Factors impacting the formation of monochloropropanediol (MCPD) fatty acid diesters during palm (Elaeis guineensis) oil production

Recently, organic and inorganic chlorinated compounds were detected in crude and commercially refined palm oils. Further, the predominant formation mechanism of monochloropropanediol (MCPD) diesters at high temperatures (>170-180°C) was revealed. The present study involved the development and comparison of solutions to mitigate MCPD diester levels in oils from various stages of palm oil production. Partially refined palm oil samples and oil extracted from fresh palm fruits were submitted to bench-top deodorisation experiments. Application of glycerol and ethanol as refining aids during the deodorisation of refined-bleached palm oil proved to be moderately effective; about 25%-35% reduction of MCPD diester levels was achieved. Washing crude palm oil with ethanol-water (1:1) prior to deodorisation was also an effective strategy yielding an ～30% reduction of MCPD diester contents. Washing palm fruit pulp before oil extraction, however, was most impactful, resulting in a 95% reduction of MCPD diesters when compared to the deodorised control oil. This suggests that intervention upstream in the process chain is most efficient in reducing levels of these contaminants in refined oils. Following the study, a root-cause analysis was performed in order to map the parameters potentially responsible for the occurrence of MCPD diesters in refined palm oil and related fractions.     

Changes in lipid class and fatty acid composition during maturation of mesocarp of oil palm (Elaeis guineensis) variety dura

The deposition of oil, major lipid classes, and the constituent fatty acids of the oil palm fruit mesocarp were investigated to gain a better insight into the accumulation of these components. The oils were extracted with chloroform-methanol 1:2 (v/v) and were fractionated by silicic acid column chromatography into classes. Fatty acids were analysed by gas-liquid chromatography. Shortly after anthesis, lipids, mainly phospho- and glyco-lipids, were a small proportion of the mesocarp. With time the lipid content increased, until at maturity it accounted for about 60% of fresh mesocarp weight. Approximately 97% of the lipid at maturity was neutral lipid, essentially triacylglycerol. Maximum oil quantity was obtained at 22 weeks after anthesis. The active lipid accumulation period was from weeks 18 to 22 after pollination. Contrary to previously published data, palmitic, oleic and linoleic acids were characteristically present at all stages of oil accumulation. Linolenic acid was present in the neutral lipids from immature mesocarp of the oil palm fruit, but was probably diluted out in mature palms. Appreciable amounts of linolenic acid were present in the polar lipid fractions.     

Partial purification and some properties of the lipase present in oil palm (Elaeis guineensis) mesocarp

The fatty layer obtained by centrifuging a homogenate of oil palm fruit mesocarp contains an active lipase. The lipase which was partially purified using a combination of ammonium sulphate fractionation, ion exchange and gel filtration chromatography, indicated an optimum activity at pH 4.5 and a temperature of 30°C. The enzyme exhibited good activity towards its natural substrate, palm oil as well as glycerol trioleate and glycerol tripalmitate. It also showed a linear reaction rate for the first 20 min of incubation. Sodium cyanide, resorcinol, cholesterol, lecithin and glycylglycine strongly inhibited its activity while phenol, L-cysteine and EDTA enhanced its activity. It is suggested that the lipase is associated with the membrane of the oil droplets.     

Variation in fatty acid composition of palm oils from two varieties of the oil palm (Eelaeis guineensis)

A comparative study was carried out on the fatty acid content of palm oil samples from the red and yellow fruits of Dura and Tenera varieties of Elaeis guineensis in the dry (January) and wet (May) seasons. Significant differences in the fatty acid content of the oils from the two varieties were observed. The degree of total unsaturation of the oil samples varied, with oil from red fruits of Dura having the highest total unsaturated fatty acids.     

Verification and evaluation of monochloropropanediol (MCPD) esters and glycidyl esters in palm oil products of different regions in Malaysia

