Kinetics of 3-chloropropane-1,2-diol (3-MCPD) degradation in high temperature model systems

A study of the decay kinetics of 3-chloropropane-1,2-diol (3-MCPD) at high temperatures in aqueous model systems is reported. Data obtained over the pH range 5-6.5 and temperatures of 80-142 °C agreed well with a predicative model derived from earlier kinetic data. The results showed that 3-MCPD was unstable in aqueous solutions approaching infinite dilution at temperatures above 80 °C. Comparison of the experimental decay of 3-MCPD with that based on the kinetic parameters A (=10^{7.73347+0.83775pH}s-1) and E_a (=119.2 kJ mol^-1) was good to within 20% over the temperature and pH ranged studied. A putative mechanism for the degradation reaction is discussed together with the implications for the decay and formation of 3-MCPD in food systems.     

The simultaneous separation and determination of chloropropanols in soy sauce and other flavoring with gas chromatography-mass spectrometry in negative chemical and electron impact ionization modes

Both gas chromatography-mass spectrometry in electron ionization (GC-MS-EI) and negative chemical ionization (GC-MS-NCI) modes are reported in this paper for the simultaneous determination of 1,3-dichloropropan-2-ol (1,3-DCP), 2,3-dichloropropan-1-ol (2,3-DCP), 3-chloropropane-1,2-diol (3-MCPD) and 2-chloropropane-1,3-diol (2-MCPD) in soy sauce and other flavoring. D₅-3-MCPD (for 3-MCPD and 2-MCPD) and d₅-1,3-DCP (for 1,3-DCP and 2,3-DCP) were used as the deuterium isotopic labelled internal standards. The feasibility of using heptafluorobutyric anhydride modified with triethylamine (HFBA-Et₃N) as a new derivatization reagent to replace heptafluorobutyrylimidazole (HFBI) is proposed. Liquid/liquid extraction with hexane was introduced for high lipid content samples. A small survey was carried out of soy sauces (103 samples) and instant noodles (45 samples) and the applicability of GC-MS-NCI and GC-MS-EI was assessed in these different matrices.     

Influence of dough ingredients on 3-chloropropane-1,2-diol (3-MCPD) formation in toast.

The influence of different dough ingredients such as fat, salt, sourdough, emulsifiers, and sugar on the formation of 3-chloropropane-1,2-diol (3-MCPD) during toast preparation under domestic conditions was investigated. In comparison with a fat-free recipe, addition of 1% peanut fat considerably increased 3-MCPD formation, but varying the fat (2-5%) or salt (1.6-2.4%) contents within technological acceptable limits did not show any significant differences. A baking agent, which is usually commercially applied by many toast bakers or industrial toast manufacturers, increased 3-MCPD formation in toasted bread slices. Considerable evidence was found that the baking agent's main component sucrose had the major part in increasing 3-MCPD levels. Emulsifiers containing monoacylglycerols moderately increased 3-MCPD levels, but the addition of lecithin did not have any significant influence. 3-MCPD levels showed a good correlation with the lightness (L* value) of the bread slices; their 3-MCPD content increased exponentially towards dark coloured toasts. The relation between 3-MCPD and 2-MCPD was an average of 3:1 in all samples. Dichloropropanols such as, for example, 1,3-dichloropropanol could not be detected.     

Effects of temperature and water content on the formation of 3-chloropropane-1,2-diol fatty acid esters in palm oil under conditions simulating deep fat frying

The influence of NaCl addition, water content, heating temperature and heating time on the formation of 3-chloropropane-1,2-diol fatty acid esters (3-MCPD esters) in palm oil simulating deep fat frying was examined in this study. The results in our study showed that all those four factors had significant effects on the generation of 3-MCPD esters in palm oil during deep fat frying. There was a significant increase in the content of 3-MCPD esters formed in palm oil when heating time was 2 h. The effect of water content was the most evident in 3-MCPD esters formation. The heating process imparted an accretion of up to 130 % from 1,260 to 2,950 mg/kg with increasing the water dosage from 7 to 10 %. In addition, 3-MCPD esters were decomposed when heated at high temperatures for a long time (longer than 2 h).     

