明胶的汞盐不沉淀现象及其在乳明胶检测中的应用研究

采用苦味酸对明胶的高效沉淀作用构建了两步沉淀检测乳明胶的方法.用苦味酸对系列浓度的明胶掺假乳进行了检测,获知该方法的检测敏感度高220 mg/dL,满足日常检测要求.依据以上结论组装了便携式乳明胶检测试剂盒,其试剂稳定,结果可靠,可以推广应用.     

明胶吸附单宁酸的机理探讨及其在蓝莓汁脱涩中的应用

分别用0.01～0.11 g的明胶吸附25 mL 900 mg/L单宁酸模拟溶液,根据明胶吸附量和单宁酸去除率得到明胶的最佳用量,然后研究最佳用量的明胶对25 mL 900 mg/L单宁酸模拟溶液的吸附动力学方程和吸附等温线方程,最后研究明胶对单宁酸质量浓度为900 mg/L的25 mL蓝莓汁的脱涩效果。结果表明：吸附25 mL 900 mg/L单宁酸模拟溶液时,明胶最佳用量为0.03 g,其明胶吸附量为527.5 mg/g,单宁酸去除率为70.33%。明胶吸附单宁酸的过程符合准二级动力学方程,其吸附等温线符合Langmuir吸附方程,为单分子层吸附。当脱除单宁酸含量为900 mg/L的25 mL蓝莓汁的涩味时,明胶用量0.03 g、温度15 ℃、振荡时间20 min,在该条件下,其明胶吸附量为420.8 mg/g,单宁酸去除率为56.11%,脱涩效果良好。     

雪莲果果粒果汁饮料生产关键技术

对雪莲果果粒果汁饮料生产中的护色、产品配方确定及稳定剂选择等关键技术进行研究。采用单因素试验、正交试验及对比试验分别确定复合护色剂的最优配比、产品配方及复合稳定剂的比例和用量。结果表明：复合护色剂的最优配比为VC 0.20g/100mL、柠檬酸0.20g/100mL、Na2SO3 0.15g/100mL;雪莲果果粒果汁饮料最优配方为雪莲果原汁用量25.0g/100mL、雪莲果粒用量6.0g/100mL、柠檬酸用量0.15g/100mL、蔗糖用量7.0g/100mL;复合稳定剂组成为卡拉胶:明胶＝1:2,用量0.25g/100mL。     

高效液相色谱检测乳制品中的乳铁蛋白含量

目的：借助高效液相色谱法测定乳制品中乳铁蛋白。方法：先通过额外加入的二价铁离子使乳铁蛋白的构型更利于沉淀。然后用体积分数60% 乙醇溶液沉淀蛋白除去糖分,再用醋酸盐缓冲液提取乳铁蛋白并分离掉酪蛋白,最后用高效液相色谱检测,采用LiChrosorb RP-C18 色谱柱,在质量浓度0.1g/100mL 的三氟乙酸溶液协助下,甲醇与水线性梯度洗脱。结果：乳铁蛋白的线性范围是0.4～2mg/mL(R2=0.9980),平均回收率95.4%。结论：此方法可以用于乳制品中乳铁蛋白的测定。     

原料乳及乳粉中水解蛋白掺假检测方法的改进

为了监控原料奶和奶粉中是否掺有水解蛋白,采用人为添加水解蛋白到原料乳和奶粉中的方法,使用硝酸汞沉淀除去乳酪蛋白,其中水解蛋白不会被除去,与饱和苦味酸产生沉淀反应的方法进行准确性和检出限的验证,对原料乳和奶粉中水解蛋白检测方法进行改进,满足对阳性样品的分级判定。该方法对原料乳的最低检出量0．05％,对奶粉的最低检出量为0．5％。     

茚三酮比色法测定湘西腊肉甘氨酸含量

利用氨基酸与茚三酮反应显色的原理,建立了茚三酮比色法测定湘西腊肉中甘氨酸含量。方法优化了溶液pH、显色剂用量、乙醇用量、加热温度、加热时间和冷却时间对茚三酮比色法定量检测甘氨酸的影响。结果表明,样品前处理最优条件为:溶液pH值7.0,显色剂用量2.0 mL,乙醇用量5.0 mL,水浴温度和时间分别100℃、 15 min,冷却时间10 min。以甘氨酸为标准溶液,在568 nm波长下测定样品溶液的吸光度,根据朗伯-比尔定律计算样品中甘氨酸含量。甘氨酸测定的线性范围为0.14 ug/mL～50 ug/mL,检出限为0.14 ug/mL,线性相关系数达0.999 4。甘氨酸的加标回收率为99.1%～100.5%,测量结果的相对偏差为0.3%～1.5%(n=6)。该方法简便、廉价、快速、准确,可用于湘西腊肉甘氨酸含量的测定。     

