分光光度法测定焦糖色中4-甲基咪唑

本采用分光光度法对焦糖色中4-甲基咪唑进行了定量测定，克服了传统薄层法的精密度、准确度不高的弱点。实验结果表明，4-甲基咪唑经重氮化后在波长440nm处具有最大吸收，据此进行准确定量测定，重现性好。该方法灵敏度高，其线性方程为：C=0．0717A 0．0007，线性相关系数为0．999，检出限为1．4μg，RSD为3．5N。加标回收率为96N～102％。将本法用于实际样品的测定获得满意的结果。     

Development of caramel colour with improved colour stability and reduced 4-methylimidazole

ABSTRACT

This study investigated the effect of chemical substances, such as Mg²⁺ (as magnesium sulphate), Zn²⁺ (as zinc sulphate), Fe²⁺ (as iron sulphate), ascorbic acid, and citric acid, on the formation of 4-methylimidazole (4-MI) and colour stability of caramel colour. The 4-MI concentration in the caramel colour without chemical substances was 963.10 μg/g, and this decreased the most (67.7%) with the addition of 0.1 molar ratio of citric acid. Colour stability was evaluated by measuring the total colour change (ΔE) after storage, and heating in pH 2, 4, and 7 solutions and 50% solution in ethyl alcohol. Among the chemical substances added to reduce 4-MI in the caramel colour, Mg²⁺ (0.1 molar ratio) and ascorbic acid improved the colour stability more than the others.     

顶空进样-毛细管气相色谱法检测饮料用焦糖色素中的4-甲基咪唑

建立了顶空进样-毛细管气相色谱法测定饮料用焦糖色素中4-甲基咪唑含量的方法。采用HP-5毛细管柱、氮磷检测器,溶剂为二氯甲烷,内标为N,N-二甲基苯胺。方法的线性范围为0．025μg／ml-0．295μg／ml,最低检测浓度为0．01μg/ml;回收率在99％以上,相对标准偏差在2％之内。该方法重现性好、简单、快速、准确,能满足分析检测的需要。     

Determination of 4(5)-methylimidazole in carbonated beverages by isotope-dilution liquid chromatography-tandem mass spectrometry

The purpose of this study was to develop a method to quantify 4(5)-methylimidazole (4-MEI), a suspected carcinogen, in carbonated beverages by simple sample dilution and isotope-dilution reverse-phase LC-MS/MS. Isotope dilution using hexa-deuterated methylimidazole (d₆-4-MEI) was used to quantify native 4-MEI and to assess matrix effects quantitatively. The accuracy of the method was assessed by intentionally fortifying a negative control sample at three doses: low, medium and high (replicates of n = 5 each) with a known amount of 4-MEI. The respective absolute error in each case was 18.7 ± 0.7%, 14.6 ± 2.8% and 21.1 ± 9.7%. Within-day (intra-) and day-to-day (inter-) repeatability, determined as the relative standard deviation by fortifying a negative control sample (n = 5), were 9.5% and 15.4%, respectively. Average ion suppression of d₆-4-MEI in beer was 63.9 ± 3.2%, while no suppression or enhancement was seen in non-alcoholic samples. The instrument and method limit of detection were calculated as 0.6 and 5.8 ng ml^–1, respectively. 4(5)-Methylimidazole was quantified in a variety of store-bought consumer beverages and it was found that in many of the samples tested consuming a single can of beer would result in intake levels of 4-MEI that exceed the no significant risk guideline of 29 µg day^–1. Conversely, 4-MEI in the samples was orders of magnitude smaller than the European Food Safety Authority acceptable daily intake threshold value of 100 mg kg^–1 bw day^–1.     

Analysis and risk assessment of 4(5)-methylimidazole in brown colored foods and beverages

In this study, the 4(5)-methylimidazole (4(5)-MI) levels in various 144 brown coloured foods and beverages were determined. The brown coloured foods and beverages were 62 processed sauces, 40 coffee, 9 caramel syrups, 18 red ginseng juice and 15 Japanese apricot fruit juice. The amount of 4(5)-MI in brewed coffee (1821.3 ng/g) was the highest level among the samples. The 4(5)-MI concentration in processed sauce (47.6 ng/g) was the lowest level among the samples. The levels of 4(5)-MI in various samples were found as follows: 47.6–1748.5 ng/g in processed sauces, 64.1–1821.3 ng/g in commercial coffee, 115.5–491.9 ng/g in caramel syrups, 91.0–854.1 ng/g in red ginseng juice and 137.6–587.4 ng/g in Japanese apricot fruit juice. Based on the 4(5)-MI levels, the estimated daily intake (EDI) and chronic daily intake (CDI) were calculated. EDI and CDI of red ginseng juice was the highest among all samples, and they were 1618.6 and 1256.8 ng/kg bw/day, respectively.     

