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。     

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.     

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。     

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.     

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。     

鲜亮型焦糖色素的特点及应用研究

介绍了鲜亮型焦糖色素的特点,对其应用进行了详细研究,认为鲜亮型焦糖色素是生产高档调味品必不可少的添加剂。     

焦糖色素的染着性及其色调的研究

本文探讨了焦糖色的色率，色调及染着性的关系，通过对白豆腐的煮制染色试验，结果表明，焦糖的染着性及色泽的稳定性与色率及色调无直接关系，而与焦糖的制造工艺有关。     

酱油、酸水解植物蛋白、焦糖色素中乙酰丙酸的测定

对酱油、酸水解植物蛋白（HVP）、焦糖色素中乙酰丙酸的含量进行了测定。其中，酱油中乙酰丙酸含量较低，酸水解植物蛋白中乙酰丙酸含量较多（最高含量为15．79％），而焦糖色素中也测出含有乙酰丙酸（最高含量达8．02％）。故此认为采用乙酰丙酸指标来判定酿造酱油还是配制酱油是不恰当的。     

高效液相色谱-四级杆/静电场轨道肼高分辨率质谱检测蜂蜜中的4-甲基咪唑和2-甲基咪唑

目的建立高效液相色谱-四级杆/静电场轨道肼高分辨率质谱法直接测定蜂蜜中4-甲基咪唑和2-甲基咪唑的方法。方法用水溶解蜂蜜样品,经0.22μm粒径的微孔膜过滤后,采用Agilent HILIC Plus(2.1 mm×100 mm,3.5μm)色谱柱进行分离,以体积比为8:2的乙腈与5 mmol/L乙酸铵水溶液为流动相进行等度洗脱。质谱采用正离子模式,在质荷比(m/z)50~400范围内通过高分辨质谱全扫描模式提取目标化合物的精确质量数。结果在本文建立的色谱条件下,4-甲基咪唑(4-MI)和2-甲基咪唑(2-MI)能够得到较好的分离,高分辨率质谱提取的质量准确度小于5×10-6(5 ppm)。该方法对4-MI的检测限可达50μg/kg,对2-MI的检测限可达25μg/kg。两种待测物质采用外标法定量,线性良好,相关系数均大于0.99。通过加标验证,在50、100和150μg/kg三个加标水平下,蜂蜜中4-MI和2-MI的平均回收率为73.2%~107.9%,相对标准偏差(RSD)小于9.7%。结论该方法样品处理过程简单,不使用有机溶剂,灵敏度高,适用于任何蜜种的测定,可以作为蜂蜜中是否掺入焦糖色素的检测方法。利用该方法对国内外各地区12个蜜种的30个蜂蜜样品进行检测,均未检出4-MI和2-MI。     

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.     

The effects of six phenolic acids and tannic acid on colour stability and the anthocyanin content of mulberry juice during refrigerated storage

Six phenolic acids and tannic acid are added to fresh mulberry juice to enhance the colour. Effects of these copigments on colour stability and the anthocyanin content of mulberry juice are investigated while being stored at 4 °C for 30 days. Results suggest that the addition of the copigments markedly increases the maximum absorbance of mulberry juice. Cyanidin-3-glucoside is the major anthocyanin, followed by cyanidin-3-rutinoside. Furthermore, the retention rate of the total anthocyanin, cyanidin-3-rutinoside and cyanidin-3-rutinoside increases after the addition of all copigments. The effect of ferulic acid on the stability of total anthocyanin, cyanidin-3-glucoside and cyanidin-3-rutinoside in mulberry juice is the best, 89.52%, 86.90% and 94.46% respectively (66.56%, 62.58% and 73.60% in the control group). Researchers recommend the addition of ferulic acid, p-coumaric acid and caffeic acid – all of which belong to the hydroxycinnamic acid group, to the mulberry juice to enhance the colour stability and anthocyanin content.     

乳酸盐对冷却牦牛肉色泽稳定性及高铁肌红蛋白还原的影响

以牦牛背最长肌为实验材料,通过向牦牛肉糜中添加三种不同种类的乳酸盐（乳酸钙,Ca L;乳酸钾,KL;乳酸钠,Na L）和不同浓度的Ca L（0.1%、0.3%、0.5%）,研究了在（4±1）℃冷藏条件下乳酸盐对牦牛肉肉色稳定性和高铁肌红蛋白还原系统的影响。结果表明:经过7 d的贮藏,0.3%的乳酸盐可以抑制牦牛肉糜a*值的下降,但会使肉色变暗;可显著抑制牦牛肉贮藏过程中MbO₂的氧化（p<0.05）,抑制Met Mb含量的上升,提高MRA,且Ca L处理组的效果最显著（p<0.05）。添加不同质量分数的Ca L后,0.3%Ca L处理组的a*值上升速度显著高于其他3组（p<0.05）,但会使肉糜L*值降低;不同浓度的Ca L均可抑制牦牛肉贮藏过程中Mb O2的氧化（p<0.05）和Met Mb的生成（p<0.05）,并显著提高MRA（p<0.05）和肉色稳定性,其中添加0.3%的Ca L对稳定和保持肉色的作用最明显。      

Effects of pre-fermentation enzyme maceration on extraction and colour stability in Pinot Noir wine

