快速酯交换法测定不饱和脂肪酸含量的改进

目的解决目前国家标准中采用的快速酯交换法测定甘油酯型鱼油产品中不饱和脂肪酸含量偏低的问题。方法改进的方法是将试样用正己烷溶解后,以氢氧化钾-甲醇酯交换反应进行甲酯化,酯交换溶液用水洗至中性,气相色谱进行检测。结果4种主要不饱和脂肪酸的结果都在其标示值范围内。结论改进后的方法适用于鱼油产品中甘油酯型不饱和脂肪酸的测定。     

An Enzymatic Method for the Determination of Yeast Cell Wall Glucan in Foods

Processed cell wall β-glucans prepared from strains of baker's or brewer's yeast can be used as a thickening agent in aqueous food systems and they provide a fat-like mouthfeel. This article describes an analytical procedure for the determination of the glucan content added to a variety of food products. The method is based on measurement of reducing sugars produced when the food sample, after appropriate pretreatment, is treated with a commercial microbial β-glucanase (Zymolyase) that is specific for the β-linkages present in the glucan polysaccharide of the added yeast cell walls.     

A Novel Sample Preparation Method Using Rapid Nonheated Saponification Method for the Determination of Cholesterol in Emulsified Foods

Abstract: In this study, nonheated saponification was employed as a novel, rapid, and easy sample preparation method for the determination of cholesterol in emulsified foods. Cholesterol content was analyzed using gas chromatography with a flame ionization detector (GC‐FID). The cholesterol extraction method was optimized for maximum recovery from baby food and infant formula. Under these conditions, the optimum extraction solvent was 10 mL ethyl ether per 1 to 2 g sample, and the saponification solution was 0.2 mL KOH in methanol. The cholesterol content in the products was determined to be within the certified range of certified reference materials (CRMs), NIST SRM 1544 and SRM 1849. The results of the recovery test performed using spiked materials were in the range of 98.24% to 99.45% with an relative standard devitation (RSD) between 0.83% and 1.61%. This method could be used to reduce sample pretreatment time and is expected to provide an accurate determination of cholesterol in emulsified food matrices such as infant formula and baby food. Practical Application: A novel, rapid, and easy sample preparation method using nonheated saponification was developed for cholesterol detection in emulsified foods. Recovery tests of CRMs were satisfactory, and the recoveries of spiked materials were accurate and precise. This method was effective and decreased the time required for analysis by 5‐fold compared to the official method.     

基于多壁碳纳米管免疫传感器法快速测定食品中的莱克多巴胺

以改性壳聚糖包埋固定羧基化多壁碳纳米管和莱克多巴胺抗体,构建免疫传感器用于莱克多巴胺的检测。以K3[Fe(CN)6]为探针,利用循环伏安法表征传感器构建过程和差分脉冲伏安法探究莱克多巴胺抗体/抗原间免疫反应对电流的影响。结果表明,在优化条件下,免疫响应电流与溶液中莱克多巴胺质量浓度的立方根在0.05～4.05 ng/mL范围内呈线性关系,其线性方程为Ip=－4.524 4CRAC1/3＋14.259（R2= 0.990 4 ）,最低检测限为0.08 ng/mL（RSN=3）;所构建的免疫传感器的特异性、稳定性和重复性良好。该法对猪肉、羊肉等样品进行检测,其检测结果与国标方法高效液相色谱法一致,检测快捷方便,可用于食品中莱克多巴胺的快速检测。     

A Rapid and Simple Method for the Determination of 2-Alkylcyclobutanones in Irradiated Meat and Processed Foods

A rapid and simple method has been developed for the determination of 2-alkylcyclobutanone, 2-dodecylcyclobutanone (DCB), and 2-tetradecylcyclobutanone (TCB) in irradiated meat and processed foods. The procedure consists of extraction with n-hexane, following defatting and cleanup with a silica gel mini-column before gas chromatograph–mass spectrometry analysis. The method was evaluated using samples of beef, pork, Parmesan cheese, fried chicken, hamburger, gyoza (Chinese dumplings), and gyudon (boiled beef and onion seasoned with soy sauce and sugar). The recoveries of spiked DCB were 67–88 %, and those of TCB were 70–86 %. Furthermore, the method could detect DCB and TCB from samples irradiated at 1.0 and 2.6 kGy at levels dependent on dose; DCB and TCB were not detected in any nonirradiated samples. The method did not require special equipment, such as Soxhlet extraction, accelerated solvent extraction, or supercritical fluid extraction, for sample preparation. Thus, this method would be useful for determining DCB and TCB levels in irradiated meat and processed foods.     

