葛根淀粉力学性能的研究

研究了不同淀粉乳浓度下葛根淀粉的力学性能并比较了同一浓度下葛根淀粉、玉米淀粉及马铃薯淀粉的力学性能,讨论了分子结构对淀粉力学性能的影响.结果表明,在一定范围内随着浓度的增加,葛根淀粉的凝胶强度和弹性模量呈线性增加.在20%(w/v)的淀粉乳溶液中凝胶强度葛根淀粉＞马铃薯淀粉＞玉米淀粉,弹性模量马铃薯淀粉＞葛根淀粉＞玉米淀粉.     

百合淀粉的力学性能

本文运用质构测试仪为手段、以马铃薯淀粉与玉米淀粉为对照,系统研究了百合淀粉浓度、氯化钠浓度、糖的添加及pH等因素对百合淀粉凝胶力学性能的影响。结果表明：百合淀粉凝胶强度与其浓度呈正相关,弹性与其浓度呈负相关;加糖能增加百合淀粉凝胶强度与弹性;氯化钠对百合淀粉凝胶力学性能的影响表明两重性,低浓度（＜1．0％）时,其凝胶强度和弹性与氯化钠浓度呈正相关,高浓度（＞0．1％）时,与氯化钠浓度呈负相关。     

牛乳清蛋白与甘薯淀粉加热混合凝胶物化及微观结构特性的研究

研究了不同pH和NaCl、CaCl2浓度对WPI凝胶及WPI与甘薯淀粉混合凝胶物化特性和微观结构的影响。结果表明:随着pH的增加,凝胶的硬度和溶解度减小,添加淀粉进一步降低了混合凝胶的溶解度;盐浓度的增加使混合凝胶硬度增加,而蛋白溶解度、持水力和巯基含量则呈下降趋势;添加NaCl和CaCl2的混合凝胶分别呈现出多孔网状和颗粒状结构。     

莲子淀粉加工特性的研究

研究莲子淀粉的加工特性。结果表明:莲子淀粉的溶解度、膨润度均较低,属限制型膨胀淀粉;糊的透明度较低;莲子淀粉起糊温度较高(72℃),随着温度升高黏度先增加后呈减小趋势,淀粉开始降温时黏度逐渐上升;酸性条件下淀粉糊黏度降低,碱有促进淀粉糊化的作用;添加蔗糖、NaCl后淀粉糊黏度增大,蔗糖对其影响相对较小,随着蔗糖、NaCl添加量的增加黏度也相应增加。     

pH值、NaCl浓度和加热温度对猪肉匀浆物凝胶质构特性的影响

采用二次通用旋转试验设计,研究了pH值、NaCl浓度和加热温度对猪后腿肉匀浆物热诱导凝胶质构特性的影响。结果表明:不同处理条件对凝胶质构特性的影响存在差异。不同加热温度下,pH值和NaCl浓度对凝胶硬度、弹性、内聚性、胶粘性和咀嚼性影响的总体趋势一致且两者存在明显的交互作用。pH值较低时,随着NaCl浓度的增加,凝胶的硬度、弹性、内聚性、胶粘性和咀嚼性均增大;pH值较高时,NaCl浓度对凝胶硬度、弹性和胶粘性影响较小,内聚性随着NaCl浓度增加而降低。同时,随着加热温度的升高,凝胶的硬度和胶粘性增大,内聚性和咀嚼性减小,而凝胶弹性变化较小。     

牛血浆蛋白凝胶特性研究

研究不同加工条件如蛋白浓度、加热温度、离子强度和pH对牛血浆蛋白凝胶特性的影响。结果表明:蛋白浓度的提高有利于凝胶的形成,且形成凝胶的最低血浆蛋白浓度是4.0%;4.8%的血浆蛋白,线性升温到85℃保温20 min,能够很好形成凝胶,呈果冻状,光滑有弹性;NaCl浓度在1.0 mol/L以下时,血浆蛋白凝胶强度随离子强度的变化是先增加后减小,0.3 mol/L时取得最佳效果;在pH6.0~9.0范围内,pH为9.0时牛血浆蛋白凝胶的凝胶强度较好,保水性高,蒸煮损失低。NaCl和pH对于牛血浆蛋白的凝胶特性有极显著的互作效应。     

