食用植物油中脂肪酸氯丙醇酯形成机制的研究进展

脂肪酸氯丙醇酯的污染是近年来国际上新出现的热点食品安全问题之一,尤其是脂肪酸3-氯-1,2-丙二醇酯（3-chlorine-1,2-propylene glycol ester,3-MCPD酯）污染问题更为突出。研究表明,食用植物油中3-MCPD酯主要形成于精炼过程,而未精炼的食用植物油几乎不含3-MCPD酯。欧盟国家已对食用植物油中3-MCPD酯的形成机制开展了相关研究。本文主要对食用植物油种类、可能的前体物质、精炼工艺与3-MCPD酯形成的关系加以综述。     

Esters of 3-chloro-1,2-propanediol (3-MCPD) in vegetable oils: Significance in the formation of 3-MCPD

3-Mono-chloropropane-1,2-diol (3-MCPD) is a contaminant that occurs in food in its free (diol) form as well as in an esterified (with fatty acids) form. Using a simple intestinal model, it was demonstrated that 3-MCPD monoesters and 3-MCPD diesters are accepted by intestinal lipase as substrates in vitro. Under the chosen conditions, the yield of 3-MCPD from a 3-MCPD monoester was greater than 95% in approximately 1 min. Release from the diesters was slower, reaching about 45, 65 and 95% of 3-MCPD after 1, 5 and 90 min of incubation, respectively. However, in human, the hydrolysis of 3-MCPD esters is unlikely to release 100% as 3-MCPD, as triglycerides and phospholipids are hydrolysed in the intestine liberating 2-monoglycerides. Assuming a similar metabolism for 3-MCPD esters as that known for acylglycerols in humans in vivo, the de-esterification in positions 1 and 3 would thus be favoured by pancreatic lipases. Therefore, 3-MCPD, and 3-MCPD-2 monoesters would be released, respectively, from the 1-/3-monoesters, and the diesters potentially present in food. Hence, information on the exact amounts of the partial fatty acid chloroesters, i.e. 3-MCPD mono- and diesters, is important to assess the contribution of foods to the bioavailability of 3-MCPD. Therefore, a rapid method for the determination of the ratio of 3-MCPD monoesters to diesters in fats and oils was developed using gas chromatography-mass spectrometry (GC-MS) and isotopically labelled 3-MCPD esters as internal standards. The analysis of 11 different samples of fat mixes typically employed in food manufacturing demonstrated that a maximum of about 15% of the total amount of 3-MCPD bound in esters is present in the monoesterified form. The potentially slower release of 3-MCPD from 3-MCPD diesters, and the mono- to diesters ratio suggest that 3-MCPD esters may in fact contribute only marginally to the overall dietary exposure to 3-MCPD. Further work on the bioavailability, metabolism and possible toxicity of chloroesters per se is warranted.     

3-Monochloropropane-1,2-diol (3-MCPD) in food ingredients from UK food producers and ingredient suppliers.

A survey of 3-monochloropropane-1,2-diol (3-MCPD) in a range of food ingredients available in the UK is reported. The survey was conducted for the Food Standards Agency to assess the progress made by manufacturers in reducing levels of 3-MCPD in food ingredients in line with the UK Food Advisory Committee's recommendation, i.e. that 3-MCPD is undetectable (i.e. < 0.010 mg kg(-1) in foods and where technologically feasible, in food ingredients as well. Sixty-three samples of food ingredients available in the UK were analysed using a validated method of analysis with a limit of quantification of 0.010 mg kg(-1). Samples included breadcrumbs, caramels, enzyme-hydrolysed vegetable proteins, gelatines, malt products (malt extracts, malt flours and other malt-based in gredients), meat extracts, modified starches, and yeast extracts. 3-MCPD was not quantified in 49 (78%) of the samples analysed. The remaining 14 samples (22%) contained levels of 3-MCPD between 0.014 and 0.488 mg kg(-1), the highest level being in a maize yellow dextrin. Malt-based ingredients accounted for the majority of samples containing 3-MCPD > 0.010 mg kg(-1), with nine of these 24 samples (38%) having quantifiable levels of 3-MCPD.     