复合澄清剂消除酿造酱油二次沉淀的探讨

利用蛋清液、明胶、蛋白酶等对酿造酱油的二次沉淀进行澄清试验，利用紫外分光光度法对处理后的酱油吸光度值进行了测定。结果表明，每100mL酱油加入2mL蛋清液，0．4mL10％的明胶液，0．1mL0．1％的酶溶液，静置4d可达到最佳澄清效果。     

罗非鱼鱼鳞明胶微胶囊化抗坏血酸的研究

以罗非鱼鱼鳞明胶为壁材,玉米油为流动相,山梨醇酐三硬脂酸酯(司盘65)为乳化剂,结合超声波技术,制备包埋抗坏血酸的微胶囊。探讨了乳化剂用量,固化时间,流动相用量,鱼鳞明胶与抗坏血酸质量比对微胶囊包埋率的影响。结果表明:1 mL含质量比为2∶1的15 mg/mL的明胶与抗坏血酸的混合液,乳化剂用量为100μL,玉米油用量为20 mL,在40℃下以0.12 g/mL谷氨酰胺转胺酶(TG酶)固化7 h,微胶囊包埋率达到89.78%,同样条件下获得的动物源明胶制备的微胶囊包埋率仅为57.3%,且该微胶囊粒径分布较为集中,平均粒径为3.57μm,证明了鱼鳞明胶对哺乳动物源明胶具有一定的可替代性。     

固定化乳酸菌发酵草莓酸奶工艺研究

研究用海藻酸钠包埋乳酸菌发酵草莓酸奶工艺.研究结果表明固定化乳酸菌发酵草莓酸奶的最佳工艺条件为:海藻酸钠溶液浓度为1.5%,含菌种脱脂乳用量为6mL/100mL海藻酸钠溶液,胶珠的添加量为100mL海藻酸钠溶液/100 mL草莓奶液,胶珠直径为2 mm～3 mm,培养温度为40℃,白砂糖添加量为10%,草莓浆添加量15%.连续发酵结果表明固定化乳酸菌发酵草莓酸奶可连续使用10次.     

钙型糖柱—高效液相色谱—蒸发光散射检测器法测定牛乳中的乳糖

目的：实现牛乳中乳糖含量快速检测。方法：建立基于钙型糖柱和高效液相色谱测定牛乳中乳糖的新方法。牛乳通过0.2 g/mL三氯乙酸溶液沉淀蛋白质，所得滤液稀释100倍并过滤膜后进入高效液相色谱系统，经过钙型糖柱分离，蒸发光散射检测器进行检测。结果：乳糖在线性范围（20～100 mg/L）内，色谱峰面积和质量浓度之间具有较好的相关性，R²为0.999 8。乳糖加标水平为15，40，80 mg/g时，回收率为90.96%～98.23%，检出限为3.6 μg/g，定量限为12 μg/g，在6 min内实现乳糖浓度的测定。并且用该方法测定11种市售乳样品，测得结果与国标（GB 5009.8—2016）法基本一致。结论：该方法的精密度、重复性、加标回收率均符合有关规定，检测结果准确且耗时短，适用于快速检测牛乳中的乳糖含量。     

用SDS滴定奶粉中蛋白质的实验研究

目的:研究用十二烷基硫酸钠(sodium dodecyl sulfate,SDS)快速测定奶粉中蛋白质含量的实验条件。方法:一定量的奶粉用蒸馏水溶解后,在一定介质中用0.1000%的SDS溶液滴定,当被滴定溶液析出凝乳状的白色沉淀时,即为终点。研究了温度、pH值及奶粉中淀粉、蔗糖含量对测定的影响,确定了SDS溶液的滴定量与蛋白质含量的关系。结果:用该方法对同一奶粉测定8次,RSD=0.53%,用本法和凯氏定氮法对8份不同奶粉中的蛋白质含量测定,结果无显著性差异(p>0.05)。结论:该方法简便、准确、可靠,适合于奶粉中蛋白质的快速检测,检验一个样品仅仅用4min。     

Elimination of matrix effects in the determination of bisphenol A in milk by solid-phase microextraction-high-performance liquid chromatography.