A U.S. population dietary exposure assessment for 4-methylimidazole (4-MEI) from foods containing caramel colour and from formation of 4-MEI through the thermal treatment of food

ABSTRACT

4-Methylimidazole (4-MEI) is formed in caramel colours produced using ammonium compounds (Class III and Class IV caramel colours). 4-MEI can also form in food through Maillard reactions between reducing sugars and amino acids during cooking, roasting or dry-heating. The USFDA has analysed over 700 food and beverage samples collected from 2013 to 2015 for the presence of 4-MEI. These samples include foods containing added caramel colour and foods that are not labelled as containing added caramel colour, but which may contain 4-MEI resulting from thermal treatment. The 4-MEI levels in all food samples were quantified using LC-MS/MS. These data were used to develop a comprehensive dietary exposure assessment for 4-MEI for the U.S. population aged 2 years or more and several sub-populations, using two non-consecutive days of food consumption data from the combined 2009–2012 National Health and Nutrition Examination Survey and 10–14-day food consumption survey data for 2009–2012 from the NPD Group, Inc. National Eating Trends–Nutrient Intake Database. Dietary exposure estimates were prepared for each category of foods labelled as containing added caramel colour and of foods not labelled as containing added caramel colour, but which may contain 4-MEI from thermal treatment. Exposure to 4-MEI from consumption of foods containing added caramel colour was higher than that from foods that contain 4-MEI from thermal treatment for all population groups. Cola-type carbonated beverages were the highest contributors for most populations from foods containing added caramel colour. Coffee was the highest contributor for most populations from foods in which 4-MEI could be formed from thermal treatment. An overall combined exposure to 4-MEI was also estimated that included all foods identified as containing added caramel colour and foods in which 4-MEI could be formed by thermal treatment.     

Dietary intake assessment of caramel colours and their processing by-products 4-methylimidazole and 2-acetyl-4-tetrahydroxy-butylimidazole for the Chinese population

ABSTRACT

The aim of the study was to assess the dietary intake of caramel colours and their by-products 4-methylimidazole (4-MEI) and 2-acetyl-4-tetrahydroxybutylimidazole (THI) for the Chinese population. Based on the typical and maximum reported use levels of caramel colours in 15 food categories, the dietary intakes of combined and single-class caramel colours of Classes I, III and IV were estimated with the food consumption data from the China National Nutrient and Health Survey. Using the mean values of 4-MEI and THI contents in Class III and Class IV Caramel colour samples, the exposures to 4-MEI and THI from dietary caramel colours were derived. The results showed that the combined and individual average dietary caramel colour intakes for the Chinese population of different age groups were estimated to be 232–60.3 mg kg^?1 bw day^?1 for combined caramels, 5.9–29.2 mg kg^?1 bw day^?1 for Class I, 7.7–29.6 mg kg^?1 bw day^?1 for Class III, 21.2–54.3 mg kg^?1 bw day^?1 for Class IV, which were far below the group acceptable daily intake (ADI) and respective ADIs. The combined intake of 4-MEI from Class III and IV caramel colours was estimated to be 3.8–5.2 μg kg^?1 bw day^?1 on average, and 12.9–27.1 μg kg^?1 bw day^?1 at 95th-97.5th percentile for the general population. The anticipated exposure to THI from Class III caramel colours was estimated to be 0.1–0.3 μg kg^?1 bw day^?1 on average and 0.5–1.7 μg kg^?1 bw day^?1 at 95th–97.5th percentile for the general population. The dietary caramel colours intakes and the exposures to 4-MEI and THI from dietary caramel colour for the Chinese population were considered to be of low health concern based on the present toxicological data. Soy sauce, vinegar and compound seasonings were found to be the main contributors to the dietary intake of caramel colours.     

Supercritical fluid extraction (SFE) of 4(5)-methylimidazole (4-MeI) and 2-acetyl-4(5)-(1,2,3,4)-tetrahydroxybutyl-imidazole (THI) from ground-coffee with high-performance liquid chromatographic-electrospray mass spectrometric quantification (HPLC/ESI-MS).

