不同糖类对草鱼鱼糜凝胶的影响

研究葡聚糖,蔗糖,海藻糖,低聚木糖,低聚果糖对草鱼鱼糜凝胶微观结构、蛋白质结构、水分子分布及质构特性的影响.扫描电镜结果表明,与空白样相比,添加4％葡聚糖、蔗糖和海藻糖的鱼糜凝胶中能观察到更紧密的网络结构,糖的加入促进了蛋白质的交联和凝胶网络结构的紧密性,改善了鱼糜制品的凝胶特性.添加低聚果糖的样品使鱼糜蛋白α-螺旋结...     

酪蛋白与乳清蛋白比例对酸奶凝胶性质的影响

研究了乳中酪蛋白和乳清蛋白比例对凝固型酸奶流变学特性和微观结构的影响,结果表明,固定蛋白质质量分数、降低酪蛋白和乳清蛋白的比例,可以明显提高酸奶凝胶的质量.乳中蛋白质质量分数一致时,酸奶凝胶的硬度、黏度、持水力随着酪蛋白和乳清蛋白比例的减小而增大,凝胶网络结构变得更规则、致密,孔隙更小.在低蛋白质质量分数下,降低乳中酪...     

多糖分子质量对大豆蛋白聚集体/葡聚糖混合体系微观结构的影响

采用共聚焦激光扫描显微镜观察了室温下、pH 7.0时不同尺寸大小的大豆蛋白热聚集体和不同分子质量的葡聚糖混合体系的微观结构,并以天然大豆蛋白和葡聚糖混合体系的微观结构作对照。结果表明:葡聚糖分子链的排空相互作用使得蛋白质聚集体间产生了有效而不均匀的交联;蛋白质聚集体的尺寸增加和/或葡聚糖分子质量的增加促进了蛋白质富集区域的交联。对其共聚焦激光扫描图像进行灰度水平变化方差分析和灰度直方图分析表明,不同混合物间微观结构上具有显著性差异。     

不同分子量葡聚糖与大豆7S蛋白混合凝胶的流变学性质

采用哈克流变仪对不同分子量葡聚糖与大豆7S蛋白混合体系的凝胶流变学性质进行研究。结果表明:葡聚糖与大豆7S蛋白混合体系形成的蛋白多糖凝胶相对单一浓度的大豆7S蛋白凝胶具有较高的弹性模量;同分子量的葡聚糖与大豆7S蛋白混合体系形成的蛋白多糖凝胶黏弹性质随葡聚糖浓度增加而增加;同浓度葡聚糖与大豆7S蛋白混合体系形成的蛋白多糖凝胶黏弹性质随加入葡聚糖分子量的增加而增加;同浓度同类型葡聚糖体系凝胶形成的起始温度Tp0.25相似文献   

大豆蛋白/葡聚糖混合体系相行为及流变性质的研究

研究了室温下,pH 7.0时不同尺寸大小的大豆蛋白热聚集体和不同分子质量的葡聚糖混合体系的相分离行为,并以天然大豆蛋白和葡聚糖混合体系作为对照体系。通过离心、化学分析和目测建立了相图,结果表明两种大分子的相分离是由于葡聚糖分子链的排空相互作用,使得蛋白质富集部分间产生了交联;蛋白质聚集体的尺寸和葡聚糖的分子质量大小同时影响了混合体系的相行为,随着蛋白质粒子增大或多糖分子质量增加,相边界发生了位移,混合体系的均相区域变窄,凝胶区域增大。流变研究进一步证明蛋白质聚集体的尺寸和葡聚糖的分子质量大小同时影响了相分离体系的微观结构。     

葡聚糖对大豆7S蛋白凝胶流变性质及微观结构的影响

采用小变形振荡流变及激光共聚焦技术研究葡聚糖分子质量对热致大豆7S蛋白凝胶的微观结构及动态黏弹性质的影响作用.结果表明:热致大豆7S蛋白凝胶的黏弹性质随添加葡聚糖分子质量的增加而增加,主要由于大分子质量的葡聚糖可以扩大其在葡聚糖/大豆7S蛋白混合体系中的空间占有体积和降低大豆7S蛋白的临界凝胶浓度所致.同时提高变温速率和葡聚糖分子质量对大豆7S蛋白凝胶黏弹性质有协同增加效应.增加葡聚糖分子质量7S蛋白凝胶结构逐步由相分离结构转变为互穿型蛋白-多糖双连续结构.     