食品中高效氯氟氰菊酯的液相色谱快速检测方法

采用高效液相色谱对饮用水、青菜两种典型食品中高效氯氟氰菊酯的定量检测。研究表明,采用丙酮-正己烷提取饮用水中高效氯氟氰菊酯、利用丙酮- 石油醚提取青菜中高效氯氟氰菊酯效果较好,液相色谱检测时以乙腈- 水(80:20,V/V)作为流动相,230nm 条件下检测峰型较好,在农药浓度为0.1 × 10-6～10 × 10-6 时,两组萃取剂的回收率分别为97.93%～103.02% 和91.4%～113.9%,相对标准偏差均小于4%。该方法操作简单、快速,能够在食品安全检测中发挥一定的积极用。     

非预包装食品中沙门氏菌快速检测方法的建立

当前沙门氏菌传统的国家标准检测方法不能满足食品安全监管高效性的需求,尤其是针对非预包装食品这种较易腐败变质的食品。研究针对非预包装食品利用聚合酶链式反应（polymerase chain reaction,PCR）分子层析方法得出一个快速、简单、准确的沙门氏菌检测方法。通过对60批普通基质食品（面食制品、乳制品、肉制品）和40批复杂基质食品（凉菜类、生鲜蛋类）模拟不同程度被沙门氏菌污染的实验,采用国标法和PCR分子层析法对比检测。结果显示：普通基质食品PCR分子层析法检测灵敏度更高,可达1 CFU/mL～10 CFU/mL的阳性菌添加浓度;复杂基质食品尤其对生鲜蛋类食品,两种检测方法的灵敏度均较低。故对沙门氏菌的增菌液进行了优化,在沙门氏菌的增菌液缓冲蛋白胨水（buffered peptone water,BPW）中添加一定比例六水氯化镁,即利用提高增菌液渗透压和降低pH值抑制其他肠道菌群的生长的原理,使其检测灵敏度提高,由104CFU/mL的阳性菌添加浓度降低至102CFU/mL的添加浓度,灵敏度提高了100倍;经特异性试验验证,PCR分子层析法具有较强的抗干扰能力,样本体系中存在其他干扰菌株的脱氧核糖核酸（deoxyribonucleic acid,DNA）亦不会影响沙门氏菌的检测。PCR分子层析法检测时间只需22 h,对比需要6 d检测时间的传统国标方法的检测效率提高6倍。     

应用流式细胞技术快速检测液态商品中的细菌总数

建立应用流式细胞技术(flowcytometry,FCM)快速检测液态商品牛奶、果汁中的细菌总数的方法。采用膜过滤、离心技术对果汁样品进行前处理,去除影响FCM检测的基质颗粒,使样品达到FCM可检测状态,检测限达到101CFU/mL数量级。对液态商品牛奶进行重复性和验证实验,检测结果经Q检验法和方差分析,在一定范围浓度下,FCM检测液态商品中的细菌总数与平板法成线性相关。FCM是一种比平板法检测细菌总数更加快速、准确的方法。     

食品中蛋白质测定方法的改进

本文对我国食品中蛋白质的测定的国家标准GB/T5009.5-2003进行了改进。即由蒸馏滴定法改为气提滴定法。研究了各种因素对气提滴定的影响。实验结果表明,改进后的新方法与GB/T5009.5-2003标准法比较,具有五大优点:(1)节能:节约电能80%以上;(2)降耗:免除了冷却水的大量消耗;(3)增效:分析速度提高1倍;(4)安全:免除了高温作业,使分析操作更为简便安全;(5)准确:吸收液不被冷凝水稀释,使滴定结果更加准确。     

食品中抗氧化剂叔丁基对苯二酚(TBHQ)的检测方法研究

建立了食用油脂、油炸食品、干鱼制品、饼干、方便面、速煮米、干果罐头、腌制肉制品等含油食品中抗氧化剂叔丁基对苯二酚(TBHQ)的气相色谱分析方法。样品经粉碎或混匀以石油醚提取油脂后,用甲醇为提取溶剂,漩涡振荡提取充分后取清液经气相色谱分离后用氢火焰离子化检测器检测,根据样品峰面积与标准峰面积比较定量。该方法对TBHQ的检出限为0.002g/kg,相关线性系数r=0.9999,线性范围为0.1mg/mL～2.5mg/mL;相对标准偏差为0.04%。     