食品中氯丙醇脂肪酸酯风险及应对措施概述

氯丙醇酯作为食品中的一类新型污染物,得到世界各国和地区的广泛关注和研究。氯丙醇酯类物质种类繁多,其反应机制、毒理学和代谢转化研究尚不成系统,目前研究表明氯丙醇酯类物质具有一定的肾脏、生殖毒性及潜在的致癌性。国内外对氯丙醇酯的检测方法、污染水平和暴露评估等研究主要集中在3-氯-1,2-丙二醇酯和2-氯-1,3-丙二醇酯,且主要集中在婴儿配方奶粉、油炸和烘焙食品等脂肪含量较高的食品上。通过研究发现,普通消费者从日常饮食中摄入氯丙醇酯类物质一般是无风险的,但对于一些年轻群体和仅食用配方奶粉的婴幼儿来说风险较高。国内外已相继开展了对氯丙醇酯的研究和监控,以减少食品中氯丙醇酯类物质污染水平。目前只有欧盟制定了3-氯-1,2-丙二醇酯在部分食用油和婴幼儿配方食品中的限量要求,仅国际食品法典委员会制定了植物油中3-氯-1,2-丙二醇酯的控制规范,来降低氯丙醇酯的风险。鉴于此,本文主要对氯丙醇酯形成机制、代谢、毒性、国内外食品中氯丙醇酯的污染水平、风险评估研究进展及其管理控制措施等方面进行了简要概述,以期为食品安全监管提供参考。     

“水解植物蛋白液 葡萄糖”模型热反应中 3-氯-1,2-丙二醇的研究

通过设计“水解植物蛋白液 葡萄糖”模型热反应,考察了不同3-氯-1,2-丙二醇 (3-MCPD)含量的HVP液、葡萄糖用量、反应温度、反应时间等因素对热反应产物中 3-MCPD 含量的影响。结果表明：模型热反应产物中 3-MCPD 含量随着 HVP 液中 3-MCPD 的含量增加而增加;随着葡萄糖用量增加而减少;随着反应温度的升高,3-MCPD 的量先增加后减少;热反应时间越长,3-MCPD 的含量越高。     

甘油与氯化钠模型热反应中生成3-氯-1,2-丙二醇的研究

以甘油、氯化钠、水为原料建立热反应模型,结合气相色谱-质谱法（gas chromatography-mass spectrometry,GC-MS）分析,对其生成的3-氯-1,2-丙二醇（3-MCPD）进行了研究。通过正交实验,考察了反应时间、温度和各原料用量对3-MCPD生成量的影响,同时研究了在热反应模型中分别加入不同种类单糖和氨基酸后3-MCPD生成量的变化规律,并对其反应机理进行了探讨。结果表明,反应时间2h、反应温度140℃、甘油用量0.05g（占原料总量0.31%）、NaCl用量1.0g（6.23%）、水用量15g（93.46%）,3-MCPD生成量最少;葡萄糖、果糖、木糖、甘露糖、半乳糖、缬氨酸、精氨酸、赖氨酸、丝氨酸、亮氨酸、苯丙氨酸、苏氨酸、组氨酸使3-MCPD的生成量减少;谷氨酸、蛋氨酸、丙氨酸、天冬氨酸、甘氨酸使3-MCPD的生成量增加;半胱氨酸、酪氨酸、脯氨酸、色氨酸对3-MCPD的生成无明显作用。      

