柑皮高甲氧基果胶提取条件的研究

以柑皮为原料，采取稀酸提取、乙醇沉淀的方法制取高甲氧基果胶。探讨了盐酸浓度、加热温度和时间对产品得率、胶凝强度及甲氧基含量的影响，确定了柑皮果胶的最佳提取条件     

离子交换树脂法从甜菜渣中提取果胶

一、果胶的性质及用途 果胶为淡黄色至白色的粉末,溶于水,味微酸。按照酯化度来分,通常把酯化度50％以上(相当于甲氧基6％以上)的果胶称为高甲氧基果胶;酯化度在50％以下的果胶称为低甲氧基果胶。按照溶解度来分,可分为水溶性果胶和不溶性果胶两类。果胶在食品工业     

试谈柑桔高甲氧基果胶的制造

高甲氧基果胶(以下简称果胶)的制造过程,是由若干单元操作组成,但要成功地生产出合格的果胶,那就必须比较全面地掌握其工艺原理,下面试就以提高果胶产品胶凝倍数为重点,对柑桔果胶制造工艺谈一点粗浅的看法。     

黑曲霉果胶酯酶的研究

黑曲霉(As3.3324)用高甲氧基果胶诱导,当接种量为3×103个孢子,30℃恒温培养,转速90r/min,液体培养4d时果胶酯酶的活力最大,为90.2U/mL培养基。该果胶酯酶能将高甲氧基果胶的酯化度从64.54%降低到45.70%。经果胶酯酶作用后低甲氧基果胶的粘度为0.006Pa·s,与同样条件处理的高甲氧基果胶的粘度0.007Pa·s相差不大。     

用萍果皮制备果膠的研究

果胶是从植物组织中学取的一种线型天然高分子化合物．它的结构单元是半乳糖酷酸甲酯和半乳糖醛酸；它的主要成分是多缩半乳糖醛酸甲酯．果胶按其酯化度或甲氧基含量分为两大类：高甲氧基果胶和低甲氧基果股．高甲氧基果胶。甲氧基含量占总分子量的7．0～16％，其酯化度为50～100％[1]．我们所制的果胶，酯化度是50～65％，基本上属于高甲氧基果胶．果胶为白色、浅米黄色或黄色粉沫，无异味，略带苹果香味．它溶于水，但不溶于乙醇等有机溶剂，其水溶液的pH为2．8土0．2．制备果肢的方法很多：可以用酶、碱、酸为催化剂进行水解革取；也可…     

果胶

<正> 果胶是一种天然的多糖化合物,存在于所有的水果和蔬菜中,它在植物中的作用是结合水份和作植物细胞间的胶合材料。 哥本哈根果胶工厂有限公司的果胶主要分两种,高脂果胶(HM)和低脂果胶(LM)。 高脂或称高甲氧基(HM)果胶的酯化度大于50％,有效性能随酯化与分子聚合程度而有所不同。低脂或称低甲氧基(LM)的酯化度低于50％。     

低甲氧基果胶的制备及果胶碱法脱酯应用发展概况

论述了果胶的分类、来源、凝胶条件和机制以及当前最常见的四种利用高甲氧基果胶脱酯制备低甲氧基果胶的方法并进行了比较,且重点讨论了碱液催化脱酯法国内外的发展状况.对影响碱液催化脱酯的β-消去反应以及避免方法进行了讨论,对近年低甲氧基果胶凝胶影响的研究动态也进行了概括性的论述.随着人们生活质量的提高,低甲氧基果胶的需求也将剧增.国内高甲氧基果胶原料相当丰富,脱酯技术的成熟.将给我们带来巨大的社会经济效益.     

