马铃薯分离蛋白凝胶的制备及其性质研究

以新鲜马铃薯为原料,采用等电点沉淀法制备马铃薯分离蛋白。确定了马铃薯分离蛋白最低凝胶点的蛋白质浓度为6%。考察蛋白质浓度、pH 值、加热温度和加热时间4 个因素对凝胶形成的影响,采用物性仪对不同条件下制备凝胶的质构特性进行研究,通过脆度、硬度、稠度、黏聚性和黏着性这5 个指标对马铃薯分离蛋白的质构特性进行说明。优化结果表明不同评价指标得出的结论不尽相同。对马铃薯分离蛋白凝胶特性进行综合评价,可选用蛋白质浓度12%、pH7.0、加热温度95℃、加热时间15min 制备凝胶。     

制备条件和测定方法对SPI凝胶特性测定结果的影响

对影响大豆分离蛋白凝胶的形成因素进行了研究。蛋白质浓度、pH、温度和加热时间对所形成凝胶的质构特性都有较大的影响。在形成凝胶的最佳条件下制备凝胶,采用物性仪和一种简易的测定凝胶脆度的方法对几种不同大豆分离蛋白制备的凝胶的脆度进行测定,结果表明,两种方法测定结果无显著性差异,说明这种简易的测定方法可用于评价大豆分离蛋白的凝胶特性。     

花生分离蛋白凝胶形成条件及凝胶特性研究

研究了蛋白质浓度、pH值、加热时间和温度、氯化钙浓度对花生分离蛋白凝胶形成的影响,并对凝胶的特性作了测定,确定了花生分离蛋白形成凝胶的适宜条件.研究表明:在制取花生分离蛋白凝胶时,浓度控制在15%左右为宜;在酸性条件下花生分离蛋白形成凝胶最适pH值为4.0;CaCl2浓度为0.5 mol/L时形成的凝胶透明性和成形性较好.     

亲水多糖对谷氨酰胺转氨酶交联大豆分离蛋白凝胶特性的影响

目的 基于谷氨酰胺转氨(transglutaminase, TG)酶交联法研究亲水多糖对TG酶交联大豆分离蛋白凝胶特性的影响。方法 以大豆分离蛋白为主要原料,TG酶交联法为基础进行响应面优化,得到最优凝胶弹性的工艺参数,在此参数条件下将大豆分离蛋白与亲水多糖混合,制备亲水多糖-大豆分离蛋白复合凝胶,并对凝胶的质构特性、持水性、热力学性质以及结构进行表征。结果 在酶交联pH 7.3、酶交联时间2.3 h、酶交联温度48℃条件下,制备的大豆分离蛋白凝胶弹性最佳。添加了亲水多糖后,凝胶的质构特性和持水性显著提高,热稳定性增强,蛋白质二级和三级结构发生变化,凝胶的微观结构变得更致密,孔径变小。结论 亲水多糖的添加能够改善大豆分离蛋白的凝胶特性,该研究为大豆分离蛋白凝胶深加工提供了理论基础。     

白鲢鱼酸/碱等电点沉淀法分离蛋白及其凝胶特性

为制备营养特性和功能特性优良的分离蛋白,采用酸/碱等电点沉淀法制备白鲢鱼分离蛋白,并比较不同工艺（pH3.0-5.5、pH4.0-5.5、pH11.0-5.5、pH12.0-5.5 和pH13.0-5.5）制备分离蛋白的差异,结果表明：与酸法提取相比,碱法提取制备的分离蛋白的蛋白质含量高、粗脂肪含量低,溶解性强,且碱法制备（pH12.0-5.5）的分离蛋白的蛋白质含量最高,高达81.96 g/100 g,且水分含量仅为9.76 g/100 g,同时碱法（pH12.0-5.5 和pH13.0-5.5）提取的分离蛋白得率高。此外,酸/碱等电点沉淀法制备分离蛋白的氨基酸种类齐全,必需氨基酸含量占氨基酸总量比值42.27%以上,符合联合国粮农组织/世界卫生组织（Food and Agriculture Organization/World Health Organization,FAO/WHO）的蛋白质理想模式。此外,与酸法提取相比,碱法提取制备分离蛋白,其凝胶三维网络结构致密有序均匀,并具有强的凝胶特性和高的持水性,且碱法（pH12.0-5.5）提取制得的分离蛋白凝胶的凝胶特性最强,持水性最高。因此与酸法提取相比,碱法提取分离蛋白的得率高,且碱法（pH12.0-5.5）制备的分离蛋白的质量最优,且营养特性好。     