葛根淀粉磷酸酯理化特性研究

采用磷酸二氢钠、尿素和葛根淀粉制备葛根淀粉磷酸酯,研究其取代度、开始糊化温度、峰值黏度、流变特性和凝胶强度,并将其加入面包中,探讨葛根淀粉磷酸酯对面包品质的影响。结果表明:所制葛根淀粉磷酸酯的取代度为0.054,葛根淀粉磷酸酯具有热糊、冷糊稳定性好,开始糊化温度低等特点;随着葛根淀粉磷酸酯浓度的增加,其黏度和凝胶强度都逐渐增大;在研究的pH值范围内,葛根淀粉磷酸酯黏度变化不大,凝胶强度呈先上升后下降的趋势;3种盐对凝胶强度影响呈先上升后下降的趋势,其中食盐对葛根淀粉磷酸酯黏度影响较小;随着3种糖添加量的增加,对凝胶强度的影响大小顺序为白砂糖麦芽糖葡萄糖,随着白砂糖含量的增加,葛根淀粉磷酸酯的黏度逐渐增大;葛根淀粉磷酸酯添加于面包中能提高面包的比容、含水量和保水性。     

可得然胶凝胶特性及其在西式火腿中的应用研究

采用质构仪检测可得然胶的凝胶特性,并研究其对西式羊肉火腿质构的影响。结果表明,可得然胶随着质量浓度和加热温度的升高,凝胶强度逐渐增加,同时具有热不可逆性,高于80 ℃加热可得然胶水溶液,冷却形成凝胶后,重新加热凝胶结构不会破坏;合适的NaCl质量浓度、磷酸盐质量浓度和pH值可以提高可得然胶的凝胶强度,添加大豆蛋白会降低可得然胶的凝胶强度,而蔗糖和淀粉对可得然胶的凝胶强度影响不大。将可得然胶添加到肉制品西式羊肉火腿中,随着添加量的增加,质构显示出逐渐增加的趋势。     

凤爪胶原蛋白凝胶强度的研究

以新鲜凤爪为主要原料,采用酸法提取胶原蛋白,通过质构分析,对影响凤爪胶原蛋白凝胶强度的因素进行研究,结果表明,凤爪胶原蛋白凝胶强度随着胶原蛋白液浓度的增大而逐渐增大;随着温度、pH、NaCl和CaCl2浓度的增大,凝胶强度呈先增大后减小的趋势;不同的磷酸盐对凤爪胶原蛋白凝胶强度的影响不同。     

添加剂对明胶-多糖共混凝胶特性的影响

研究以明胶、甘薯淀粉、海藻酸钠为材料,以凝胶强度、透明度、凝胶持水性为主要指标,考察NaCl、蔗糖和pH对明胶-多糖共混凝胶特性的影响。结果表明:(1)NaCl在浓度小于0.2mol/L时能提高明胶/甘薯淀粉体系的凝胶强度,但凝胶的持水率显著降低,且透明度略有降低。NaCl降低明胶/海藻酸钠体系的凝胶强度,且凝胶透明度也降低,但凝胶的持水率无变化。(2)蔗糖能提高明胶/甘薯淀粉体系的透明度,且蔗糖浓度低于5%能提高体系的凝胶强度。蔗糖降低明胶/海藻酸钠体系的凝胶强度,但蔗糖浓度低于7.5%能提高体系的透明度。高浓度的蔗糖导致两体系凝胶各项性能全面下降。(3)明胶/甘薯淀粉体系在pH小于5时,凝胶透明度随pH的提高而降低,在pH5时,透明度最低,此时的吸光度值最大为2.469,当pH大于5时,透明度又随pH的增加而提高;明胶/甘薯淀粉在pH为5时有最大凝胶强度和最大持水性。pH对明胶/海藻酸钠体系凝胶透明度的影响规律明显,酸性环境下的凝胶透明度显著低于中、碱性环境下的凝胶透明度;明胶/海藻酸钠在pH为5时有最大凝胶强度和最大持水性。pH、离子强度对凝胶强度的影响显著。     

Influence of pH and NaCl on rheological properties of rennet-induced casein gels made from UF concentrated skim milk

Milk concentrates are used in the production of cast cheese. The effects of pH (5.19–6.21) and NaCl concentration (0, 1.75% and 3.50%, w/w) on the rheological and microstructural properties of rennet-induced casein gels made from ultra filtered skim milk (19.8%, w/w casein) were investigated. Low pH and high NaCl concentration reduced the development rate of the gel elasticity after coagulation of the ultra filtrated skim milk. Strain at fracture and stress at fracture from uniaxial compression of casein gels 48 h after coagulation showed maximum and minimum values at pH ∼5.8 and 5.29, respectively. Young's modulus from uniaxial compression of the same gels was almost constant between pH 5.52 and 6.21 but much lower at pH 5.28. Addition of NaCl resulted in increased Young's modulus in the interval pH 6.21–5.52. As pH decreased, the level of colloidal calcium phosphate decreased concomitantly, giving less cross-links in the casein network and partly explaining the changes in the rheological properties. Increased ionic strength by adjusting pH and addition of NaCl also influenced rheological results. The microstructure examined with confocal laser-scanning microscopy was unaffected by the changes in pH and concentrations of NaCl in the range studied as revealed by image analysis and calculations of two- and three-dimensional data from micrographs.     

