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Interactions between acidified dispersions of milk proteins and dextran or dextran sulfate 总被引:1,自引:0,他引:1
Polysaccharides are often used to stabilize cultured milk products, although the nature of these interactions is not entirely clear. The objective of this study was to investigate phase behavior of milk protein dispersions with added dextran (DX; molecular weight = 2 × 106 Da) or dextran sulfate (DS; molecular weight = 1.4 × 106 Da) as examples of uncharged and charged polysaccharides, respectively. Reconstituted skim milk (5–20% milk solids, wt/wt) was acidified to pH 4.4, 4.6, 4.8, or 4.9 at approximately 0°C (to inhibit gelation) by addition of 3 N HCl. Dextran or DS was added to acidified milk samples to give concentrations of 0 to 2% (wt/wt) and 0 to 1% (wt/wt) polysaccharide, respectively. Milk samples were observed for possible phase separation after storage at 0°C for 1 and 24 h. Possible gelation of these systems was determined by using dynamic oscillatory rheology. The type of interactions between caseins and DX or DS was probed by determining the total carbohydrate analysis of supernatants from phase-separated samples. At 5.0 to 7.5% milk solids, phase separation of milk samples occurred after 24 h even without DX or DS addition, due to destabilization of caseins in these acidic conditions, and a stabilizing effect was observed when 0.7 or 1.0% DS was added. At higher milk solids content, phase separation was not observed without DX or DS addition. Similar results were observed at all pH levels. Gelation occurred in samples containing high milk solids (≥10%) with the addition of 1.0 to 2.0% DX or 0.4 to 1.0% DS. Based on carbohydrate analysis of supernatants, we believe that DX interacted with milk proteins through a type of depletion flocculation mechanism, whereas DS appeared to interact via electrostatic-type interactions with milk proteins. This study helps to explain how uncharged and charged stabilizers influence the texture of cultured dairy products. 相似文献
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高效凝胶渗透色谱法方便且重现性好,被广泛用于各种多糖分子量及其分布的测量.研究用高效凝胶渗透色谱法直接测量大分子右旋糖酐水解液和发酵液中右旋糖酐.首先,选择出0.7%Na2SO4水溶液(内合0.02%NaN3作流动相,用已知分子量右旋糖酐作标准品,回归获得右旋糖酐分子量与保留时间方程为v=6.6811× 46.511,R2=0.9969.在流速1.0 mL/min,进样量20μL,柱温23℃.检测器温度23℃的色谱条件下,该方程用于测量发酵液中右旋糖酐和某厂家大分子右旋糖酐水解产物,可直接计算出发酵液和水解产物中右旋糖酐分子量及分布. 相似文献
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Milad Fathi Maryam Nikbakht Nasrabadi 《International Journal of Food Properties》2017,20(11):2665-2674
In this research, dextran nano?bres were produced as novel carriers for entrapment of vitamin E. Morphological studies indicated that developed fine fibres were in the nano range without spherical beads. Thermal behaviour, chemical structure, and crystalline structure of vitamin E-loaded nanofibres were analysed by differential scanning calorimetry, Fourier transform infrared spectroscopy, and X-ray diffraction which showed that the vitamin was well incorporated within the amorphous structure of fibres without chemical interactions. Nanofibres were used for fortification of cheese. Sensory analysis of the fortified product was performed which showed better acceptability and texture of cheese containing nanofibres in comparison to blank and direct fortified samples. Nanofibres showed the capability of holding water and thus increasing cheese firmness. The release of vitamin E in gastrointestinal media showed that about 14% of vitamin could be released in gastric media and about 30% released in intestinal media. Finally, the results revealed that electrospinning can be used for production of dextran ultrathin fibres to entrap hydrophobic compounds with high potential for design of novel functional foods. 相似文献