Two polar analytes, 4(5)-methylimidazole (4-MeI) and 2-acetyl-4(5)-(1,2,3,4)-tetrahydroxybutyl-imidazole (THI), were extracted with supercritical carbon dioxide (CO2) modified with aqueous methanol. The method was applied to a roasted coffee powder with good recovery rates. Method efficiency was compared with that of solid-phase extraction using SCX Disc cartridges and validated for spiked solid matrix. The analytes were determined using isocratic liquid chromatography-mass spectrometry (LC/MS) on an Atlantis HILIC Silica column (150 x 2.1 mm, 3 microm) with 80% methanol and 20% 0.01 mol l-1 ammonium formate as the mobile phase. The limit of quantification was around 1.5 pg for 4-MeI and 2.0 pg for THI. The linearity of the calibration curves was satisfactory as indicated by correlation coefficients of >0.999. The coefficient of variation for the intra-day and inter-day precisions was <4% (n = 6). Accuracy was in the range 98-101%; recovery rates were > or = 98 and > or = 99% for THI and 4-MeI, respectively. Several samples of Arabica coffee from various locations and commercially available 'off-the-shelf' coffee products (Arabica/Robusta mixtures) were analysed to test the method.     

食品中4-甲基咪唑的分析方法

该文介绍了食品中4-甲基咪唑的常见来源,以及4-甲基咪唑对人体健康可能存在的风险,并对近年来食品中4-甲基咪唑含量的分析方法进行了总结,介绍了各分析方法的优缺点以及在国内外的应用情况。最后对食品中4-甲基咪唑检测技术的发展进行了展望。     

超高效液相色谱-串联质谱法同时测定客家娘酒中的2-甲基咪唑、4-甲基咪唑及5-羟甲基糠醛

目的 建立超高效液相色谱-串联质谱法同时测定客家娘酒中的2-甲基咪唑(2-methylimidazole, 2-MEI)、4-甲基咪唑(4-methylimidazole, 4-MEI)和5-羟甲基糠醛(5-hydroxymethylfurfural, 5-HMF)的分析方法。方法 样品经过直接稀释法和标准加入法分别进行前处理, 使用ACQUITY UPLC BEH HILIC (100 mm× 2.1 mm, 1.7 μm)色谱柱进行样品分离, 以甲醇-5 mmol/L氨水为流动相进行梯度洗脱, 采用电喷雾离子源正离子模式和多反应监测模式进行检测。结果 在优化条件下, 2-MEI和4-MEI在1~500 ng/mL范围内线性关系良好, 相关系数(r2)为0.9998和0.9998, 5-HMF在50~8000 ng/mL线性范围内r2为0.9970。2-MEI、4-MEI和5-HMF在低、中、高3个浓度添加水平下的回收率范围分别为88.7%~108%、77.5%~102%和95.7%~98.4%, 相对标准偏差分别为4.16%~10.50%、2.04%~5.49%和3.10%~6.62%。2-MEI、4-MEI和5-HMF的检出限分别为3、3和17 ng/mL, 定量限分别为10、10和50 ng/mL。结论 本方法操作简便、线性关系良好、回收率高, 适用于客家娘酒中2-MEI、4-MEI和5-HMF的检测。     

选择离子气质联用法同时测定食醋中2-甲基咪唑和4-甲基咪唑

建立了选择离子气/质联用法同时测定食醋中2-甲基咪唑和4-甲基咪唑的新方法。对色谱条件进行了筛选优化。样品经碱处理,硅藻土吸附,二氯甲烷洗脱,合并洗脱液并浓缩,以N-甲基甲酰苯胺为内标物,用二氯甲烷定容至10mL容量瓶后进行气/质联用测定。结果表明,2-甲基咪唑和4-甲基咪唑均在0¹5.2mg/L范围内呈良好线性关系,其相关系数分别为0.9997和0.9996;相对标准偏差分别为3.0%和3.1%;2-甲基咪唑和4-甲基咪唑的平均回收率分别为101.3%和99.3%。使用该法对市售食醋中2-甲基咪唑和4-甲基咪唑的含量进行了同时测定,结果较优。      

液相法测定焦糖色中4-甲基咪唑的不确定度评定

4-甲基咪唑是焦糖色生产中容易出现的一种副产物,对人体有较强的副作用.而焦糖色是目前应用非常广泛的一种食品着色剂,易造成4-甲基眯唑进入食物链.本研究通过对高效液相色谱法(HPLC)测定焦糖色中4-甲基咪唑所得实验数据的分析和处理,对不确定度进行逐层分析,用以确定测量结果和测量方法的可信度.     

