加热和冷却速率对大豆蛋白凝胶特性的影响

凝胶性是植物蛋白最重要的性质。采用小变形振荡(动态)流变测试研究大豆分离蛋白凝胶网络结构形成。结果表明:在加热阶段,储能模量(G')和耗能模量(G″)都低于1 Pa,G'G″且基本保持恒定直到达到凝胶点。Tanδ值随着加热的进行逐渐降低,然后急剧下降,冷却阶段时降至最低且保持恒定,说明形成强而稳定的凝胶网络结构。当加热和冷却速率增大时(从0.5~4℃/min)G'值逐渐下降,表明最终形成凝胶强度下降;慢的加热(冷却)速率时(0.5、1、2℃/min)tanδ较小,说明相对于快的加热速率(4℃/min)形成了更好三维网络结构的凝胶;凝胶点和加热速率有关而不受冷却速率的影响。随着蛋白质浓度的增大,其凝胶G'值增大、tanδ值减少、凝胶点下降。因此,控制加热和冷却速率可以最大限度的提高热诱导大豆蛋白的凝胶强度,而不用改变蛋白质的浓度。     

氧化羟丙基木薯淀粉的流变特性

利用DHR-1流变仪,研究了氧化羟丙基木薯淀粉的静态流变和动态流变特性。结果表明,氧化羟丙基木薯淀粉糊为假塑性流体（n＜1）,符合Herschel-Bulkley模型（R2＞0.98）。随着羧基含量和羟丙基摩尔取代度（molar substitution,MS）的增大,稠度系数k减小,非牛顿性减弱,趋近于牛顿流体。在整个振幅范围（1×10－4～1 rad）,主要表现为黏性特性;随着振幅增加,样品的弹性模量（G’）和黏性模量（G”）变化不明显;随着羧基含量和羟丙基摩尔取代度（molar substitution,MS）的增大,G’和G”降低,损耗角正切（tanδ＝G”/G’）增加。在频率范围（0.1～12.5 rad）内,随着频率增加,样品的G’和G”增加,tanδ变化不明显;随着羧基含量和MS的增大,G’和G”降低,tanδ增加。     

加热速率对鸡胸肉匀浆物凝胶特性影响

分别采用慢速加热1 ℃/min和快速加热2 ℃/min的速率,对鸡胸肉匀浆物进行加热,使其最终中心温度分别达到65、70、75、80、85 ℃。结果发现：加热方式对鸡胸肉匀浆物凝胶的保水性有显著影响（P＜0.05）,对鸡胸肉凝胶硬度有极显著影响（P＜0.01）;以1 ℃/min进行加热当最终中心温度达到70 ℃时形成热诱导凝胶的保水性和硬度最好;1 ℃/min进行加热的鸡胸肉蛋白的G’和G”都好于以2 ℃/min加热的G’和G”,且慢速加热鸡肉蛋白的变相温度比快速加热提前,出现的两个峰值也都高于快速加热。扫描电镜结果显示慢速加热形成的蛋白凝胶结构较快速加热形成的凝胶结构均匀、致密。     

豌豆蛋白对牛肉盐溶蛋白共混凝胶特性的影响

为改善牛肉盐溶蛋白凝胶特性,提高豌豆蛋白附加值,研究了豌豆蛋白对牛肉盐溶蛋白共混凝胶色泽、保水性、蒸煮得率、质构、动态流变、微观结构、水分迁移等特性的影响。结果表明:随豌豆蛋白添加量增加,凝胶L*值先升高后下降,a*值下降,b*值上升;豌豆蛋白的添加显著提高了不易流动水T_(21)的相对百分含量,降低了自由水T_(22)的相对百分含量,使T_(21)、T_(22)向快弛豫时间方向移动,保水性与蒸煮得率进一步提升,在添加质量浓度为0. 12 g/mL时,分别为88. 85%、89. 49%;硬度、咀嚼性持续上升;弹性与恢复性先升高后下降,添加质量浓度为0. 12 g/mL时最大,分别为0. 969、0. 432;豌豆蛋白能提高肌球蛋白头部变性温度,由53℃增加到58℃,G'初始值和终值均随豌豆蛋白添加量增加而升高;添加量为0. 12 g/mL时,凝胶网络结构最好,细致均匀、高度有序。     

