液相色谱示差折光法测定蜂蜜中的果糖、葡萄糖、蔗糖和麦芽糖

本实验对反相高效液相色谱示差折光检测法测定蜂蜜中的果糖、葡萄糖、蔗糖和麦芽糖的方法进行了详细地探讨,结果表明:均匀称取约2.5g样品,加30ml水溶解后,再用乙腈定容至50ml,既能够有效地提取蜂蜜中的糖类物质,又保证了和流动相的相对一致性.同时对样品溶解时的分层机理作了初步推测.用该方法处理所得的样品稳定性高,测试结果重复性好.该法加标回收率均在97%~103%之间,相对标准偏差均在0.8%～1.6%之间.采用本研究方法测试了8种不同蜂蜜样品,均获得满意结果.     

Crystallization Kinetics of Lactose and Sucrose Based On Isothermal Differential Scanning Calorimetry

Isothermal Differential Scanning Calorimetry (DSC) was used to study the crystallization kinetics of freeze-dried samples of lactose and sucrose at several temperatures between Tg and Tm. The sample was rapidly heated to the required temperature. After subtraction of an induction time, the Avrami equation was used to model the data and a Lauritzen-Hoffman like expression used to fit the derived rates of crystallization over the temperature range Tg相似文献   

离子色谱法同时测定蛋白胨中葡萄糖、果糖、蔗糖、麦芽糖、乳糖含量

目的建立离子色谱法同时检测蛋白胨中葡萄糖、果糖、蔗糖、麦芽糖、乳糖的分析方法。方法样品用水作为提取剂,用OnGuard Ⅱ RP柱和OnGuard Ⅱ H柱净化,50mmol/LNaOH溶液作为流动相,用Carbopac PA20柱进行离子色谱分析。结果在该条件下5种糖都能得到较好分离,线性良好,葡萄糖、果糖、蔗糖、乳糖和麦芽糖的检出限为0.002、0.004、0.011、0.007、0.018 mg/L,平均回收率为90.59%～97.68%(n=9)。结论该方法操作简便、灵敏度高,可用于作为蛋白胨中葡萄糖、果糖、蔗糖、麦芽糖、乳糖的检测。     

Lactose: Use,measurement, and expression of results

Lactose has different uses in the dairy, food, and pharmaceutical industries. Being aware of the different forms of lactose and their concentrations can be very helpful in managing dairy product quality, properties, and manufacturing efficiency. Correct measurement and reporting of lactose concentration in milk and other dairy products will be of increased importance in the future as more value-added uses of lactose are developed and as milk lactose data are used in farm management decision making. Lactose should be reported as anhydrous lactose because lactose data will be used to make increasingly important decisions in dairy processing, dairy product labeling, and milk production in the future. Lactose also plays an important role in milk synthesis within a cow. Milk production factors and dairy cattle breed selection influence the amount of high value fat and protein produced per unit of lactose. If the off-farm value of lactose remains low, more attention may be focused on using ultrafiltration to process milk and leave 50 to 60% of the lactose and water from milk at the farm to recover the energy value of the lactose as feed and reduce the hauling cost of the high value components of milk to a dairy product manufacturing factory. Many methods exist to determine lactose concentration, but the most important methods are enzymatic assays, HPLC, and mid-infrared analysis. New, value-added uses for lactose need to be developed. Consistent and accurate methods of lactose measurement and consistent expression of lactose results will support this development process. Starting in January 2017, the USDA Federal Milk Market Laboratories began reporting lactose content of milk as anhydrous lactose and discontinued the reporting of lactose by difference.     