ABSTRACT

This study was conducted to investigate on the effect of different sampling regions of palm-refined oils and fats on the 2- and 3-monochloropropanediol fatty acid esters (MCPDE) and glycidol fatty acid esters (GE) levels. The American Oil Chemists’ Society (AOCS) Official Method Cd 29a-13 on the determination of MCPDE and GE in edible oils and fats by acid transesterification was successfully verified and optimised, with slight modification using 7890A Agilent GC system equipped with 5975C quadrupole detector. The determined limits of detection (LOD) for MCPDE were 0.02 mg kg^-1 and 0.05 mg kg^-1 for GE. The method performance has showed good recovery between 80% and 120% for all pertinent compounds with seven replicates assayed in three separate days. Round robin test with two European laboratories, i.e. Eurofins and SGS, has shown compliance results with those of the present study. Among the sampling regions, only one refinery located in the central region of Malaysia showed a significant increment of the MCPDE and GE levels after refining process. The GE level averaging at 2.5 mg kg^-1 was slightly higher than that of 3-MCPDE averaging at 1.3 mg kg^-1. Both esters were preferentially partitioned into the liquid phase rather than the solid phase after fractionation. However, the overall results exhibited no direct correlation between the esters content and the different sampling locations of the palm oil products in Malaysia. Analysis of total chlorine content also displayed significant variations between sampling locations which clearly show its effect on the chlorine content in the CPO samples.     

Formation mechanisms of monochloropropanediol (MCPD) fatty acid diesters in refined palm (Elaeis guineensis) oil and related fractions

Monochloropropanediol (MCPD) fatty acid esters are process contaminants generated during the deodorisation of edible oils. In particular, MCPD diesters are found in higher abundance in refined palm oil than other edible oils. In the present study, a series of model reactions mimicking palm oil deodorisation has been conducted with pure acylglycerols in the presence or absence of either organic or inorganic chlorine-containing compounds. Results showed that the bulk of MCPD diesters are formed above 200°C through the reaction of organochlorines with triacylglycerols (TAG). Additional experiments confirmed that this reaction can be initiated during palm oil deodorisation by hydrogen chloride (HCl) gas evolved through the thermal degradation of organochlorines present in the oil. Therein, the majority of the ultimately produced MCPD diesters are the result of HCl reacting with TAG, via protonation, followed by the elimination of a fatty acid residue. Two possible MCPD diester formation mechanisms are highlighted, both of which involve acyloxonium ion reactive intermediates. Investigations with pure TAG regio-isomers showed that MCPD ester formation is regioselective and the sn-1(3) position of the glycerol backbone is favoured.     

Fatty acid esters of monochloropropanediol (MCPD) and glycidol in refined edible oils

Recently, fatty acid esters of monochloropropanediol (MCPD) and that of glycidol have been reported in refined edible oils. Since then a wealth of research has been published on the factors influencing the formation of these contaminants in foods. It can be noted that the predominant precursors in a given matrix will not necessarily be the same as in other matrices. Further, proven relationships in the past between precursors responsible for free MCPD or free glycidol formation will not necessarily be valid for their fatty acid-esterified counterparts. This review attempts to summarise the current status of the literature as it pertains to the reasons surrounding the manifestation of MCPD esters and glycidyl esters in oils and fats. Recent efforts to mitigate the levels of these contaminants were highlighted and put into the context of their respective reaction matrices. As more accurate occurrence data for MCPD esters and glycidyl esters in other foods are collected, more targeted mitigation experiments can be formulated with respect to the reaction matrices under investigation.     

热加工过程中棕榈油理化特性、脂肪酸与自由基的变化研究

以棕榈油（24℃）为原料,采用国标法测定棕榈油在不同温度（160、180、200℃）下常规理化指标（酸价、过氧化值、丙二醛值、p-茴香胺值和总氧化值）随时间的变化,在此基础之上,分别采用GC-MS法与电子自旋共振（ESR）法对180℃下棕榈油脂肪酸组成和自由基含量变化进行测定。结果表明,加热温度越高和加热时间越长棕榈油理化指标值越大,其中过氧化值呈现先上升后下降趋势。脂肪酸组成结果表明,棕榈油中饱和脂肪酸与不饱和脂肪酸比例约为1∶1,且随着加热时间延长,比例基本不变。ESR实验表明,加热时间越长,2-苯叔丁基硝酮（PBN）捕获的自由基量越多,棕榈油氧化程度越深。      

Extraction and physicochemical properties of low free fatty acid crude palm oil

Response surface methodology was applied to optimize the pre-treatment of oil palm (Elaeis guineensis) fruit spikelets before oil extraction. The treatment applied was drying at different times and temperatures. The dried spikelets were then subjected to mechanical processes and crude oil was extracted. A central composite design was employed to study the responses, namely percentage of free fatty acids (FFA) and oil yield, and the optimum conditions for minimum FFA and maximum oil yield were identified from their respective contour plots. It was concluded that the pre-treatment should be carried out for 12.8 h at 66.8 °C. Under the optimum conditions, the corresponding response values for FFA and oil yield were 1% and 33.6%, respectively. Some of the physicochemical properties of the extracted oil were then determined. The low free fatty acid crude palm oil exhibited good physicochemical properties and could be useful for industrial applications.     