油脂微波加热模型中3-氯-1,2-丙二醇脂肪酸酯的形成

通过建立油脂微波加热模型,研究不同的油脂微波加热后3-氯-1,2-丙二醇（3-chloropropane-1,2-diol,3-MCPD）脂肪酸酯含量的变化情况以及NaCl溶液、pH值、时间、不连续微波和金属离子等因素对3-MCPD脂肪酸酯形成的影响。结果表明：1）熟榨植物油微波加热后3-MCPD脂肪酸酯含量增加均超过9 mg/kg,远超过其他植物油。2）3-MCPD脂肪酸酯含量随NaCl的质量浓度增加而增加,随NaCl溶液体积分数的增加呈先增加后减少趋势。3）酸性环境促进3-MCPD脂肪酸酯形成。4）微波加热10 min内,3-MCPD脂肪酸酯含量与时间呈正相关。5）微波总时间一定的情况下,不连续微波产生的3-MCPD脂肪酸酯明显少于连续微波。6）金属离子作为催化剂参与活性中间物的形成,能明显地促进3-MCPD脂肪酸酯的形成。上述结果可为食品微波加工处理过程中危害物3-MCPD脂肪酸酯的控制研究提供数据支持。     

Formation of 3-chloropropane-1,2-diol in systems simulating processed foods

Formation of 3-chloropropane-1,2-diol (3-MCPD) from the precursors glycerol, triolein and soy lecithin in the presence of sodium chloride was studied. The precursors were reacted with sodium chloride in an emulsion stabilised with an emulsifier under conditions which modelled the thermal treatment of foods during processing. Three sets of experiments were carried out aimed to monitor the influence of various factors (NaCl, water content and temperature) on the yield of 3-MCPD. The formation of 3-MCPD strongly depended on the concentration of NaCl and reached a maximum level at about 4–7% NaCl. The highest amount of 3-MCPD was formed in media containing approximately 13–17% water. The amount of 3-MCPD increased with increasing temperature over the range 100–230 °C and reached its highest value at 230 °C. The production of 3-MCPD was also followed in models very closely related to selected foods which had been shown to have a high potential to yield 3-MCPD during processing (salami, beefburgers, processed cheese, biscuits, crackers, doughnuts). The highest levels of 3-MCPD were formed in models simulating salami as they had the highest content of both fat and salt of all the samples. The lowest amount of 3-MCPD was formed in the models simulating biscuits and crackers as they had a low salt content and, at the same time, their water content was below the optimum level.     

Occurrence of 3-chloropropane-1,2-diol and its esters in coffee

Fifteen coffee samples comprising green, roasted, decaffeinated and instant coffees were analysed for their content of free and bound 3-chloropropane-1,2-diol (3-MCPD). Green coffees contained only traces of the free 3-MCPD. 3-MCPD in roasted coffees was found at the level of 10.1–18.5 µg/kg. The highest 3-MCPD level of 18.5 µg/kg was found in one instant coffee sample and in coffees with very long time application during roasting. The final colour of the roasted coffee beans was directly linked to the 3-MCPD formed, the darker beans having the greatest concentration, and arabica coffees contained lower 3-MCPD levels than robusta coffees. The level of bound 3-MCPD varied between 6 µg/kg (soluble coffees) and 390 µg/kg (decaffeinated coffee) and exceeded the free 3-MCPD level 8–33 times. Arabica coffees contained higher levels of the bound 3-MCPD than robusta coffees. The recognised precursors of 3-MCPD (salt, glycerol, lipids) were also determined and their influence on the formation of the free and bound 3-MCPD was discussed.     

气相色谱-质谱联用法测定食用油中3-MCPD脂肪酸酯

本研究在德国油脂科学协会(DGF)标准检测方法的基础上进行方法优化,利用气相色谱-质谱联用(GC-MS)技术,建立了油脂中3-氯-1,2-丙二醇(3-MCPD)脂肪酸酯的分析方法。根据结果可知,该方法线性相关性良好,检出限为0.022 5 mg/kg,定量限为0.076 0 mg/kg,线性范围为0.05~5.0 mg/kg,回收率为95.36%~101.18%,相对标准偏差为1.36%~8.14%。试验中同时利用该方法对7种常见油脂中3-MCPD脂肪酸酯进行了检测。结果表明:该分析方法定性定量准确、灵敏度高、重现性好,能满足油脂中3-MCPD脂肪酸酯分析检测的要求。     

Survey of chloropropanols in soy sauces and related products purchased in the UK in 2000 and 2002.