Effects of pre-fermentation enzyme maceration on anthocyanins, phenolics, colour and colour parameters were investigated in Pinot Noir ( Vitis vinifera L.) wines made from musts that were macerated for 12 hours at 20°C with a commercial enzyme preparation, Rohapect VR-C (Rohm, Darmstadt, Germany), with and without additions of SO₂. Anthocyanins and phenolics were determined by spectrophotometric and HPLC methods. Standard triplicate microvinifications were conducted in glass vessels. Extraction of anthocyanins was not increased by enzyme treatment. However, wines produced by enzyme maceration had increased visible colour intensity, colour density and polymeric pigment formation. By the end of fermentation, enzyme-treated wines had more polymeric pigment, and less monomeric anthocyanins than non-enzyme-treated wines. The wines were bottled, stored at 12°C and sampled at three, six, eight and 18 months after bottling. Over 18 months, differences between the treatments were maintained. The promotion of the formation of polymeric pigments in enzyme-treated wines continued after the wines were bottled, and the greater content of polymeric pigment led to greater colour density in the enzyme-treated wines. The promotion of polymeric pigment formation in wines by macerating enzyme treatment of the must may be due to the breakdown of protective polysaccharide-protein colloids by hemicellulase and protease activities in the enzyme preparation.     

Effects of fining with different bentonite labels and doses on colloidal stability and colour of a Valpolicella red wine

This study addressed four different labels of activated sodium bentonite during the fining of a young Valpolicella red wine. Preliminary tests determined the bentonite dose (0.15, 0.30 or 0.50 g L^?1) that would achieve colloidal stability, and this dose was further applied during laboratory‐scale trials. The bentonites were characterised by physico‐chemical parameters, and the effects of the label and dose on the wine colloidal stability, proteins, colour indices and phenolic compounds were measured. The results demonstrated that 0.50 g L^?1 for every bentonite label provided colloidal stabilisation without harshly affecting the colour. Unlike to what happens in white wines the least charged bentonite labels were effective at stabilising the red wine colloidal state by partially reducing its protein content. Simultaneously, the most negatively charged clay samples determined the largest depletions on the total polyphenols, anthocyanins, tannins and polymeric pigments. The differentiated action of clays with different surface charge density among white and red wines may be explained by the interaction mediated by positively charged anthocyanins towards either protein or tannin depletion. Although pioneering, these results may move towards the definition of a safe, allergen‐free, and effective adjuvant for colloidal stabilisation targeted to wine type.     

Effects of pre‐freezing,puree content and pasteurisation regime on colour stability of strawberry nectar made from puree

BACKGROUND: Heat treatment during processing of strawberry products has been proposed to negatively affect colour stability. Moreover, the role of enzymes with respect to colour stability is ambiguous when consulting the existing literature. The aim of the present study was to investigate the impact of various processing parameters (pre‐freezing, puree content, pasteurisation temperature and heating time) on the colour stability and anthocyanin monomer and L ‐ascorbic acid contents of strawberry nectars made from puree. In addition, the effect of different enzyme activities on colour stability during storage of strawberry nectars was investigated. RESULTS: Pre‐freezing of strawberries before processing had a significant positive effect on the colour stability of nectars made from puree. No significant effect on colour stability was found for higher puree contents. Increasing both the pasteurisation temperature and the heating time had a significant positive effect on colour stability. Results showed that colour degradation during storage was mainly due to residual enzyme activities. The shelf‐life of strawberry nectar could be extended about fivefold by adding an enzyme inhibitor. CONCLUSION: The colour stability of strawberry nectar made from fresh puree may be improved to some extent by an appropriate pasteurisation regime. Enzymes play an important role in colour degradation during storage of the nectar. Inactivation of these enzyme activities, however, could not be achieved even after a heat treatment at 90 °C for 60 min. Copyright © 2008 Society of Chemical Industry     

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.     

Development of natural dyed jute fabric with improved colour yield and UV protection characteristics

Premordanting of jute fabric was carried out following single mordanting by biomordants (myrobolan and pomegranate) and ecofriendly chemical mordants (ferrous sulphate and potash alum) and double mordanting by sequential treatment of biomordant and ecofriendly chemical mordant. Extraction condition of natural dyes from manjistha, annatto, ratanjot and babool was standardised and applied on premordanted jute fabric. There is a substantial improvement of colour yield, levelness of dyeing and wash fastness properties of natural dyed jute fabric after double premordanting using bio and chemical mordant. Light fastness ratings are moderate to good while rubbing fastness are very good to excellent for all the natural dyed jute fabric. Very good ultraviolet (UV) protection ratings are achieved in case of dyeing of jute fabric using natural dyes extracted from manjistha, annatto, ratanjot and babool after premordanting with sequential treatment of biomordant and chemical mordant. UV protection properties of natural dyed jute fabric follows the order babool?>?annatto?>?manjistha?>?ratanjot.     

Effect of Various Food Additives on the Levels of 4(5)‐Methylimidazole in a Soy Sauce Model System

In this study, the effect of food additives such as iron sulfate, magnesium sulfate, zinc sulfate, citric acid, gallic acid, and ascorbic acid on the reduction of 4(5)‐methylimidazole (4(5)‐MI) was investigated using a soy sauce model system. The concentration of 4(5)‐MI in the soy sauce model system with 5% (v/v) caramel colorant III was 1404.13 μg/L. The reduction rate of 4(5)‐MI level with the addition of 0.1M additives followed in order: iron sulfate (81%) > zinc sulfate (61%) > citric acid (40%) > gallic acid (38%) > ascorbic acid (24%) > magnesium sulfate (13%). Correlations between 4(5)‐MI levels and the physicochemical properties of soy sauce, including the amount of caramel colorant, pH value, and color differences, were determined. The highest correlations were found between 4(5)‐MI levels and the amount of caramel colorant and pH values (r² = 0.9712, r² = 0.9378). The concentration of caramel colorants in 8 commercial soy sauces were estimated, and ranged from 0.01 to 1.34% (v/v).