Solid-phase microextraction coupled to high-performance liquid chromatography (SPME-HPLC) with fluorescence detection was employed to determine bisphenol A (BPA) in milk samples. The potential influence of the milk matrix on the determination of BPA by SPME-HPLC were investigated. Optimal conditions to eliminate any matrix effects were as follows: milk samples were deproteinized with trichloroacetic acid, diluted 20-fold with BPA-free Ultrapure water, dissolved in methanol, the precipitated protein was filtered out, rinsed with methanol and evaporated to remove the methanol. Then, a 40.0-ml solution was used for SPME extraction and HPLC analysis. Satisfactory recoveries (milk: 93.1-101%; soybean milk: 93.9-102%) were achieved. The proposed method was successfully applied to real samples, BPA being detected within the range 1.6-2.6 ng ml(-1) in four brands of commercial milk but not in soybean milk.     

Elimination of matrix effects in the determination of bisphenol A in milk by solid-phase microextraction-high-performance liquid chromatography

Solid-phase microextraction coupled to high-performance liquid chromatography (SPME-HPLC) with fluorescence detection was employed to determine bisphenol A (BPA) in milk samples. The potential influence of the milk matrix on the determination of BPA by SPME-HPLC were investigated. Optimal conditions to eliminate any matrix effects were as follows: milk samples were deproteinized with trichloroacetic acid, diluted 20-fold with BPA-free Ultrapure water, dissolved in methanol, the precipitated protein was filtered out, rinsed with methanol and evaporated to remove the methanol. Then, a 40.0-ml solution was used for SPME extraction and HPLC analysis. Satisfactory recoveries (milk: 93.1-101%; soybean milk: 93.9-102%) were achieved. The proposed method was successfully applied to real samples, BPA being detected within the range 1.6-2.6 ng ml(-1) in four brands of commercial milk but not in soybean milk.     

反相高效液相色谱法快速测定乳铁蛋白含量

目的建立一种反相高效液相色谱法(RP-HPLC)快速测定乳铁蛋白在乳原料及乳制品中含量的方法。方法根据酪蛋白在等电点(p H 4.6)凝聚沉淀特点,采用RP-HPLC法,用p H4.6醋酸盐缓冲液溶解分离乳铁蛋白,用C18色谱柱快速分离,用流动相A为0.1%三氟乙酸水溶液,流动相B为含有0.09%(V:V)三氟乙酸的90%(V:V)乙腈水溶液,进行梯度洗脱,检测波长214 nm,流速0.7 m L/min。结果乳铁蛋白在10~500 mg/L之间呈现良好的线性,相关系数为0.9999,平均回收率为98.0%,RSD=0.8%(n=9)。结论该方法推广性高、快速,简便、准确,可用于乳铁蛋白原料、奶粉、牛奶及保健品等中乳铁蛋白的含量检测。     

MALDI-TOF质谱法分析与鉴定骆驼乳中的磷酸肽

建立一种基于基质辅助激光解吸电离-飞行时间质谱（MALDI-TOF MS）为基础的方法检测并鉴定骆驼乳中的磷酸化肽段。通过商品化的二氧化钛（Ti O₂）材料富集驼乳中低丰度的磷酸肽,并优化出Ti O₂富集材料与驼乳中磷酸肽相互作用最适宜的吸附洗脱条件,孵育缓冲液:乙腈/水（50∶50,v/v）+1%三氟乙酸,洗脱液为10%氨水。再将得到的磷酸肽溶液用MALDI-TOF MS方法检测,用Mascot数据库进行数据检索,能够从驼乳中鉴定出四个磷酸化肽段。本研究为不同哺乳动物乳中磷酸化肽段的检测提供了一些新的思路且能够应用于掺假乳的鉴别。      

释放剂对火焰原子吸收光谱法测定乳粉中镁的影响

目的:分析释放剂的加入对火焰原子吸收光谱法(FAAS)测定乳粉中镁含量的影响。方法:向经微波消解法预处理的乳粉中分别加入2%硝酸溶液、镧溶液和锶溶液,然后采用FAAS测定乳粉中的镁含量,并与电感耦合等离子体原子发射光谱法(ICP-AES)的检测结果进行比较。结果:释放剂的加入可以有效提高FAAS测定的准确性,尤其是以镧溶液作为释放剂时,RSD在1.6%~2.0%之间,回收率在97.7%~102.3%之间,FAAS测定的镁含量与ICP-AES的检测结果一致。结论:采用FAAS测定乳粉中的镁含量时,加入镧溶液为释放剂,结果更加准确可靠。     

