研究油泡沫对蛋黄酱流变学特性、色泽、稳定性的影响。结果表明：随着搅打时间的延长,气泡表面吸附的晶体数量明显增多,气泡粒径增大,起泡率先增大后基本保持不变,搅打时间为15 min时油泡沫起泡率最高,且此时的油泡沫储存2个月体积无明显变化;采用油泡沫部分替代及完全替代大豆油后可降低蛋黄酱的黏度,增加蛋黄酱在应力及频率扫描下的弹性模量,蛋黄酱表现出良好的塑性和稳定性,且蛋黄酱的色泽L^*值增加,a^*值和b^*值降低。采用月桂酸型DAG搅打获得的油泡沫可有效降低蛋黄酱的油脂含量和热量,可作为油脂替代物用于新型蛋黄酱产品的开发。     

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.     

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.     

米糠蛋白的起泡特性及其泡沫微观形态

考察pH值和NaCl浓度对米糠蛋白起泡特性及泡沫微观形态的影响,并对二者之间的内在关系进行阐述。结果表明,当米糠蛋白溶液中不添加NaCl、pH?4时起泡能力较差,但泡沫稳定性可达最大值（88.3±7.3）%,而当溶液的pH值偏离4时起泡能力增加,在pH10和12条件下起泡能力分别可达（73.3±0）%和（168.9±10.2）%,泡沫稳定性分别为（74.7±2.5）%和（68.5±2.1）%;另外在米糠蛋白溶液pH值为4和7条件下分别添加1%的NaCl后,可显著提高起泡能力至（77.8±3.8）%和（90.0±5.8）%。米糠蛋白泡沫的微观形态随时间变化规律说明,不同pH值条件下起始阶段气泡的直径大小分布与泡沫稳定性相关,而当添加NaCl后米糠蛋白起泡能力和泡沫稳定性的改变则与气泡数量和平均面积二者的综合效应有关。     

Large amplitudes oscillatory shear (LAOS) behavior of egg white foams with apple pectins and xanthan gum

The study presents the results of research on non-linear rheological properties of foams based on egg white protein, xanthan gum and apple pectin of various levels of methylation. The rheological studies were carried out by means of large amplitude oscillatory shear (LAOS) and Fourier transform rheology (FTR) methods. The obtained foams revealed elastoviscoplastic properties. The analysis of the results allowed determination of yield stress, shear exponents and the Fourier spectra, which enabled estimation of the quantity and intensity of individual harmonics. The Lissajous patterns as well as coefficients of energy dissipation were also demonstrated. The foam containing solely egg white revealed the largest number of harmonics in the Fourier spectrum (17th), whereas supplementation with hydrocolloids induced a decrease in the amount of harmonics (9th). The image of the Fourier spectra was reflected by the Lissajous curves, which gradually acquired an ellipsoidal shape as the hydrocolloid concentration increased. The coefficient of energy dissipation in the function of the deformation amplitude demonstrated a sigmoid dependence and tended towards the value of approximately 0.8 for higher amplitudes. This indicated that the investigated foams were in a flow area. The statistical analysis (two/three-way ANOVA) of the abovementioned values showed that neither the level of methylation nor the pectin concentration in foam influences the yield stress.     

Determination of foaming properties of proteins

Comparing typical examples of equipment for performing the whipping operation, dispersions and colloidal solutions (13%) respectively of 9 diverse protein based whipping agents were differently aerated, and the foaming properties were determined. Whipping was performed in an industrial manner (batch operation at atmospheric pressure and continuous operation using compressed air and static dispersors) as well as devices widely used in laboratory (household-type mixer and motor-driven plungers moving in vertical glass cylinders) were employed. Moreover a new direct current motor-driven whisk/stirrer, the steplessly adjustable rotation speed of which had been made constant and independent of the rheological properties of the protein solutions to be whipped, was tested. Foaming properties measured suggest that only the new laboratory whipping principle reflects the actual performance of protein based whipping agents and that it is far better adapted to large-scale processing then the laboratory equipment most commonly used. Optimum foam forming need distinct rotation speeds and stirring times as well as pH values typical for each product. In creating sugar containing protein foams with a high degree of aeration however in no case of laboratory operational conditions the amount of energy and air available for whipping was sufficiently large. Because of the advantages of the new whipping principle over the otherwise tested ones the motor output and the stirring conditions now are being improved.     

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.     

The microstructure of foamed maltodextrin/sodium caseinate powders: a comparative study by microscopy and physical techniques

Microscopy followed by image analysis is combined with physical characterisation techniques in order to obtain information about the structure of solid foams consisting of maltodextrin DE12 and sodium caseinate (10–30% w/w) processed under varying foaming conditions. Thin sections of solid foam were analysed by microscopy and image analysis for closed porosity, bubble size distribution and bubble connectivity. The bubble size distribution in the range up to about 25 μm was found to be largely independent of the degree of foaming. The total porosity of the solid foams, as determined by image analysis, was in very good agreement with the results from helium pycnometry and a direct relationship between the porosity and surface area as measured by BET nitrogen adsorption is obtained. Mercury intrusion porosimetry was found to be of limited use for the analysis of the open pore structure because of the fragility of the powders and the overlap in size between bubbles and interstitial spaces between the powder particles.     

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.     

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.     

Effects of soy protein isolate and egg white solids on the physicochemical properties of gluten-free bread

Gluten-free formulations are often supplemented with proteins to improve their quality. To determine the effects of alternative proteins on a hydroxypropyl methylcellulose (HPMC)-treated gluten-free dough system, soy protein isolate was added at 1%, 2% and 3% while egg white solids were investigated at 5%, 10% and 15%. The formulated doughs were analysed using thermoanalytic and rheological techniques to determine the role of water and subsequent flow behaviour upon hydrocolloid addition. The baked loaves were measured for specific loaf volume and tensile strength to determine bread quality. The addition of soy protein isolate and egg white solids (5% and 10%) reduced dough stability by suppressing HPMC functionality, reducing available water, weakening HPMC interactions with the starch matrix and reducing foam stability. At 15% addition, egg white solids became the primary protein scaffolding in the dough and overcame negative interactions with HPMC, improving the loaf volume. However, this formulation may need further optimisation to meet full consumer acceptability.