气质联用法测定食品中特丁基对苯二酚

建立了气相色谱-质谱检测食品中的特丁基对苯二酚的检测方法。样品经乙酸乙酯提取浓缩后,再经饱和乙腈溶解,正己烷脱脂,以气质联用仪选择离子定性、定量,方法简便、快速、准确、可靠。测定低限0.05mg/kg,回收率90%～102%,相对标准偏差1.10%。     

强化淀粉类食品中7 种水溶性维生素的快速测定

建立高效液相色谱-二极管阵列-荧光联用法同时检测营养强化淀粉类食品中7 种水溶性维生素含量的方法。样品经淀粉酶60 ℃酶解45 min,调pH值提取后,经十二烷基硫酸钠（5 mmol/L,加入0.1%磷酸,三乙胺调pH 3.0）-乙腈梯度洗脱,VB1、烟酸、烟酰胺在不同波长下进行检测,VB2、吡哆醛、吡哆醇、吡哆胺采用目标物出峰时间段转变激发、发射波长检测。7 种维生素在各自线性范围内线性关系良好,相关系数r2为0.999 6～0.999 9,加标回收率为90.5%～102.5%,检出限为0.01～0.08 mg/100 g,定量限为0.025～0.26 mg/100 g。方法快速、高效,适用于大批量强化淀粉类食品中7 种水溶性维生素的同时测定。     

食品中微量硅测定方法的研究

本文采用恒温石墨炉原子吸收技术系统地研究比较了PE普通石墨管、703所热解涂层石墨管、涂锆PE普通石墨管管壁原子化测硅的灵敏度及精度差异;考察了用PE普通石墨管测硅时灰化温度、原子化温度对灵敏度的影响;试验了常用酸和盐,特别是食品中常见的一些共存物质对硅测定的干扰,并对各种食品基体的干扰性质和消除方法进行了研究;试验了氯化铵消除硝酸对石墨管寿命影响的效果。并通过采用较先进的微波消化技术,进而建立了食品中微量硅测定的快速、可靠的分析方法。其样品的最低检出浓度为0.05ug/ml;平均加标回收率为98.1±4.6％;对8种食品中硅进行重复测定,其变异系数均小于8.0％。研究结果表明,本方法能够满足食品中微量硅测定的要求。     

食品中铁测定法的研究

本文概述了食品中微量铁测定的意义、测定特点和问题。实验研究了食品中铁的比色和吸光光度的三种测定方法,就三法的灵敏度、稳定性及与比耳定律符合的程度作了比较,并用三种味精产品进行实测,得出邻二氮菲亚铁法较磺基水杨酸铁法、硫氰酸铁法为优。对邻二氮菲亚铁法,采用回归直线方程求铁含量,更加准确,简便。     

Diffusion of Glucose in Carrageenan Gels

From an experimental set-up with boundary conditions of an extended initial distribution the diffusion coefficient for glucose in a high K-content carrageenan gel was evaluated as a function of the carrageenan concentration (1, 2 and 4%) and temperature (0.0, 5.0, 10.0, 15.0, 25.0, and 36.0°C). According to an Arrhenius-type equation, the activation energies at 1, 2 and 4% of carrageenan were calculated as 18.1, 17.4, and 19.1 kJ/mol. From these data it was concluded that carrageenan affects diffusion mainly by an obstruction effect.     

快速检测牛奶中体细胞数方法的改进

为探求1种简单、快速、准确的牛奶体细胞数测定方法,将牛奶样品经表面活性剂十二烷基硫酸钠处理后,奶样中体细胞的细胞膜和核膜被破坏,细胞核DNA大量释放,引起奶样稠度发生很大的变化,可用Lamb-lewis稠度计测量其稠度的变化。通过分析缓冲液pH、处理时间、温度等条件对奶样稠度的影响,结果表明,在一恒定温度条件下,缓冲液pH7.5、处理时间15～20min时,乳样体细胞数与SDS处理后奶样稠度之间存在显著的线性关系;通过测定SDS处理后奶样的稠度,可以快速、准确地检测出其中的体细胞数。     

