微生物多糖物质的发酵生产

本文对两种微生物多糖--黄原胶和凝胶多糖的进行了介绍.描述了它们的分子结构,并对它们的菌种选育和培养条件进行了综述.     

国外多糖胶质的发展趋势

亲水性胶体每年在国际市场上所占据的份额大约为２５亿美元。它所具有一系列功能特性，例如：粘稠性、凝胶性和稳定性等使得食品和饮料拥有诱人的口感和稳定的性能。近几年来，亲水性胶体在低脂肪、无脂肪和低热量食品中也有着广泛的应用。黄原胶一直在粘稠剂中占据主导地位；由于瓜尔豆的严重短缺，导致瓜尔豆胶的价格剧烈上涨；与此正相反的是近几年槐豆胶的原材料供应充足，因此它的价格逐步赵于稳定。亚洲，尤其是中国，早已成为     

多糖胶质的国际发展趋势

一、引言食品的六大基本组分为脂肪、碳水化合物、蛋白质、维生素、矿物质和纤维素。用于食品加工的碳水化合物中一个非常重要的分支是由以单糖为基本组成单位，按一定方式重复排列而成的聚合物，即多糖（Polysadriaride）。食品工艺师则将这些多糖称之为胶质（G）、亲水胶体（Hydrocolloid）、稳定剂（Stabilirers）、悬浮剂（SuspendingAgents）、增稠剂（Thickeners），和胶凝剂（GellingAgentS）。有时多糖也被错误地称作乳化剂（Emchifiers）或起泡剂（FoaAnngAgents）。淀粉及变性淀粉是使用量最大的一种多糖。1996年全球包含淀…     

虫草多糖的制备、性质及应用

从冬虫夏草的发酵工艺.虫草多糖的提取方法,虫草多糖的分子结构、功能及发展趋势等方面对近年来研究的成果做了简要概述.     

三种微生物多糖的研究进展

微生物多糖以其安全、无毒、理化性质独特等优良特性,被广泛应用于工业生产中,具有较强的市场竞争力和广阔的发展前景。本文介绍了黄原胶、结冷胶和短梗霉多糖及这三种微生物多糖的发酵生产工艺。     

复合多糖稳定剂在乳白鱼肝油中的应用

采用ＨａａｋｅＲＶ１２粘度仪测定复配胶溶液、７７９６胶溶液以及乳白鱼肝油的流变性质,用光散射仪测定乳白鱼肝油中油滴大小分布,结果表明,复配胶与进口的７７９６胶相比,不仅价格低,而且稳定性能优于７７９６胶。使用ＤＬＶＯ理论探讨了复配胶稳定乳白鱼肝油的稳定机理。     

多糖对制糖生产的影响

目前许多甜菜糖厂原糖的加工。原糖大多是一种以甘蔗为原料制成的半成品,原糖中多糖的存在导致生产低效和糖份损失,生产的多糖主要是淀粉和葡聚糖。本文讨论多糖的结构与特征及降低其负效应的方法。     

瓜尔豆胶和黄原胶对淀粉理化性质的影响

为改善淀粉的加工品质特性,以玉米淀粉和甘薯淀粉为研究对象,将瓜尔豆胶和黄原胶分别以不同比例(0.1%~0.5%)与淀粉进行复配,系统研究亲水胶体对淀粉理化特性等的影响。结果表明,添加亲水胶体后,随着胶体浓度的增加,复配体系的透光率逐渐下降,凝沉稳定性增大,膨胀度增大,淀粉胶体的硬度下降。RVA分析表明,加入亲水胶体使复配体系的糊化温度升高,峰值黏度、崩解值和终值黏度增加,而甘薯淀粉-黄原胶混合体系的峰值黏度显著降低。     

黄原胶对木薯阴阳离子淀粉糊性质的影响

本文采用Brabender黏度计和哈克流变仪研究了黄原胶对木薯阴、阳离子淀粉糊黏度、冻融稳定性及流变学性质的影响。结果表明:黄原胶使木薯阴、阳离子淀粉糊的峰值黏度和崩解值均显著增加,但其起始糊化温度有所降低;添加黄原胶后,阳离子淀粉的析水率有了一定程度的提高,冻融稳定性减弱,而阴离子淀粉的析水率下降;黄原胶的加入使两种变性淀粉凝胶的tanα值降低,储能模量(G’)增大,这使得木薯阴阳离子淀粉凝胶向趋于固性的方向发展。      

微生物代谢来源的亲水性胶体

本文介绍了微生物代谢亲水性胶体(黄原胶、结冷胶、普鲁兰多糖、凝结多糖和葡聚糖)的结构、性质及其在食品工业中的应用,并且阐述了我国微生物代谢亲水性胶体的发展趋势.     

