Rheological investigation of soy protein hydrogels induced by Maillard-type reaction

Rheological measurements were used to determine the power law relationship between gel elastic modulus and protein concentration (solid volume fraction) for soy protein hydrogels. The slope calculated from the log–log plot was used to determine gel fractal dimension. The validity of the prefactor in the power law relationship was also studied. Soy protein at 6.5–9.5% was gelled using monofunctional (glyceraldehyde) or bifunctional (glutaraldehyde) Maillard cross-linkers with or without salt.Gel fractal dimension did not vary with cross-linker type or concentration, while prefactor values increased with cross-linker concentration and when salt was used. The invariability of the fractal dimension is believed related to the absence of effect of the cross-linking agents on protein ionic repulsions, while prefactor value is believed inversely proportional to the number of inter-floc particle–particle interactions in the three-dimensional network and to floc size. The prefactor value was thus shown to increase as cross-linking degree increased and gel lacunarity decreased.     

两种海藻酸钠基凝胶的溶胀和质构性能

壳聚糖、果胶和海藻酸钠是天然多糖,具有良好的生物相容性和生物可降解性等优点。以CaCl_2为交联剂制备壳聚糖-海藻酸钠水凝胶和果胶-海藻酸钠水凝胶,研究Ca Cl2浓度、多糖质量比(壳聚糖与海藻酸钠、果胶与海藻酸钠)和交联温度对水凝胶在模拟人体胃肠道环境(pH 1.2胃、pH 6.8小肠、pH 7.4结肠缓冲溶液)中溶胀性能的影响。当壳聚糖或果胶和海藻酸钠质量比为1.25∶1、CaCl_2浓度为0.09 mol/L、温度为60℃时,制备的水凝胶在pH 1.2溶液中溶胀率最小,在pH 6.8和pH 7.4溶液中溶胀率较大;结果表明所制备水凝胶具有pH值敏感性。此外,在优化条件下水凝胶具有较好的质构性能。     

Physicochemical properties of gelatin gels from walleye pollock (Theragra chalcogramma) skin cross-linked by gallic acid and rutin

Gelatin gels were cross-linked by gallic acid and rutin. The gel strength, viscoelastic properties, thermal stability, swelling property, ultrastructure, X-ray diffraction patterns and FTIR spectra were determined to evaluate the physicochemical properties of the modified gels. The gel strength increased with increasing gallic acid concentration up to 20 mg/g dry gelatin, and then decreased at further elevated gallic acid concentration, while it continuously increased with increasing levels of rutin. Either cross-linking agent could enhance the elastic modulus (G′) and the viscous modulus (G″) of hydrogels, but the gelling and melting points didn’t show a notable improvement. Rutin boosted the thermal stability of xerogels, but decreased the equilibrium swelling ratio significantly, while as for gallic acid, there were no obvious effects on the thermal stability and equilibrium swelling ratio of xerogels. Scanning electron microscopy (SEM) was applied to observe the ultrastructure changes of the modified xerogels suggesting that gelatin xerogel at rutin concentration of 8 mg/g dry gelatin showed the highest cross-linking density. X-ray diffraction revealed that both gallic acid and rutin could enter the spacing of polypeptide chains of gelatin to reinforce the intermolecular interaction. And FTIR spectra verified that gallic acid and rutin molecules mainly interacted with skeletal C–N–C group and carboxyl group of gelatin molecules in the formation of gels. The results suggested that rutin was a better cross-linking agent for gelatin, and gels treated with rutin could be found with different physicochemical properties.     

米蛋白-海藻酸钠互穿网络水凝胶的制备及性能表征

为满足食品领域目前对于高机械强度水凝胶的需求,本研究以碎米蛋白和海藻酸钠为主要原料,通过热处理和离子交联法制备一种高力学性能的食品级碎米蛋白（RP）-海藻酸钠(SA)互穿聚合物网络（IPN）水凝胶。通过改变米蛋白与海藻酸钠凝胶体系中米蛋白的浓度（80、100、120、140、160 mg/mL）调节IPN水凝胶的力学性能,混合液加热及钙离子交联形成水凝胶后,测定其质构性能、流变性能、白度、溶胀性、含水量等性质。结果表明:随着凝胶体系中碎米蛋白浓度的增大,RP-SA IPN水凝胶的储存模量G'、损耗模量G"和凝胶硬度均增加,当碎米蛋白浓度达到为140 mg/mL时,凝胶硬度增加幅度变小。水凝胶溶胀性先降低后趋于平缓,但水分分布更为均匀。因此,适量的碎米蛋白能对RP-SA IPN水凝胶网络有很好的填充效果,并对水凝胶的形态没有太大的改变,同时可通过调节蛋白的添加量来调节水凝胶的力学性能,该研究为米蛋白在食品领域的应用提供了理论基础。     