3-Monochloro-1,2-propandiol (3-MCPD) in soy sauce from the Bulgarian market

The 3-monochloro-1,2-propandiol (3-MCPD) levels in soy sauces which contained hydrolysed vegetable protein were evaluated for the Bulgarian market. For analysis of 3-MCPD, a gas chromatography–mass spectrometry (GC-MS) method was applied with a linear range of 0.03–2.00 μg mL^?1 and a limit of detection (LOD) of 2.3 μg kg^?1 and a limit of quantification (LOQ) of 3.4 μg kg^?1. At these levels, the standard deviation was 5.1%, with recoveries between 81% and 102%. The method was applied to the analysis of 21 samples of soy sauce from the Bulgarian market. Results ranged from 3.7 to 185.6 μg kg^?1. Soy sauces produced from hydrolysed soy protein contained higher levels of 3-MCPD than naturally fermented sauces. In 38.4% of samples of Bulgarian origin, the 3-MCPD content was above the EU limit of 20 μg kg^?1. In all analysed samples, 33.3% had a 3-MCPD content above the EU limit.     

Esters of 3-chloro-1,2-propanediol (3-MCPD) in vegetable oils: Significance in the formation of 3-MCPD

3-Mono-chloropropane-1,2-diol (3-MCPD) is a contaminant that occurs in food in its free (diol) form as well as in an esterified (with fatty acids) form. Using a simple intestinal model, it was demonstrated that 3-MCPD monoesters and 3-MCPD diesters are accepted by intestinal lipase as substrates in vitro. Under the chosen conditions, the yield of 3-MCPD from a 3-MCPD monoester was greater than 95% in approximately 1 min. Release from the diesters was slower, reaching about 45, 65 and 95% of 3-MCPD after 1, 5 and 90 min of incubation, respectively. However, in human, the hydrolysis of 3-MCPD esters is unlikely to release 100% as 3-MCPD, as triglycerides and phospholipids are hydrolysed in the intestine liberating 2-monoglycerides. Assuming a similar metabolism for 3-MCPD esters as that known for acylglycerols in humans in vivo, the de-esterification in positions 1 and 3 would thus be favoured by pancreatic lipases. Therefore, 3-MCPD, and 3-MCPD-2 monoesters would be released, respectively, from the 1-/3-monoesters, and the diesters potentially present in food. Hence, information on the exact amounts of the partial fatty acid chloroesters, i.e. 3-MCPD mono- and diesters, is important to assess the contribution of foods to the bioavailability of 3-MCPD. Therefore, a rapid method for the determination of the ratio of 3-MCPD monoesters to diesters in fats and oils was developed using gas chromatography-mass spectrometry (GC-MS) and isotopically labelled 3-MCPD esters as internal standards. The analysis of 11 different samples of fat mixes typically employed in food manufacturing demonstrated that a maximum of about 15% of the total amount of 3-MCPD bound in esters is present in the monoesterified form. The potentially slower release of 3-MCPD from 3-MCPD diesters, and the mono- to diesters ratio suggest that 3-MCPD esters may in fact contribute only marginally to the overall dietary exposure to 3-MCPD. Further work on the bioavailability, metabolism and possible toxicity of chloroesters per se is warranted.     