低甲氧基果胶的胶凝机理及防止预凝胶形成的措施

<正> 果胶广泛应用于食品工业,主要用途是作为酸性条件下的胶凝剂,但高氧甲基果胶和低甲氧基果胶的胶凝条件完全不同,低甲氧基果胶不易受糖、酸浓度的影响,但需与钙、镁等二价金属离子交联才能形成凝胶,胶凝条件的pH值范围可宽至2.6～6.8,可溶性固形物含量可低至10％,形成的凝胶经加热搅拌而可逆,并有良好的弹性。目前,我国已开始     

贮藏期间芦荟果胶含量变化及影响果胶粘度因素的研究

果胶作为由植物中提取的天然添加剂,具有良好的胶凝化和稳定化作用。从具有保健作用和药用价值的芦荟中提取果胶已广泛应用于食品工业、化妆品、医药等领域。本文对贮藏期间芦荟果胶含量态变化进行研究,并确定影响果胶粘度的因素,对芦荟果胶提取具有指导意义。本文采用酸水解醇析法提取芦荟中的果胶,确定提取果胶醇析过程中的最优pH和温度,并明确贮藏0～60d芦荟中果胶含量,此外还确定各种影响因素对果胶成品粘度的影响。结果表明,醇析过程中的最佳pH3.5,最佳温度为50℃。果胶成品的pH2.79（符合国标）,甲氧基含量为8.518%,属于高甲氧基果胶。贮藏0～60d库拉索芦荟中的果胶含量在贮藏10d时达到峰值。而后果胶含量随贮藏时间的延长而降低,并且在20d之后明显下降。因此,最适宜芦荟果胶提取和加工的时间为0～20d。所得芦荟果胶粘度与温度、柠檬酸和氯化钠添加量呈负相关,而与果胶浓度和蔗糖添加量呈正相关。     

高甲氧基果胶对酸奶饮料的稳定作用

总结了高甲氧基果胶对酸奶饮料的稳定机理及其影响稳定效果的因素,并对不同的影响因素(饮料的pH、蛋白质的浓度、高甲氧基果胶浓度、均质条件、调配搅拌速度、杀菌条件和酪蛋白粒子直径等)进行了详细的分析,为使用以高甲氧基果胶做稳定剂的酸奶饮料生产提供了较为全面的参考依据。     

黏度法测定γ-聚谷氨酸含量

采用乌氏黏度计测定了不同浓度下γ-聚谷氨酸稀溶液的黏度,由哈金斯(Huggins)方程和克拉默(Kraemer)方程结合外推法求得室温下γ-聚谷氨酸在中性水溶液中的特性黏度[η]为7.830 L/g,并推导出由溶液的相对黏度ηr与增比黏度ηsp计算γ-聚谷氨酸溶液浓度的公式。依据溶液黏度与浓度的关系,可以简便、快速、准确地估算出γ-聚谷氨酸的浓度。     

马铃薯果胶流变特性的研究

以马铃薯果胶(potato pectin extracted by chelating agent,PPCH)为研究对象,研究果胶溶液质量分数、剪切速率、温度、pH、金属离子等因素对马铃薯果胶流变学特性的影响。研究表明,PPCH溶液的黏度随溶液质量分数上升而增加。随着剪切速率的增大,PPCH溶液黏度下降,剪切变稀现象随着果胶质量分数的增加而更加明显,属于非牛顿流体。PPCH溶液流体行为受温度的影响。在剪切速率为50 s^-1时,温度10~47℃为时,PPCH溶液黏度随着温度升高而急速下降;温度为47~65℃时PPCH溶液黏度随着温度升高而缓慢波动,较难以用Arrhenius方程加以解释;温度为65~80℃时,PPCH溶液黏度随着温度升高而缓慢下降。在剪切速率为100、500 s^-1时,PPCH溶液黏度随着温度升高而缓慢下降。温度为10~47℃时,PPCH溶液活化能与剪切速率有较大的相关性,而温度为47~80℃时,活化能与剪切速率相关性较小。pH值对PPCH溶液流动性能有较大的影响。随着pH的升高,果胶溶液的黏度呈先增加后减小的趋势,在pH 4.0时,果胶溶液黏度最低,流动性最差。二价金属离子(Ca^2+、Mg^2+)可提高PPCH溶液的黏度,Ca^2+对于PPCH溶液黏度的增加幅度明显高于Mg^2+。     

