大豆分离蛋白及其美拉德反应产物成膜条件探究

本论文研究不同p H（10、11、12）、不同加热温度（70、80、90℃）和不同甘油浓度（0³.0 m L/100 m L）对浓度为6 g/100 m L大豆分离蛋白溶液及大豆分离蛋白-葡萄糖（w/w=1）美拉德反应溶液、大豆分离蛋白-木糖（w/w=1）美拉德反应溶液成膜条件的影响。通过测定大豆分离蛋白-葡萄糖/木糖溶液的色差值及吸光值来判断美拉德反应程度,通过肉眼和手感观察和评价膜的可揭性、颜色和表观特征。实验结果表明:当大豆分离蛋白和糖浓度均为6 g/100 m L的条件下,大豆分离蛋白的成膜条件为甘油浓度:2.5 m L/100 m L、溶液p H11、80℃加热60 min;大豆分离蛋白与木糖美拉德反应产物成膜条件为甘油浓度:0.125 m L/100 m L、溶液p H11、80℃加热60 min;而大豆分离蛋白与葡萄糖在此条件下美拉德反应程度不明显,因此未对其进行膜的制备。      

Gelation properties of salt-extracted pea protein isolate induced by heat treatment: Effect of heating and cooling rate

Gel network formation of a salt-extracted pea protein isolate was studied using dynamic rheological measurements. The gelling point was dependent on heating rate and was unaffected by cooling rate. When both the heating and cooling rates were increased (from 0.5 to 4 °C/min) final G′ value decreased, indicative of decreased gel strength. During the heating phase, the storage modulus and loss modulus fluctuated below 1 Pa at almost constant values with the storage modulus smaller than the loss modulus until the gelling point was reached. The rate of cooling has a greater impact on the development of storage modulus than that of heating. Compared to the gel strength of commercial pea protein isolate (PPIc) and soy protein isolate (SPIc) at the same protein concentration, salt-extracted pea protein isolate (PPIs) was much stronger than PPIc but weaker than SPIc. Careful control of the heating and cooling rates enable maximum gel strength for heat-induced pea protein gel, thus enhancing utilisation of pea protein as an additive in meat food industry.     

Effect of solution pH on solubility and some structural properties of soybean protein isolate films

Changes in solubility and molecular properties of protein films obtained from soy protein isolate (SPI) solutions at different pH values (2, 8 and 11) were investigated to study protein behavior during film formation. Proteins retained their native conformation in films at pH 8, but were partially or extensively denatured at pH 11 and 2. Although film protein networks were maintained by the same type of interactions at different pH values—covalent (disulfide bonds) and non‐covalent bonds (especially hydrophobic interactions and hydrogen bonds)—the intensity of each type of interaction (predicted from solubility tests in buffers with different chemical action) depended on the pH of the initial solution. Films obtained at pH 8 presented the highest solubility in all the buffers, whereas films at formed pH 2 presented the lowest, except in the buffer of pH 8 that contained urea, SDS and 2‐mercaptoethanol, which totally dissolved 100% of the film proteins. Films prepared at extreme pH values had a denser microstructure than those at pH 8. SDS–PAGE patterns indicated that films were mainly formed by β‐conglycinin and glycinin, which aggregated in different forms during film formation, depending on the pH of the initial solutions. Some of these proteins remained weakly bonded and/or were held by the network of films. These differences in the protein networks structure would affect the physical, mechanical and barrier properties of the films. Copyright © 2006 Society of Chemical Industry     

Lysozyme release from isolate pea protein and starch based films and their antimicrobial properties

The objective of the current research was to analyze the effects of the pea protein and corn starch films as well as the temperature influence (10 and 25 °C) on the release of lysozyme to a food simulant (agar gel). Lysozyme concentration at different depths of food simulant was measured, as a function of diffusion time, through its enzyme activity. In both polymer matrices, a loss of lysozyme activity was observed after film formation. Diffusion of lysozyme was enhanced when temperature increased, mainly when pea protein films were tested. A higher retention of lysozyme in the film starch matrix was significantly detected which could be attributed to the different hydration degree of the film in contact with the agar medium and the different interactions between the enzyme and the film polymer chains. The antimicrobial effectiveness of pea protein and starch films containing lysozyme (0, 50, 75 and 100 mg lysozyme/g hydrocolloid), against Listeria monocytogenes was proved. At 10 °C, both matrices were effective against the pathogen. At 25 °C, the effectiveness of films significantly decreased and pea protein films showed the best antimicrobial activity.     

