响应曲面法优化木瓜蛋白酶改善蛋清蛋白起泡性能工艺

优化木瓜蛋白酶改善蛋清蛋白起泡性能的工艺。在单因素试验基础上,确定自变量酶解时间、木瓜蛋白酶添加量、酶解温度、pH值的试验水平,以起泡性和泡沫稳定性为响应值,采用Box-Behnken试验设计方法,研究各自变量及其交互作用对蛋清蛋白起泡性和泡沫稳定性的影响。然后利用Design Expert软件进行响应面分析,模拟得到二次多项式回归方程的预测模型,并确定蛋清蛋白酶改性的最佳条件组合。结果表明：蛋清蛋白泡沫稳定性酶解模型不显著,而起泡性酶解模型显著,在最佳工艺参数酶解时间45min、酶添加量38.2mg/5mL蛋清、酶解温度47.5℃、pH6.3的条件下,蛋白起泡性可达2.09,此条件下可使蛋清蛋白起泡性提高140%左右。     

球磨处理对鸡蛋清蛋白结构、性质及起泡性的影响

蛋清因具有优良的起泡性而在焙烤等食品加工领域中被广泛应用,因此,提升蛋清蛋白的起泡性有重要意义。本实验对鸡蛋清蛋白进行球磨处理,通过测定球磨处理后蛋清蛋白的游离巯基含量、表面疏水性、水解度、Zeta-电位和粒径,并分析其热力学性质、二级结构、起泡特性和微观结构,以研究球磨处理对蛋清蛋白结构性质及其起泡性的影响。结果表明：球磨处理后的蛋清蛋白粉随处理时间的延长起泡性无明显变化,泡沫稳定性呈现先升高后降低的趋势,且在球磨处理40 min时达到最大值（33.5 s）,比对照组提高近3 倍;此外,球磨处理可显著降低蛋清蛋白表面疏水性和热变性焓（ΔH）（P＜0.05）,显著提高水解度和降低Zeta-电位绝对值（P＜0.05）,并增大粒径,但对游离巯基含量和变性温度无显著影响（P＞0.05）;随着球磨时间的延长,蛋清蛋白β-折叠结构相对含量显著升高（P＜0.05）,α-螺旋结构相对含量先降低后升高,而β-转角结构相对含量先升高后降低;扫描电子显微镜结果显示球磨处理使蛋清蛋白呈现出零散碎片化和絮状。综上,适度球磨处理可以改变蛋清蛋白分子结构,进而提升其泡沫稳定性。     

不同碱液对含盐蛋清功能性质的影响

为拓宽蛋清在食品加工中的应用,提高其功能性质,以含盐蛋清为原料,探讨了不同碱液对蛋清起泡性、起泡稳定性、乳化性、乳化稳定性、蛋白质溶解度以及黏度的影响。结果表明:不添加碱液时,含盐蛋清的起泡性为12.2%,起泡稳定性为41.5%,乳化活性为0.388,乳化稳定性为17 min,蛋清蛋白溶解度为89.8%,蛋清黏度为214 m Pa·s。添加不同浓度的碱液后,使得蛋清的功能性质有了很大提高。含盐蛋清的起泡性可达75%,起泡稳定性可达65%,乳化活性可达1.279,乳化稳定性可达69 min,蛋清蛋白溶解度可达99%,但蛋清黏度显著下降。碱液的加入大为改善了含盐蛋清的功能性质,拓宽了咸蛋清的应用范围。     

盐和糖对巴氏杀菌蛋清液功能性质的影响

研究添加不同浓度食盐、白砂糖对巴氏杀菌(61℃、1.5 min)蛋清液功能性质的影响。结果表明:添加4%~10%的白砂糖与食盐可以提高蛋清液的耐热性;添加4%~10%食盐可使蛋清液在杀菌后具有良好的蛋白溶解度、乳化活力、起泡性,但乳化稳定性及泡沫稳定性较未加热蛋清液略有下降;添加4%~10%白砂糖的蛋清液的蛋白溶解度、乳化活力、乳化稳定性、起泡性、泡沫稳定性都高于未加热蛋清液。可通过添加4%~10%白砂糖来提高蛋清液耐受巴氏杀菌强度,对保证蛋清液卫生安全具有重要意义。     