高效液相色谱-激光蒸发光散射检测法测定低蔗糖食品中葡萄糖、蔗糖、麦芽糖和乳糖含量

建立了同时测定低蔗糖食品中葡萄糖、蔗糖、麦芽糖和乳糖的高效液相色谱方法。样品经水超声波浸取,采用HypersilNH2柱分离,以乙腈/水(80/20体积比)为流动相,使用激光蒸发光散射检测器进行检测。结果表明,葡萄糖、蔗糖、麦芽糖和乳糖的线性范围分别为15～1000、20～1500、15～1000、12～1000mg/L;检出限为4.5～6mg/L,样品的加标平均回收率为92.9%～99.0%,相对标准偏差在1.9%～3.5%之间。该法用于实际样品的测定,结果另人满意。     

莱茵-埃农氏法和高效液相色谱-示差折光法检测奶粉中乳糖和蔗糖的比较研究

选用市售同种品牌不同年龄段的奶粉,采用莱茵-埃农氏法和高效液相色谱-示差折光检测法对其乳糖和蔗糖进行测定,分析乳糖和蔗糖的差异,并对两种分析方法的结果进行比较,为奶粉中乳糖和蔗糖的检测方法提供依据。结果表明,莱茵-埃农氏法和高效液相色谱-示差折光检测法相比,高效液相色谱-示差折光检测法测定乳糖和蔗糖含量的准确度更高,蔗糖和乳糖的线性范围均为2～12 mg/mL,相关系数分别为0.999 3、0.999 6,精密度实验结果表明,相对标准偏差分别为2.53%、3.81%,平均加样回收率分别为99.70%、101.06%。高效液相色谱-示差折光检测法结果准确、分析时间短、前处理简单,适用于快速测定奶粉中蔗糖和乳糖含量。     

α结晶麦芽糖的制备及其功能性质

报导了从水溶液中结晶α结晶麦芽糖的新工艺并对其功能性质进行了研究，结果表明，α结晶麦芽糖与β结晶麦芽糖相比，具有熔点高（３０℃以上），在水中的溶解度和乳化能力分别为β结晶麦芽糖的３倍以上和２倍。α结晶麦芽糖还具有较高的醇水溶性，此外对β结晶麦芽糖的纯度与形成α结晶麦芽糖的关系也进行了探讨。     

HPLC-ELSD法测定微胶囊中阿拉伯糖、果糖、葡萄糖、蔗糖、麦芽糖、乳糖含量

建立高效液相色谱-蒸发光散射法(High performance liquid chromatography with evaporative light-scattering detection,HPLC-ELSD)同时测定微胶囊中阿拉伯糖、果糖、葡萄糖、蔗糖、麦芽糖、乳糖含量的高效液相色谱方法。样品经乙腈水超声波浸取,采用Waters Amide色谱柱(4.6×250mm3.5μm)分离,以1%氨水和乙腈为流动相,使用蒸发光散射检测器进行检测。结果表明,阿拉伯糖:0.44~7.06mg/mL、果糖:0.30~4.74mg/mL、葡萄糖:0.40~6.45mg/mL、蔗糖:0.32~5.04mg/mL、麦芽糖:0.40~6.47mg/mL及乳糖:0.41~6.61mg/mL范围内线性关系良好;方法检出限为0.02~0.03mg/mL;回收率为95.31%~105.33%,6种糖含量相对标准偏差在2.30%~3.50%之间。该方法前处理简单、灵敏度高和检测速度快,适用于微胶囊中阿拉伯糖、果糖、葡萄糖、蔗糖、麦芽糖、乳糖的定量检测。     

十二烯基琥珀酸单麦芽糖酯的合成研究及表征

将溶于一定量有机溶剂的十二烯基琥珀酸酐滴加入麦芽糖碱性水溶液中反应得十二烯基琥珀酸单麦芽糖酯。通过考察原料配比、酸酐溶剂、酸酐滴加速度、反应时间等因素对十二烯基琥珀酸单麦芽糖酯产率的影响,确定了最佳反应条件:原料配比麦芽糖∶酸酐(物质的量比)为4∶1,酸酐溶剂为丙酮,酸酐滴加1 h,在35℃条件下反应6 h,十二烯基琥珀酸单麦芽糖酯的产率为83.1%。当十二烯基琥珀酸单麦芽糖酯水溶液的质量浓度为1.35 mg/mL时,产物的表面张力约为36.64×10-3 N/m。     