菜籽油脂肪酸单乙醇酰胺的合成

对以菜籽油脂肪酸甲酯和单乙醇胺为原料合成菜籽油脂肪酸单乙醇酰胺进行了研究。考察了反应温度、反应时间、碱性催化剂用量、体系压力等因素对反应的影响。通过正交实验优化得到的较佳反应条件为：反应温度125℃,反应时间6h,体系压力0．06MPa,碱性催化剂KOH不用为宜。在较佳反应条件下收率可达97．52％。利用无水乙醇对反应产物进行了重结晶,并进行了红外分析,证明得到了目标产物。     

棕榈油与猪油在组成结构和功能特性上的比较

比较了3种棕榈油和6种猪油产品在理化指标、营养与功能特性指标以及脂肪酸组成及其在甘油三酯Sn-2位上的分布情况,以判断棕榈油对猪油的可替代性.结果表明,棕榈油和猪油的熔点、碘值、酸值、过氧化值等理化指标很接近;棕榈油不含胆固醇,具有比猪油较高的V_E含量和氧化稳定性;在可塑性方面,精炼棕榈油与猪板油相当,而且好于猪杂油和猪膘油,棕榈硬脂与猪骨油相当,棕榈液油与猪皮油相当;虽然棕榈油和猪油的脂肪酸组成具有相似性,猪油的不饱和脂肪酸含量略高于棕榈油的不饱和脂肪酸含量,但是棕榈油的Sn-2位上主要分布不饱和脂肪酸,而猪油的Sn-2位上主要分布饱和脂肪酸,使棕榈油比猪油更加容易消化吸收.     

Glycidyl esters in refined palm (Elaeis guineensis) oil and related fractions. Part II: Practical recommendations for effective mitigation

In a previous work, it was shown that at high temperatures (up to 280 °C) glycidyl esters (GE) are formed from diacylglycerols (DAG) via elimination of free fatty acid (FFA). In the present study, the impact of DAG content and temperature on the formation of GE using a model vacuum system mimicking industrial edible oil deodorization is investigated. These deodorization experiments confirmed that the formation of GE from DAG is extensive at temperatures above 230-240 °C, and therefore, this value should be considered as an upper limit for refining operations. Furthermore, experimental data suggest that the formation of GE accelerates in particular when the DAG levels in refined oils exceed 3-4% of total lipids. Analysis of the lipid composition of crude palm oil (CPO) samples allowed the estimation that this critical DAG content corresponds to about 1.9-2.5% of FFA, which is the conventional quality marker of CPO. Moreover, high levels (>100 ppm) of GE were also found in palm fatty acid distillate samples, which may indicate that the level of GE in fully refined palm oils also depends on the elimination rate of GE into the fatty acid distillate.     

粗大鲵油的精制及其脂肪酸组成分析

粗大鲵油通过精制可除去其中的一些磷脂、蛋白质、游离脂肪酸和色素等杂质。结果表明：粗大鲵油精制工艺最佳参数为采用40%磷酸,添加量为1%（占油质量）,70℃脱胶1 min;采用3%氢氧化钠溶液,添加量为1.5%（占油质量）,65℃脱酸30 min;添加1%（占油质量）的活性白土,60℃脱色30 min;85℃下减压蒸馏脱臭30 min。在最佳工艺条件下,所得精制大鲵油澄清透明,略显淡黄色,鱼腥味较轻。对精制后的大鲵油采用气相色谱法共鉴定出25种脂肪酸,其中不饱和脂肪酸（UFA）含量为6981%,多不饱和脂肪酸（PUFA）含量为2760%,饱和脂肪酸（SFA）含量为2264%。     

高油酸葵花籽油煎炸过程中MCPD酯及缩水甘油酯的变化

以高油酸葵花籽油为煎炸用油对鱼排、鸡块和薯条进行煎炸实验,探究3-氯丙醇(3-MCPD)酯、2-氯丙醇(2-MCPD)酯和缩水甘油酯在煎炸过程中的变化。结果表明:原油中3-MCPD酯、2-MCPD酯及缩水甘油酯含量分别为0.26、0.05 mg/kg和0.58 mg/kg;在煎炸过程中2-MCPD酯含量与3-MCPD酯含量呈现极显著相关(p0.01);煎炸油中的MCPD酯在煎炸后有明显的生成;受煎炸材料的影响,3-MCPD酯含量在煎炸鱼排和鸡块体系煎炸12 h时达到最大值,分别为2.22 mg/kg和2.05 mg/kg,而后逐渐下降;3-MCPD酯含量在煎炸薯条体系中变化不大;缩水甘油酯含量则在所有体系中均下降,受煎炸材料的影响,缩水甘油酯分别在煎炸24 h(鱼排)、60 h(鸡块)和96 h(薯条)中基本降解完全。     