热处理对浓缩乳清蛋白起泡性的影响及其在咖啡奶盖中的应用

乳清蛋白是一种优质的蛋白补充剂，因其优良的泡沫特性而广泛应用于咖啡奶盖等泡沫食品。通过热处理对乳清蛋白进行改性，测定溶解度、浊度、巯基含量、粒径、电泳、泡沫微观结构来研究乳清蛋白在不同热处理温度下的理化性质和起泡性。结果表明在50～90℃条件下，热处理对乳清蛋白溶液的溶解性、巯基含量、浊度等产生显著影响（P<0.05）。SDS-PAGE电泳结果表明，当温度大于70℃时，乳球蛋白的条带明显的变浅，在电泳凝胶的上层形成大分子的聚集物。随着温度的升高，起泡性逐渐增加，在60℃时起泡能力达到最大值为102.13%，在70℃时泡沫稳定性达到最大值为61.36%。与对照组相比，70℃热处理后咖啡上的乳清蛋白奶盖泡沫更加细密且具有较好的稳定性。为热处理提升乳清蛋白起泡性提供了理论依据和技术支撑。     

均质与加糖对蛋清液凝胶性与起泡性的影响

试验以鸡蛋蛋清液为对象,通过在不等的均质转速和时间条件下及加糖量不等的条件下处理,研究均质与加糖对蛋清液凝胶性与起泡性的影响。结果表明,随着转速增加,蛋清液的起泡性先递增后递减,在均质转速16 000r/min、均质时间4 min、加糖量5%时蛋清液起泡性最好;在均质转速10 000 r/min、均质时间2 min、加糖量5%时凝胶硬度具有最大值;在实际工业生产中,最适均质转速和时间条件分别为16 000 r/min和4 min。通过起泡性对加糖量作图可得,加糖量对蛋清液起泡性的影响不显著。经过均质和加糖处理后得到的蛋清凝胶的硬度也有不同变化趋势,一定速率和时间的均质对蛋清液的凝胶硬度有促进作用,较高速率和较长时间的均质会使凝胶硬度逐渐减小。     

不同多糖对鸡蛋清功能性质的影响

为提高蛋清功能性质,使之能更加广泛地应用于食品工业,以鸡蛋清为原料,探讨了不同多糖对蛋清起泡性、起泡稳定性、乳化性、乳化稳定性、蛋白质溶解度以及黏度的影响。结果表明:不添加多糖时,蛋清的起泡性为12.36%,起泡稳定性为74.21%,乳化活性为0.225,乳化稳定性为18.06min,蛋清蛋白溶解度为75.60%,蛋清黏度为178m Pa.s。添加一定浓度的多糖后,使得蛋清的功能性质有了很大提高。蛋清的起泡性可达34.50%,起泡稳定性可达88.66%,乳化活性可达0.801,乳化稳定性可达46.55min,蛋清蛋白溶解度可达98.64%,蛋清黏度可达224m Pa.s。实际生产中,可以考虑选择黄原胶作为蛋清的起泡剂和乳化剂,魔芋胶作为蛋清的稳泡剂。     

热处理辅助木瓜蛋白酶改善蛋清蛋白的起泡特性

为获得起泡特性优良的蛋清蛋白制品,试验以新鲜鸡蛋蛋清为原料,采用热处理辅助木瓜蛋白酶有限酶解的方法来改性蛋清蛋白,通过单因素实验,分析了底物浓度、酶的添加量、酶解时间、酶解温度、酶解pH等因素对起泡能力、泡沫稳定性的影响,并在单因素实验的基础上,以起泡能力和泡沫稳定性为响应值,通过响应面分析和方差分析得出热处理辅助木瓜蛋白酶改性蛋清蛋白的最佳工艺条件:底物质量分数3%、热处理温度90℃、热处理时间10 min、酶的添加量3 500 u/g、酶解时间2.5 h、酶解温度55℃、酶解pH 7。在此条件下,蛋清蛋白的起泡力为1741.38%,泡沫稳定性为93.38%。与未改性的蛋清蛋白相比,起泡力提高了112.97%,泡沫稳定性提高了93.27%。泡沫流变学特性结果表明改性蛋白的泡沫储存模量G′是未改性蛋白的1.5倍,泡沫更加稳定。     