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水溶性葡聚糖亲和-超滤载体对溶菌酶吸附分离特性的研究 总被引:1,自引:0,他引:1
亲和-超滤载体决定了亲和-超滤膜分离蛋白质的效率。以溶菌酶为对象,探讨了pH、离子浓度、反应时间等操作条件对葡聚糖亲和-超滤载体吸附溶菌酶的影响,随pH增加,亲和-超滤载体对溶菌酶的吸附量呈增长趋势,而随着离子浓度的增加,其吸附作用受到了抑制,此外亲和-超滤载体与溶菌酶的吸附能够在短时间内达到吸附平衡。应用Langmuir方程拟合了等温条件下亲和-超滤载体对溶菌酶的吸附曲线,得到最大理论吸附量为13.65mg/g,解离常数为3.019mg/mL。用醋酸缓冲溶液对载体进行洗脱,测得溶菌酶的平均洗脱率为91.74%。 相似文献
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Comparison of PEG/fractionated dextran and PEG/industrial grade dextran aqueous two-phase systems for the enzymic hydrolysis of starch 总被引:2,自引:0,他引:2
The aqueous two phase systems of polyethylene glycol (PEG)/fractionated dextran (DEX500) and PEG/industrial grade dextran (DEXI) were examined for the semi-continuous hydrolysis of starch. DEXI coagulates immediately as agitation stops and forms a biphasic system promptly whereas DEX500 forms clearer phases at a slower rate though. The partitioning of DEXI in the PEG phase is considerably lower compared to that for DEX500. Addition of starch in the biphasic systems was found to increase phase separation rate and dextran partition to dextran phase. Viscosities of the DEXI systems were only 10% higher than those of DEX500. Semi-continuous hydrolysis in the two phase systems exhibit steady performance for five cycles with 123.5% and 100.2% conversion of the initial starch load, for DEX500 and DEXI, respectively. The PEG/DEXI system presents almost equivalent performance to PEG/DEX500 system and has considerable lower cost than the latter. 相似文献
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Hills BP Buff C Wright KM Sutcliffe LH Ridge Y 《International journal of food microbiology》2001,68(3):187-197
Evolving microstructure in a model dextran solution is shown to exert a major influence on the survival of Escherichia coli K-12 frag 1 and Salmonella typhimurium LT2. The microstructure results from microscopic phase separation, which develops over several hours resulting in hardening of the solution into a glassy state. The microstructure is characterized by an array of physical methods including image analysis, electron spin resonance and bulk rheology, and it is shown that bacterial survival depends on the formation of microscopic. water-rich domains and not primarily on bulk water activity or hardness. 相似文献
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《Food Hydrocolloids》2006,20(2-3):240-244
Diffusing-wave-spectroscopy-based micro-rheology was used to measure the rheological behaviour of dextran solutions of concentration up to 40%. Three dextrans of different molecular weights, namely 2×105, 5×105 and 2×106 Daltons, were studied. It was found that these solutions were mainly viscous, with the loss modulus G″ higher than the elastic modulus G′. However, at high frequencies and for high dextran concentrations, a crossover between G′ and G″ was observed. A plot of the specific viscosity ηsp as a function of the dextran concentration showed two critical concentrations c* and c**. For c<c*, ηsp∼c1.4, for c*<c<c**, ηsp∼c2, and for c>c**, ηsp∼c3.8. These results were in very good agreement with those found in the literature. 相似文献
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Properties of dextran as a cryoprotectant in ice cream 总被引:1,自引:0,他引:1
In order to determine the usefulness of dextran as a stabilizer in frozen dairy products, ice cream mixes with varying concentrations of this microbial polysaccharide were prepared and tested by sensory, physical and mechanical means. Although previous results had shown that aqueous solutions of dextran exhibited remarkably low viscosities, the addition of dextrans to ice cream mixes resulted in much higher values. This is thought to result from interactions among dextrans, dairy proteins and, perhaps, other stabilizers. Dextran addition effectively increased the Tg of ice cream mixes, indicative of its value as a cryoprotectant. Also, dextran significantly reduced the sensory perception of ‘iciness intensity’ in heat-shocked ice cream samples. This resulted from the ability of dextran to slow ice crystal growth during storage and thermal abuse, as indicated by reduced ice crystal size as compared to a control formulation. However, dextran also produced unwanted firmness and melting characteristics in ice cream that could influence commercial acceptability. 相似文献