Physicochemical properties and microstructure of soy protein hydrogels co-induced by Maillard type cross-linking and salts

The relationship between macroscopic (elasticity, swelling), microstructural and molecular properties was investigated in soy protein hydrogels formed by cross-linking to different degrees with a model Maillard type cross-linking agent (glutaraldehyde) in the absence or presence of 120 mM NaCl. Hydrogel macroscopic properties were not influenced by protein secondary structure. In contrast, rheological properties were strongly influenced by degree of cross-linking and microstructure. Cross-linking soy protein in the absence of salt led to the formation of a more porous network consisting of bigger flocs and/or bigger particles and to weaker gels. Gel swelling did not appear to depend on microstructural properties. The influence of cross-linking and salt on swelling would be connected to their respective impacts on elastic and ionic contributions to swelling.     

焦磷酸钠对氧化猪肉肌原纤维蛋白的谷氨酰胺转移酶交联反应及凝胶性能的影响

以猪肉肌原纤维蛋白为研究对象,考察焦磷酸钠(sodium pyrophosphate,TSPP)对微生物谷氨酰胺转移酶(microbial transglutaminase,MTG)催化天然和氧化肌原纤维蛋白交联的程度及后续蛋白凝胶特性的影响。结果表明,肌原纤维蛋白的氧化程度随着H2O2溶液浓度的升高而增加,但TSPP在一定程度上可抑制羟自由基对蛋白的攻击,且TSPP处理(+TSPP)样品的MTG交联程度明显高于未经TSPP处理(-TSPP)样品。无论是否添加TSPP,随着H2O2溶液浓度的升高,蛋白凝胶的储能模量(G’)和凝胶强度均逐渐降低,加入MTG后均有所回升,且增幅随着H2O2溶液浓度升高逐渐降低。相对于未经TSPP处理样品,TSPP处理条件下未氧化样品的G’和凝胶强度增幅更高,但氧化时增幅降低速度更快。说明虽然TSPP处理有利于MTG交联引起的凝胶性能提高,但当受到氧化胁迫时,TSPP处理反而对其不利。     

谷氨酰胺转氨酶对山杏仁蛋白凝胶特性的影响

为提高山杏仁蛋白的凝胶特性,采用谷氨酰胺转氨酶(TG酶)作为交联剂,通过单因素实验研究了TG酶添加量、pH、交联温度、交联时间对蛋白凝胶硬度、弹性、内聚力的影响,并以凝胶强度为指标,利用响应面法对山杏蛋白形成条件进行优化。优化的TG酶交联山杏仁蛋白形成凝胶的条件如下:TG酶添加量17 U/g,交联温度43℃,pH为7.2,交联时间2.5 h时,此时凝胶硬度达到(135±7.14) g。结果表明利用TG酶交联山杏仁蛋白形成凝胶具有可行性,为提高山杏仁蛋白的功能性质和应用价值提供参考。     

Maillard-Type Cross-Linked Soy Protein Hydrogels as Devices for the Release of Ionic Compounds: An In Vitro Study

The contribution of cross-linking degree on soy protein hydrogels release properties was studied in vitro using a Maillard-type cross linker and amaranth and methylene blue as tracers. Increased cross-linker concentration or salt presence in the gel generally led to decreased swelling/release rates in the absence of digestive enzyme. Surprisingly, at pH 1.2, amaranth was not released. In the presence of pepsin or pancreatin, increased cross-linker concentration or the presence of salt in the gel was also shown to decrease compound release, particularly for methylene blue at pH 7.5. Compound release was strongly dependent on medium pH and compound ionic status. Amaranth, an anionic molecule, showed slower release in gastric conditions, whereas methylene blue, a cationic drug, showed the opposite result. Partition coefficients of these compounds matched these results. This paper demonstrates the potential of food proteins as carriers of ionic compounds.     

脂质体水凝胶结构变化与形成机理

通过明胶和壳聚糖为原料制备互穿聚合物网络结构（interpenetrating polymer network,IPN）水凝胶,采用质构考察不同比例配方和交联剂转谷氨酰胺酶（microbial transglutaminase,mTG）质量浓度对IPN水凝胶的影响,同时研究将脂质体包埋进IPN水凝胶后形成的脂质体水凝胶结构及胶联机理。结果表明：明胶与壳聚糖按质量比4∶1混合、mTG质量浓度10 mg/mL条件下,制备的脂质体水凝胶可成胶且质构性质表现最优,硬度可达到18.68 g;通过膨胀系数、傅里叶变换红外光谱、差热分析及交联率分析等可知,脂质体与水凝胶通过化学方式进行联接,同时存在氢键的作用,且脂质体被包裹入凝胶内部网状结构。脂质体水凝胶的研究多以包埋缓释为主,较少有针对其结构和交联方式的报道。本研究结果对开发新型脂质体和脂质体水凝胶等运载体系并将其应用于食品营养物的包埋、缓释提供新思路。     