pH值对罗非鱼蛋白-大豆蛋白混合热凝胶特性及体外消化性的影响

以罗非鱼和大豆为原料分别提取鱼分离蛋白(fish protein isolate,FPI)和大豆分离蛋白(soy protein isolate,SPI),制备罗非鱼蛋白-大豆蛋白(FPI∶SPI=1∶1,质量比)热诱导凝胶,探讨pH值(6.0、6.5、7.0、7.5)对混合蛋白热凝胶特性和体外消化性的影响。结果表明:pH 6.5时罗非鱼蛋白-大豆蛋白混合蛋白热凝胶储能模量G′值大于单一蛋白,凝胶特性最好,硬度和胶黏性相比FPI都得到提升。pH值会影响蛋白质与水分子的结合能力,混合蛋白热凝胶的持水性在pH 6.5时比其它pH值条件下强(P<0.05),达到最大值84.02%,与扫描电镜结果一致,网络结构致密且光滑平整。pH 6.5时,混合蛋白热凝胶的消化率达91.57%,高于其它pH值下的消化率(P<0.05)。因此,通过调节pH值可以改善FPI和SPI混合蛋白热凝胶的凝胶特性和消化性。     

大豆分离蛋白凝胶制备和凝胶质构特性研究

本研究以大豆分离蛋白为原料，考察蛋白质浓度、pH值、加热温度、加热时间对凝胶形成的影响，采用物性仪对不同务件下制备的凝胶的质构特性进行研究，不同评价指标得出的结论不尽相同。通过正交实验得出形成凝胶硬度最大的制备条件为：蛋白浓度12％，pH值6．5，加热温度95℃，加热时间35min；形成凝胶脆性最大的制备凝胶争件为：蛋白浓度12％，pH值7．0，加热温度95℃，加热时间25min；形成凝胶弹性最好的制备凝胶务件为：蛋白浓度12％，pH值7．0，加热温度85℃，加热时间35min；形成凝胶粘附性最大的制备凝胶条件为：蛋白浓度12％，pH值7．0，加热温度95℃，加热时间35min。     

κ-卡拉胶对大豆分离蛋白乳浊凝胶特性的影响

研究了κ 卡拉胶在不同pH的条件下对大豆分离蛋白乳浊凝胶质构特性和流变特性的影响。研究结果表明 ,pH 7 3条件下的乳浊体系比 pH 6 8的体系更易形成凝胶。卡拉胶质量分数为 0 0 5 %时 ,因与大豆分离蛋白发生静电吸引相互作用形成连接型凝胶而显著提高了凝胶的质构特性和流变特性。 0 2 %时则形成相分离型凝胶 ,降低了凝胶的弹性和内聚性。     

大豆蛋白凝胶制备及其性质研究

研究以NaCl作为凝固剂,将大豆分离蛋白(SPI)80℃预热处理10 h,在不同浓度、离子强度及pH值条件下,通过95℃加热蛋白液30min使蛋白变性来制备大豆蛋白凝胶,并对凝胶的质构及凝胶特性进行了分析。结果表明:pH值7.0、80℃预热处理10 h的大豆蛋白溶解性明显小于普通SPI,其他pH值条件下两者溶解性差异不大;pH值2.0、80℃预热处理10 h的蛋白凝胶情况明显优于普通SPI,在一定范围内,随着蛋白浓度及离子强度的增加,凝胶情况越来越好。     

GDL诱导大豆分离蛋白冷凝胶对益生菌的保护

主要研究了葡萄糖酸内酯(GDL)诱导大豆分离蛋白冷凝胶在胃酸pH环境下对乳酸菌的保护情况.利用GDL诱导形成的大豆分离蛋白冷凝胶在胃酸pH环境下作用30min后乳酸菌的存活率为评价指标,用以评价大豆分离蛋白冷凝胶对乳酸菌的保护情况通过正交实验得出,在pH1.2的胃酸环境下,大豆分离蛋白冷凝胶的成胶条件为变性温度90℃、SPI浓度9％、GDL浓度1.2％,对乳酸菌的保护效果最佳.活菌落菌落计数的数量级由初始的107变为105 cfu/mL,仅下降了2个数量级,乳酸菌的存活率达到26.61％,得到显著提高.实验结果表明,在胃酸pH环境下GDL诱导的大豆分离蛋白冷凝胶能很好的保护乳酸菌,为益生菌和大豆分离蛋白在食品中的应用提供了参考.     