Gelation properties of salt-extracted pea protein isolate catalyzed by microbial transglutaminase cross-linking

Gelation is a fundamental functional characteristic of plant proteins. In this paper, a salt-extracted pea protein isolate (PPI) was mixed with microbial transglutaminase (MTG) to produce gels and the gelation properties were studied. When the MTG level increased, the magnitude of both the G′ and G″ moduli also increased, which means the gel strength increased. A second order polynomial equation was used to describe the relationships between the G′, G″ modulus and TG level. It was found that with increased heating and cooling rate at the same MTG level, G′ and G″ tended to decrease, resulting in a weaker gel. This was attributed to the rearrangement time of pea protein molecules; slower heating and cooling rates enabled protein molecules to have more time to rearrange and therefore form a stronger gel. At the same MTG level, higher pea protein concentration resulted in higher G′ and G″ values and a power law relationship was found between G′ and pea protein concentration or G″ and pea protein concentration. Frequency sweep data of PPI show that the MTG treatment resulted in higher G′ values and lower tan delta values, indicative of a stronger more elastic gel. The minimum gelation concentration was found to be 3% (w/v) with 10 U MTG treatment, lower than 5.5% required when no MTG was present. When compared to PPI and soy protein isolate (SPI) with and without 10 U MTG treatment, the gel strength of PPI with MTG was stronger than that of SPI with MTG treatment, whereas the opposite was true without the MTG treatment. SDS-PAGE showed that at the same pea protein concentration, higher MTG level induced more cross-linking as fainter bands were seen on the gel and there was a shift in the relative intensities of the bands in the molecular weight range of 35–100 kDa.     

Stability of the mechanical properties of edible films based on whey protein isolate during storage at different relative humidity

Formulations for whey protein isolate (WPI)-based films include low molecular weight plasticizers, which implies certain degree of instability of films properties due to plasticizer migration. The aim of this work was to study the effect of storage time on the mechanical properties of WPI films plasticized with two low molecular weight polyols: glycerol (Gly) and sorbitol (Sor). Films were stored inside cabins at 50% or 75% relative humidity (RH) and at room temperature. Mechanical properties and moisture content were measured at regular intervals for 30 weeks. The effect of plasticizer type and content and RH on mechanical properties right after equilibrium (1 week) was also included in this study.     

赤藓糖醇对豌豆分离蛋白结构和功能特性的影响

为研究赤藓糖醇对豌豆分离蛋白结构和功能特性的影响,利用8-苯胺基-1-萘磺酸钠荧光探针法、紫外和荧光光谱法,研究赤藓糖醇对豌豆分离蛋白溶解性、持水性、起泡性、乳化性及表面疏水性等的影响。结果表明:随赤藓糖醇质量分数的增加,豌豆分离蛋白的溶解性基本呈先增加后下降趋势,且均在pH4.0处最低。持水性逐渐增加,且均在pH5.0处最低。起泡性和乳化性均先增加后趋于平稳。当赤藓糖醇质量分数在0~10%范围内,表面疏水性逐渐增加,随后趋于稳定。随赤藓糖醇质量分数增加,色氨酸残基暴露在蛋白质分子表面,荧光强度先增加后趋于稳定,且与表面疏水性变化趋势相同。该研究表明,适度赤藓糖醇处理可改善豌豆分离蛋白的结构和功能特性。     

Preparation and properties of dialdehyde carboxymethyl cellulose crosslinked gelatin edible films

Glycerol-plasticized gelatin edible films with a new kind of dialdehyde polysaccharide, dialdehyde carboxymethyl cellulose (DCMC) as crosslinking agent are successful prepared using casting techniques. The mechanical properties, thermal stability, light barrier properties, swelling behavior as well as water vapor permeability (WVP) of the gelatin-DCMC films are investigated. The results indicate that the addition of DCMC causes tensile strength (TS) and thermal stability to increase and elongation at break (EB) to decrease, suggesting the occurrence of crosslinking between gelatin and DCMC. The light barrier measurements present high values of transparency at 280 nm and low values of transparency at 600 nm of the gelatin-DCMC films, indicating that gelatin-DCMC films are very transparent (lower in transparency value) while they have excellent barrier properties against UV light. Moreover, the values of transparency at 280 nm increase with the increased DCMC and glycerol content, suggesting the potential preventive effect of gelatin-DCMC films on the retardation of product oxidation induced by UV light. Furthermore, the addition of DCMC can greatly decrease the water vapor permeability (WVP) and equilibrium swelling ratio (ESR) down to values about 1.5 × 10⁻¹⁰ g m/m² s Pa and 150%, revealing the potential of DCMC in reducing the water sensitivity of gelatin-based films. In common for hygroscopic plasticizer in edible films, the addition of glycerol gives increase of EB and WVP and decrease of thermal stabilities and ESR of the gelatin-DCMC films.     