食用油中3-氯丙醇酯的研究进展

氯丙醇酯污染是近年来国际上出现的食品安全热点问题之一,尤其是3-氯丙醇酯污染更为突出,各种食用油或油脂食品中都含有一定量的3-氯丙醇酯。总结了国内外对3-氯丙醇酯的研究现状,介绍了3-氯丙醇酯来源、毒理和安全性、可能的形成机制、检测方法、污染水平、控制措施和精炼过程中形成的影响因素等方面的内容,并提出了目前急需解决的问题。旨在推动我国油脂食品行业的健康发展。     

3-MCPD: A Worldwide Problem of Food Chemistry

3-Monochloropropane-1,2-diol (3-MCPD) is a heat-induced food contaminant that has been widely investigated for decades. This paper presents an overview of current knowledge about 3-MCPD, including its formation routes, occurrence in various foodstuffs, analytical approach, toxicological aspects, and future research perspectives. So far, 3-MCPD was determined in its free and bound form in thermally treated foods, edible oils and fats, and infant foods including human breast milk. Contaminants in infant foods and human breast milk were highlighted in this paper as a serious problem as they can pose a potential hazard for infants. The analytical approach of 3-MCPD determination has been modified for over a decade. Nowadays, the method based on determining the derivative of this compound by using gas chromatography and mass spectrometry is widely used. However, there is still a big need for developing new methods that would produce repeatable results. Some of the toxicologic aspects associated with 3-MCPD still remain unknown. A number of studies on the carcinogenicity and genotoxicity of 3-MCPD were carried out on rodents; however, no clinical studies on humans have been reported so far. Moreover, both detrimental effect on kidneys and antifertility activity have been widely reported. The knowledge of 3-MCPD absorption into body fluids and tissues and its metabolic pathways is based on sometimes conflicting data derived from different studies. In conclusion, although a lot of research has been carried out on 3-MCPD, there is still a need for further research in this area.     

毛细管气相色谱法测定酸水解植物蛋白中3-氯-1,2-丙二醇的方法

采用配有FID的毛细管气相色谱仪测定酸水解植物蛋白中的3－氯－1，2－丙二醇。样品以1，2－丙二醇作内标，经苯基硼酸衍生化处理后，用正己烷萃取，衍生物萃取液供GC／FID测定。本方法操作简便、快速、准确，最低检出限为0．2mg/kg，加料回收率为92．0％－108．0％，其重复测定的相对标准偏差为3．1％－5．1％。     

食品中3-氯-1,2-丙二醇脂肪酸酯的检测方法及防控措施研究进展

3-氯-1,2-丙二醇脂肪酸酯(3-monochloropropane-1, 2-diol fatty acid esters, 3-MCPD酯)是一种在食品加工过程中产生的化学污染物,其在精炼植物油、脂肪、酱油甚至婴儿配方奶粉中含量均相对较高。3-MCPD酯已被证明可在体内诱导产生肾脏毒性、生殖毒性、神经毒性、免疫毒性和致突变性作用,对人类健康存在潜在风险,引起了国内外的广泛关注和高度重视。国际和我国已设立了对3-MCPD酯的检测标准,但是检测方法烦琐、耗时,安全隐患较大,对实验室仪器要求高,因此,建立简单、快速、适用性强的3-MCPD酯检测方法对食品中3-MCPD酯的污染水平监测、暴露评估和风险防范等具有重大的意义。本文综合介绍了国内外最新的3-MCPD酯监测方法,并对相关的检测方法及其适用范围进行了简单概括,根据3-MCPD酯的影响因素综合描述了对各种食物中3-MCPD酯控制措施,并展望了3-MCPD酯未来发展方向。     

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。     

Influence of composition,moisture, pH and temperature on the formation and decay kinetics of monochloropropanediols in wheat flour dough

A study of the formation and decay kinetics of 3-chloropropane-1,2-diol (3-MCPD) and 2-chloropropane-1,3-diol (2-MCPD) in model dough systems is reported. The influence of ingredient composition, moisture, pH and temperature were assessed. It was shown that white flour, salt and water alone were sufficient to generate 2-MCPD and 3-MCPD. The formation of 3-MCPD agreed with zero order kinetics and occurred most readily in dry, full recipe dough; below 15%, the exact moisture content was not critical. The formation of 2-MCPD followed that of 3-MCPD but at approximately one fifth of the rate, irrespective of dough type. The decay of 3-MCPD was consistent with first order kinetics and the overall rate in dough was slower than that in pure water. The decay reaction was inhibited by a decrease in moisture content and a drop in pH seen at high temperatures in the cereal systems investigated. One of the products of 3-MCPD decay in dough was 2-chloropropane-1,3-diol (2-MCPD). Data obtained from the model system studies showed good agreement with 3-MCPD levels formed in real foods. Possible mechanisms of decay and formation in dough are discussed.     