乳清中乳糖的酶法水解

本文研究了Aapergillur niger CWL2NU-3乳糖酶在乳清中的应用,探讨了温度、pH、金属离子、底物浓度、酶浓度及水解时间等因素对乳清中乳糖的酶法水解速度的影响,在此基础上确定了主要影响因素,通过正交试验,获得乳清中乳糖水解的最佳工艺条件(65℃、pH4.5、乳糖15%、[E]/[L]=0.03、水解时间2.5h),在此条件下乳糖水解率为91.0%。     

不同贮藏温度条件下菜用大豆蔗糖代谢与相关酶活性变化

以‘新大粒1号’菜用大豆为试材,研究不同贮藏温度（1、5、10、20 ℃）条件下菜用大豆蔗糖代谢及相关酶活性的变化情况。结果表明,贮藏期间菜用大豆蔗糖、果糖及葡萄糖含量均呈整体下降趋势,1 ℃有效控制了蔗糖降解;酸性转化酶（AI）活性在第1天达到峰值后逐渐下降,不受贮藏温度影响;20 ℃条件下中性转化酶（NI）活性持续增加,至第4天达到最大值,其他温度组变化差异不显著（P＞0.05）;蔗糖合成酶（SS）活性略有降低后快速升高,至第4天达到峰值后逐渐下降;蔗糖磷酸合成酶（SPS）活性呈整体下降趋势,与蔗糖含量呈极显著正相关（P＜0.01）,与果糖含量呈显著正相关（P＜0.05）,其他酶活性与糖含量之间均无显著相关性（P＞0.05）。这表明SPS可能与‘新大粒1号’菜用大豆中蔗糖降解密切相关。     

马克斯克鲁维酵母对发酵乳中糖代谢的影响

采用高效液相色谱等方法,对乳酸菌单独发酵和向其中添加马克斯克鲁维酵母这两种发酵乳中乳糖代谢主要产物及关键酶活力的变化情况进行对比分析,以确定添加酵母菌对乳糖无氧代谢产生乳酸途径的影响。结果表明：添加酵母菌后乳糖降解速率明显加快（P＜0.05）,贮藏期间马克斯克鲁维酵母可以对积累的半乳糖进行利用;发酵过程中,由于酵母菌的添加使β-半乳糖苷酶及乳酸脱氢酶活力有显著提高（P＜0.05）,糖酵解途径关键限速酶--己糖激酶和丙酮酸激酶活力增加（P＜0.05）;含有酵母菌的发酵乳pH值下降（滴定酸度上升）较乳酸菌单菌发酵快（P＜0.05）,这与添加酵母菌后发酵乳中乳酸含量显著增加（P＜0.05）有关;丙酮酸含量变化不显著（P＞0.05）。该研究揭示了马克斯克鲁维酵母的添加对乳糖酵解具有一定促进作用。     

Water Plasticization and Crystallization of Lactose in Spray-dried Lactose/Protein Mixtures

ABSTRACT: Water plasticization led to depression of the glass transition causing significant changes in the physico-chemical and crystallization properties in storage of lactose and lactose/protein (3:1) mixtures. Glass transition (Tg) and crystallization temperatures (Tcr) were determined using differential scanning calorimetry. Whey protein isolate (WPI), albumin, and gelatin increased the Tg of dry powders; when Na-caseinate was used, a decrease was observed. In the presence of proteins and water, a decrease of Tg at aw ≤ 0.23 was observed. At aw ≤ 0.33, proteins increased the Tg In the anhydrous state, Tcr decreased in the presence of proteins possibly because of browning. WPI, Na-caseinate, albumin, and gelatin delayed lactose crystallization in humidified samples, with albumin and gelatin delaying it more than WPI at all storage humidities. Temperature difference between an observed instant crystallization and glass transition (Tcr to Tg) was larger for humidified samples containing proteins than for lactose. Various proteins and water affect crystallization behavior of amorphous lactose differently in spray-dried powders. This should be considered in evaluating sugar crystallization properties in food products including dairy powders.     