Preparation,Characterisation, and Rheological Behaviour of Starch-Sodium Trimetaphosphate Hydrogels

Ionic biopolymer hydrogels were prepared by the cross-linking of starches with sodium trimetaphosphate in alkaline medium at 40°C for 2 hours. The swelling capacity is relatively high — up to 310 g H₂0/g polymer. Salt solutions have a marked influence, and result in shrinkage but not in a total collapse. The effect of both the cross-linker and substrate concentrations on the swelling and rheological properties was investigated. The influence of temperature and NaOH concentration on the rheological behaviour suggests that they are both significant in determining the gel properties because of the readiness of the diester phosphate bonds to undergo hydrolysis. The molecular weight between two entanglement points (M_e) and the effectiveness of cross-linking [n_e(r)/n_e(t)] were estimated from the observed G_p′ values, and those calculated from complete conversion of the cross-linker. The effectiveness of cross-linking lay between 0.2 and 2.74% for 10% wlw gels, and reached a maximum of 48.1% at the higher substrate concentration of 20% wlw. ¹³C-NMR signals from the anhydroglucose units became broader and decreased in intensity with rising cross-linker concentration due to the restricted motion arising from the additional bonding.     

Influence of ultrasound and enzymatic cross-linking on freeze-thaw stability and release properties of whey protein isolate hydrogel

This study investigated the effect of ultrasound and enzymatic cross-linking on the freeze-thaw (FT) stability and release properties of whey protein isolate hydrogels. We evaluated the FT stability by the changes in the microstructure, riboflavin retention, syneresis, water holding capacity (WHC), and texture of gels subjected to 3 FT cycles. High-intensity ultrasound (HUS) and transglutaminase (TGase)-mediated cross-linking improved the FT stability of whey protein isolate hydrogels loaded with riboflavin (WPISAR), as demonstrated by a more uniform and denser porous structure, significantly higher riboflavin retention, WHC, and textural properties, and lower syneresis after 3 FT cycles than those of untreated hydrogels. Furthermore, HUS- and TGase-mediated cross-linking decreased protein erosion and swelling ratio of WPISAR in simulated gastrointestinal fluids (SGIF) and reduced the riboflavin release rate in SGIF both with and without the addition of digestive enzymes. After 3 FT cycles, faster riboflavin release occurred due to a more porous structure induced by ice crystal formation compared with their unfrozen counterparts as detected by confocal laser scanning microscopy. High-intensity ultrasound- and TGase-mediated cross-linking alleviated the FT-induced faster riboflavin release rate in SGIF. High-intensity ultrasound- and TGase-treated gel samples showed that both diffusion and network erosion were responsible for riboflavin release regardless of FT. These results suggest that HUS- and TGase-mediated cross-linking improved the FT stability of WPISAR with a high riboflavin retention, and might be a good candidate as a controlled-release vehicle for riboflavin delivery to overcome undesired FT processing.     

亚甲基丁二酸交联变性对淀粉浆料性能的影响

为提升淀粉浆料的使用性能,以亚甲基丁二酸(MSA)为交联剂,采用半干法制备了不同交联度的亚甲基丁二酸交联淀粉(MSACLS)。对其颗粒结构与表观形貌进行了表征分析,考察了MSA交联变性对淀粉浆液黏度热稳定性、黏附性以及对浆膜力学性能与水溶性的影响。结果表明:这种交联变性能够明显提升淀粉浆液的黏度热稳定性及其对涤纶纤维的黏附性,提高浆膜的力学性能,降低浆膜的水溶性;随着交联度的增大,MSACLS浆液的黏度热稳定性、对涤纶纤维的黏附力及其膜的断裂强度逐渐提高,浆膜的断裂伸长率呈现先提高后降低的趋势,水溶性逐渐降低;选择交联度为49.4的MSACLS在涤纶经纱上浆中使用为宜。     

交联淀粉对甘薯浊汁饮料稳定性的影响

将不同浓度交联剂(6%,8%,10%,12%,14%)制备得到的交联马铃薯淀粉(Cross-linked potato starch,CLPS)应用于甘薯浊汁饮料中,测定浊汁饮料的浑浊度、流变特性、稳定性、Zeta电位和离心沉淀率。结果显示,随着交联程度的增加,浊汁饮料的浑浊度上升,但30d内浑浊度的变化程度降低,饮料体系的假塑性、黏度、黏弹性、凝胶强度与Zeta电位绝对值随着交联程度的增加而增加,在交联剂浓度为12%时取得最大值;交联淀粉能够抑制浊汁饮料底部出现沉淀,但对浊汁饮料顶部析水的控制有限,稳定性动力学指数与离心沉淀率随着交联程度的提高而下降,表明交联淀粉能够提高甘薯浊汁饮料体系的稳定性。综合结果表明,交联淀粉使甘薯浊汁饮料的稳定性有一定程度的提高,12%CLPS可作为稳定剂应用于淀粉质浊汁饮料中。     