芋艿分离蛋白质的流变特性

以芋艿分离蛋白为材料,研究了不同pH值环境条件下芋艿分离蛋白的流变特性、紫外和荧光光谱。结果表明：pH值环境对芋艿蛋白的变性及聚集有明显的影响。在pH值接近芋艿蛋白的等电点时,芋艿分离蛋白因聚集导致其表观黏度较高,滞后现象明显,胶凝点温度（Tgel）及凝胶储能模量（G’）较高;当pH值升高至8.0时（大于芋艿蛋白的等电点）,芋艿分离蛋白解聚集,构象展开,表观黏度较低,滞后现象减弱,Tgel及凝胶G’降低。随溶液pH值的升高,频率扫描曲线G’与损耗模量（G”）的交点逐渐向高频方向移动并最终消失。在pH 7.0时,芋艿分离蛋白的紫外吸收峰位于284 nm波长处;其荧光光谱最大激发波长为289.7 nm,最大发射波长为330.3 nm。     

影响猪血浆蛋白热诱导凝胶质构特性及持水性因素的研究

本实验研究在一定的加热条件下猪血浆蛋白质量浓度、加热温度、加热时间、离子种类、离子强度和pH 值对猪血浆蛋白热诱导凝胶的质构、持水性等性质的影响。利用质构仪测定猪血浆蛋白热诱导凝胶的硬度和黏附性,利用离心的方法测定凝胶的持水性。结果表明,在80℃下加热45min,猪血浆蛋白质量浓度超过6g/100mL可以形成凝胶,并且随蛋白质量浓度的增大,凝胶强度和持水性也增大;凝胶强度随pH 值(3～9)增加而增大,pH5 时凝胶的持水性最小,pH3 时最大;NaCl 浓度0.2mol/L,CaCl2 浓度0.6mol/L 时,凝胶硬度最大。实验得出,猪血浆蛋白热诱导凝胶的质构特性及持水性受许多因素影响,在实际生产中应该控制加热条件,以获得高质量的凝胶。     

芡实分离蛋白的凝胶特性及流变特性

以芡实分离蛋白为原料,研究芡实分离蛋白溶液的凝胶特性和流变特性。确定芡实分离蛋白溶液的最低凝胶点蛋白质量浓度为5g/100mL,考察分离蛋白质量浓度和pH值对凝胶形成的影响;测定放置时间和蔗糖添加量对芡实分离蛋白溶液流变特性的影响。结果表明：分离蛋白质质量浓度和pH值对凝胶硬度、稠度和脆度影响较大,对黏着性和黏聚性影响比较小;随着溶液放置时间的增加,蛋白分子水合作用减弱,其蛋白-蛋白分子间作用力增强,芡实分离蛋白溶液表观黏度上升;蔗糖的添加能明显增加蛋白溶液的表观黏度,降低溶液的流动性,增加溶液的稳定性。     

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。     

氯化钠与L-精氨酸/L-赖氨酸复合提取鸡胸蛋白的凝胶性质

考察以0.55 g/100 mL L-精氨酸（精氨酸）/L-赖氨酸（赖氨酸）＋1.5 g/100 mL NaCl溶液为提取剂提取的 鸡胸肉蛋白的凝胶特性。差示扫描量热法和动态流变结果表明：与对照组相比,添加精氨酸/赖氨酸的提取剂所对 应的蛋白提取物在加热过程中具有3 个明显的变性温度点和4 个明显的温度区间,其在加热和冷却的过程中均具有 更高的储能模量;添加精氨酸/赖氨酸的提取剂所对应的蛋白提取物形成的蛋白凝胶具有连续的三维网络结构、更 高的保水性和凝胶强度以及更低的蒸煮损失。因此,提取剂中包含精氨酸/赖氨酸的蛋白提取物具有更好的凝胶特 性,所形成的凝胶具有更好的保水和质构等特性。     