The effects of domestic cooking on the levels of 3-monochloropropanediol in foods

The results are reported of a study to determine the effect of domestic cooking procedures on the level of 3-monochloropropane-1,2-diol (3-MCPD) in selected foods. Samples of 23 foods comprising stock cubes, gravies, a cake mix, batters, breads, cheese and meats were subjected to a range of cooking procedures including grilling, toasting and microwaving. The resulting levels of 3-MCPD were compared with those present in the foods before cooking. Grilling and toasting produced substantial increases in the 3-MCPD content of bread, forming up to 0.3mg/kg, and of most cheeses, resulting in levels of up to about 0.1mg/kg. Microwave cooking produced elevated 3-MCPD levels in some cheeses. Frying laboratoryproduced batters increased 3-MCPD levels to about 0.1mg/kg whereas a retail batter contained no detectable 3-MCPD when fried. The remaining foods showed little or no discernible increase on cooking.     

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.     

河北省部分地区食用植物油中3-氯丙醇酯的污染水平研究

目的调查河北省部分地区市售食用植物油中3-氯丙醇酯的污染情况。方法称叐0.1 g植物油样品,用0.5 mol/L甲醇钠溶液将脂肪中的3-氯丙醇酯水解成游离的3-氯丙醇,用硅藻土小柱净化后,丂氟丁酰基咪唑迚行衍生化处理,气相色谱-质谱联用法检测3-氯丙醇酯含量,同位素内标法定量。结果测得市售的32份植物油样品中,全部检出含有3-氯丙醇酯,检出范围0.15～1.32 mg/kg, 3-氯丙醇酯平均值为0.47 mg/kg。结论食用植物油中3-氯丙醇酯污染问题必须引起持续关注,其中菜籽油和花生油污染问题较为突出,因此有必要加大监测力度,以获叐更多数据,制定限量标准,保障食品安全。     

Occurrence of chloropropanols in soy sauce and other foods in China between 2002 and 2004.

A survey of chloropropanols in soy sauce and some selected foods in China is reported. Thirty-seven traditionally brewed soy sauce samples contained 3-MCPD below the EC maximum limit (ML) of 0.02 mg kg(-1). All soy sauce samples (629) from retailers contained levels of 3-MCPD ranging between <0.005 (LOQ) and 189 mg kg(-1), and only 12.2% had levels in excess of the Chinese ML of 1.0 mg kg(-1) for acid hydrolyzed vegetable protein (acid HVP). This indicates that the necessary processing changes have been made to decrease levels of chloropropanols in soy sauce. 2-Monochloropropane-1,3-diol (2-MCPD), 1,3-dichloro-2-propanol (1,3-DCP) and 2,3-dichloro-1-propanol (2,3-DCP) were detected in 48.1 19.1 and 3.78% of the soy sauce samples, respectively; the highest levels being 20.3, 8.26 and 0.50 mg kg(-1), respectively. A good linear correlation was found between the amount of 3-MCPD and 2-MCPD, with the level of 3-MCPD being generally higher than that of other chloropropanols for the same soy sauce. Acid HVP contained 3-MCPD at a level of 0.010-117.7 mg kg(-1) (on a liquid basis) and 80% of samples contained levels exceeding 1.0 mg kg(-1). In some other foods investigated, relatively high levels of 3-MCPD were found in soy sauce powder, oyster sauce, beef products, instant noodle spices and health foods, ranging from 0.029 to 13.64 mg kg(-1). It is concluded that abnormal levels of 3-MCPD in soy sauce or other foods produced in China may result from acid hydrolysis or the addition of the contaminated acid HVP.     

