Verifying the geographical origin of poultry: The application of stable isotope and trace element (SITE) analysis

Stable isotope and elemental analysis, together with statistical processing of the resultant data has been used to determine the geographical origin of poultry and hence provide a means to verify poultry labels originating from major producing countries/regions. Multivariate statistical analysis has demonstrated that 18 variables, including carbon, hydrogen and nitrogen stable isotope ratios and elemental concentrations of magnesium, thallium, rubidium and molybdenum, are important parameters in poultry origin determination. Using cross-validated discriminant analysis 88.3% of poultry geographical origins were correctly classified (n = 339). Individual correct-classification rates were as follows; China, 100% (n = 36); Brazil, 94.1% (n = 101); Europe 92% (n = 87); Chile 82.6% (n = 46); Thailand, 70.3% (n = 46) and Argentina 50% (n = 10). The main identification errors were associated with miss-classification of Argentinean samples with those originating from Chile and Thailand. Carbon stable isotope ratios of chicken meat indicate the quantity of maize in the diet and this leads to useful discrimination between a large proportion of European poultry and poultry reared in locations such as South America, Thailand and China where maize feeding predominates. The use of poultry carbon isotope values as a simple ‘screening’ parameter to differentiate European poultry meat from other major importers is not as reliable as for the differentiation of European and South American beef. However carbon isotope ratios will be useful in most instances to corroborate suspicion of mislabelling of non corn-fed European poultry. The stable isotopes of hydrogen and oxygen in chicken meat change in a similar way to surface waters around the globe. Our findings support the hypothesis that the global isotopic variation of stable isotopes in drinking water and feed are transferred into animal tissue and can be used to help establish an animal's geographic origin. This is a significant finding and mirrors our observations for beef skeletal muscle δ²H ‰ and δ¹⁸O ‰ values. These systematic variations can be exploited to give a ‘low-resolution’ indication of an animal's geographic origin (e.g. Northern Europe versus the tropics).     

Review of the current methods of analytical traceability allowing determination of the origin of foodstuffs

Modern analytical techniques, in particular molecular biology techniques, can determine the plant or animal species present in a foodstuff. It is actually very difficult to determine the geographical origin of a food. The new European regulation 178/2002, applicable on January 1st, 2005 imposes this requirement for the traceability of food. This article gives a progress report on the physicochemical and microbiological analytical techniques available which make it possible to determine the origin of a food with some precision.     

基于电化学适体传感器的一步法快速检测 赭曲霉毒素A

目的构建一种基于目标物诱导核酸适配体构象变换的电化学传感器一步法快速灵敏检测赭曲霉毒素A(ochratoxinA,OTA)的含量。方法适配体一端标有巯基,另一端标有羧基二茂铁,通过Au-S共价作用将适配体固定到电极表面;当加入目标分子OTA时,引起构象变换,使二茂铁远离电极表面,电信号降低。结果OTA与核酸适配体最佳作用时间为20 min。在0.1~100 ng/mL浓度范围内,传感器产生的电信号和OTA浓度的对数呈线性关系,相关系数R~2为0.9908,检测下限达0.08 ng/mL。在5、10和50 ng/mL 3个浓度加标水平下,OTA回收率为89.2%~106.9%。选用含10%异丙醇的PBS(pH 7.4)缓冲溶液清洗反应电极并连续使用8次,测定OTA的相对标准偏差为4.2%,说明该传感器可再生重复使用。结论该传感器具有较高的灵敏度和选择性,操作简单、样品消耗少、易实现阵列化检测和仪器微型化,可用于OTA污染的农产品的检测。     

基于Fe3+催化荧光增强的抗坏血酸检测

目的建立了一种基于Fe~(3+)催化的荧光增强的传感平台用于抗坏血酸的灵敏检测。方法抗坏血酸可以和邻苯二胺反应生成一种具有π键共轭结构的氮杂环的荧光化合物,从而实现检测抗坏血酸;Fe~(2+)能够加速上述反应的进程。结果在0.2~1.7 mmol/L浓度范围内,体系荧光信号和抗坏血酸浓度成线性关系,相关系数r=0.997,检测限为0.35μmol/L。此外,常见的干扰物不影响抗坏血酸的选择性测定。结论该方法具有较高的灵敏度,低廉的成本和简便的操作步骤,并且易于实现定量分析。     