Application of intrinsic viscosity and the interaction coefficient to some ionic galacturonan dispersions

Aqueous dispersions of a number of galacturonans, commercially called pectins, were made to contain different concentrations of ethanol, and the corresponding slope ([η]²k′) of the viscosity number versus concentration graphs was factored into intrinsic viscosity ([η]) and an interaction coefficient (k′). Factoring was also done for purely aqueous dispersions at different temperatures. Low-OMe pectins appeared to be more susceptible to ethanol and heat than high-OMe pectins. This susceptibility is believed to arise from a tendency toward greater hydrogen bonding which in turn is quite sensitive to solution (dispersion) forces. At ethanol concentrations of 15–25%, all pectins exhibited large increases in [η]²k′, a development that is attributable to OMe—OMe bonding and a consequent increase in the frictional component of viscosity. Squaring or multiplication of small numerical differences in [η] and k′ leads to the conclusion that the slope is a more reliable index of dispersion behavior than is [η] or k′ separately. Although [η] is basically an inherent molecular property, theoretically free of interference in a given solvent system, and k′ is an independent property of that pectin-solvent system, any numerical value acquired by one will automatically impose a limit on the other. Comparisons of [η] or k′ under variable conditions are therefore meaningless without an appraisal of the impact of those conditions on the other parameter. Ageing the dispersions did not show any trend in either factor, but it was expected that OMe—OMe contacts would increase as a pre-condition of fractional deposition of solute.     

Gel and Molecular Properties of Nonwaxy Rice Starch

A study of the factors that determine the gel consistency values of nonwaxy milled rice and rice starch showed that these values (in mm) were correlated negatively with the corresponding gel viscosities as measured with a Wells-Brookfield viscometer. In 6 IRRI rice varieties and an intermediate amylose variety, C 4–63 G, amylopectin contributed more to gel viscosity than did the amylose fraction of the starch. Differences in gel viscosity were observed only at starch concentration of 40 mg in 2 ml 0.2-N KOH or higher and were not simply related to differences in the intrinsic viscosity [η] of starch. However, gel consistency of starch was significantly correlated negatively with [η] of amylopectin. Gel viscosity was higher in KOH than in potassium acetate but the difference in viscosity was greater for the starch and amylopectin than for amylose.     

Conformation of a low methoxyl citrus pectin in aqueous solution

Viscosimetric measurements, small angle neutron scattering, light scattering and photon correlation spectroscopy have been performed on a 38% esterified citrus pectin in 0.1 M NaCl pH = 7 aqueous solution. The citrus pectin can be visualized as a semiflexible molecule with a persistence length of 10 monomers and a ratio of contour length on persistence length of 200. In dilute solutions the pectin behaves as a non-draining coil with radius of gyration of 320 Å. The overlap concentration c^* was found to be such that c^* [η] =0.8 and the intrinsic viscosity showed a 0.62 power dependence on the molecular weight.     

The formation of oil droplets in a pectin solution and the viscosity of the oil-in-pectin solution emulsion

Oil droplets were produced in a pectin solution by microchannel emulsification and by conventional homogenization, and the rheological properties of the oil-in-pectin solution emulsion were investigated. The effect of the pectin concentration on the emulsification ability was studied using a dead-end-type microchannel plate. A monodisperse emulsion was produced when the pectin concentration was 1 wt% or lower. When the pectin concentration was 2 wt%, a polydisperse emulsion was produced due to the increase in the viscosity of the continuous phase (the pectin solution). Oil-in-pectin solution emulsions were also continuously produced using a crossflow-type microchannel plate. The viscosity of the emulsion increased as the volume fraction of oil increased. The relationship between the volume fraction of oil and the viscosity was well explained by a simple equation, which describes the viscosity of emulsions.     