Elimination of matrix effects in the determination of bisphenol A in milk by solid-phase microextraction–high-performance liquid chromatography

Solid-phase microextraction coupled to high-performance liquid chromatography (SPME–HPLC) with fluorescence detection was employed to determine bisphenol A (BPA) in milk samples. The potential influence of the milk matrix on the determination of BPA by SPME–HPLC were investigated. Optimal conditions to eliminate any matrix effects were as follows: milk samples were deproteinized with trichloroacetic acid, diluted 20-fold with BPA-free Ultrapure water, dissolved in methanol, the precipitated protein was filtered out, rinsed with methanol and evaporated to remove the methanol. Then, a 40.0-ml solution was used for SPME extraction and HPLC analysis. Satisfactory recoveries (milk: 93.1–101%; soybean milk: 93.9–102%) were achieved. The proposed method was successfully applied to real samples, BPA being detected within the range 1.6–2.6 ng ml^?1 in four brands of commercial milk but not in soybean milk.     

微孔板式微生物法测定婴幼儿配方乳粉中泛酸含量

目的：通过对国标微生物法的改进,采用微孔板的方法对婴幼儿配方乳粉中泛酸的含量进行测定研究。方法：采用国标微生物法的改进方法-微孔板法,将合适浓度的植物乳杆菌液接种至含有试样液与培养液的无菌微孔板中,培养一定时间后测定吸光度值,根据泛酸含量与吸光度值的标准曲线计算出试样中泛酸的含量。通过精密度实验、准确度实验、加标回收实验对此方法进行评价。 结果：实验室所采用微孔板式微生物法的标准曲线线性良好,相关系数r=0.9965,精密度实验的相对标准偏差RSD为1.90%-5.32,准确度实验结果表明质控样品的泛酸含量各平行检测值均在定量值范围内,且平均值为6.91mg/100g,测定值结果间RSD为1.08%,回收率为89.7%-108.2%,说明方法精密度较高,对样品检测结果准确性较高,方法的系统误差小。结论: 采用的国标物法改进的微孔板式微生物法操作简便、结果准确、能够降低工作量,提高工作效率,能够应用于实验室对婴幼儿配方乳粉中泛酸含量的测定。     

Automated determination of oxytetracycline residues in muscle, liver, milk and egg by on-line dialysis and post-column reaction detection HPLC.

An automated method for control of oxytetracycline (OTC) residues in chicken and bovine muscle, salmon liver, bovine milk and hen egg has been developed. Tissue homogenate, decreamed milk or whole egg solution was dialysed and the dialysate enriched on a small polystyrene column on-line to HPLC. OTC and the internal standard (tetracycline) were separated on a polystyrene column by ion-pair chromatography. The column effluent was mixed with sodium hydroxide and irradiated at 366 nm. Monitoring the resulting derivatives with a fluorescence detector (excitation: 358 nm, emission: 460 nm), OTC could be detected at 1 ng/ml in milk, 1 ng/g in egg, 3-4 ng/g in muscle and 8 ng/g in liver. Relative standard deviations at 50 and 200 ng/g (milk: 20 and 100 ng/ml) ranged from 1.6 to 3.1%.     

Determination of calcium and phosphorus in milk

A fast, accurate method for determining Ca and P in milk was developed. A 1-ml samples of milk was ashed without pre-drying for 1 h and the diluted HCl extract was used for the determination of Ca by atomic absorption spectroscopy and P by colorimetry with measurement of the phosphomolybdenum blue complex at 880 nm for maximum sensitivity. Results were in good agreement with those found for 2 h ashing with or without the preliminary step for evaporating to dryness prior to ashing. Recovery ranged fiom 101.3 to 102.0% for Ca and 99.1 to 100.1 % for P when 1 ml sample of milk was spiked with a 1-ml aliquot of a CaHPO₄ standard solution and analysed by the method. The method had a precision of approximately 1.0 % coeficient of variation for both Ca and P in milk and in the CaHPO₄ standard solution.