基于石墨烯/离子液体构建免疫传感器快速测定食品中黄曲霉毒素B1

采用壳聚糖、石墨烯和1-丁基-3-甲基咪唑基四氟硼酸盐复合膜修饰玻碳电极,包埋固定黄曲霉毒素B1（aflatoxin B1,AFB1）抗体,构建了一种免疫传感器,用于快速测定食品中的AFB1。在pH值为7.0含1 mmol/LK3[Fe(CN)6]和0.1 mmol/L KCl的磷酸盐缓冲溶液中,基于AFB1抗体与抗原之间的特异性免疫反应,以K3[Fe(CN)6]为探针,运用循环伏安法和差分脉冲伏安法研究免疫反应对传感器响应电流的影响。在优化实验条件下,免疫传感器峰电流的降低值随溶液中AFB1质量浓度对数的增大而增大,且二者在0.1～8.1 ng/mL范围内呈线性关系,其检出限为0.04 ng/mL（RSN=3）。该免疫传感器的稳定性和重复性较好,利用该法对花生和玉米油样品中AFB1进行检测,回收率为94.73%～104.41%,检测结果与高效液相色谱法基本一致,用于食品中AFB1的快速检测是可行的。     

极谱法快速测定罐头食品中的痕量铅

<正> 引言 铅是人体中有害微量元素之一,食品中铅含量的测定,对于防止铅污染具有重要意义。以往对铅的测定一般采用比色法,近年来痕量铅的导数示波极谱测定虽有报道,但尚未见应用于罐头食品分析。据此,我们进行了罐头食品中铅的导数极谱吸附波测定的试验,发现在醋酸铵—三乙醇胺—铜铁试剂底液体系中,于-0.78伏至-0.88伏之间可得到一个清晰、灵敏而稳定的铅极谱吸附波,其导数波峰电位在-0.85伏左右(对饱和甘汞电极),检测限量可达1.0×10~(-8)g/ml,试样测定结果的变异系数小于5％,回收率相对误差低于~10％,与原子吸收法进行对照,分析结果基本一致。     

Water Diffusion from a Bacterial Cell in Low‐Moisture Foods

We used a Fick's unsteady state diffusion equation to estimate the time required for a single spherical shaped bacterium (assuming Enterococcus faecium as the target microorganism) in low‐moisture foods to equilibrate with the environment. We generated water sorption isotherms of freeze‐dried E. faecium. The water activity of bacterial cells at given water content increased considerably as temperature increased from 20 to 80 °C, as observed in the sorption isotherms of bacterial cells. When the water vapor diffusion coefficient was assumed as between 10^?12 and 10^?10 m²/s for bacterial cells, the predicted equilibration times (t_eq) ranged from 8.24×10^?4 to 8.24×10^?2 s. Considering a cell membrane barrier with a lower water diffusion coefficient (10^?15 m²/s) around the bacterial cell with a water diffusion coefficient of 10^?12 m²/s, the t_eq predicted using COMSOL Multiphysics program was 3.8×10^?1 s. This result suggests that a single bacterium equilibrates rapidly (within seconds) with change in environmental humidity and temperature.     

胶体金试纸条快速检测动物源性食品中头孢氨苄残留

头孢菌素类抗生素属于第二种类型的β-内酰胺类抗生素,其在动物源性食品中的残留问题引起普遍关注。为保障食品安全,实现对食品中头孢菌素类抗生素残留的快速检测,该研究利用金纳米颗粒标记头孢氨苄(cefalexin,CEX)兔多克隆抗体作为可视化信号探针,基于硝酸纤维素膜研制一种能够检测头孢菌素类抗生素的免疫层析检测试纸。试纸条以CEX包被原为检测线,以羊抗兔二抗为质控线,对试验条件进行优化后,所构建的试纸条在缓冲液体系中对CEX、头孢拉定(cefradine,RAD)和头孢羟氨苄(cefadroxil,CFR)的检测限分别可达到20、25、25μg/L。为验证方法的实用性,将一定浓度的CEX添加至虾肉、牛奶、牛肉、猪肉、生猪肝和熟猪肝6种常见的动物源性食品中进行添加回收测定。结果显示:经过简单的样品处理,所构建的试纸条在10 min内即可实现对目标物的快速可视化检测。该方法操作简便、快速,适用于大批量动物性食品中多种头孢菌素类残留的高通量筛查。