响应面法优化桑葚酵素食用凝胶的制备工艺

以海藻酸钠、壳聚糖、桑葚酵素为原料,氯化钙为离子交联剂,制备酵素食用凝胶。通过单因素实验和Box-Behnken响应面法,研究海藻酸钠与壳聚糖质量比、交联时间、氯化钙浓度对酵素凝胶硬度、胶着性、咀嚼性等质构指标的影响。结果表明,酵素凝胶最佳的制备工艺为:海藻酸钠与壳聚糖质量比5:2.82、交联时间131 min、氯化钙浓度17.9 mg/mL。在此优化工艺条件下,测得酵素凝胶硬度为7.19 N、胶着性为6.60 N、咀嚼性为0.70 kgf。优化所得结果准确可靠,可为酵素功能性食品的进一步开发与利用提供理论依据和技术参考。     

肌原纤维蛋白转谷氨酰胺酶交联程度对鱼糜凝胶及其风味释放影响的研究进展

转谷氨酰胺酶可以催化肌原纤维蛋白发生交联反应。随着交联程度的增加,鱼糜凝胶从弹黏体变为弹脆体,风味也随之改变。风味物质的扩散、释放与凝胶网络的交联程度密切相关,因此深入了解交联程度与食品品质的关系及风味物质在凝胶网络中的扩散行为显得尤为重要。本文总结转谷氨酰胺酶催化肌原纤维蛋白的交联机理,归纳了国内外对肌原纤维蛋白交联程郭彩霞度的测定方法与影响因素,探讨交联程度对鱼糜蛋白的凝胶特性与风味释放的影响,并对今后的研究方向提出思考与展望。     

交联淀粉性能与鲜粉丝耐煮性关系

本文以马铃薯淀粉、红薯淀粉和木薯淀粉为原料,三氯氧磷为交联剂,氯化钠为膨胀抑制剂,制备了不同交联度的交联淀粉,研究了交联对薯类淀粉性能及鲜粉丝耐煮性的影响。采用断条率、吸水率表征鲜粉丝的耐煮性,采用沉降积法测定淀粉的交联度。结果表明:交联淀粉用量和交联度对鲜粉丝耐煮性均有影响。淀粉经交联后,其蓝值、膨胀能力降低,但其冻融稳定性增加。     

Deformation and fracture of emulsion-filled gels: Effect of gelling agent concentration and oil droplet size

The effect of the ratio between the modulus of the oil droplets and that of the gel matrix (varied by changing gelling agent concentration and oil droplet size) on the large deformation properties of gelatine, κ-carrageenan and whey protein isolate (WPI) gels was studied at different compression speeds. The effect of gelling agent concentration and oil droplet size on strain-dependency of modulus and viscoelastic properties was also studied. An increase in the concentration of gelling agent resulted in denser gels with more bonds between structural elements. This induced an increase of both Young's modulus and fracture stress for all gels. With increasing gelling agent concentration, polymer gels (gelatine and κ-carrageenan) became less strain-hardening, and the particle gels (WPI) even became strain-softening. The effect of a decrease in the oil droplet size on the Young's modulus was generally according to the Van der Poel theory, unless when the oil droplets were aggregated. Moreover, a decrease in oil droplet size induced a decrease of the fracture strain in gels with non-aggregated bound droplets. The extent of these changes was shown to depend on the gelling agent concentration. The effect of a decrease of the oil droplet size on other fracture parameters and in other gel systems was minor. With decreasing oil droplet size gelatine gels with unbound droplets and WPI gels became more viscous and less elastic.     

丝胶对棉织物改性的研究

以二氯均三嗪化合物作为交联剂,采用丝胶对棉织物进行改性,探讨了不同丝胶质量浓度对改性棉织物性能的影响。结果表明,棉织物用丝胶改性,能提高其尺寸稳定性、抗皱性、吸湿性,但对白度影响不大。     

小麦交联淀粉的制备工艺研究

采用环氧氯丙烷为交联剂，以小麦淀粉为原料制备小麦交联淀粉。探讨了环氧氯丙烷用量，氢氧化钠用量，反应温度，反应时间对交联度的影响并利用design-expert6.0.3软件响应面中心组合实验优化得出制备不同交联淀粉的最佳工艺条件，分析了双因素间的交互效应。     

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。