超声处理的大豆分离蛋白/麦芽糊精混合物酸诱导凝胶性质研究

对大豆分离蛋白(SPI)与麦芽糊精(MD)形成的混合溶液进行超声处理,添加葡萄糖酸内酯(GDL)形成酸诱导凝胶,测定凝胶流变性、微观结构、凝胶强度和持水性,探讨超声处理对SPI/MD混合物酸诱导凝胶性质的影响。在SPI中混入MD,由于相分离作用会促进蛋白凝聚物的交联,形成更加致密、均一的网络结构,所以导致凝胶网络的强化和凝胶时间的缩短。超声处理使SPI/MD混合物凝胶由链状结构变为颗粒状结构,且随着超声时间的延长,这种颗粒状结构更明显。超声处理5 min能够进一步增强SPI/MD混合物凝胶网络结构和抗破坏能力,且凝胶网络保持较好的结构完整性;然而,超声处理15 min和25 min不利于混合物凝胶网络的建立,且凝胶微观结构中出现较大裂痕,网络结构的完整性被破坏,导致凝胶强度和持水性降低。     

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。     

β-葡聚糖对大豆分离蛋白酸致混合凝胶流变性的影响

采用乳酸菌对大豆分离蛋白(SPI)/β-葡聚糖混合体系进行发酵制备酸致凝胶,研究β-葡聚糖浓度(0.4~1.6 mg/100 m L)和分子质量(OGL80~OGL360)对SPI(4、6、8 mg/100 m L)酸致混合凝胶流变性的影响。结果表明:在SPI中添加β-葡聚糖不会改变大豆蛋白的变性温度,但会使表面疏水性由81.97降低至71.83。一定浓度β-葡聚糖会使SPI酸致凝胶的起点由1 Pa降至0.01~0.1 Pa,甚至降低凝胶终点G'至10 Pa以下不能形成凝胶。而高分子质量β-葡聚糖通过增加体系黏度而减少分层现象并保持体系稳定,从而降低或消除β-葡聚糖对SPI酸致混合凝胶的弱化作用,甚至会改善混合体系凝胶强度。     

糖基化对大豆7S球蛋白凝胶流变性质的影响(Ⅱ)

基于Maillard反应的机理,采用干热法分别制备出β-伴大豆球蛋白和不同分子量葡聚糖(67 kDa、150 kDa、500 kDa)的三种糖基化产物,从大豆7S球蛋白的热致凝胶性质出发,通过对不同链长糖基化产物的流变学性质和微观结构的研究,研究糖基化对于大豆7S球蛋白热致凝胶的影响机理,结果显示,葡聚糖以非共价键接入蛋白质肽链和以共价键接入的糖链所起的空间位阻作用给予大豆7S球蛋白热致凝胶体系的作用机制不同,并且以共价键结合的葡聚糖能够和蛋白质分子均匀的分布在凝胶网络结构中,不会引起相分离。     

Microstructural characterization of β-lactoglobulin–konjac glucomannan systems: Effect of NaCl concentration and heating conditions

