在线捕集分离联用技术对食品调料中砷形态分析方法研究

成功建立了冷捕集-气相色谱-氢化物发生-原子荧光光谱分析测定食品调料(酱油和醋)中砷形态的方法。以脱脂棉为分离介质,用液氮对样品中生成的气态砷化合物进行冷捕集,常温下不同砷形态化合物即可以实现基线分离,随后被原子荧光光谱检测。实验考查了酸介质的种类和酸度、KBH₄溶液的浓度、反应时间以及载气(He)的流量等实验条件对测定结果的影响。结果表明,在优化后的实验条件下,方法对As(Ⅲ),As(Ⅴ),MMA(Ⅴ)和DMA(Ⅴ)的检出限分别为0.2,0.2,0.3,0.8 ng·mL-1,对酱油和醋As(Ⅲ),As(Ⅴ),MMA(Ⅴ)和DMA(Ⅴ)的回收率为93.07%～103.54%。与传统的液相色谱分离方法相比,该方法不用对样品进行特殊前处理,分析速度快,灵敏度高,适合于对食品调料中砷形态尤其是无机砷形态的准确、快速分析测定。     

近红外分析技术在食品氨基酸检测中应用的研究进展

综述了近红外分析技术在农作物生长及食品加工处理过程中氨基酸检测的应用情况,及其研究进展。对近红外分析食品氨基酸应用中涉及的化学值HPLC检测以及化学计量学方法进行总结,对相关原始文献中的数据、资料和主要观点进行整理和归纳。对氨基酸的HPLC、化学计量学分析方法及其在农作物品质监测、茶叶中氨基酸和茶多酚含量的同时测定、饲料品质鉴定、奶酪火腿肉制品中氨基酸及其他化学成分含量的测定情况进行了综述,分析了方法的优缺点并对近红外分析技术在食品氨基酸检测中应用进行了展望。近红外光谱在氨基酸检测中应用的发展需基于氨基酸高效液相色谱检测的化学值来建立相应的模型,模型传递的问题是目前制约其大范围推广的主要原因。在线分析可以监测从原料到产品的整个反应变化过程,满足食品从生产到销售等领域中品质实时监控的需求,将是今后重要的发展方向。     

应用荧光光谱和径向基函数神经网络定量检测三聚氰胺

实验发现三聚氰胺溶液在紫外光激发下产生较强荧光,测得其荧光峰在310～600 nm之间,荧光峰值波长为420 nm左右,荧光相对强度与三聚氰胺溶液浓度呈现复杂的非线性关系。提出了采用径向基函数神经网络结合荧光光谱对三聚氰胺溶液浓度进行测定的方法。对每个样本选取30个发射波长值所对应的荧光强度作为网络数据,训练、建立了径向基函数神经网络。应用训练好的径向基函数神经网络,对5种三聚氰胺溶液的浓度进行预测,结果相对误差分别为0.93%,0.09%,0.31%,1.55%,4.61%。该方法能快捷、准确地测定三聚氰胺在溶液中的含量,为三聚氰胺检测及食品安全监管提供了一种新方法。     

An improved method of simultaneous determination of lutein and zeaxanthin in food

Based on an official standard method of lutein analysis, an improved high performance liquid chromatography (HPLC) method for simultaneously detecting lutein and zeaxanthin was developed as focusing on the sample preparation protocol. The optimal pretreatment conditions included a saponification in a water bath for 15?min at a constant temperature of 50?°C, using a 10?mL 60% (w/v) potassium hydroxide solution, followed by extraction using 100?mL mixture of n-hexane, ethyl ether and cyclohexane (40: 40: 20, v/v/v). A mixture of dichloromethane, acetonitrile and methanol (20: 30: 50, v/v/v) was validated to elute lutein and zeaxanthin on a C₃₀ column (4.6?×?250?mm, 5?µm). The resolution between lutein and zeaxanthin is ≥2.5. A millet sample was used for methodological verification and the results showed that the linear relations for lutein and zeaxanthin were good in ranges of 0.23–9.37?μg/mL and 0.30–12.02?μg/mL, respectively. The relative standard deviations of lutein and zeaxanthin were 1.40% and 5.09%, respectively, and their spiked recoveries were between 86.60% and 98.75%. The lutein and zeaxanthin results from this modified HPLC method are superior to those from the Chinese official method and ultrasonic extraction method.     