燕麦蛋白-结冷胶冷诱导凝胶微观结构与控释特性的关联性研究

热变性后的燕麦蛋白(oat protein isolate,OPI)与结冷胶(gellan gum,GG)通过添加不同浓度的葡糖酸-δ-内酯(glucono-delta-lactone,GDL)形成OPI-GG冷诱导凝胶,通过质构分析、扫描电子显微镜、激光共聚焦显微镜以及傅里叶红外光谱,研究不同条件下形成的凝胶微结构以及分子构象的变化,探究不同凝胶微结构与凝胶控释特性的关联性。结果表明,在GG添加量为0.1%、pH 5时,凝胶硬度最大,随着GG浓度升高,凝胶硬度逐渐变弱。通过扫描电镜和激光共聚焦的观察可知OPI-GG凝胶可形成两种网络微结构,在pH 4和pH 5时,OPI与GG之间由于静电引力使其相互作用力增强,形成致密且均匀的单网络微结构;在pH 6和pH 7时,OPI与GG由于静电斥力的作用产生相分离,从而形成双网络结构。具有不同微结构的OPI-GG凝胶可作为基质包埋核黄素,双网络结构的凝胶可有效提高核黄素的包埋率(75%),其在pH 1.2磷酸缓冲溶液(phosphate buffer saline,PBS)中浸泡2 h后核黄素的释放率为33%;致密的单网络结构OPI-GG凝胶包埋率为61%,在pH1.2 PBS中可有效阻止核黄素的释放,其释放率为18%,并在pH 7.4 PBS中使核黄素逐步释放,8 h后释放率为53%。该研究结果表明,在中性条件下制备的OPI-GG双网络结构冷凝胶具有较好的核黄素包埋能力,在酸性条件下制备的OPI-GG单网络冷凝胶具有较好的控释能力,因此,不同微结构的OPI-GG冷凝胶具有作为营养素包埋和递送体系的潜力。     

超声波辅助酸/碱溶解等电点沉淀法提取鸡架分离蛋白的组成及其凝胶特性

利用高强度超声（high intensity ultrasound,HIU）辅助酸/碱溶解等电点沉淀（isoelectric solubilization/precipitation,ISP）法提取鸡架分离蛋白（protein isolate,PI）,采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳研究PI组成,并分析PI凝胶特性。结果表明：PI主要由肌原纤维蛋白组成;酸溶解会导致肌球蛋白重链降解,HIU可减弱降解程度;碱溶PI凝胶的硬度、蒸煮损失率、离心损失率与对照（鸡胸肉糜凝胶,后同）无显著差异,显著高于酸溶PI凝胶（P＜0.05）;HIU显著提高了酸溶PI凝胶的硬度和弹性（P＜0.05）,降低了蒸煮损失率及离心损失率（P＜0.05）;PI凝胶白度均显著低于对照（P＜0.05）。碱溶PI凝胶对水分子的结合力和束缚力均优于酸溶PI凝胶;碱溶PI凝胶与对照凝胶均具有均匀致密微观结构,而酸溶PI凝胶微观结构明显粗糙、不均匀。结论：HIU辅助碱溶ISP法可高效提取鸡架中肌原纤维蛋白并保持其凝胶特性,有助于鸡架增值利用。     