沙棘油脂肪酸、sn-2位脂肪酸及甘三酯的测定与分析

采用超临界CO_2萃取得到沙棘籽油和沙棘全果油,并采用气相色谱和超高效液相色谱-飞行时间质谱对其脂肪酸、sn-2位脂肪酸及甘三酯组成进行测定与分析。结果表明:沙棘籽油中亚油酸、亚麻酸和油酸的含量较多,分别为38.71%、25.66%和20.68%,这3种脂肪酸也是其主要的sn-2位脂肪酸,含量分别为46.46%、25.49%和23.02%;LOL(13.65%)、OLO(12.06%)和LLn O(11.23%)是沙棘籽油的主要甘三酯类型;沙棘全果油中棕榈油酸(36.86%)、棕榈酸(27.27%)和油酸(18.00%)的含量较高,主要的sn-2位脂肪酸为棕榈油酸(45.57%)和油酸(32.06%);沙棘全果油的主要甘三酯为POPo(14.38%)、PoOPo(13.77%)和OPO(12.06%)。     

Separation/fractionation of triglycerides in terms of fatty acid constituents in palm kernel oil using supercritical CO2

Separation of triglycerides in terms of fatty acid constituents in palm kernel oil (PKO) from dehulled ground palm kernel using supercritical carbon dioxide (SC‐CO₂) as a solvent at 40 and 80 °C and pressures of 20.7, 27.6, 34.5, 41.4 and 48.3 MPa was studied. The extraction was continuous and PKO was fractionated into four fractions. Triglycerides with differing fatty acid contents of caprylic (C8), capric (C10), lauric (C12), myristic (C14), palmitic (C16), stearic (C18:0), oleic (C18:1) and linoleic (C18:2) acid were separated in different percentages in different fractions. About 70% of PKO comprises triglycerides with C8–C12 fatty acids and these fatty acids were mostly extracted in fractions 1and 2. As a result, higher yields were observed in these fractions, especially at pressures higher than 27.6 MPa. The C16 and C18:2 components were extracted in fractions 3 and 4. These triglycerides form only a part of the remaining 30% of the fatty acid composition of PKO, hence the evidently diminishing yield in the later fractions. However, the compositions were found to be statistically significant for higher pressures and fraction times according to the type of fatty acid constituents. Copyright © 2006 Society of Chemical Industry     

金枪鱼油的精炼及其脂肪酸组成特征

粗鱼油中通常含有一定量的非甘油三酯杂质成分,这些杂质会影响鱼油的稳定性和进一步的深加工,通过精炼可以除去这部分杂质.研究表明,黄鳍金枪鱼鱼油精炼的工艺参数为:80%的H3PO4脱胶,添加量为油量的1%;30%的NaOH脱酸,添加量为油量的2%;活性白土脱色,添加量为油量的10%;85℃减压蒸馏脱臭15 min.经过精炼,鱼油呈淡黄色,澄清透明,具有较淡的鱼腥味,理化指标均达到鱼油的SC/T 3502-2000标准的精制鱼油一级要求,精制鱼油中PUFA的总含量达37.06%,DHA和EPA含量分别为25.10%和4.45%.     

Comparison of nutrient composition in kernel of tenera and clonal materials of oil palm (Elaeis guineensis Jacq.)

Nutritive information about oil palm kernel is scarce, especially on the composition of sugars and water-soluble vitamins. This study aims to evaluate both tenera and clonal materials for their proximate composition, fatty acid profile, amino acid composition, sugar, mineral and water-soluble vitamin contents. The tenera material had a higher moisture, fat and fibre content as compared to the clonal material, whereas protein, carbohydrate and ash content were higher in the clonal material. The major fatty acid constituents in palm kernel oil were lauric acid, myristic acid and oleic acid. The palm kernel proteins were deficient in lysine and tryptophan but rich in glutamic acid, arginine and aspartic acid. Sucrose was the most abundant sugar in palm kernel. The mineral analysis of the samples showed high levels of potassium, phosphorus, magnesium, calcium and manganese, while niacin was the water-soluble vitamin present at the highest concentrations in palm kernel.