Survey of 3-monochloropropane-1,2-diol (3-MCPD) in selected food groups, 1999-2000.

A survey of the levels of 3-monochloropropane-1,2-diol (3-MCPD) in a range of selected food products available in the UK is reported. The survey was carried out on behalf of the Food Standards Agency (FSA) to identify the food groups that might provide a significant contribution to 3-MCPD exposure from the diet. Three hundred samples comprising meat, dairy, cereal, soup and miscellaneous products were purchased from retail outlets and analysed using a GC-MS procedure, which had been formally validated by an earlier collaborative trial. 3-MCPD was detected in 89 (30%) of the samples. Three samples, all crackers, contained levels of 3-MCPD > 0.1 mg kg(-1), the highest level being 0.134 mg kg(-1). Levels of 3-MCPD were generally slightly higher in foods after cooking. In all cases where 3-MCPD was detected in cooked foods, it was also present in the uncooked sample.     

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.     

河南省市售食用植物油中氯丙醇酯污染状况分析

旨在为河南省食品安全风险监测提供参考,对河南省市售的205份食用植物油中3-氯-1,2-丙二醇酯(3-MCPD酯)和2-氯-1,3-丙二醇酯(2-MCPD酯)的污染状况进行调查分析。结果显示：205份食用植物油中,3-MCPD酯污染水平高于2-MCPD酯,其中3-MCPD酯检出率为79.0%,均值为1.83 mg/kg,中位值为1.30 mg/kg;大豆油的3-MCPD酯检出率最高,为93.3%,中位值为1.72 mg/kg,其次是花生油,检出率为89.2%,中位值为1.06 mg/kg,橄榄油的3-MCPD酯和2-MCPD酯污染水平最低;2021年食用植物油中3-MCPD酯、2-MCPD酯检出率均高于2020年;城市、农村人群经由食用植物油摄入3-MCPD酯健康风险较低。不同食用植物油氯丙醇酯的污染水平差别较大,虽然居民经食用植物油摄入3-MCPD酯健康风险较低,但需要继续加强监测。     

Updated occurrence of 3-monochloropropane-1,2-diol esters (3-MCPD) and glycidyl esters in infant formulas purchased in the United States between 2017 and 2019

ABSTRACT

Fatty acid esters of 3-monochloropropane-1,2-diol (3-MCPD) and glycidol are potentially carcinogenic and/or genotoxic processing contaminants that are formed during the process of edible oil refining. Because of their toxicological properties, the presence of these compounds in refined oils and foods containing these oils, particularly infant formula, poses a potential food safety concern. For this reason, recent research efforts have focussed on the development of methods for the analysis of MCPD and glycidyl esters in infant formula in order to estimate levels of exposure. This work presents occurrence data for 3-MCPD and glycidyl esters in 222 infant formulas purchased in the United States between December 2017 and January 2019. The results of this study show a wide range of contaminant concentrations across four different manufacturers, with average bound 3-MCPD concentrations ranging from 0.035 µg g^?1 to 0.63 µg g^?1 and average bound glycidol concentrations ranging from 0.019 µg g^?1 to 0.22 µg g^?1. The data suggest that manufacturers B and C source palm oil produced with mitigation measures, leading to reduced amounts of 3-MCPD and glycidyl esters in their infant formulas. Additionally, comparison with a previously published study in our laboratory of the occurrence of 3-MCPD and glycidyl esters in infant formula purchased in the U.S. between 2013 and 2016 revealed that, since 2016, contaminant concentrations have decreased in products produced by manufacturers A, B, and C, while contaminant amounts in formulas from manufacturer D have slightly increased.     

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.