热处理和乳酸钙对蛋液起泡性的影响

起泡性变化是影响蛋品加工品质控制的关键因素,一直被该领域所重点关注。以鸡蛋为试验对象,考察热处理和乳酸钙对蛋清液与蛋黄液起泡性的影响。结果表明:蛋清液起泡性整体高于蛋黄液,且几乎不受乳酸钙的影响;40℃～60℃热处理显著提高蛋黄液的起泡能力与泡沫稳定性,而对蛋清液起泡性却有降低作用;乳酸钙对蛋黄液起泡性的影响程度高于蛋清液,以泡沫稳定性最为明显。热处理和乳酸钙可用于调控蛋液起泡性变化,为蛋品精深加工提供较好的理论基础。     

多酚单体影响鸡蛋清打发性的研究

多酚作为一种具有明显抗氧化功效的食品组分越来越受到研究人员和消费者的关注。以打发性和泡沫稳定性为研究对象,重点分析了柚皮苷、儿茶素、芦丁、绿原酸、橙皮苷等几种多酚单体对鸡蛋清打发性的影响。研究结果显示多酚单体将在不同程度上影响鸡蛋清的打发性,几种多酚单体的应用可以明显地提高蛋清的打发效果,可以缩短达到蛋清最大打发体积的时间,提高蛋清的最大打发体积,或者增强鸡蛋泡沫稳定性的效果。芦丁和橙皮苷在泡沫体积及对打发效率方面的作用效果最明显,柚皮苷的添加增加了鸡蛋泡沫的稳定性,添加量为0.5%的柚皮苷可以使蛋清的消泡系数降低74%。不同的多酚单体影响蛋清打发性和泡沫稳定性的作用机理不尽相同。     

Characterization of Apple Juice Foams for Foam-mat Drying Prepared with Egg White Protein and Methylcellulose

ABSTRACT: Intrinsic stability and rheological properties of apple juice foams for foam mat drying were studied. Foams were prepared from clarified apple juice by adding various concentrations of 2 foaming agents of different nature: a protein (egg white at 0.5%, 1%, 2%, and 3% w/w) and a polysaccharide (methylcellulose at 0.1%, 0.2%, 0.5%, 1%, and 2% w/w), and whipping at different times (3, 5, and 7 min). In general, egg white foams were less stable but showed a higher degree of solidity (stronger structures), higher foaming capacity, and smaller bubble average diameter than methylcellulose foams. Foam stability increased with increasing concentrations of either methylcellulose or egg white. Increasing whipping times increased the stability of egg white foams only. Stability parameters (maximum drainage and drainage half-time) were correlated in terms of rheological parameters of the continuous phase (consistency index and apparent viscosity at 30/s, respectively). The correlations ( R ²= 0.766 and 0.951, respectively) were considered acceptable because they were independent of whipping time and foaming agent nature and concentration. Results on foam rheology obtained by dynamic and vane tests were in agreement, but the latter method was more sensitive. Optimal concentrations to obtain the most solid foams (0.2% methylcellulose and 2% to 3% egg white, respectively) were the same concentrations required for maximum foaming capacity. Based on this observation and previous models, an empirical expression was proposed to predict the degree of solidity (in terms of inverse phase angle and yield stress) only as a function of foam structural properties (air volume fraction and average bubble size). The model proved to be satisfactory to fit experimental results ( R ²= 0.848 and 0.975, respectively), independently of whipping time, foaming agent nature and concentration.     