Potential carcinogenic heterocyclic aromatic amines (HAAs) in foodstuffs: Formation,extraction, analytical methods,and mitigation strategies

During the heat treatment of proteinaceous food, heterocyclic aromatic amines (HAAs), a kind of strong mutagens/carcinogens are formed. HAAs can be classified into two major groups based on the heating temperature, which are thermic HAAs generally formed in 150 to 300 °C and pyrolytic HAAs produced above 300 °C. This review focuses on the formation mechanisms of HAAs and identifies different mechanisms of the formation of HAAs in foodstuffs. Moreover, an overview of the available extraction, purification methods, and instrumental analytical methods in the last two decades is shown to determine the HAAs in various foodstuffs. Finally, based on the factors that affect the formation of HAAs in heat‐processed foodstuffs, such as the cooking method, food type, the recipe, and the content of substances with enhancing or inhibiting effects on the formation of HAAs, this review also highlights the most promising strategies for mitigating HAAs, which include adjusting cooking methods or process conditions, adding natural product extracts, antioxidants or other compounds, or reasonable selection of types of foodstuff. The review intends to provide a broad but comprehensive understanding of the formation, extraction, purification, analytical methods, and possible mitigation strategies for isolated and identified HAAs.     

高效液相色谱法测定饮料中的4-甲基咪唑

建立了高效液相色谱法检测饮料中的4-甲基咪唑的检测方法.样品经过萃取、洗涤,利用高效液相色谱仪在波长210nm处检测.该方法对4-甲基咪唑的检测限为1.0mg/kg,在1μg/mL～ 100μg/mL的范围内有很好的线性,样品的加标回收率为(80.90±0.05)％～(115.50±0.05)％.该方法有很好的准确度和重复性,为各种饮料中4-甲基咪唑的检测提供了依据.     

UPLC-MS/MS法同时测定焙烤食品中的丙烯酰胺、4-甲基咪唑与5-羟甲基糠醛

建立了同时测定焙烤食品中丙烯酰胺、4-甲基咪唑和5-羟甲基糠醛的超高效液相色谱-串联质谱(UPLC-MS/MS)分析方法。样品中加入同位素内标后,以水和乙腈超声提取,QuEChERS净化,正己烷脱脂,UPLC-MS/MS分离检测,丙烯酰胺和4-甲基咪唑以同位素内标定量。在优化条件下,3种待测物的方法检出限在1.5μg/kg~7.0μg/kg之间;在2.0μg/L~500μg/L浓度范围内线性关系良好,相关系数均大于0.9990;在面包、蛋糕和饼干样品中进行3个水平的添加实验,平均回收率(n=6)为87.8~115.7%,日内精密度为3.2~9.6%;日间精密度(n=5)小于11.5%。本方法净化效果好,灵敏度高、准确性好,适用于焙烤食品中丙烯酰胺、4-甲基咪唑和5-羟甲基糠醛的同时测定。     

高效液相色谱法测定焦糖色素中的4-甲基咪唑

建立了高效液相色谱测焦糖色素中4-甲基咪唑的方法。样品经碱性条件下三氯甲烷-无水乙醇萃取和硫酸水溶液反萃取后,用反向色谱柱HypersilBDSC18(4.6mmi.d.×250mm,5um)分离,以体积比为5∶95的甲醇-0.05mol/L磷酸二氢钾缓冲液(含0.005mol/L庚烷磺酸钠,pH3.5)为流动相,在UV215nm波长条件下检测了自制及几种市售焦糖色素中的4-甲基咪唑的含量。并试验了不同流动相pH值和甲醇浓度对4-甲基咪唑分离的影响。本法平均加标回收率为94.7%,检出限为0.7ng。     

高品质焦糖色素(Ⅳ)的制备工艺优化

为优化制备高色率焦糖色素的工艺,以葡萄糖为反应物,亚硫酸铵为助剂,制备焦糖色素(Ⅳ)。通过控制葡萄糖浓度、铵含量、反应温度、反应时间等因素,以色素色率为主要检测指标,红色指数和黄色指数为辅助检测指标对结果进行优化。结果表明,高品质焦糖色素(Ⅳ)的最佳工艺条件为:葡萄糖浓度1000g/L,亚硫酸铵添加质量分数(以NH4+的量计)为6%,反应温度为150℃,反应时间为60min。制成焦糖色素的色率达7.47×104EBC。