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.     

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.     

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.     

Influence of chemical refining process and oil type on bound 3-chloro-1,2-propanediol contents in palm oil and rapeseed oil

The formation of bound 3-chloro-1,2-propanediol (3-MCPD-ester) in oils during chemical refining process was investigated for two palm oils and one rapeseed oil. Additionally, contents of mono- and diglycerides as well as total chlorine and chloride were determined. For all oils the deodorisation step representing one part of the refining process had the main impact on formation of 3-MCPD-esters whereas a direct effect of the other process steps could be neglected. 3-MCPD values in the range of 4–5 ppm for palm oil and 1 ppm for rapeseed oil were found. The chloride content was below detection limit. However, measurable amounts of total chlorine were found in palm oil with the highest 3-MCPD-ester contents. A considerable part of this total chlorine in the refined palm oil was embedded in the 3-MCPD-esters. On the other hand, content of diglycerides as the other potential pre-cursor was between 1% and 10% exceeding the 3-MCPD-ester contents by up to five magnitudes.     

毛细管气相色谱法检测方便面中棕榈油主要脂肪酸含量

方便面经酸水解后用乙醚提取,其中脂肪酸用ＫＯＨ一甲醇快速甲脂化,用毛细管气相色谱法测定,并重点对某企业生产的方便面产生异味原因进行剖析     

Effect of using interesterified and non-interesterified corn and palm oil blends on quality and fatty acid composition of Turkish White cheese

Chemically interesterified blends (CIB) and non‐interesterified blends (NIB) of corn and palm oils (75%w/25%w) were studied in the production of Turkish White cheese (TWC) to modify the fatty acid composition of traditional product. Milk fat (3%) was replaced by CIB and NIB for 25%, 50%, 75% and 100%. All cheese groups were ripened at 5 °C for 90 days. Samples were taken from each group after 3, 30, 60 and 90 days and analysed for their basic composition, lipolysis and proteolysis. CIB‐incorporated cheeses showed a higher degree of lipolysis than the control sample and the NIB‐incorporated counterparts. Fatty acid composition and sensory properties of the final product showed that the incorporation of CIB and NIB in TWC improved the nutritional content of the product because it altered the fatty acid composition without any adverse effect on sensorial quality. We concluded that in production of TWC, 50% of milk fat could be successfully replaced with CIB and NIB, preferably CIB, because of its superior sensory quality.     

Detection of fresh palm oil adulteration with recycled cooking oil using fatty acid composition and FTIR spectral analysis

There is a growing concern over the food safety issue related to increased incidence of cooking oil adulteration with recycled cooking oil (RCO). The objective of this study was to detect fresh palm olein (FPO) adulteration with RCO using fatty acid composition (FAC) and Fourier-transform infrared spectroscopy (FTIR) spectral analyses combined with chemometrics. RCO prepared in the laboratory was mixed with FPO in the proportion ranged from 1% to 50% (v/v) to obtain the adulterated oil samples (AO). FACs for FPO, RCO, and AO were determined using gas chromatography equipped with a flame ionization detector (GC-FID). The compositions of most fatty acids in RCO lied within the normal ranges of Codex standard, except for C8:0, C10:0, C11:0, C15:0, trans C18:1, and polyunsaturated fatty acids (PUFAs), C20:5. PUFAs showed a consistent decreasing trend with increasing magnitude of change with respect to increasing adulteration level and thus might be a good indicator for detecting FPO adulteration with RCO. The evaluation parameters (coefficient of determination, root mean standard error) of the FTIR-partial least square (PLS) model of palm oil adulteration with recycled oil are R² = 0.995 and 3.25, respectively. For FTIR spectral analysis, the distinct variations in spectral regions and aberrations in characteristic bands between FPO and RCO were observed. The optimized PLS calibration model developed from normal spectral of the combined region at 3602–3398, 3016–2642, and 1845–650 cm^?1 overpredict the adulteration level. On the other hand, the discriminant analysis classification model was able to classify the FPO and AO into two distinct groups. Improvement of the principles of combined techniques in authenticating AO from fresh oil is beneficial as a guideline to detect adulteration in cooking oil.     

Glycidyl esters in refined palm (Elaeis guineensis) oil and related fractions. Part I: Formation mechanism

Glycidyl esters (GE) are process contaminants generated during the deodorisation step of edible oil refining. In particular, GE are found in high abundance in refined palm oil. Palm oil is unique in that it contains a high amount of diacylglycerols (DAG, 4-12%). In the present study, a series of model reactions mimicking palm oil deodorisation has been conducted with pure tri-, di- and mono-acylglycerols (MAG). Results showed that GE are formed from DAG and MAG, but not from TAG, at temperatures (T) above 200 °C. Our observations suggest that GE are formed predominantly by intramolecular elimination of a fatty acid from DAG. In addition, isomers of GE, formed from DAG heated at T > 140 °C, were identified as oxopropyl esters. These new isomers were found to represent approximately 10% of GE levels in refined palm oil. Based on these considerations, the final GE content of palm oil could be limited by reducing DAG levels before oil processing and minimising deodorisation temperatures.     

Directed interesterification of a brazilian palm oil and analysis of the original and interesterified oil and its fractions

A commercial sample of the Brazilian palm oil from the north eastern State of Bahia after neutralisation, washing and drying was interesterified in the presence of sodium-potassium alloy (NaK) at 30°C in a nitrogen atmosphere. The catalyst was destroyed by addition of water in a carbon dioxide atmosphere and the interesterified oil was crystallised from light petroleum, yielding an olein and stearin fraction. The fatty acid and triacylglycerol composition of the neutralised oil was determined by gas chromatography (g.c.) and high-performance liquid chromatography (h.p.l.c.) respectively and was shown to be similar to that of Malaysian and African palm oil. The compositions of the interesterified Brazilian oil and its liquid and solid fractions were also determined. The physicochemical characteristics of the olein obtained by interesterification with NaK, such as iodine value (96.8) and its softening point (below ?8°C) indicated its suitability for the use as salad oil.