Chemical,textural, rheological,and sensorial properties of wheyless feta cheese as influenced by replacement of milk protein concentrate with pea protein isolate

Replacement of milk protein with protein isolates from vegetable resources can significantly influence the characteristics of feta whey less cheese and also decrease the cost of final production. In this study, various blends of milk protein concentrate (MPC) and pea protein isolate (PPI) were mixed at levels of 12% MPC and 0% PPI (MP0), 10% MPC and 2% PPI (MP2), 9% MPC and 3% PPI (MP3), 8% MPC and 4% PPI (MP4), 7% MPC and 5% PPI (MP5), 6% MPC and 6% PPI (MP6) and used in the manufacture of wheyless feta cheese. The chemical, textural, rheological, and sensorial properties, as well as the microstructure of the cheese samples, were evaluated after 1, 15, and 30 days of storage. The general linear model procedure of SAS statistical software was used for statistical analysis. Duncan's multiple range tests was used to compare the means of different treatments. The results showed that all properties of the cheeses were influenced by different levels of PPI due to different total solids content. The use of high concentrations of PPI resulted in a more open protein network, softer structure and decreasing the storage (G′) and loss (G″) moduli in the cheeses. Sensory evaluation of the samples revealed that total score in terms of flavor, texture and overall acceptability was gradually decreased with increasing PPI levels, but still preferable for the panelists. Furthermore, for each sample, with increasing levels of PPI, the whiteness and the greenness were decreased, but the yellowness was increased.     

不同分子量葡聚糖对大豆分离蛋白冷致混合凝胶的流变性质和质构性质的影响

为研究不同分子量葡聚糖对大豆分离蛋白冷致凝胶强度的影响,采用流变仪和质构仪等手段进行分析。研究结果表明:GDL诱导的大豆分离蛋白冷致凝胶是一种弱蛋白凝胶,酸化速率随着GDL含量的增加而增加。高酸化速率条件下形成的大豆分离蛋白冷致凝胶的凝胶起始点早且最快达到模量峰值;低酸化速率条件下形成的大豆分离蛋白冷致凝胶的凝胶起始点晚且最终模量较低。不同分子量和浓度的葡聚糖添加会改变大豆分离蛋白冷致凝胶的凝胶强度。同分子量的葡聚糖与大豆分离蛋白混合体系形成的冷致蛋白多糖凝胶随着葡聚糖浓度的增加其粘弹性质呈现先上升后下降的趋势;而随着葡聚糖分子量增加混合凝胶的粘弹性质变化越显著。     

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。     

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.     

Evaluation of red bean protein [Vigna angularis] isolate on rheological properties of pork myofibrillar protein gels induced by microbial transglutaminase

The effects of 1% red bean protein isolate (RBPI) on the gel properties of myofibrillar protein (MP) in various levels of microbial transglutaminase (MTG: 0%, 0.1%, 0.5%, & 1%) were evaluated. The cooking yield (CY) of the MP gels decreased with increasing MTG level, while the addition of RBPI improved the CY of the MP gels. Gel strength (GS) was also improved when RBPI was incorporated into the MP gels containing higher than 0.5% of MTG. The addition of MTG and RBPI was slightly changed the endothermic peak temperatures. Scanning electron microscopy (SEM) showed that the three‐dimensional structure of MP with RBPI alone or in combined with MTG was compacted as compared to the control. Based on the results, RBPI could be functioned as a substrate for MTG (0.5–1.0%) and a water binder of meat protein gel mediated by MTG.     

干燥方式对pH改性豌豆分离蛋白功能性和结构的影响

以豌豆为原料制备豌豆分离蛋白(PPI),比较了常用的两种干燥方式对pH改性PPI功能性的影响,并利用SDS-PAGE和红外光谱法研究了两种干燥方式对pH改性PPI结构的影响。研究结果表明:与冷冻干燥相比,喷雾干燥使改性处理后的PPI形成较多聚集体,同时使蛋白质的功能性质(溶解性、乳化性、胶凝性)略微降低;经过pH改性处理喷雾干燥PPI的乳化性和胶凝性显著高于未改性处理冷冻干燥PPI,喷雾干燥后PPI亚基发生更多的非二硫键共价聚集,使PPI发生部分变性,二级结构发生了变化。总之,喷雾干燥对PPI的功能性质有降低趋势,而pH改性处理可以大大改善PPI的功能性质从而弥补喷雾干燥带来的不足。     

Effect of protein composition on the rheological properties of acid-induced whey protein gels

Protein dispersions with different ratios of α-lactalbumin to β-lactoglobulin were heat-denatured at pH 7.5 and then acidified with glucono-δ-lactone to form gels at room temperature. Heat treatment induced the formation of whey protein polymers with reactive thiol group concentrations ranging from 1 to 50 μmol/g, depending on protein composition. During acidification, the first sign of aggregation occurred when the zeta potential reached −18.2 mV. Increasing the proportion of α-lactalbumin in the polymer dispersions resulted in more turbid gels characterized by an open microstructure. Elastic and viscous moduli were reduced, while the relaxation coefficient and the stress decay rate constants were increased by raising the proportion of α-lactalbumin in the gel. After one week of storage at 5 °C, gel hardness increased by 12%. The effect of protein composition on acid-induced gelation of whey protein is discussed in relation to the availability and reactivity of thiol groups during gel formation and storage.     