In the initial part of this study, the high temperature (85 °C) microscopic phase behaviour of β-lactoglobulin (0.4–6%, w/w)–konjac (0.05–0.75%, w/w) mixtures containing 50 mM NaCl was established using confocal laser scanning microscopy (CLSM). Also, the effects of heating time (heating temperature: 78 °C) and NaCl concentration (0–75 mM) on protein denaturation kinetics and the phase behaviour in 2%, w/w, β-lactoglobulin–0.4%, w/w, konjac mixtures were investigated using turbidimetry, protein denaturation measurement, CLSM and image analysis techniques. Segregative phase separation occurred in heat-treated β-lactoglobulin–konjac mixtures containing biopolymer and NaCl concentrations exceeding certain critical levels, due to heat and NaCl induced β-lactoglobulin denaturation/aggregation. The microstructural properties of selected heated (to 85 °C for 30 min) and cooled (to 25 °C) β-lactoglobulin–konjac mixtures containing different NaCl levels were studied using CLSM and rheological measurements and the results showed that the microstructure can be distinguished as miscible, phase separated or phase separated containing stable protein inclusions dependent on NaCl concentration. Response surface methodology was used to determine the minimum NaCl concentrations required for phase separation and for formation of phase separated systems containing stable inclusions in a wide concentration range of heated and cooled β-lactoglobulin (0.8–2%, w/w)–konjac (0.2–0.75%, w/w) mixtures. The results show that the microstructural and rheological properties of β-lactoglobulin–konjac mixtures can be controlled by selecting appropriate mixture biopolymer and NaCl concentrations and heating conditions.     

Viscoelastic behavior and microstructure of aqueous mixtures of cross-linked waxy maize starch,whey protein isolate and κ-carrageenan

The viscoelasticity and microstructure of mixtures of cross-linked waxy maize starch (CH10), whey protein isolate (WPI) and κ-carrageenan (κC) at pH 7.0 with 100 mM NaCl were investigated by oscillatory rheometry and confocal laser scanning microscopy (CLSM). Mixtures were heated to 90 °C (1.5 °C/min), held for 10 min at this temperature and cooled. Within the range of concentrations studied, CH10 swollen granules reinforced WPI and κC networks. The mechanical behavior of the three-component mixtures was modified by different WPI concentrations, but κC governed the overall response due to its gelling ability. CLSM images of three-component mixtures showed particulate systems in which swollen starch granules are surrounded by κC and WPI. CH10 granules were immersed in a single phase and a separate phase of κC and WPI, for low and high concentrations of these components, respectively. Therefore, it is possible to obtain two- and three-phase mixtures.     

Protein aggregation induced by phase separation in a pea proteins–sodium alginate–water ternary system

The physicochemical properties of a native, globular plant protein–linear anionic polysaccharide aqueous system at 20 °C were investigated in conditions where biopolymers carry a net negative charge (pH 7.2, 0.1 M NaCl). The pea proteins–sodium alginate mixtures showed a phase separation mainly by thermodynamic incompatibility, characterized at both the macroscopic and microscopic scale. Phase diagram was established and confocal laser scanning microscopy (CLSM) provided accurate data on the microstructure morphology of the system, regarding its phase behavior. In admixture, sodium alginate induced a protein aggregation, certainly by a local depletion of the polysaccharide. Protein aggregates were present in both single-phase and biphasic mixtures, while increasing the sodium alginate concentration provided larger and denser protein microdomains, leading to a non-equilibrium state. By phase separation, the pea protein aggregates entrapped a part of the sodium alginate phase, thus modifying the protein volume fraction. Along a tie-line, a phase inversion phenomenon was detected, from a sodium alginate to a pea proteins-continuous phase. Rheological properties of the mixed systems depended on the biopolymer composition and were modified with respect to individual components. The protein-enriched phase volume fraction modified the flow behavior to non-Newtonian for starting concentrated mixtures; a shear-thinning at high shear rates was evidenced, while mixtures with a particularly high sodium alginate concentration (>0.8 wt%) had an apparent yield stress for low shear rates. Mechanical spectra showed that both protein enrichment within microdomains in the presence of alginate and stronger protein–protein interaction with time impacted the viscoelastic properties (G′ and G″ moduli) of the whole mixture.     