NaCl对添加丝氨酸蛋白酶的肌原纤维蛋白凝胶特性的影响

以养殖大黄鱼作为研究对象,探究NaCl对添加了丝氨酸蛋白酶的肌原纤维蛋白凝胶特性的影响。首先对养殖大黄鱼肉经过提取分离纯化得到的丝氨酸蛋白酶进行研究,探讨其最适温度、最适pH以及NaCl对丝氨酸蛋白酶活性的影响。并进一步研究NaCl对含有丝氨酸蛋白酶的肌原纤维蛋白凝胶的质构特性、持水性、白度、拉曼光谱、荧光分析、微观结构等特性的影响。结果发现,丝氨酸蛋白酶的最适温度为50℃,最适pH值为7.0。NaCl的添加使肌原纤维蛋白凝胶的二级结构发生改变,蛋白凝胶结构越来越紧密稳定,但荧光强度相对有所下降。在NaCl质量浓度为0~20 g/L时,肌原纤维蛋白凝胶的胶黏性、咀嚼性不断上升,且白度增大。在NaCl添加量为40 g/L时,肌原纤维蛋白凝胶的持水性最强。因此可得出结论,添加NaCl后,丝氨酸蛋白酶的活性受到抑制,使其对肌原纤维蛋白凝胶的破坏减弱,从而改善鱼糜凝胶特性。     

L-组氨酸修饰乳清蛋白结构及其热诱导凝胶特性

采用L-组氨酸（L-His）作为蛋白凝胶功能性的增强剂,将其加入乳清分离蛋白溶液中制备热诱导凝胶,研究L-His对乳清蛋白结构及其凝胶特性的影响。结果表明：在乳清蛋白等电点（pI 5.2）时蛋白形成尺度约1 700 nm、具有极小比表面积且几乎不带电的蛋白聚集体,远离蛋白等电点时则所形成的聚集体大小约为400 nm;L-His抑制蛋白聚集体的形成而减小粒径、显著提高聚集体比表面积,促进蛋白分子结构展开并提高其带电量。在经历热诱导后,乳清蛋白在其等电点时形成持水性差的白色凝胶,而在其他pH值时则形成持水性高的黄色凝胶且越远离等电点,胶体黄度值越大;L-His的加入对凝胶颜色变化无显著影响,但能够显著提高凝胶的持水性（P＜0.05）;有效提高凝胶的质地特性,特别是在pH 7.59和pH 9.74时显著提高乳清蛋白凝胶的弹性及咀嚼性（P＜0.05）。这些质构变化可能主要归结于L-His改变了凝胶内的氢键、二硫键和疏水作用力的重排。总之,L-His修饰乳清蛋白结构而改变其凝胶性能且同时受到pH值的影响。     

磷酸盐-大豆分离蛋白联合处理对草鱼肌原纤维蛋白凝胶化的影响

为探讨磷酸盐(三聚磷酸钠、六偏磷酸钠、焦磷酸钠(tetrasodium pyrophosphate,TSPP))和大豆分离蛋白(soy protein isolate,SPI)对草鱼肌原纤维蛋白凝胶化的影响,采用热处理方法,将不同质量浓度的磷酸盐、SPI与草鱼肌原纤维蛋白混合制成凝胶.用黏度、嫩度、持水性、显微结构和粗...     

Effects of partial hydrolysis on structure and gelling properties of oat globular proteins

The effects of partial hydrolysis and the environmental conditions (pH and temperature) on the gelling properties of oat protein isolate (OPI) were investigated. OPI was treated with flavourzyme, alcalase, pepsin and trypsin. The changes in protein structure were observed by SDS-PAGE, size exclusion high performance liquid chromatography (SE-HPLC) and amino acid analysis. Gel mechanical properties were evaluated by textural profile analysis (TPA). The results revealed that the acidic polypeptides (12S-A) of oat globulin exerted great influence over the gelling ability of oat protein. Partial hydrolysis by flavourzyme and trypsin could significantly improve oat protein gel strength, especially at pHs 8–9 by modulating the balance between the electrostatically repulsive force and the hydrophobic attractive force among polypeptide chains during the gelling process. The gels prepared with flavourzyme and trypsin treated oat proteins have comparable or higher mechanical strength than soy protein gels at neutral pH. At pH 9 the gel made of trypsin treated oat protein even showed comparable mechanical strength to egg white protein gels under the same pH. Both oat protein and its hydrolysate gel exhibited excellent water-holding capacity at neutral or mildly alkaline conditions. The results of this study indicate that oat protein has a promising potential to be used as new and cost-effective gelling ingredient of plant origin to provide texture and structure in food products.     