Determining the geographic origin of milk in Australasia using multi-element stable isotope ratio analysis

A pilot study was conducted to evaluate the suitability of multi-element isotope ratio analysis for determining the origin of cows’ milk produced within Australasia. A milk sample from pasture-fed cows was obtained from seven dairying regions in Australia and New Zealand and analysed for the ratios of ¹³C/¹²C, ¹⁵N/¹⁴N, ¹⁸O/¹⁶O, ³⁴S/³²S, and ⁸⁷Sr/⁸⁶Sr. Each milk sample displayed a distinct isotopic fingerprint. Isotope ratios for ¹⁸O/¹⁶O and ¹³C/¹²C, in particular, conformed to predicted isotope fractionation patterns based on the latitude and climate of each region. Relative to skim milk, casein was enriched in ¹³C and ¹⁵N, and depleted of ³⁴S, whereas, predictably, ⁸⁷Sr/⁸⁶Sr ratios remained equivalent in both skim milk and casein. The milk samples from Australasia were considerably enriched in ¹⁸O and ³⁴S compared with reported values for most European dairy products. Overall, multi-element isotopic analysis has good potential for determining the geographic origin of dairy products produced within Australasia.     

核酸适体分子信标探针用于三磷酸腺苷的 选择性检测

目的构建一种基于分子信标与核酸适体的荧光传感器,用于三磷酸腺苷分子的选择性检测。方法将三磷酸腺苷的核酸适体序列与分子信标结合形成新的荧光探针,利用腺苷和分子信标互补DNA的竞争,引发分子信标的构型转换,从而产生可检测的荧光响应信号实现检测腺苷的目的。结果荧光响应信号随着腺苷浓度的增加而减弱。在3.70×10~(-6)~5.56×10~(-4)mol/L的浓度范围内,腺苷浓度的对数和响应信号成线性关系,相关系数为0.9974。加标回收率为92.0%~110.0%,相对标准偏差为0.68%~1.85%(n=3)。结论该方法耗时较少、步骤简单,可满足当前生化分析快速而精确的分析要求。     

基于荧光探针的汞离子检测方法研究

目的建立基于荧光探针的汞离子快速检测方法。方法基于汞离子促进硫羰基脱硫的不可逆反应,设计合成了含有双硫羰基的荧光探针HgP1。通过紫外-可见光谱法和荧光光谱法研究了探针HgP1在甲醇水溶液中对金属离子的识别特性,并探讨了其识别机制。结果探针HgP1对Hg~(2+)具有高效专一的选择性,具有较强的抗金属阳离子和阴离子干扰能力,并能通过溶液颜色变化实现对汞离子的裸眼识别。Hg~(2+)浓度在0.01~0.1μmol/L范围内与该探针溶液荧光发射强度值间呈良好的线性关系(R~2=0.988),该方法对汞离子的最低检测限为0.256μg/kg。结论 HgP1探针对汞离子具有高效专一的选择性,其最低检测限满足国家标准对食品中汞离子的限量要求,具备较强的实际应用价值。     

基于自由基反应荧光增强的葡萄糖检测

目的建立一种基于自由基反应荧光增强的葡萄糖检测方法。方法葡萄糖分子被葡萄糖氧化酶氧化,酶反应产物H_2O_2和Fe~(3+)一起组成Fenton试剂,Fe~(3+)催化H_2O_2产生羟基自由基,催化产物迅速的和OPDA反应生成一种荧光低聚物并产生增强的荧光信号,实现葡萄糖的间接检测。结果在0.20~12.50 mmol/L浓度范围内,荧光强度和葡萄糖浓度呈线性关系,相关系数r=0.98,检测限为25μmol/L。结论该方法具有较高的灵敏度和简便的操作步骤,并且易于实现定量分析。