The results of surveys to investigate the levels of 3-monochloropropane-1,2-diol (3-MCPD) and 1,3-dichloropropanol (1,3-DCP) in UK retail samples of soy sauces and similar products are reported. The products, sampled in 2000 and 2002, were analysed for 3-MCPD using an established solvent extraction technique with a reporting limit of 0.01 mg kg(-1), which also detected 2-monochloropropane-1,2-diol (2-MCPD), and for 1,3-DCP by an automated headspace method with a reporting limit of 0.005 mg kg(-1), which also detected 2,3-dichloropropanol (2,3-DCP). In the 2000 survey, 3-MCPD was quantified in 32 of 100 samples. After normalization to 40% dry matter, it was quantified at or above 0.02 mg kg(-1) in 25 of the samples and in excess of 1 mg kg(-1) in 16 samples, the highest containing 82.8 mg kg(-1). 2-MCPD was found in 26 samples, at up to 17.6 mg kg(-1) after normalization to 40% dry matter. The presence of 1,3-DCP was detected in 17 of the samples, at levels between 0.006 and 0.345 mg kg(-1). 1,3-DCP was only detected where 3-MCPD was present, but the levels of 1,3-DCP and 3-MCPD were not correlated. 2,3-DCP was detected in 11 samples at levels ranging from 0.006 to 0.043 mg kg(-1). In the 2002 survey, 3-MCPD was quantified (> 0.01 mg kg(-1)) in only eight of 99 samples and 2-MCPD in three samples. After normalization to 40% dry matter, 3-MCPD was present at or above 0.02 mg kg(-1) in seven of these, the maximum level being 35.9 mg kg(-1). 1,3-DCP was detected in this sample alone, at 0.017 mg kg(-1).     

Effects of yeast stress and pH on 3-monochloropropanediol (3-MCPD)-producing reactions in model dough systems

A major precursor of 3-monochloropropanediol (3-MCPD) in leavened cereal products is glycerol, which is formed as a natural by-product of yeast fermentation. However, yeast metabolism is affected by stresses such as low osmotic pressure from, for example, the incorporation of sugar or salt in the dough recipe. Tests with model doughs have shown that glycerol production was proportional to yeast mass and limited by available sugars, but that high levels of yeast inhibited 3-MCPD formation. The yeast fraction responsible for the inhibition of 3-MCPD in model dough was shown to be the soluble cytosol proteins, and the inhibition mechanism could be explained by the known reactions of 3-MCPD and/or its precursors with ammonia/amino acids (from yeast proteins). Added glucose did not increase the production of glycerol by yeast but it did promote the generation of 3-MCPD in cooked doughs. The latter effect was attributed to the removal of 3-MCPD inhibitors such as ammonia and amino acids by their reactions with added glucose (e.g. Maillard). The thermal generation of organic acids from added glucose also reduced the pH of cooked doughs, so the effect of pH and short-chain organic acids on 3-MCPD generation in dough was measured. There was a good correlation between initial dough pH and the level of 3-MCPD generated. The effect was weaker than that predicted by simple kinetic modelling, suggesting that the involvement of H⁺ and/or the organic acid was catalytic. The results showed that modifications to dough recipes involving the addition of reducing sugars and/or organic acids can have a significant impact on 3-MPCD generation in bakery products.     