Gel properties of a protein fraction of Vicia faba in dependence on some influencing factors

The shear modulus of Vicia faba protein gels formed by thermal denaturation can be lowered by increasing the pH value and the sunflower oil concentration, it can be increased by increasing concentrations of NaCl, CaCl₂, AlCl₃, glucose, sucrose, and starch. These changes of the shear modulus are connected with a shift of the ratio of the plastic component of the gels to an elastic one.     

Effect of pH adjustment at heating on the rheological properties of acid skim milk gels with added potato starch

The rheological properties of acid skim milk gels, prepared from milk with added potato starch and pH adjusted (pH 6.5–7.1) prior to heat treatment and acidification, were investigated. The storage modulus, G′, of the final acid gels was increased by heating the milk at higher pH and further increased by adding starch. The effect of pH at heating and addition of starch appeared to be additive and independent of each other up to a starch addition level of 1%. Above this starch level, the pH at heating had a lesser effect. This may have been due to the increased viscosity of the aqueous phase as a result of starch gelatinization or to direct contributions of the starch to the gel network structure. Confocal microscopy showed that milk proteins developed fewer but broader protein clusters at higher pH than at lower pH. Starch addition resulted in an increased density of the protein network.     

Comparison of Transparent Gels with Turbid Gels Prepared from Egg White: Creep Analysis of Gels

Egg white from which the precipitate occurring during dialysis against water had been removed gave a transparent gel on heating at lower salt concentrations and pH 3.54. The addition of NaCl or a shift of pH from 3.54 to 4.50 brought about the turbid gels. Creep analyses of these transparent and turbid gels were done using a four-element mechanical model. The instantaneous elastic modulus, E₀, Newtonian modulus, ηn and retarded viscoelastic moduli, E₁ and η₁ increased with NaCl up to 125 mM and then decreased with increase in NaCl concentration at pH 3.54. At 125 mM NaCl and pH 3.54, a translucent gel was obtained. E₀ and η₁ decreased with the temperature of the gel, while E₁ and η₁did not change depending of temperature.     

The effect of shear on the rheology and structure of heat‐induced whey protein gels

The influence of mechanical shearing on the small deformation properties and microstructure of heat‐induced whey protein gel has been studied. The viscoelastic properties of these gels at different concentrations of 10% and 20% (w/w) exposed to different shear rates of 0, 50, 100, 200 and 500 s^?1 during gelation were measured using dynamic oscillatory rheometry. The structure of both the shear treated and unsheared gels was then investigated using light microscopy. The results showed that the storage modulus of the gels at both concentrations was increased by increasing the shear rate exposure during gelation while the shear‐treated gels were more elastic and showed frequency‐independent behaviour. As the total protein concentration of the gel increased, the viscoelastic properties of the gels also increased significantly and the gels showed greater elasticity. The gels obtained from the higher shear rate exposure were stronger with higher elastic moduli at both protein concentrations. Images of the gels obtained using light microscopy showed that shearing resulted in phase separation and some aggregation in the structure of the gels at both concentrations. However, the shearing rates applied in this study were not enough to cause aggregation breakdown in the gel network.     

Rheological studies on commercial egg white using creep and compression measurements

The gel properties of commercial egg white (EW) with high gelling ability were compared with those of standard type using creep and compression measurements. The effects of heating time, temperature, and protein concentration on gel properties were investigated at pH 7.5. The experimental creep curves were analyzed using four elements of the Maxwell–Voigt model. The difference in rheological properties of the two types of EW was reflected in the values of elastic modulus and viscosity. The experimental stress–strain curves for all EW gels were fitted using the BST equation with high accuracy. This equation contained two fitting parameters, i.e. Young's modulus and the elasticity parameter n_BST. The elasticity parameter n_BST characterized non-linear elastic behavior for large deformation. At 80°C, n_BST of both types of EW gels did not change with increasing heating time. However, n_BST decreased with increasing temperature in a range of 70–85°C.     

Factors Affecting the Gelation Properties of Hydrolyzed Sunflower Proteins

The effects of temperature and several chemicals on gelation time and strength of gels formed by heating (pH 8) 5% solutions of trypsin hydrolyzed sunflower proteins were studied by dynamic rheological methods. The storage modulus reached a maximum at 80°C. Ca₂Cl (and NaCl at > 0.2M) accelerated gelation and weakened the gel. NaCOCH₃Na₂SO₄ and NaSCN decreased the storage modulus. Urea decreased gelstrength and at high concentrations slowed gelation. Time for gelation diminished and gel strength increased with increasing mercaptoethanol concentration up to 0.1M. Propylene glycol at 5–20% concentrations accelerated gelation and at 5% also increased gel strength. Trypsin hydrolyzed sunflower proteins could be useful in products requiring strong gels at high temperatures.     