超声辐射对大豆分离蛋白膜性能的影响

研究了超声辐射在频率为20kHz,功率为800W条件下,不同处理时间对大豆分离蛋白膜性能的影响。结果表明,超声辐射对膜性能有明显的改善作用。经超声辐射处理2min可以显著提高膜的抗拉强度,相对于对照样提高了64.08%(P≤0.05);同时也明显降低了膜的水蒸汽透过系数,相对于对照样降低了25.70%(P≤0.05)。经超声处理后的膜机械强度和阻湿性能均得到了提高,同时具有均匀透明的外观。     

pH和AOT添加物对大豆分离蛋白基可降解膜机械性能影响

运用响应面分析法分析pH和AOT(琥珀酸二异辛酯磺酸钠)添加物对大豆分离蛋白(SPI)基生物可降解膜机械性质影响,确定影响该种膜机械性能最优工艺参数;测试膜机械性质,包括抗拉强度、穿刺强度、断裂伸长率;分析结果表明,在pH为8.95,AOT添加量为13.00%(w/w)时,膜综合机械性能达到最优。     

Influence of heating,protein and glycerol concentrations of film-forming solution on the film properties of Argentine anchovy (Engraulis anchoita) protein isolate

This study was conducted to evaluate the influence of thermal treatment (74, 82, and 90 °C), glycerol (30%, 35%, and 40%, w/w) and protein concentrations (3.0%, 3.5%, and 4.0% w/w) of film-forming solution on the properties of Argentine anchovy (Engraulis anchoita) protein isolate (API) films produced by casting. The API presented 88.8% of proteins, 5.5% moisture, 1.3% lipids, 1.0% ash and 53.3% of polar amino acids. The DSC of protein isolate was observed at maximum temperature of 62.2 °C and ΔH 6.4 J/g. The thickness, water vapor permeability, color difference and opacity of the films were not affected by the experimental variables studied (p > 0.05). The lowest solubility, elongation, and highest tensile strength of the films occurred at low temperature, low protein and glycerol concentrations (p < 0.05). Micrographs obtained by scanning electron microscopy of the films showed homogeneous surfaces at low temperature.     

Use of edible films based on whey protein isolate to protect foods rich in polyunsaturated fatty acids

Whey protein isolate (WPI) films acting as oxygen barriers can be used to delay lipid oxidation in foods with high content in polyunsaturated fatty acids (PUFA). The aim of this work was to study as to what extent WPI films are capable of delaying lipid oxidation in vegetable oil, as an example of a food rich in PUFA. The effect of plasticizer type (glycerol or sorbitol) and content (30, 40, 50 and 60%), as well as film thickness (60, 100 and 180 μm) and relative humidity (50 or 75%) were analyzed. In order to evaluate the film protective capability, specially designed methacrylate cells and an accelerated test of oxidative rancidity were used. Results obtained showed that WPI films delayed the rancidity in vegetable oil. Films with sorbitol were more effective than films with glycerol, providing a protection as effective as aluminum foil. Both plasticizer content and film thickness affected its protective capacity significantly. The thickest films with the lowest plasticizer content provided the greatest protection against lipid oxidation. Plasticizer content affected film protection much more intensively than thickness. WPI films presented a more effective protection at 50% RH than at 75% RH.     

热烘改性对大豆分离蛋白功能性的影响

研究了利用热处理对大豆分离蛋白(SPI)进行改性。热烘改性对SPI的吸水性、吸油性、发泡性和泡沫稳定性无显著性影响,常温粘度、高温粘度、耐热性、凝胶性和保水性分别比对照提高了118%、135%、108%、81%和83%。比较适宜的热烘改性条件为10min/85℃。     

超声处理对大豆蛋白膜性能和微观结构的影响

研究了超声处理对大豆分离蛋白膜性能和微观结构的影响。结果表明,大豆分离蛋白膜液经超声功率20W、10min的处理,可显著地增加膜的抗拉强度及阻湿性能;红外和扫描电镜结果显示,超声处理改变了膜的空间结构,使膜表面平滑、均匀。     

大豆分离蛋白与谷朊粉可食性复合膜研究

该文报道影响大豆分离蛋白与谷朊粉复合膜成膜因素,分析各种因素对复合膜性能影响,并对正交试验结果采用极差分析和综合评分法进行评定,得到制备综合性能良好的可食性膜最佳条件为:谷朊粉与大豆分离蛋白比例为1∶5,甘油量为20%,pH为11,预热处理温度和时间分别为80℃和40min;此时,膜的透光率、拉伸强度、撕裂强度、水分含量和水蒸汽透过率依次为60.5%、38.38MPa、198.02N/mm、13.87%和0.507g·mm/kPa·h·m2。     