Occurrence of 3-MCPD fatty acid esters in human breast milk

A series of twelve breast milk samples were analysed by gas chromatography-mass spectrometry (GC/MS) operated in selected ion monitoring mode for 3-chloropropane-1,2-diol (3-MCPD). Whilst none of the samples contained 3-MCPD above the limit of detection of 3 microg kg(-1) milk, all contained high amounts of 3-MCPD esterified with higher fatty acids. The levels of 3-MCPD released by hydrolysis of these esters (bound 3-MCPD) ranged from the limit of detection (300 microg kg(-1), expressed on a fat basis) to 2195 microg kg(-1); with a mean level of bound 3-MCPD of 1014 microg kg(-1), which corresponded to 35.5 microg kg(-1) milk. The presence of bound 3-MCPD was confirmed using orthogonal gas chromatography coupled with high-speed time-of-flight mass spectrometry analysis for four randomly selected breast milk samples. Six breast milks collected from one of the nursing mothers 14-76 days after childbirth contained bound 3-MCPD within the range of 328-2078 microg kg(-1) fat (mean 930 microg kg(-1) fat). The calculated bound 3-MCPD content of these samples was within the range of 6 and 19 microg kg(-1) milk (mean of 12 microg kg(-1) milk). The major types of 3-MCPD esters were the symmetric diesters with lauric, palmitic, and oleic acids, and asymmetric diesters with palmitic acid/oleic acid among which 3-chloro-1,2-propanediol 1,2-dioleate prevailed.     

Occurrence of 3-MCPD fatty acid esters in human breast milk.

A series of twelve breast milk samples were analysed by gas chromatography-mass spectrometry (GC/MS) operated in selected ion monitoring mode for 3-chloropropane-1,2-diol (3-MCPD). Whilst none of the samples contained 3-MCPD above the limit of detection of 3 microg kg(-1) milk, all contained high amounts of 3-MCPD esterified with higher fatty acids. The levels of 3-MCPD released by hydrolysis of these esters (bound 3-MCPD) ranged from the limit of detection (300 microg kg(-1), expressed on a fat basis) to 2195 microg kg(-1); with a mean level of bound 3-MCPD of 1014 microg kg(-1), which corresponded to 35.5 microg kg(-1) milk. The presence of bound 3-MCPD was confirmed using orthogonal gas chromatography coupled with high-speed time-of-flight mass spectrometry analysis for four randomly selected breast milk samples. Six breast milks collected from one of the nursing mothers 14-76 days after childbirth contained bound 3-MCPD within the range of 328-2078 microg kg(-1) fat (mean 930 microg kg(-1) fat). The calculated bound 3-MCPD content of these samples was within the range of 6 and 19 microg kg(-1) milk (mean of 12 microg kg(-1) milk). The major types of 3-MCPD esters were the symmetric diesters with lauric, palmitic, and oleic acids, and asymmetric diesters with palmitic acid/oleic acid among which 3-chloro-1,2-propanediol 1,2-dioleate prevailed.     

Occurrence of 3-chloro-propane-1,2-diol (3-MCPD) and related compounds in foods: a review

A critical review of the occurrence of 3-chloro-propane-1,2-diol (3-MCPD) in foods not known to contain hydrolysed vegetable proteins is presented. The review covers the properties and chemistry of 3-MCPD and the current methods of analysis in foodstuffs. The results of UK surveys of 3-MCPD occurrence in both retail foods and commercial food ingredients are discussed with particular reference to cereal, meat and dairy products. The possible mechanisms for the formation and decay of 3-MCPD in foods are suggested. The review does not cover the detailed toxicology of 3-MCPD and its occurrence in hydrolysed vegetable proteins, which have been considered elsewhere, nor possible issues such as in-vivo formation.     

食用植物油中4种氯丙醇脂肪酸酯的GC-MS测定方法研究

采用气相色谱-质谱(GC-MS)联用技术,建立了同时测定食用植物油中3-氯-1,2-丙二醇脂肪酸酯(3-MCPD酯)、2-氯-1,3-丙二醇脂肪酸酯(2-MCPD酯)、1,3-二氯-2-丙二醇脂肪酸酯(1,3-DCP酯)和2,3-二氯-1-丙二醇脂肪酸酯(2,3-DCP酯)含量的分析方法。该方法在0.005~0.5 mg/L范围内线性关系良好,检出限0.1 mg/kg,定量限0.2 mg/kg,加标回收率在97.2%~106.0%之间,相对标准偏差在3.4%~7.1%之间。该方法操作简便,灵敏度高,重复性好,定性定量准确,对仪器污染小,能满足食用植物油中氯丙醇酯的检测需求。     