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.     

Utilizing whey protein isolate and polysaccharide complexes to stabilize aerated dairy gels

Heated soluble complexes of whey protein isolate (WPI) with polysaccharides may be used to modify the properties of aerated dairy gels, which could be formulated into novel-textured high-protein desserts. The objective of this study was to determine the effect of polysaccharide charge density and concentration within a WPI-polysaccharide complex on the physical properties of aerated gels. Three polysaccharides having different degrees of charge density were chosen: low-methoxyl pectin, high-methoxyl type D pectin, and guar gum. Heated complexes were prepared by heating the mixed dispersions (8% protein, 0 to 1% polysaccharide) at pH 7. To form aerated gels, 2% glucono-δ-lactone was added to the dispersions of skim milk powder and heated complex and foam was generated by whipping with a handheld frother. The foam set into a gel as the glucono-δ-lactone acidified to a final pH of 4.5. The aerated gels were evaluated for overrun, drainage, gel strength, and viscoelastic properties. Without heated complexes, stable aerated gels could not be formed. Overrun of aerated gel decreased (up to 73%) as polysaccharide concentration increased from 0.105 to 0.315% due to increased viscosity, which limited air incorporation. A negative relationship was found between percent drainage and dispersion viscosity. However, plotting of drainage against dispersion viscosity separated by polysaccharide type revealed that drainage decreased most in samples with high-charge-density, low-methoxyl pectin followed by those with low-charge-density, high-methoxyl type D pectin. Aerated gels with guar gum (no charge) did not show improvement to stability. Rheological results showed no significant difference in gelation time among samples; therefore, stronger interactions between WPI and high-charge-density polysaccharide were likely responsible for increased stability. Stable dairy aerated gels can be created from WPI-polysaccharide complexes. High-charge-density polysaccharides, at concentrations that provide adequate viscosity, are needed to achieve stability while also maintaining dispersion overrun capabilities.     

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.     

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.     

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。     

Structural and Rheological Properties of Aerated High Sugar Systems Containing Egg Albumen

ABSTRACT: Structural and rheological properties have been investigated for an aerated system containing a high content of invert sugar and 2 to 10 wt% egg albumen. The specific gravity and the overrun were found to be influenced by the protein concentration and the whipping time. The systems exhibited rheopexy and shear-thinning at high shear rate, with flow data fitted to a power-law model. At small deformations, viscous character was found to dominate over elastic character over the frequency range 10⁻² to 10 Hz. Images taken from confocal microscopy indicated that mean bubble size and concentration varied systematically with protein concentration and whipping time, and that more protein accumulated on the bubble surfaces as whipping proceeded. The study of this model system illustrates how the texture of a high sugar content aerated food depends on protein content and whipping conditions.     

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.     

High hydrostatic pressure modification of whey protein concentrate for use in low-fat whipping cream improves foaming properties

Whey is the inevitable by-product of cheese production. Whey can be incorporated into a variety of foods, but little has been done to investigate its suitability in whipping cream. The objective of this work was to evaluate the foaming properties of selected low-fat whipping cream formulations containing whey protein concentrate (WPC) that did or did not undergo high hydrostatic pressure (HHP) treatment. Fresh whey was concentrated by ultrafiltration, pasteurized, and standardized to 8.23% total solids and treated with HHP at 300 MPa for 15 min. Viscosity, overrun, and foam stability were determined to assess foaming properties. Sensory evaluation was conducted with 57 panelists using a duo-trio difference test. The optimal whipping time for the selected formulations was 3 min. Whipping cream containing untreated WPC and HHP-treated WPC resulted in greater overrun and foam stability than the control whipping cream without WPC. Panelists distinguished a difference between whipping cream containing untreated WPC and whipping cream containing HHP-treated WPC. High hydrostatic pressure-treated WPC can improve the foaming properties of low-fat whipping cream, which may justify expansion of the use of whey in whipping cream and application of HHP technology in the dairy 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.