橙皮果胶流变学性质的影响因素

以采用离子交换树脂法从橙皮中提取的果胶为研究对象,研究浓度、温度、pH、金属离子Ca2+、糖、盐等对果胶流变性质的影响.结果表明:橙皮果胶溶液的黏度随剪切速率的增加而降低,为典型的非牛顿流体.这种剪切稀化现象受果胶溶液黏度的影响.随着果胶浓度的增大,浓度对果胶溶液流变学性质的影响增强.当热处理一定时间后果胶溶液黏度急剧下降直至表现出理想的牛顿流体性质;偏酸或偏碱环境下都导致果胶溶液黏度下降且碱性条件下降低更显著;果胶分子间疏水作用的增强使果胶溶液的黏度降低,共聚物之间氢键的形成受到抑制会使果胶溶液的黏度降低,较强的静电作用可以增强果胶网络结构的强度,使果胶溶液黏度升高.     

Chemical modification of proteins. Part 12. Effect of succinylation on some physico-chemical and functional properties of the albumin fraction from rapeseed (Brassica napus L.)

The effect of succinylation on native rapeseed albumin was studied using polyacrylamide gel electrophoresis (PAGE), isoelectric focusing, viscometry, turbidimetry and by investigation of some functional properties (heat-induced aggregation, emulsifying and foaming properties). The protein can be quickly modified with a relatively small excess of succinic anhydride. A 98% succinylation of the protein amino groups could be attained. The PAGE patterns point out a relatively high heterogeneity of the succinylated protein. The isoelectric focusing shows, however, a concentration of the succinylated protein fractions in a near pI range (pH 4.45 to 4.60). The intrinsic viscosity [η] of the native albumin drops after a 50% succinylation from 0.15 dl· g^?1 to 0.06–0.07 dl. g¹. Increasing the degree of succinylation to 88% increases [η] to 0.09 dl· g^?1. The native albumin possesses excellent whipping properties and high foam stability. Succinylation did not improve the foam capacity but decreases the foam stability. The emulsifying properties could not be improved by succinylation. The heat-induced aggregation of the rapeseed albumin in dilute solution is inhibited by a moderate or high succinylation.     

微波降解果胶对其流变性质的影响及动力学

对不同质量浓度(0.5、1.0、1.5、2.0 g/100 m L)的果胶溶液微波处理不同时间(0、1、3、5、8、15、20、30 min)后的流变性质及动力学进行考察。结果表明,随着果胶溶液质量浓度降低、微波处理时间延长、剪切速率增大,样品的表观黏度和特性黏度[η]均降低。用牛顿幂律方程描述溶液的流体行为,果胶溶液是剪切稀化的假塑性非牛顿流体,在低质量浓度时,微波处理对溶液的流体行为影响最大。根据特性黏度对样品进行反应动力学拟合,发现果胶的微波降解遵循反应一级动力学,在质量浓度0.5 g/100 m L时降解速率最快,质量浓度1.5 g/100 m L时降解速率最慢。经与沸水浴无微波的空白组对比,发现微波降解果胶的过程还存在非热效应。     

Flavour/taste perception in thickened systems: the effect of guar gum above and below c*

The effect of polymer concentration on flavour/taste perception in thickened systems has been investigated using solutions incorporating a fixed concentration of sucrose and flavouring and a wide range of concentrations of three different samples of guar gum, with intrinsic viscosity values of [η] = 16.7, 8.4 and 5.04 dl/g, respectively. For all three samples the perceived intensity of both attributes (assessed by 18 panellists using magnitude estimation against a fixed control solution) was independent of polymer concentration up to c^* ( ≈ 2.85/[η]), but decreased steeply at higher degrees of space occupancy by the polymer, with both sweetness and flavour intensity showing essentially the same dependence on polymer concentration. This behaviour is interpreted in terms of restricted replenishment of surface depletion with increasing coil overlap and entanglement.