Survey of chloropropanols in soy sauces and related products

A survey of soy sauces and related products available in the USA was conducted to determine the levels of 3-monochloropropane-1,2-diol (3-MCPD) and 1,3-dichloro-2-propanol (1,3-DCP) in these products. Fifty-five retail samples were purchased and analysed for 3-MCPD. 3-MCPD determinations were made according to a gas chromatography/mass spectrometry method validated by a collaborative trial. Eighty-five per cent of the samples analysed contained greater than the detection limit of 0.005 ppm (μg g^-1) for 3-MCPD. Thirty-three per cent contained greater than 1 ppm; the highest level was 876 ppm 3-MCPD. Thirty-nine of the samples analysed for 3-MCPD also were analysed for 1,3-DCP by using a modified method developed and validated in-house. Fifty-six per cent of the samples analysed for 1,3-DCP contained greater than the detection limit of 0.055 ppb (ng g^-1) for 1,3-DCP; the highest level was 9.8 ppm 1,3-DCP. Products manufactured in Asia contained the highest chloropropanol levels.     

Study of chloropropanols in soy sauce by gas chromatography-triple quadrupole mass spectrometry with coupled column separation without derivatisation

A qualitative and quantitative determination method for chloropropanols in soy sauce was developed by GC-MS/MS with coupled column separation without derivatisation. The target compounds were 1,3-dichloropropan-2-ol (1,3-DCP), 2,3-dichloropropan-1-ol (2,3-DCP), 3-monochloropropane-1,2-diol (3-MCPD) and 2-monochloropropane-1,3-diol (2-MCPD). 3-MCPD-d₅ was used as an isotope internal standard for MCPDs and 1,3-DCP-d₅ for DCPs. After spiking with internal standards and mixed with 1?g of Extrelut? NT, about 1?g of the sample was washed by 4?ml of hexane and the analytes were eluted with 15?ml of 95% (v/v) ethyl ether/hexane mixture. The concentrated extract was directly injected without derivatisation, separated by a coupled column – a 3?m Innowax (polyethylene glycol) combined with a 30?m DB-5?ms ((5%-phenyl)-methylpolysiloxane) by a quartz capillary column connector – and detected by GC-MS/MS. The limits of detection (LODs) in the sample matrix were 1.0, 2.5, 5.0 and 5.0?µg?kg^?1 for the above chloropropanols, respectively. The relative proportions of 2-MCPD/3-MCPD ranged from 0.19 to 3.74 in soy sauce samples. 2,3-DCP and 2-MCPD were more stable than 1,3-DCP and 3-MCPD under alkaline condition. The levels of chloropropanols can be decreased by an alkaline treatment process.     

单糖与氯化钠模型反应中3-氯-1,2-丙二醇的形成

以"单糖+氯化钠+水"为模型进行热反应,研究3-氯-1,2-丙二醇(3-monochloropropane-1,2-diol,3-MCPD)的形成机理和消长规律。结果表明,在"葡萄糖+氯化钠+水"模型反应中,反应温度对3-MCPD的形成影响最大,其次是氯化钠添加量、反应时间和葡萄糖添加量;在"单糖+氯化钠+水"模型中,6种单糖都生成了3-MCPD,其中核糖和氯化钠反应生成的3-MCPD量最大(30.604μg/kg),果糖生成的量最小(2.498 6μg/kg);在"葡萄糖+氯化钠+水"模型中,反应后生成的挥发性成分5-羟甲基糠醛含量最大,然后是糠醛和2,5-二甲酰基呋喃。根据实验结果探讨3-MCPD的形成机理,提出在单糖模型反应中缩水甘油可能是关键的中间体。