The Young's Modulus,Fracture Stress,and Fracture Strain of Gellan Hydrogels Filled with Whey Protein Microparticles

Texture modifying abilities of whey protein microparticles are expected to be dependent on pH during heat‐induced aggregation of whey protein in the microparticulation process. Therefore, whey protein microparticles were prepared at either pH 5.5 or 6.8 and their effects on small and large deformation properties of gellan gels containing whey protein microparticles as fillers were investigated. The majority of whey protein microparticles had diameters around 2 μm. Atomic force microscopy images showed that whey protein microparticles prepared at pH 6.8 partially collapsed and flatted by air‐drying, while those prepared at pH 5.5 did not. The Young's modulus of filled gels adjusted to pH 5.5 decreased by the addition of whey protein microparticles, while those of filled gels adjusted to pH 6.8 increased with increasing volume fraction of filler particles. These results suggest that filler particles were weakly bonded to gel matrices at pH 5.5 but strongly at pH 6.8. Whey protein microparticles prepared at pH 5.5 showed more enhanced increases in the Young's modulus than those prepared at pH 6.8 at volume fractions between 0.2 and 0.4, indicating that microparticles prepared at pH 5.5 were mechanically stronger. The fracture stress of filled gels showed trends somewhat similar to those of the Young's modulus, while their fracture strains decreased by the addition of whey protein microparticles in all examined conditions, indicating that the primary effect of these filler particles was to enhance the brittleness of filled gels.     

Mixtures of whey protein microgels and soluble aggregates as building blocks to control rheology and structure of acid induced cold-set gels

Whey proteins (WP) today offer an extremely high potential for innovative development of functional and nutritious food products. Acid cold-set gels present an interesting approach of gelation at low temperature upon acidification of preformed whey protein (WP) aggregates. In the present work, we aimed to demonstrate how structure and rheological properties of acid gels can be controlled by combining two types of WP aggregates with different structural and chemical properties. Whey protein microgels (WPM) and soluble aggregates (WPSA) were generated upon heating WP isolate in specific pH conditions and temperature, leading to Z-average hydrodynamic diameters close to 270 nm for WPM and 100 nm for WPSA. Mixtures of WPM and WPSA were prepared at different weight ratios ranging from 100% WPM to 100% WPSA. The total protein concentration was set to 4 or 8%wt. Acidification was performed at 40 °C by addition of 1%wt glucono-δ-lactone (GDL). Gelation was followed using turbidimetry and small deformation rheology as function of pH. Microstructures of the gel were investigated at different length scales using various microscopy techniques (CLSM, SEM, AFM). When the WPM/WPSA ratio decreased, the pH of gelation and the gel strength increased because of the different structure and chemical reactivity of the two types of WP aggregates. The final pH had a strong impact on the structure of the gels. When final pH decreased below pH 4.3, a structure change was suggested by turbidimetry measurements. This resulted in a non self-supporting gel or in a decrease of gel strength. For pH above 4.3, self supporting gel were obtained. The rheological properties of the gel could therefore be modulated depending on the properties of the building blocks used (WPM versus WPSA). Interestingly, the gel microstructures observed for WPM/WPSA mixtures or WPM were comparable to those of acidified skimmed milk gels ranging from coarse structures with clumps of aggregates or to homogeneous fine networks (WPSA only) that have been described for WP gels obtained upon direct heating at various pH.     

Effect of grinding on the structure of pea protein isolate and the rheological properties of its acid-induced gels

The purpose of this study was to expand the application range of pea protein isolates by improving the rheological properties of their acid-induced gels. A pea protein isolate was ground for different durations, and changes in the structure and properties of its gels were studied. Furthermore, the influence mechanism of grinding on gelation was revealed. The results showed that grinding slightly changed the secondary structure of the pea protein isolate and had a great impact on its tertiary structure. Compared with the unground pea protein isolate, the solubility of the ground pea protein isolate increased from 45.89% to 69.84%, and the water-holding capacity of the gels increased from 52.04% to 94.67% at 7.5 min of grinding. After grinding for 15 min, the particle size of the pea protein isolate decreased from 1292.4 to 945.7 nm, and the polydispersity index decreased from 0.387 to 0.321. Rheological measurements showed that the storage modulus (G′), viscosity and recovery of protein gel samples improved after grinding. Thus, grinding enhanced the potential of protein gels for new applications.