添加黄原胶的纯胶乳液稳定性及流变特性研究

通过对添加黄原胶(XG)的纯胶乳液粒径、稳定动力学参数、静态和动态流变特性的考察,探讨不同含量XG导致纯胶乳液失稳及致稳的机理,并制备出具有长期贮藏稳定性的纯胶乳液。研究发现,含0.1%、0.2%XG的纯胶乳液较易发生排斥絮凝,稳定性分析结果显示未添加XG的纯胶乳液30 d内的稳定性系数(SI)较低,90 d后底部背散射光强度(BS)降低,而含0.5%XG的纯胶乳液90 d内稳定性较好;流变特性检测结果表明随着XG含量的增加,纯胶乳液的表观黏度增加,流动性指数(n)由0.939降为0.414,触变环变大,体系的假塑性增强,含0.5%XG的纯胶乳液贮能模量(G')大于耗能模量(G″)且δ值小于45°,形成弱凝胶结构,具有长期贮藏稳定性。     

降解黄原胶与降解瓜胶凝胶体系的流变性研究

降解黄原胶与降解瓜胶在一定条件下共混,形成凝胶体系.通过对其流变特性进行研究,表明该体系具有显著的黏弹性和剪切变稀性.考察了总胶浓度、蔗糖、共混比例及降解食品多糖的分子量等因素对共混凝胶体系流变特性的影响.研究了该凝胶体系的本构方程,结果表明,修正Williamous-Oldroyld-4参数模型可确切描述凝胶体系的黏度曲线,计算值与实验值吻合良好.     

黄原胶对酪蛋白酸钠乳状液稳定性的影响

研究了一定pH条件下,黄原胶浓度及剪切稀化效应对酪蛋白酸钠乳状液稳定性的影响。结果表明,在酸性条件下,黄原胶无法抑制酪蛋白的变性沉淀,乳液在制备之初,即产生严重絮凝。在中性和弱碱性条件下,黄原胶在一定浓度范围内,诱发了乳状液的排斥絮凝;体系的pH显著影响了乳状液的稳定性,pH6条件下,较低的黄原胶浓度(0.2wt%)便可赋予乳状液良好的稳定性。均质过程大大降低了黄原胶的粘度,导致乳状液的稳定性下降,与添加未经均质处理的黄原胶相比,添加量增大近一倍,才能获得稳定的乳状液。     

黄原胶的流变性及与魔芋胶等的协效性研究

研究前期筛选获得一株多糖胶质高产菌Xanthomonas axonopodis所产的黄原胶FJAT-10151-DTJZ的品质,为该黄原胶的开发应用提供基础数据及参考。通过分析浓度、剪切速率、p H、加热温度、时间、冻融处理等对FJAT-10151-DTJZ粘度的影响研究其流变性,并研究其与结冷胶、黄原胶、凝胶多糖、瓜尔豆胶、刺槐豆胶、魔芋胶、果胶和壳聚糖8种胶的协效性。实验结果表明,FJAT-10151-DTJZ溶液的粘度随浓度的升高而升高,且为非牛顿流体;当FJAT-10151-DTJZ的浓度为1%时,其粘度为343 m Pa·s;p H、冻融对FJAT-10151-DTJZ的粘度影响不大;FJAT-10151-DTJZ的最佳加热温度为75℃;粘度随加热时间先增大后减小,当加热温度为75℃,加热时间为150 min,1%浓度的FJAT-10151-DTJZ溶液的粘度为808 m Pa·s。FJAT-10151-DTJZ只与魔芋胶有强烈的协同增效作用,与壳聚糖、结冷胶、黄原胶、凝胶多糖、瓜尔豆胶、刺槐豆胶、果胶无协效性。      

Effect of xanthan gum on processing and cooking quality of nontraditional pasta

The physicochemical properties of three different commercial sources of xanthan gum (XG) were determined, and its subsequent effect on the processing and cooking quality of pasta containing nontraditional ingredients was characterised. Commercial durum flour was fortified with nontraditional ingredients (soya flour or oat flour, 10% w/w) and XG (2% w/w). Protein content, ash content, bulk density, water‐holding capacity and total glucose content significantly varied among XG samples from different vendors. Xanthan gum increased dough strength of durum flour and the extent of strengthening varied with vendor of XG. For example, time‐to‐peak ranged from 2.75 to 4.25 min; peak width from 2.5 to 3.75 BU; and end width from 2 to 3 BU depending on the vendor of XG. Processing properties differed depending on commercial source. Commercial XG that had the finest particle size required the lowest mechanical energy (range 253–270 J s^?1) and had the greatest extrusion rate (range 3.38–3.65 g s^?1), both of which resulted in the lowest specific mechanical energy (range 69–79 J g^?1) required to extrude spaghetti samples.     