“Influence of physicochemical properties of enzymatically modified starch gel on the encapsulation efficiency of W/O/W emulsion containing NaCl”

We investigated the molecular characteristics of 4-α-glucanotransferase (4αGTase)-modified rice starch (MRS) and corn starch (MCS) gels and the NaCl release properties depending on their mechanical properties. Also, encapsulation efficiency (EE) and oil globule size of water-in-oil-in-water (W/O/W) emulsions containing MRS or MCS in the inner aqueous phase (W₁) with NaCl as a model core material were measured after preparation and 14 days of storage. The characteristics of MRS and MCS were examined by analyzing amylose content, molecular fine structure, microstructure, and mechanical properties to better understand their associations with emulsion stability. At 20 % concentration, the gel strength of MCS (~10⁵ pa) was greater than that of MRS (~10³ pa) as MCS had higher apparent amylose content than MRS. The rate of NaCl release from the gel was highly correlated with the gel strength that depended on the type and concentration of the enzymatically-modified starch. As the gel strength increased, EE of freshly prepared and stored W/O/W emulsions increased. Osmotic swelling of NaCl-containing W/O/W was significantly reduced with the incorporation of the modified starch gels in W₁ phase. These results indicated that physicochemical properties of 4αGTase-modified starch gels in W/O/W emulsions largely affected the encapsulation efficiency and stability of the emulsions, which could be utilized to formulate W/O/W emulsions with improved stability and the potential for broader applications.     

Acid-induced gelation of whey protein polymers: effects of pH and calcium concentration during polymerization

Heating whey protein dispersions (90°C for 15 min) at low ionic strength and pH values far from isoelectric point (pH>6.5) induced the formation of soluble polymers. The effect of mineral environment during heating on the hydrodynamic characteristics and acid-induced gelation properties of polymers was studied. Whey protein dispersions (80 g/l) were denatured at different pH (6.5–8.5) and calcium concentrations (0–4 mm) according to a factorial design. At pH 6.5, the hydrodynamic radius of protein polymers increased with increasing calcium concentration, while the opposite trend was observed at pH 8.5. Intrinsic viscosity results suggested that heating conditions altered the shape of protein polymers. Whey protein polymers were acidified to pH 4.6 with glucono-δ-lactone and formed opaque particulate gels. The storage modulus and firmness of gels were both affected by conditions used to prepare protein polymers. As a general trend, polymers with high intrinsic viscosity produced stronger gels, suggesting a relationship between polymer shape and gel strength.Acid gelation properties of whey protein polymers makes them suitable ingredients for yoghurt applications. Using whey protein polymers to standardize protein content increased yoghurt viscosity to 813 Pa.s while using skim milk powder at same protein concentration increased yoghurt viscosity to 393 Pa.s. Water holding capacity of protein polymers in yoghurt was 19.8 ml/g compared to 7.2 ml/g for skim milk powder protein. Acid gelation properties of whey protein polymers are modulated by calcium concentration and heating pH and offers new alternatives to control the texture of fermented dairy products.     

Comparison of pressure treatment and heat treatment of skim milk with added starch on subsequent acid gelation of milk

Skim milk with added starch (waxy rice starch or potato starch at levels of 0-1.5 g/100 g) was either pressure-treated (500 MPa, 20 °C, 30 min) or heat-treated (80 °C, 30 min) and subsequently acidified (using glucono-δ-lactone) to form acid milk gels. In the second part of the study, the pH of the skim milk samples was adjusted from the natural condition (pH 6.64) to pH 6.5, 6.6 or 6.9 before the pressure or heat treatment and re-adjusted back to pH 6.64 after the respective treatment. The rheological properties of the samples during acidification and of the final acid gels were studied. The storage modulus, G′, of the final acid milk gels increased as more waxy rice starch was added to milk before pressure or heat treatment. However, acid milk gels made from pressure-treated milk with added potato starch did not show significant changes in the G′ of the final acid gels whereas those made from the heat-treated counterparts showed a marked increase in the final G′ as the potato starch level increased. Waxy rice starch was gelatinised in milk by both pressure treatment and heat treatment whereas potato starch was gelatinised by heat treatment only. Increasing the pH of milk before pressure or heat treatment increased the final G′ of the acid milk gel produced on subsequent acidification of the milk and the final G′ was increased further by the addition of waxy rice starch before the pressure or heat treatment.