南极磷虾(Euphausia superba)分离蛋白的成膜特性探究

本研究以脱脂南极磷虾粉为原料,采用碱溶酸沉法提取分离蛋白,以磷虾分离蛋白、甘油和水构建成膜体系,以乳清分离蛋白和大豆分离蛋白为对照样品,在相同的成膜条件下,评估磷虾分离蛋白的成膜能力。结果表明,在该膜体系中,磷虾分离蛋白膜的厚度(0.070±0.002)mm、水分含量(15.53%±0.70%)和不透明指数(1.22±0.06)与大豆分离蛋白膜无显著差别。扫描电镜结果表明:热处理后磷虾蛋白膜的表面和截面均表现为细密、平滑、无空隙的结构,具有良好的成膜能力。热处理后磷虾蛋白膜的断裂伸长率为21.09%±0.39%,显著高于未加热的磷虾分离蛋白膜(8.13%±0.41%),小于大豆分离蛋白膜;但三者的拉伸强度无明显差异。实验证明磷虾分离蛋白具有成膜能力,可以在食品加工中用于构建成膜体系。      

Physicochemical and textural properties of heat-induced pea protein isolate gels

Chemical and thermal properties of pea protein isolates (laboratory prepared or native; PPIn and commercial; PPIc) and textural properties of heat-set gels obtained from pea protein isolates were compared with homologous soy protein isolates (laboratory prepared, or native; SPIn and commercial; SPIc). The protein banding pattern resulting from electrophoresis separation confirmed the presence of predominant storage proteins of pea and soy seeds in the respective protein products. PPIc and SPIc had lower nitrogen solubility than their native counterparts, likely due to their denaturated state which was further confirmed by the absence of distinct endotherms in these commercial materials compared to the laboratory prepared ones. Addition of NaCl at 1.0–2.0% (w/w) to PPIn and SPIn slurries increased thermal transition temperatures for both proteins.     

不同方法处理花生分离蛋白成膜液对膜性能的影响

采用加热处理、超声波处理和微波处理对可食性花生分离蛋白成膜液进行处理,观察不同处理对所制得的蛋白膜的机械性能、阻湿性能和透光性能的影响。结果表明:采用75℃热处理30 min、功率1 000 W超声波处理3 min和功率500 W微波处理2 min,都能够显著增加膜的抗拉强度和透光性;通过热变性处理和超声波处理能够提高膜的阻湿性能,而微波处理对膜的阻湿性能影响较小。     

干热处理和pH偏移对汉麻分离蛋白/卡拉胶接枝物凝胶性质的影响

摘 要： 目的：利用植物蛋白代替动物蛋白有利于减少动物蛋白消耗，改善汉麻分离蛋白在蛋白凝胶中的应用前景。方法：以未经pH偏移及干热处理组分为空白对照，研究了不同干热处理时间（0、24、48、72 h ）和pH偏移（2、12）条件对汉麻分离蛋白/卡拉胶接枝物凝胶硬度、流变特性、水分分布和微观结构的影响。结果：与对照组相比，经干热处理和pH偏移处理的蛋白凝胶硬度、持水性和储能模量（G’ ）均显著提高（P<0.05），其中干热处理48 h和pH 2偏移处理组分是对照组的1.38、1.10和19.45倍。干热处理和pH偏移增加了凝胶中不可流动水的含量（92.88%）且电镜结果显示凝胶的微观结构逐渐致密，pH2偏移和干热处理48h最光滑，复合凝胶中蛋白的α-螺旋的含量减少，β-折叠含量增加（P<0.05），这表明蛋白分子内部的有序结构增加。结论：综上，在pH 2偏移干热处理48h条件下，汉麻分离蛋白凝胶性质最佳研究表明，这为汉麻分离蛋白在食品工业中的应用提供了新的理论依据。     

Functional properties and structural characteristics of phosphorylated pea protein isolate

In order to expand the application of pea proteins in the food industry, pea protein isolate (PPI) was chemically phosphorylated to improve its functional properties. Based on the comprehensive membership value (CMV) degree, the optimal condition for PPI phosphorylation modification was as follows: pH 12, modification temperature at 70 °C and an addition of 7.0% (w/v) sodium tripolyphosphate (STP). Under this condition, the solubility, emulsifying property, emulsifying stability, foaming property and oil absorption capacity of the modified PPI were improved substantially. In addition, the structure of modified PPI was characterised by scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy. The results showed that the modified PPI had a smooth and uniform lamellar structure, where the content of α-helix and β-sheet structure increased, but the content of β-corner and random coil structure decreased. The thermodynamic properties were analysed by differential scanning calorimetry (DSC) and the results showed that ∆H of the modified PPI increased significantly. Finally, the optimum phosphorylated PPI was mixed with 0.4% (w/v) xanthan gum to form PPI fat mimics (PPI-FM). PPI-FM was added into mango mousse cake to reduce the amount of light cream, and the result showed up to 20% of light cream could be substituted.