商业橘皮果胶与大豆果胶流变性质的比较

通过流变学方法对商业橘皮果胶及大豆果胶溶液黏度及凝胶过程进行分析。结果表明：相同条件下,商业橘皮果胶的黏度高于大豆果胶;在形成凝胶过程中,商业橘皮果胶凝胶体系储能模量要远高于大豆果胶。果胶质量浓度为2 g/100 mL、蔗糖添加量为55、60 g/100 mL,葡萄糖酸内酯（D-glucono-δ-lactone,GDL）添加量为3、4 g/100 mL的商业橘皮果胶与相同条件下的大豆果胶储能模量差异不大;通过加入蔗糖及GDL或提高大豆果胶质量浓度,可明显提高大豆果胶凝胶体系的储能模量,增加大豆果胶的凝胶强度。     

Gelation properties of salt-extracted pea protein induced by heat treatment

Gelation is one of the most important properties of plant proteins. In this paper, a low denaturation salt extraction method was used to extract pea (Pisum sativum L.) protein isolate from commercial pea flour. The gelation properties of this isolate were examined and compared to commercial products. The pea protein isolate followed the three-step process of gelation that is generally accepted for heat-induced gelation of globular proteins. The minimum gelation concentration of salt-extracted pea protein isolate (PPIs) was 5.5% while that of commercial pea protein isolate (PPIc) was 14.5%. The gelling point was in the range of 82–86 °C for 14.5% PPIs, 0.3 M NaCl at natural pH (5.65). With increasing heating rate, the gelling point tended to increase. Higher heating and cooling rates resulted in decreased final G′ (storage modulus) and G″ (loss modulus) values, indicative of decreased gel strength. A higher protein concentration resulted in higher G′ and G″ values and it was found that there was a power law relationship between protein concentration and G′ and G″. Tan delta (δ) values decreased with increasing protein concentration and at concentrations of 5.5% and above, tan δ remained constant which means the critical concentration for gel formation was 5.5%. The values of G′ and G″ for PPIs were greater than those of PPIc, and tan δ of PPIs was smaller, indicative of a stronger gel network. DSC data showed that PPIc had undergone denaturation whereas PPIs had not (ΔH = 15.81 J/g protein). Although rheometer data showed that the final G′ value of commercial soy protein isolate (SPIc) was smaller than that of PPIs, the gel prepared with SPIc was visually stronger than that of PPIs. The rheological data obtained with small amplitude oscillatory testing was not consistent with the actual observations. Overall, the low degree of denaturation of the PPIs resulted in a stronger gel than that of PPIc making the PPIs a more attractive food ingredient.     

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.     

交联程度对木薯淀粉特性的影响

为探讨交联作用对木薯淀粉凝胶的影响,利用快速黏度分析仪和动态流变仪研究不同交联度木薯淀粉的糊化特性和流变特性。黏度特性测试结果表明,随着交联度的增加,交联木薯淀粉的回生值和最终黏度先增加后减小,崩解值减小。由静态流变测试结果可知,不同交联木薯淀粉屈服应力T0大于0,流动指数n均小于1,表明该实验条件下木薯淀粉糊均为屈服-假塑性流体。淀粉糊(质量分数为6%)动态流变测试结果表明,在0.1~10.0 Hz频率范围内,交联木薯淀粉的储能模量(G’)和损耗模量(G")均高于原木薯淀粉G’和G";在4℃条件下老化2 h,适当的交联可以使木薯淀粉G’升高,损耗角正切值(tanδ=G"/G’)降低。淀粉糊(质量分数为15%)动态流变测试结果表明,在整个升温和降温过程中,交联木薯淀粉的G’和G"大于原木薯淀粉,降温过程中,淀粉凝胶的G’随交联度增加迅速增加,表现出更优越的凝胶特性。     

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.     

牦牛肌原纤维蛋白与热改性大豆分离蛋白共凝胶条件的优化

牦牛肉是纯天然食品原料,然而牦牛肉蛋白资源的开发利用不够,特别是利用质构重组技术将牦牛肉中的肌原纤维蛋白和大豆分离蛋白用于开发凝胶产品鲜见研究报道。本研究以牦牛肌原纤维蛋白（myofibrillar proteinisolate,MPI）与热改性大豆分离蛋白（soybean protein isolate,SPI）为原料,分别采用单因素试验和正交试验设计,研究SPI-MPI溶液体积比、SPI热改性温度、离子强度和转谷氨酰胺酶（TGase）用量对共凝胶硬度、弹性和持水性的影响。单因素试验结果表明：改变4 个因素条件均能显著地提高热改性SPI-MPI溶液的凝胶性能,各因素对共凝胶特性综合指标影响的主次顺序为SPI-MPI溶液体积比＞TG用量＞离子强度＞SPI热改性温度。正交试验结果表明形成共凝胶的最优条件是：SPI-MPI溶液体积比1∶9、SPI热改性温度100 ℃、TG用量50 U/g、不添加镁离子。     