Effect of ionic strength on the heat-induced soy protein aggregation and the phase separation of soy protein aggregate/dextran mixtures

The effects of ionic strength on heat-induced aggregation of soy protein and phase separation of different soy protein aggregates with dextran were investigated. The increase of ionic strength accelerated protein aggregation as shown by an increase in turbidity, aggregate fraction and particle size of salt-induced aggregates (SA). Adding salt (NaCl) to the aggregates formed at the ionic strength of zero (non-salt aggregates, non-SA), the increase of aggregate size was also found. Zeta potential results evidenced the charge screening effects of NaCl. The results of phase diagrams indicated that the compatibility of mixtures at higher ionic strength was lower than those at lower ionic strength, and SA was more incompatible with dextran than non-SA. The effects of the increase of aggregate size on the phase separation outweighed the ionic strength, which indicated that the depletion interaction also played an important role in the phase separation of soy protein aggregates and dextran. CLSM (Confocal Laser Scanning Microscopy) and rheological observations provided additional information of the microstructures of the mixtures.     

Rapeseed protein concentrate as a potential ingredient for meat analogues

The potential for using rapeseed protein concentrate (RPC) as a novel protein source for meat analogues was investigated using shear cell technology with RPC-only and RPC-wheat gluten (WG) mixtures. The resulting products were characterized by texture analyser, confocal laser scanning microscopy (CLSM) and X-ray microtomography. Soy protein concentrate (SPC) was chosen as the benchmark because of its known capacity to create fibrous structures. Both RPC-only and RPC-WG mixtures could be transformed into fibrous products when processed at 140 °C and 150 °C with 40 wt% dry matter. The fibrous structure was improved by adding of WG into RPC at 140 °C and the colour of the RPC-WG product became lighter with more WG added. CLSM images revealed that the protein formed a continuous phase, and the RPC inherent polysaccharides acted as a dispersed phase. Overall, RPC is concluded as a promising alternative protein source after SPC for meat analogue applications.Industrial relevanceRapeseed meal, which is a by-product from extraction of rapeseed oil, is currently mainly used as animal feed and seldom applied as a food ingredient. This study provides valuable insights into the potential of rapeseed protein concentrate produced by washing rapeseed meal with aqueous ethanol as an alternative plant protein for meat analogues. The outcomes of this study demonstrated the potential of rapeseed protein concentrates for structuring purposes, which is a step towards its commercial use as an environmentally sustainable meat analogue ingredient.     

Structural properties of stirred yoghurt as influenced by whey proteins

The effect of whey protein addition on structural properties of stirred yoghurt systems at different protein and fat content was studied using laser diffraction spectroscopy, rheology and confocal laser scanning microscopy (CLSM). The composition of heated milk systems affected micro- and macroscopic properties of yoghurt gels. Particle size increased as a function of increasing whey protein content and decreased as a function of increased fat level. Firmness (elastic modulus) and apparent viscosity of manufactured yoghurt samples increased as a function of increased interparticle interactions, mainly caused by self-aggregation of whey proteins or aggregated whey protein-coated fat globules, respectively. The resistance towards shear-induced disruption of yoghurt gels increased with an increasing proportion of casein protein in the protein mixture, whereas products with high whey protein level revealed lower resistance behaviour towards shear-forces. CLSM images illustrated that the presence of large whey protein aggregates and lower number of fat globules lead to the formation of an interrupted and coarse gel microstructure characterised by large interstitial spaces. The higher the casein fraction and/or the fat level, the less interspaced voids in the network were observed. However, it is evident that the addition of whey proteins reinforces firmness properties of low-fat yoghurts comparable to characteristics of full-fat yoghurt.     