糖化麦汁麦芽糖含量预测模型的建立

采用正交实验设计法研究了糖化条件对麦汁中麦芽糖含量的影响。通过实验发现，所选的4个糖化条件，即麦芽选择，辅料比例、糖化温度和保温时间都对麦芽糖含量有显著影响。在此基础上，建立了麦汁麦芽糖含量预测神经网络模型，采用10组数据进行网络训练和仿真，并且用3组未参加训练的数据进行预测。模型的仿真最大相对误差为1.87％，预测最大相对误差为7.85％。     

蔗糖异构酶基因在Escherichia coli BL21(DE3)中的表达及重组菌的细胞固定化

分别利用IPTG和乳糖两种诱导物诱导蔗糖异构酶(SIase)基因在E.coliBL21(DE3)中实现表达,对诱导温度、诱导时机、诱导物浓度、诱导持续时间进行比较分析并优化,确定了二者的最佳诱导条件,在E.coli培养3h后(OD600约为0.9)添加终浓度为0.8mmol/L的IPTG(0.5mmol/L乳糖)在20℃(24℃)条件下诱导14h(12h)能获得最高的蛋白表达量及SIase酶活。在最优条件下以IPTG为诱导物时目的蛋白占总蛋白的41.6%,单位体积培养液中SIase酶活为12.37U/mL,以乳糖为诱导物时分别为27.2%,14.72U/mL,从收获酶活角度考虑可见乳糖作为诱导物的优势;而后利用海藻酸钠包埋法固定化重组菌,转化初始浓度为500g/L的蔗糖溶液,转化10～11h后异麦芽酮糖平均得率在83%以上,蔗糖平均转化率大于99%,固定化细胞能够连续稳定转化25批次,转化效率相对于原始菌提高了近55%。     

麦芽糖酯的合成及分析

本实验首次以麦芽糖浆为原料微乳化法合成麦芽糖酯,以酯得率为考察目标,主要探讨了反应过程中时间、温度、反应物配比等因素的影响,并对产品的理化性质作初步分析。     

液相色谱-示差折光法测定蜂蜜中果糖、葡萄糖、蔗糖、麦芽糖的改进研究

实验对反相高效液相色谱示差折光检测法测定蜂蜜中的果糖、葡萄糖、蔗糖、麦芽糖的方法进行了探讨.结果表明,均匀称取约5g蜂蜜样品,用乙腈+水(40∶60)稀释定容至100mL,既有效地提取蜂蜜中糖类物质,又确保与标准工作溶液的稀释液相对一致性,且稳定性高,重复性好.经过测试10种不同产地的蜂蜜样品,溶解时均无出现分层现象.     

Lactose crystallization delay in model infant foods made with lactose, beta-lactoglobulin, and starch

Handling and storage alter infant food powders due to lactose crystallization and interactions among components. Model infant foods were prepared by colyophilization of lactose, β-lactoglobulin (β-LG), and gelatinized starch. A mixture design was used to define the percentage of each mixture component to simulate a wide range of infant food powders. The kinetics of crystallization was studied by a gravimetric method (dynamic vapor sorption) at 70% relative humidity (RH). After freeze-drying, lactose was amorphous and crystallized at 70% RH. The delay before crystallization depends on the contents of β-LG and starch in the formulations. A mathematical model was proposed to predict crystallization time (delay) at 70% RH. For the formulation containing 50% lactose, 25% β-LG, and 25% starch, lactose was still amorphous after 42 h at 70% RH, whereas pure amorphous lactose crystallized after approximately 70 min. Calculated and experimental results of adsorbed moisture from the formulations were compared. Adsorbed water of formulation containing lactose could not be calculated from moisture sorption properties of each component at a given RH because β-LG and gelatinized starch prevented lactose crystal growth.     

麦芽糖纳米银的制备及其对棉织物的改性研究

制备了麦芽糖纳米银溶液,利用激光粒度仪(HPPS)和透射电镜(TEM)考察了麦芽糖纳米银的尺寸及分布。用制备的麦芽糖纳米银溶液对棉织物进行整理,研究了织物的白度、抗菌性能和耐洗性能。结果表明,生成的麦芽糖纳米银的平均粒径在20nm左右,且分散性和均匀性好;抗菌实验表明整理后的棉织物具有很好的抗菌效果。经50次洗涤后,抑菌率在98%以上,说明织物具有优异的抗菌耐洗性。