Effect of whey protein enzymatic hydrolysis on the rheological properties of acid-induced gels

A protein dispersion blend of β-lactoglobulin and α-lactalbumin was heat-denatured at pH 7.5, hydrolyzed by α-chymotrypsin and then acidified with glucono-δ-lactone to form gels at room temperature. Heat treatment induced the formation of whey protein polymers with high concentration of reactive thiol groups (37 μmol/g). The reactive thiol group concentration was reduced by half after 40 min enzymatic hydrolysis. It was further reduced after enzyme thermal deactivation. During acidification, the first sign of aggregation for hydrolyzed polymers occurred earlier than for non hydrolyzed polymers. Increasing the hydrolysis duration up to 30 min resulted in more turbid gels characterized by an open microstructure. Elastic and viscous moduli were both reduced, while the relaxation coefficient and the stress decay rate constants were increased by increasing the hydrolysis duration. After one week storage at 5 °C, the hardness of gels made from hydrolyzed polymers increased by more than 50%. The effect of polymer hydrolysis on acid-induced gelation is discussed in relation to the availability and reactivity of thiol groups during gel formation and storage.     

Effect of sesame protein isolate in partial replacement of milk protein on the rheological,textural and microstructural characteristics of fresh cheese

Soft cheeses were manufactured from bovine milk with the addition of 0–12% sesame protein isolate (SPI) were utilised to investigate rheology, texture and microstructure at different stages of cheese making. SPI addition reduced the speed of milk fermentation, kappa‐casein proteolysis of rennet and elongated the time of cheese curd formation. Renneted milk storage modulus G′_60min was decreased and coagulation time increased with increasing SPI content. Low SPI supplements (4% and 8%) enhanced the hardness, cohesiveness, adhesiveness and gumminess of the soft cheese, while high SPI addition (12%) deteriorated the texture. In the cheese curd gel matrix, SPI distributed as specific SPI‐gel clusters on the surface of curd fractures, stacked or fused with ball‐shaped casein micelles and wrapped up to casein gel strands. In summary, SPI actively interacted with casein colloid throughout the cheese making process.     

挤压处理对豌豆蛋白功能特性及结构的影响

目的:研究挤压处理对豌豆蛋白功能特性及结构的影响,提高豌豆蛋白的功能性质。方法:采用全自动测色色差计对豌豆蛋白挤出物颜色的变化进行分析,用化学分析法对蛋白质的持水性和乳化特性进行测试,用扫描电子显微镜观察豌豆蛋白及其挤出物的微观结构,利用傅里叶变换红外光谱仪分析挤出物的二级结构变化。结果:豌豆蛋白经挤压处理后,颜色无显著差异,产品色泽良好,持水性显著下降(P<0.05),乳化性和乳化稳定性显著增加(P<0.05)。挤压处理后微观结构改变明显,产生蛋白聚集体,结构紧密。挤压处理后无新的特征峰出现,但二级结构各组分之间发生转化,β-折叠、α-螺旋结构向β-转角、无规卷曲结构转化,结构稳定性增加。结论:豌豆蛋白经过挤压处理后,保留了原来的产品色泽,乳化特性显著改善,结构致密,稳定性得到了提高。     

Textural properties of legume protein isolate and polysaccharide gels

The influence of legume proteins from lupin, pea and fababean on the formation of gels prepared by heat treatment in the absence or presence of xanthan gum, locust bean gum and NaCl was investigated. The resulting fracture and texture properties of gels not only are associated with the heating process used to form the gel but also depend on the conformational aspects of xanthan–locust bean gum in admixture with legume proteins, which after 10 days of aging reinforce the system. The fracture and textural properties are explained in terms of the effect of the protein–polysaccharide molecular structure and physicochemical conditions applied in the gel system during the gel preparation and measurements. Copyright © 2006 Society of Chemical Industry     

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.     

不同因素对乳清蛋白乳化凝胶特性的影响

探讨了葡萄糖酸-δ-内酯（GDL）、中性盐（NaCl、CaCl₂）以及增稠剂对乳清分离蛋白乳化凝胶强度、弹性以及保水性的影响。结果表明:GDL为0.6%、NaCl为1%、CaCl₂为0.25%、增稠剂卡拉胶为0.2%以及黄原胶为0.1%制备的乳化凝胶强度显著提高。GDL为0.4%、NaCl为0.75%、CaCl₂为0.25%、增稠剂卡拉胶为0.05%以及黄原胶为0.15%制备的乳化凝胶弹性显著提高。增稠剂卡拉胶为0.15%、黄原胶为0.1%所制备的乳化凝胶保水性显著提高。      

Rheological,thermal and microstructural properties of whey protein isolate‐modified cassava starch mixed gels at different pH values