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《中国食品添加剂》2015,(12)
葡聚糖蔗糖酶可以催化单底物蔗糖生成葡聚糖和果糖。本论文研究了不同酶活总量的固定化葡聚糖蔗糖酶对葡聚糖分子量的影响。实验发现高效凝胶渗透色谱(HPGPC)在线检测催化反应混合液可以实现蔗糖和果糖的良好分离,同时得到每个批次的蔗糖使用和果糖生成情况,从而达到监控葡聚糖生成的目的。在催化反应条件一定的情况下,改变催化反应体系中固定化酶的酶活总量,可以改变葡聚糖的分子量分布情况,酶浓度越大,蔗糖的使用率越高,催化反应产物中小分子量葡聚糖的含量也越高。批次反应的往后,蔗糖的使用率下降,催化反应产物中小分子量的葡聚糖含量降低。论文为实现特定分子量葡聚糖的连续生产和固定化酶合成葡聚糖相关模型的建立提供重要的数据基础。 相似文献
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Soy protein isolate–dextran mixtures were incubated for up to three weeks and an improvement of their ability to stabilize emulsions against creaming, giving emulsions with lower droplet size, at pH values near the protein isoelectric point, was observed. Analysis of the adsorbed protein fraction indicated that the protein–polysaccharide hybrid can adsorb, together with the other mixture constituents, at the interface, during emulsion formation and in this way may contribute to droplet stabilization by enhancing repulsive steric forces by interpenetrating neighbouring droplets and polysaccharide chains. 相似文献
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用还原胺化法制备大分子葡聚糖-牛血清蛋白(BSA)拟糖蛋白抗原,通过SDS-聚丙烯酰胺凝胶电泳结合考马斯亮蓝和过碘酸-品红两种染色方法验证偶联物的生成。考察不同反应条件(葡聚糖T40的氧化度,偶联pH,氧化葡聚糖和蛋白质的比值,偶联时间)对偶联反应的影响。确定拟糖蛋白抗原的最佳偶联条件为:葡聚糖T40/氧化剂NaIO4=1/120(物质的量比),偶联溶液pH8.0,葡聚糖T40/BSA=1/1(物质的量比),偶联时间24h。并将此反应条件用于T10和T100拟糖蛋白抗原的合成。 相似文献
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A novel quantitative method for the determination of degree of branching in Leuconostoc mesenteroides B-512F dextran was developed by using the combination of 3 dextran-degrading enzymes. First, Paenibacillus sp. endo-dextranase was randomly degraded B-512F dextran into linear or branched isomalto-oligosaccharides with various degree
of polymerization (2–8). Second, Streptococcus mutans dextran glucosidase hydrolyzed linear or branched isomalto-oligosaccharides into glucose and branched isomalto-penta-saccharides.
Third, the branched isomaltopenta-saccharide was degraded into glucose by using Bacteroides thetaimicron α-glucosidase. The number of branching points in B-512F dextran (5.42%) was determined by the difference in the amount of
glucose in the reaction digest between BTGase-PDex and DGase-PDex treatments. 相似文献
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《食品与发酵工业》2016,(1):7-12
以右旋糖酐发酵废液为原料利用琥珀酸放线杆菌发酵生产丁二酸,在比较不同糖浓度废液对发酵产酸影响的基础上,通过Plackett-Burman试验筛选出对摇瓶发酵产丁二酸的主要影响因素Na H2PO4·2H2O,并用单因素试验确定其最适质量浓度为2.8 g/L。在3 L发酵罐上进行分批发酵和补料分批发酵,以60 g/L初糖质量浓度的右旋糖酐发酵废液为碳源,分批发酵46.8 h产丁二酸40.5 g/L;采用30 g/L葡萄糖为起始发酵培养基的碳源,后续补加浓缩右旋糖酐发酵废液的方式进行补料分批发酵,丁二酸质量浓度达到55.0 g/L,生产强度1 g/(L·h),糖酸转化率为0.83 g/g。结果表明:以右旋糖酐发酵废液为原料发酵生产丁二酸,为解决废液处理排放提供了新途径,具有良好的应用前景。 相似文献
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为了快速准确测定糖厂蔗汁中α-葡聚糖含量,对传统的酒精Haze法进行改良。利用淀粉酶与α-葡聚糖酶降解蔗汁中的淀粉与α-葡聚糖,以无淀粉与蔗汁α-葡聚糖的蔗汁作为空白制作α-葡聚糖在蔗汁中的工作曲线,测定样品α-葡聚糖含量。试验结果表明:该方法RSD为2.95%,加标回收率在94.2%~96.7%之间。与传统酒精Haze法测定结果相比准确度有了显著提高。该方法克服了其他检测方法的缺点,简化了实验步骤,加快了实验速度,为糖厂实时检测糖汁中的α-葡聚糖含量提供了新的途径。 相似文献
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通过大分子拥挤体系发生Maillard反应制备大豆蛋白-葡聚糖共价复合物,系统研究了不同反应条件对制备产物的影响,得出最佳条件为:pH6.5的磷酸盐缓冲液中,反应物总浓度为40%,60℃反应30h,SPI与葡聚糖共价接枝效果最好,表现出了优越的乳化性质.采用十二烷基磺酸钠聚丙烯酰胺凝胶电泳法(SDS-PAGE)证实了大豆分离蛋白与葡聚糖之间发生共价结合,产生了共价复合物.该方法制备的产物色泽良好,褐变颜色较少,反应时间大大缩短,只需30h即可完成,而传统的干热制备反应一般需要几天或者数周才能完成.该实验模拟大分子拥挤环境,将多糖和蛋白质作为生物大分子处于该环境中,得到的产物大豆蛋白-葡聚糖共价复合物,可作为一种“绿色”乳化剂,可广泛应用到食品工业中. 相似文献