The effect of concentration and botanical source on the gelation and retrogradation of starch

The changes in shear modulus of pea, wheat, maize and potato starch gels with time, at concentrations between 10 and 40% w/w, were followed. In this range, the cooling of gelatinised dispersions of starch resulted in turbid, elastic gels. The initial rate of development of stiffness of the gels followed the order: pea>maize>wheat>potato, and was related to the amount of amylose solubilised during gelatinisation. The initial gelation was not reversed on heating to 100° C. There was also a long-term increase in gel stiffness, which was thermally reversible. This long-term increase, linked to a crystallisation involving amylopectin, followed the order: pea>potato>maize>wheat. With increasing starch concentration this latter process becomes more important.     

不同温度下亚麻籽胶对肌原纤维蛋白凝胶特性的影响及机制

本实验研究了不同加热温度下,添加亚麻籽胶对肌原纤维蛋白保水性、凝胶强度、流变特性、二级结构、微观结构的影响及其作用机制。结果表明,随着温度升高,肌原纤维蛋白凝胶保水性显著下降（P＜0.05）,凝胶强度显著上升（P＜0.05）,加热温度高于50 ℃时添加亚麻籽胶显著提高了肌原纤维蛋白凝胶保水性（P＜0.05）,同时显著降低了凝胶强度（P＜0.05）;拉曼光谱结果表明随着温度从30 ℃上升至80 ℃,凝胶α-螺旋含量显著下降,β-折叠含量显著上升;添加亚麻籽胶使得肌原纤维蛋白存在α-螺旋含量下降,β-折叠含量上升现象,影响凝胶的形成及性质。流变学特性结果显示高于50 ℃时添加亚麻籽胶后肌原纤维蛋白储能模量G’下降。从微观结构发现,添加亚麻籽胶后肌原纤维蛋白在50 ℃出现更多凝胶孔洞,且在70、80 ℃时形成的凝胶三维网络结构更为致密均一。     

宰后高温诱导制备类PSE兔肉

研究了类苍白、松软、表面汁液渗出（pale soft exudative,PSE）兔肉的制备方法,以保证PSE兔肉科学研究用实验材料品质的一致性。以新鲜的兔背最长肌和后腿肉为实验材料,参照猪、家禽PSE肉的制备方法,研究37 ℃水浴条件下兔背最长肌和腿肌肉感官品质、pH值、色泽、失水率、弹性、肌原纤维蛋白溶解度及弹性储能模量（G′）的变化。结果表明：随着处理时间的延长,兔背肌和腿肌的感官品质下降;pH值、a*值、弹性、蛋白质的溶解度及凝胶G′值均显著下降（P＜0.05）;L*值和失水率显著增加（P＜0.05）。水浴2 h时,兔背肌肉的极限pH＜5.74,L*＞63.40,汁液损失率＞25.36%;3 h时,兔腿肌肉的极限pH＜5.84,L*＞56.82,汁液损失率＞17.85%。在37 ℃保温2 h,兔背肌肉表现出了PSE肉的特征;在37 ℃保温3 h,兔腿肌肉表现出了PSE肉的特征。     

3种不同香辛料提取物对猪肉肌原纤维蛋白功能特性的影响

将迷迭香、丁香、肉桂3种香辛料提取物添加到猪肉肌原纤维蛋白中(0.005、0.010、0.020 g/g pro),研究其对蛋白质巯基、表面疏水性、溶解度及凝胶特性的影响。结果表明,3种香辛料提取物均降低了蛋白质的总巯基含量和溶解性,表面疏水性随添加量的增加先升高后降低。3个添加量在加热最终阶段弹性模量(G’)均高于对照组,低、中添加量提取物使凝胶强度增加,有利于蛋白凝胶的形成,而高添加量提取物对凝胶形成有破坏作用。因此,香辛料提取物与肌原纤维蛋白发生相互作用,从而对蛋白质的结构和凝胶特性产生影响。