Micellar properties of OSA starch and interaction with xanthan gum in aqueous solution

Octenyl succinate (OSA) modified starches are used, as emulsifiers and stabilizers, in many food, cosmetics and pharmaceutical products. The aim of this study was to determine critical micellar concentration (CMC) of two different octenyl succinate modified waxy corn starches at 25 °C, and to examine possibility of their interactions with xanthan gum in aqueous solution. The CMC was determined by viscometry, conductometry, surface tension and dye solubilization. The CMC values for two OSA starches (OS1 and OS2) varied from 0.050 to 0.088 g/100 cm³ and from 0.041 to 0.081 g/100 cm³ respectively, depending on applied technique. The same techniques were used for investigation of the interactions between OSA starch and xanthan gum. The addition of xanthan gum decreases the specific viscosity and increases surface tension and the CMC values compared to the single OSA starch solutions.     

Effect of non-starch polysaccharides on the in vitro digestibility and rheological properties of rice starch gel

The starch digestibility and rheological properties of gels were evaluated in the presence of three non-starch polysaccharides (agar, xanthan gum and konjac glucomannan) with rice starch. Each polysaccharide was added to 30% (w/w) rice starch suspension at defined concentrations and starch gels were prepared. The extent of starch gel digestibility was determined by an in vitro method and rheological properties by a dynamic oscillatory test and a compression test. The added polysaccharides suppressed starch hydrolysis in the gels compared with the control, and a concentration dependency of this suppressive effect was observed. Adding agar and xanthan gum increased the storage shear modulus (G′) of starch gels, while adding konjac glucomannan decreased G′ values. The results indicate that the suppressive effect of non-starch polysaccharides on starch digestibility appears to be not only due to the rigidity of the gel, but also the interaction between starch and non-starch polysaccharides.     

The effect of electrostatic interactions on pasting properties of potato starch/xanthan gum combinations

The effects of electrostatic interactions on pasting properties of potato starch (PS)/xanthan gum (XG) combinations were investigated. The RVA peak viscosity of combinations was decreased firstly and then increased with the adding of XG. The analysis and regression model performance of RVA measurement showed that there was the relationship between pasting properties of combinations and XG concentrations. Electrostatic repulsions between native potato starch or anionic modified potato starches (AP) and XG could be present by decreasing peak viscosity, but the pasting temperatures showed increasing trend. However, electrostatic attractions between cationic modified potato starch (CP) and XG showed the opposite effect. Negative zeta potential determination for combinations (− 54.6 mv) was higher than PS (− 35.2 mv) illustrated that combinations had more electronegativity and stability, in addition a phase-separated microstructure was exhibited in the combinations determined by Zeta potential results. SEM micrographs presented that XG film attached to the surface of PS granules, which inhibited the starch granules destruction and leaching of amylase. The electrostatic repulsion leaded to more stability of the three dimensional network structures of combinations. The strong electrostatic interactions between PS and XG were found to play an important role on the pasting properties of the combinations.     

Evaluation of the time-dependent stability of starch-hydrocolloid binary gels involving NMR relaxation time measurements

A novel, non-destructive method of evaluation of the time-dependent stability of starch gels and binary starch-non-starchy hydrocolloid gels is presented. The low-field NMR technique applied provided the following results. On storage at room temperature, binary potato starch gels with xanthan gum are more stable in time than gels with guar gum and κ-carrageenan. Xanthan and guar gums as well as κ-carrageenan are dispensable as stabilizers of stored potato starch gel and building the cassava gel structure lasted over 96 h. In the binary system with cassava starch, guar gum performed best regardless storage temperature. At room temperature, admixture of hydrocolloids to plain cornstarch gels resulted in remove of water molecules from the gel network. Stabilization of cornstarch gels with hydrocolloids was, practically, dispensable and even non-beneficial regardless storage temperature. None among tested hydrocolloids stabilized the oat starch gel. On cold storage, κ-carrageenan performed best.     