The objective of this study was to investigate the rheological, thermal and microstructural properties of whey protein isolate (WPI)‐hydroxypropylated cassava starch (HPCS) gels and WPI‐cross‐linked cassava starch (CLCS) gels at different pH values (5.75, 7.00 and 9.00). The rheological results showed that the WPI‐modified starch gels had greater storage modulus (G?) values than the WPI‐native cassava starch gels at pH 5.75 and 7.00. Differential scanning calorimetry curves suggested that the phase transition order of the WPI and modified starch changed as the pH increased. Scanning electron microscopy images showed that the addition of HPCS and CLCS contributed to the formation of a compact microstructure at pH 5.75 and 7.00. A comprehensive analysis showed that the gelling properties of the WPI‐modified starch were affected by the difference between the WPI denaturation temperature and modified starch gelatinisation temperature and by the granular properties of the modified starch during gelatinisation. These results may contribute to the application of WPI‐modified starch mixtures in food preparation.     

Effects of β‐glucans on properties of soya bean protein isolate thermal gels

The effects of concentration and molecular weight of oat β‐glucans on properties of soya bean protein isolate (SPI) thermal gels prepared by heating at 90℃for 30 min were investigated. Compared with control (free of β‐glucan) formulations, the presence of β‐glucans (0.5–1.5%, w/v) largely enhanced storage modulus (G′) and texture properties of SPI (12%, w/v) thermal gels measured by dynamic oscillatory rheometry and texture profile analysis, which were developed as increasing β‐glucan concentration and molecular weight. It is possible that β‐glucans could cause the formation of protein aggregates to produce gels through hydrophobic interactions. Mixed gel systems at low ionic strength showed higher G′ resulting from the lower denaturation temperature of SPI, which was beneficial to the formation of gel structure. In addition, although adding a certain amount of β‐glucan into SPI reduced water‐holding capacity of mixed gels, high molecular weight of β‐glucan improved their water‐holding capacity compared to control formulations attributed to the improvement of the structural integrity of the mixed gel network.     

Functional properties of protein hydrolysates from pea (Pisum sativum,L) seeds

The aim of this study was to investigate the effects of partial enzymatic hydrolysis on functional properties of two different pea protein isolates obtained from two pea genotypes, Maja and L1. Papain and commercial protease (Streptomyces griseus protease) were used for protein modification. Solubility, emulsifying and foaming properties were estimated at four different pH values (3.0, 5.0, 7.0 and 8.0). Papain increased solubility of L1 pea protein isolate at pH 3.0, 5.0 and 8.0, emulsifying properties and foaming capacity at all pH values. Otherwise, papain increased solubility of Maja pea protein isolate only at pH 8.0. This pea protein isolate modified with both enzymes formed emulsions with improved stability at lower pH (3.0, 5.0). The commercial protease‐prepared pea protein isolates showed generally low solubility and different emulsifying and foaming properties. Proper selection of enzyme, conditions of hydrolysis and genotypes could result in production of pea protein isolates with desirable functional properties.     

Effects of cornstarch on the gel properties of black bean protein isolate

The effects of common starch (CS) and high amylopectin starch (HAS) from corn on the properties of heat induced black bean protein isolate (BBPI) gels prepared by heating at 95°C for 30 min were investigated by using dynamic oscillatory rheometer, texture analyzer, and scanning electron microscopy (SEM). Compared with BBPI alone, the presence of cornstarch (1–4%, wt/vol) could improve storage modulus (G′) and textural properties of BBPI (10%, wt/vol) gels. The mixed system of BBPI and 4% (wt/vol) HAS exhibited the highest G′ and formed the gel faster and more easily, which resulted in firmer and more elastic gel than BBPI‐CS at all starch concentrations. It was possible that HAS had lower pasting temperature and higher viscosity than CS, which was beneficial to the formation of BBPI gel network and strengthened the stability of network structure. Moreover, it might also be related to the synergistic effect between protein and starch. The CS and HAS existed in the BBPI gel network could bind water, leading to the increase in the water‐holding capacity (WHC) of mixed gels, especially 4% (wt/vol) HAS, which was related to homogeneous and compact microstructure with small pores.     

Transglutaminase treatment of pea proteins: Effect on physicochemical and rheological properties of heat-induced protein gels

Rheological properties of heat-induced pea protein isolate (PPI) gels with added microbial transglutaminase (MTGase) were studied under various reaction conditions. A positive linear relationship was observed between level of MTGase used (0 to 0.7% w/w) and shear stress and shear strain of heat-set commercial pea protein isolate (PPIc) gels at 92 °C following incubation at 50 °C. Use of MTGase allowed for preparation of PPIc gels of similar strength and elasticity as commercial soy protein isolate gels and commercial meat bologna. MTGase treatment did not alter thermal properties of PPI gels. The shear stress and strain of PPIc gels were also improved following low temperature (4 °C) incubation of PPI with MTGase. Enhancement of shear strain or gel elasticity of heat-induced PPI gels with MTGase has not been reported before and provides opportunities for extending the properties of pea proteins when developing new food products.