大豆7S蛋白组分-卡拉胶共混体系的相行为及热性质

主要采用浊度测量、差示量热法(DSC)、相图构建及激光共聚焦(CLSM)技术研究3种不同荷电量卡拉胶(κ-、ι-、λ-型)与大豆7S蛋白组成的共混体系的热性质、相行为及形貌结构。结果表明：同质量浓度多糖添加时,7S蛋白热稳定性随卡拉胶携带电荷量的增加而增加。添加卡拉胶均提高大豆7S蛋白的热变性温度,同时降低热焓值,影响效果依次是λ-卡拉胶＞ι-卡拉胶＞κ-卡拉胶。λ-卡拉胶/7S蛋白相图的均相区域面积低于κ-卡拉胶-7S蛋白相图及ι-卡拉胶-7S蛋白相图的对应值,非均相区域面积则高于后两者。共混体系非均相区域宏观和微观结构均显示为相分离态,而均相区域蛋白多糖呈均一共混态,宏观上无相分离。大豆7S蛋白-卡拉胶共混体系相行为和微结构的多样性有利于构建新型风味和功能性生物因子控释食品材料。     

Effect of calcium on microstructure and meltability of part skim mozzarella cheese

The role of calcium in the microstructure of part skim Mozzarella cheese was evaluated using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Part skim Mozzarella cheeses with 4 calcium levels (control 0.65%, T1 0.48%, T2, 0.42%, and T3 0.35%) were manufactured and stored at 4 degrees C. Microstructure and meltability of cheeses were studied on d 1 and 30. The micrographs were analyzed for numbers, area, perimeter, roundness, and size of the fat particles. Reduced calcium cheeses had greater meltability and more hydrated protein matrix with greater number of fat particles (control=125, T1=193, T2=184, and T3=215 with SEM and control = 86, T1=87, T2= 125, and T3= 140 with CLSM). Further, area and perimeter of these fat particles were also greater in reduced calcium cheeses. Area, perimeter, and size of fat particles increased and their roundness decreased upon storage of 30 d. Decrease in free serum in the protein matrix of all cheeses upon refrigerated storage was evident from the CLSM. Hydrated protein network and better emulsified fat in low calcium cheeses might have improved melt properties of Mozzarella cheese.     

Soybean protein isolate-rice starch interactions during the simulated gluten-free rice bread making process

Gluten-free bread (GFB) is usually of poor quality due to lack of gluten. Addition of exogenous protein is one of the important ways to improve the quality of GFB products. In this study, different levels of soybean protein isolate (SPI) mixed with rice starch (RS) system were prepared to simulate different processing stages during bread making. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), rapid viscosity analysis (RVA), confocal laser scanning microscopy (CLSM), texture analyser and rheometer were used to analyse the effects of SPI on the structural, microstructure and functional properties of RS. The results showed that: hydrogen bonds could be formed between SPI and RS, thus improving the stability of RS; compared with RS, the ∆H and setback values of the blend were reduced by 43.79% and 34.53%, respectively, when SPI was added at 12%; and the storage modulus (G') and loss modulus (G") reached the minimum value at 9% SPI content. CLSM and texture analysis show that the addition of protein inhibits the leaching of starch, reduces the hardness, chewiness and gumminess of the system, which is conducive to the quality of GFB.     

Effect of ultrasound on physicochemical properties of emulsion stabilized by fish myofibrillar protein and xanthan gum

To investigate the effects ultrasound (20 kHz, 150–600 W) on physicochemical properties of emulsion stabilized by myofibrillar protein (MP) and xanthan gum (XG), the emulsions were characterized by Fourier transform infrared (FT-IR) spectroscopy, ζ-potential, particle size, rheology, surface tension, and confocal laser scanning microscopy (CLSM). FT-IR spectra confirmed the complexation of MP and XG, and ultrasound did not change the functional groups in the complexes. The emulsion treated at 300 W showed the best stability, with the lowest particle size, the lowest surface tension (26.7 mNm⁻¹) and the largest ζ-potential absolute value (25.4 mV), that were confirmed in the CLSM photos. Ultrasound reduced the apparent viscosity of the MP-XG emulsions, and the changes of particle size were manifested in flow properties. Generally, ultrasound was successfully applied to improve the physical stability of MP-XG emulsion, which could be used as a novel delivery system for functional material.