Physicochemical stability of egg protein‐stabilised oil‐in‐water emulsions supplemented with vegetable powders

The effect of vegetable powders on the physicochemical stability of egg protein‐stabilised oil‐in‐water emulsions was studied. Vegetable powders (beetroot, broccoli, carrot, celery, green pea, red pepper, spinach, swede, tomato and yellow pea) were added at 2.5% (w/v) to emulsions prepared with rapeseed oil. The physical stability of the emulsions was characterised using the emulsifying activity (EAI) and the emulsifying stability indices (ESI) in addition to bright field microscopy. The oxidative stability of the emulsions was monitored by means of an accelerated oxidation test (Rancimat method). The addition of most vegetable powders did not markedly affect the physical stability of the emulsions although an adverse effect of tomato was observed. The oxidative stability of the emulsions was significantly improved in most cases as indicated by the Rancimat method with broccoli exhibiting the highest increase in induction time (98.2%) compared with the control. Both polar and nonpolar antioxidants are likely to contribute to the overall chemical stability of this complex food system in a concentration‐dependent manner.     

Study of emulsions and foams stabilized with Phaseolus vulgaris or Phaseolus coccineus with the addition of xanthan gum or NaCl

The properties of oil/water emulsions stabilized with 1% w/v common bean (Phaseolus vulgaris L.) or scarlet runner bean (P. coccineus L.) proteins, extracted by isoelectric precipitation or ultrafiltration, at pH 7.0 and 5.5 were studied. The stability of emulsions, evaluated on the basis of droplet size, creaming, viscosity and protein adsorption measurements, is increased by the addition of xanthan (0.1 and 0.25% w/v). This is probably due to the increase in the continuous phase viscosity and the creation of a network, which prevents the oil droplets from coalescing. Also, the ability and stability of 1 or 2% w/v foams was studied. Xanthan (0.25% w/v) does not enhance foam formation, but promotes foam stability, possibly owing to the increased viscosity of the aqueous phase, making it more difficult for air to enter the system and create a satisfactory foam volume. The addition of NaCl destabilizes emulsions by lowering the energy barrier and therefore increasing the tendency of the oil droplets to aggregate. However, NaCl at a certain concentration seems to promote the emulsion stability and foaming ability and foam stability. This could be attributed to the alteration of the protein molecule configuration leading to the building of a rigid and viscoelastic protein film around the droplet. Copyright © 2006 Society of Chemical Industry     

Optimisation of wheat flour‐based sponge cake formulation containing tapioca starch and xanthan gum

The optimum formulation for wheat flour (WF)‐based sponge cakes containing tapioca starch (TS) and xanthan gum (Xan) was determined using the central composite design with two factors and response surface methodology (RSM). Effects of partial substitution of TS (5–15%) for WF in a 20% total flour blend and Xan (0.1–0.3%) on specific volume, parameters of texture profile analysis and sensory liking scores of baked sponge cakes were investigated. A second‐order polynomial response surface was used to explain the influence of TS and Xan on the dependent variables. Coefficients of determination (R² ≥ 0.75) of the response variables and significant regression models were used for RSM optimisation. Based on the RSM contour plots, the cake formulation containing 16% butter with desired physical properties (maximum specific volume; minimum hardness, gumminess and chewiness) and sensory quality (maximum overall liking) was found to be 11.09–11.88% TS and 0.10–0.11% Xan.     

乳清分离蛋白-黄原胶复合乳化剂制备南瓜籽油O/W型乳液及其稳定性北大核心CSCD

为提高南瓜籽油(PSO)的稳定性,以及提高由单一乳清分离蛋白(WPI)作为乳化剂制备的水包油(O/W)型乳液的稳定性,制备了黄原胶(XG)与乳清分离蛋白协同稳定的南瓜籽油O/W型乳液,探究了黄原胶添加量及添加顺序对乳液性质及其稳定性的影响。结果表明:黄原胶质量浓度为2.0 mg/mL时,乳液平均粒径最小,为(10.53±0.06)μm,而ζ-电位绝对值最大,为(37.92±0.61)mV,乳液稳定性最好;黄原胶添加顺序不同,乳液稳定性有所差别,其中乳液WPI-PSO-XG(乳清分离蛋白与南瓜籽油乳化得粗乳液,再加黄原胶二次分散得到的乳液)的物理和化学稳定性最好;加速氧化实验显示,乳液的过氧化值(POV)及硫代巴比妥酸反应物(TBARS)值均低于南瓜籽油,其中乳液WPI-PSO-XG的POV和TBARS值最低,与南瓜籽油相比,分别降低了16.13 mmol/kg和17.63μmol/L,表现出良好的氧化稳定性。说明南瓜籽油与乳清分离蛋白制备成初乳液,再加入黄原胶,可使乳液稳定性提高。     

Effects of protein concentration and oil-phase volume fraction on the stability and rheology of menhaden oil-in-water emulsions stabilized by whey protein isolate with xanthan gum