Preparation of resistant starch from starch–guar gum extrudates and their properties

Mixtures of starch, guar gum and citric acid were extruded at a temperature of 150 °C and screw speed of 180 rpm. Properties of the extrudates such as bulk density, expansion ratio, apparent viscosity and resistant starch content were measured with different concentrations of guar gum. Extrusion with citric acid influenced the physical properties and resistant starch content of the extrudate. Expansion ratios were lower for samples extruded with citric acid, and decreased as starch–gum concentration increased. The apparent viscosity of the extrudate increased with increasing guar gum concentration; however, citric acid at 2.0% concentration was found to lower the viscosity of the extrudate. Resistant starch content increased from 6.23% for extruded starch only to 14.21% for starch–gum extrudate, and further enhanced to 16.19% with the addition of 2.0% citric acid to the starch–gum extrudate. Resistant starch increased with increase of gum concentration and decreased with increase of starch–gum concentration from 7.5% to 12.5%.     

黄原胶的特性及其在饮料工业中的应用研究

本介绍了黄原胶的基本特性，并探讨了它与其它几种常用食用胶的协同增效作用；从而进一步研究它在饮料加工中的应用范围及其使用方法。     

Rheological properties of xanthan gum-gelatine spray-dried mixtures. Application in a custard-like formulation

 The effect of a spray-drying process on the rheological and textural properties of xanthan gum-gelatine dispersions was studied. Remarkable differences were found between co-dried samples and dispersion samples. Apparent viscosity and extrusion values were higher and shear-thinning behavior more pronounced than in non-dried samples. Also, stronger thickening and stabilizing properties were noticed. With regard to viscoelastic properties, an increase in the elastic component was observed. The new product was used in a standard confectioner's custard formulation and its properties were studied. When these samples were compared with a traditional custard made with starch, although enhanced rheological properties were recorded a similar visual appearance between samples was observed. Received: 27 March 2000     

Effect of modified tapioca starch and xanthan gum on low temperature texture stability and dough viscoelasticity of a starch-based food gel

This work investigated the effect of modified tapioca starch and xanthan gum on dough viscoelasticity and texture stability during storage at 4 °C of starch sheets for Chinese shrimp dumplings. Hydroxypropylated starch and hydroxypropylated-crosslinked starch were used to substitute for tapioca starch in the control formulation, and xanthan gum was added to adjust the formulation. During storage, texture of the control became firmer due to amylopectin retrogradation confirmed by differential scanning calorimetry and X-ray diffraction. Conversely, gel sheets containing modified starches showed less texture change. Dough viscoelasticity of the formulations substituted by hydroxypropylated starch were much softer and easier to deform than that of the control one. Dough with hydroxypropylated-crosslinked starch was, however, stiffer and more strain-resistant. Moreover, the formulation comprising the mixture of both types of modified starches and xanthan gum gave dough viscoelasticity similar to that of the control, and provided gel sheet the least texture change. Consequently, this modified formulation could be beneficial for the application of frozen/chilled dumpling wrappers.     

Impact of xanthan gum,sucrose and fructose on the viscoelastic properties of agarose hydrogels

Mixed carbohydrate systems are of special interest for the food and non-food industry as they offer a versatile range of unique and novel functional properties. However, intense research is required to understand the complex processes occurring in such systems on a molecular level and to be able to modify them aim-oriented. In food, characteristic properties are based on the physicochemical functions of the biopolymers added. Thus, small deformation tests and moisture analysis have been applied to study the impact of xanthan gum and two types of sugar on the viscoelastic properties, the sol–gel transition and the water holding capacity of 1% agarose hydrogels. Agarose gels are very elastic, turbid and prone to synaeresis, which impinges on their mouth feeling. Additions of xanthan gum revealed less elastic gels with an unaffected water holding capacity. Progressive addition of two different types of up to 40% of sugar yield an increase of the elasticity of agarose gels, whereby sugar concentrations of 60% partially result in a structural breakdown and thus a significant lower network structure but better water holding. In ternary systems, the effect of the sugar concentration and sugar type used is diminished by xanthan gum. The gelation mechanism of agarose gels with a distinct amount of co-solutes is presumably mainly affected by the water shortage evolved from the competition for it of all solutes present.