二极管阵列检测-流动注射分光光度法同时测定食品中铁铜钴

目的在于建立同时测定食品中铁、铜、钴三种微量元素的新方法。以2-(5-溴-2-吡啶偶氮)-5-二乙氨基酚(5-Br-PADAP)为显色剂,Triton X-100为增敏剂,采用流动注射-CCD二极管阵列检测-分光光度分析法同时对其进行测定。优化了实验参数,并用偏最小二乘法计算程序解析重叠光谱。结果显示,铁、铜和钴的线性范围分别为0.2～10 μg·mL-1,0.1～5.0 μg·mL-1,0.01～1.0 μg·mL-1,检出限分别为：0.2,0.1,0.01 μg·mL-1,进样频率为45样·h-1。所建方法用于茶叶、芝麻、小米等食品测定时,样品加标回收率分别为铁89.4%～102.3%、铜92.2%～108.0%、钴93.2%～110.8%,相对标准偏差为1.1%～12.1%。对国家一级标准参考物质茶叶和桃叶进行测定(ｎ＝8),结果在其给出的保证值范围之内。     

傅里叶变换近红外光谱结合RVM与新聚类算法鉴别灵芝孢子油多样掺假类别

食品掺假种类众多,手段隐蔽,成为食品安全检测一个重要难题。为摆脱传统模型识别食品中是否存在新掺假类别的局限性,实验以纯净的灵芝孢子油和掺杂不同比例花生油、玉米油、薏仁油、地沟油的五种类别为研究对象,采用傅里叶变换近红外光谱(Fourier transform near infrared spectroscopy, FT-NIR)收集12 400～4 000 cm-1范围内的近红外光谱。假设掺杂地沟油为新掺假类别,利用前四种类别的校正集样本构建相关向量机(RVM)多分类器,分别对建模的预测集样本和掺杂地沟油样本进行判别,并借助新聚类算法对判别为纯净的灵芝孢子油的样本做进一步分析验证。研究表明,RVM分类器对于建模的预测集样本判别准确率高达93.75%,说明模型有较强的判别能力,但由于模型局限性,掺杂地沟油样品被误判为纯净的灵芝孢子油;在新聚类算法的决策图上,纯净灵芝孢子油校正集和预测集混合样本的聚类中心数为1,而纯净灵芝孢子油校正集和掺杂了地沟油混合样本聚类中心数为2,直观验证判别结果的准确性。结果表明利用FT-NIR技术结合RVM分类器与新聚类算法对于灵芝孢子油掺假能够有效识别,并且能够定性识别新型掺假类型,为解决食品掺假多样化问题提供一种新思路。     

Stir bar sorptive extraction-gas chromatography-mass spectrometry analysis of tetramethylene disulfotetramine in food: Method development and comparison to solid-phase microextraction

A stir bar sorptive extraction-gas chromatography-mass spectrometry (SBSE-GC-MS) method for the determination of tetramethylene disulfotetramine is presented. The limits of detection (LOD) of the optimized method was 0.2 ng g⁻¹ for extractions from water and 0.3-2.1 ng g⁻¹ for extractions from foods. Recovery was highly matrix dependent (36-130%) and quantification required standard addition calibrations. Standard addition calibration lines had high linearity (R² > 0.97) and replicate extractions had good reproducibility (R.S.D. = 4.4-9.8%). A comparison of the SBSE method and a previously developed headspace (HS)-solid-phase microextraction (SPME) method was performed. Generally, SBSE provided higher sensitivity with decreased analysis time.     

快速去除硝酸和亚硝酸对氢化物发生原子荧光法测定砷的干扰

为了避免繁琐、耗时的"赶酸"操作, 研究了尿素结合NaOH除去微波消解液中过量的HNO3和HNO2的干扰,继用L-半胱氨酸在低酸度下将As(Ⅴ)还原为As(Ⅲ)的样品消化和预还原方法.用氢化物发生-原子荧光法准确、快速地测定了食品中痕量砷.该方法的检出限为0.03 μg/L;连续11次测定4 μg/L As(Ⅲ)标准溶液的相对标准偏差为1.6%; 测定国家标准物质的结果与标准值非常吻合.     

Centurion — a revolutionary irradiator

The facility characteristics for irradiation of red meat and poultry differ significantly from those of medical disposables. This paper presents the results of the market requirement definition which resulted in an innovative conceptual design. The process and the “state of the art tools” used to bring this abstract idea into a proof of concept are presented.     

New Aspects of the Maillard Reaction in Foods and in the Human Body

The reactions that occur during the cooking, baking, and preservation of foods of all kinds are of great importance for the production of aroma, taste, and color. However, more recently it has been shown that these reactions may be accompanied by a reduction in nutritive value and the formation of toxic compounds. For these reasons, the very complex reactions between reducing sugars and the free amino groups of amino acids or proteins, known as non-enzymatic browning or the Maillard reaction, have again caught the interest of chemists. The Maillard reaction came to be seen in a new light as it was realized that it actually occurred in the human body. As a general rule, the longer the half-life of a protein, the larger the amount of its Maillard products found, i.e., important factors are the ‘age’ or persistence of the protein in the body and the glucose concentration, particularly in diabetics. Many of the symptoms developed by diabetics resemble those of premature aging, which leads to the possibility that glucose, because of its reactivity towards proteins, is fundamentally involved in the normally slow progress of aging.