The influences of protein concentration (0.2, 1, 2 wt%) and oil-phase volume fraction (5%, 20%, 40% v/v) on emulsion stability and rheological properties were investigated in whey protein isolate (WPI)-stabilized oil-in-water emulsions containing 0.2 wt% xanthan gum (XG). The data of droplet size, surface charge, creaming index, oxidative stability, and emulsion rheology were obtained. The results showed that increasing WPI concentration significantly affected droplet size, surface charge, and oxidative stability, but had little effect on creaming stability and emulsion rheology. At 0.2 wt% WPI, increasing oil-phase volume fraction greatly increased droplet size but no significant effect on surface charge. At 1 or 2 wt% WPI, increasing oil-phase volume fraction had less influence on droplet size but led to surface charge more negative. Increasing oil-phase volume fraction facilitated the inhibition of lipid oxidation. Meanwhile, oil-phase volume fraction played a dominant role in creaming stability and emulsion viscosity. The rheological data indicated the emulsions may undergo a behavior transition from an entropic polymer gel to an enthalpic particle gel when oil-phase volume fraction increased from 20% to 40% v/v.     

Physicochemical and sensory properties of milk fortified with iron microcapsules prepared with water‐in‐oil‐in‐water emulsion during storage

This study investigated the possibility of fortifying iron microcapsule powder into milk and the effects of the fortification on the physicochemical and sensory properties of the products during storage. The iron microcapsules were prepared by the water‐in‐oil‐in‐water (W/O/W) emulsion technique. Fortifying the lower concentrations (0.1–0.3%, w/v) of iron microcapsules into the milk samples did not significantly change thiobarbituric acid values. The L‐values for the milk samples were not significantly influenced by fortifying iron microcapsules (0.1–0.7%, w/v). The overall acceptability scores were not affected when the lowest concentration of iron microcapsules (0.1%, w/v) was fortified into the milk.     

Effect of processing treatments and storage conditions on stability of fruit juice based beverages enriched with dietary fibers alone and in mixture with xanthan gum

The present work aims to study the synergistic effect between xanthan gum (X) with a range of hydrocolloids such as barley β-glucan (Bg), guar gum (G), and konjac-mannan (K) on the viscosity of heat-treated fruit juice based beverages. The protective effect of X on the stability of Bg, G, and K in a fruit juice based beverage during processing and storage (0–16 weeks at 4 °C or 20 °C) was also evaluated. The results showed that pasteurization stabilized viscosity and turbidity of beverages enriched in Bg and BgX. However, the viscosity of pasteurized beverages enriched in K and G varied with storage time. In general, addition of X showed a complete protective effect against degradation at 4 °C for K (KX) whereas it provides no protection at all for G (GX). Viscosity and turbidity of beverages prepared with Bg and BgX increased significantly while those with G and K decreased slightly over time. Viscosity and turbidity changes are rapid when beverages are stored at 20 °C. We clearly evidenced that processing and storage treatments along with proper formulation are crucial to ensure technological stability of dietary fibers and X proved to be efficient to stabilize other fibers.     

响应面优化大豆分离蛋白、黄原胶和羟丙基糯玉米淀粉对熟制麻团微波复热后脆性影响

油炸食品冻藏后经过微波复热会出现微波浸湿现象,使表面失脆。大豆分离蛋白、黄原胶以及羟丙基糯玉米淀粉都是具有保水功能的食品添加剂。本文采用响应面法,以麻团脆性为响应值,对麻团中添加大豆分离蛋白、黄原胶、羟丙基糯玉米淀粉的添加量进行了优化。结果表明:大豆分离蛋白、黄原胶和羟丙基糯玉米淀粉对麻团脆性有极显著影响(p<0.01)。三种添加剂的最优配方为:大豆分离蛋白添加量3.1%、黄原胶添加量1.6%、羟丙基糯玉米淀粉添加量3.1%,此条件下微波复热后麻团的脆性为1569.4 g;而未添加三种添加剂的麻团微波复热后脆性为1019.5 g,由此证明添加大豆分离蛋白、黄原胶和羟丙基糯玉米淀粉可改善微波复热后麻团的脆性。      

卡拉胶对米糠蛋白稳定水包油乳状液乳化稳定性的影响

本研究将卡拉胶添加到米糠蛋白制备的水包油乳状液中,研究不同浓度的卡拉胶（0%、0.2%、0.3%、0.4%、0.5%）对水包油乳状液乳化稳定性的影响。测定了乳状活性、电位、粒径以及分层指数的影响。结果表明,随着卡拉胶浓度的增加,卡拉胶与米糠蛋白共同稳定乳状液的粒径从9.35μm逐渐减小到4.26μm,ζ-电位绝对值从9.45mV显著增大到24.26mV,乳化稳定性从57.79%显著增加到91.54%。卡拉胶使米糠蛋白形成的乳状液的黏度增加6倍,并增强了液滴之间的空间排斥和静电排斥,防止液滴聚集,使乳状液的分层指数明显降低并提高了乳状液的稳定性。可见,卡拉胶具有作为乳状液稳定剂的潜力。