The physicochemical and thermal properties of Malaysian high free fatty acid crude palm oil , Murad Awadh Bahadi, Jumat Salimon , and Abd-Wali M. Japir
Citation: AIP Conference Proceedings 1784, 030002 (2016); doi: 10.1063/1.4966740 View online: http://dx.doi.org/10.1063/1.4966740 View Table of Contents: http://aip.scitation.org/toc/apc/1784/1 Published by the American Institute of Physics
The Physicochemical and Thermal Properties of Malaysian High Free Fatty Acid Crude Palm Oil Murad Awadh Bahadi1, 2, Jumat Salimon1*, Abd-Wali M. Japir1 1
School of Chemical Sciences and Food Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia. 2
Faculty of Education and Sciences, Hadhramout University, Yemen. *
Corresponding author:
[email protected]
Abstract. This study was carried out to determine the physicochemical properties and the thermal behavior of Malaysian high free fatty acid crude palm oil (HFFA-CPO). The physicochemical properties showed that the free fatty acid (FFA %), acid value, iodine value, saponification value, unsaponifiable matter, hydroxyl value, specific gravity, refractive index at 28°C, moisture content, viscosity at 28°C and colour at 28°C values were 9.4±0.1 %, 21.3±0.1 mg/g, 50.6±0.2 mg/g, 203.1±0.1 mg/g, 0.7±0.1%, 43.4±0.2 mg/g, 0.878 g/ml, 1.4669, 0.6 %, 52 cP and 50R–40Y respectively. Gas chromatography (GC) was used to determine the fatty acid (FA) composition in HFFA-CPO. The fatty acids were found to be comprised mostly with 45.7 % palmitic acid (C16:0), 39.5 % oleic acid (C18:1), 9.4 % linoleic acid (C18:2) and 4.3 % stearic acid (C18:0). The analysis of triacylglycerol components with high performance liquid chromatography (HPLC) has resulted with 3.5 % triunsaturated (OOO, OLL and OLO), 32.7 % monosaturated (POO, PLO, SOO and PLL), 35.7 % disaturated (MLP, PPL, PPO, POS and SOS) and 2.32 % trisaturated fatty acids (PPP and PPS). The differential scanning calorimetry (DSC) showed that the crystallization of TAG displayed two major exothermic regions of HFFA-CPO with the di and trisaturated TAG at 23.11°C and the di and triunsaturated TAG at 9.31 °C. The melting curve displayed multiple endothermic peak regions at 25.13 °C and 35.31 °C could be attributed to the di and trisaturated TAGs. While the peaks at 0.95 °C, 6.94 °C and 9.77 °C could be attributed to the mono, di and triunsaturated TAGs.
Keywords: High free fatty crude palm oil, physicochemical properties, thermal properties
INTRODUCTION The oil palm tree is a monocotyledon, a flowering plant that grows extensively in most parts of the tropical and subtropical regions around the world [1]. Today, oil palm trees can be found mainly in the western part of Africa, Indonesia, Malaysia and most recently in Brazil and Colombia [2]. As the name implies, the oil palm is highlyfavoured for its oil, of which is extracted from the flesh of the fruit (mesocarp) and the seed or kernel. Oil from the mesocarp is known as the crude palm oil (CPO) and oil from the seed or kernel is termed crude palm kernel oil (CPKO). Yet, having been extracted from the same tree is utterly contradictory to the fact that both types of oil have different physical and chemical properties. In general, crude palm oil comprises mainly of acylglycerols and small quantities of non- acylglycerols components which include free fatty acids (FFAs), trace metals, moisture, impurities and minor components [3]. The fatty acid composition of crude palm oil is mainly 50% saturated and 50% unsaturated fatty acids [4] and the triacylglycerols composition of palm oil consist of 6.4 % trisaturated, 44.7% disaturated, 37.7 % monosaturated and 6.5 % triunsaturated [5] . The crude palm oil comprises minor components; 3–8% diglycerides, less than 3% monoglyceridesand 3–4% free fatty acids and approximately 1% of minor components which include carotenoids, vitamin E (tocopherols and tocotrienols), sterols, phospholipids, glycolipids, and terpenic and aliphatic hydrocarbons [6] . Saad et al [7] reported that the range of free fatty acid content of crude palm oil was 2.3–6.7%. Most frequently, rancidity and spoilt-taste become the major issues of the palm oil industry.
The 2016 UKM FST Postgraduate Colloquium AIP Conf. Proc. 1784, 030002-1–030002-7; doi: 10.1063/1.4966740 Published by AIP Publishing. 978-0-7354-1446-4/$30.00
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This problematic condition may develop from increased FFA content caused by enzymeic and microbial lipase reactions of palm fruit. Basically, high FFA content is a consequence of nature, that is, from elevated temperature and high moisture storage conditions [8]. A palm oil is considered as a high-FFA-CPO for having more than 5 % of fatty acids. Increasing this level will conspicuously affect the palm oil quality and usage, either in the food or nonfood applications [9]. The thermal behavior of oil is characterized by studying the effect of heating rates on oil melting curves and cooling rates on oil crystallization curve using a differential scanning calorimetry (DSC) [10]. DSC provides information on the excess specific heat over a wide range of temperatures [11]. In fact, that melting and crystallization behaviors of oils and fats are two important properties for the functionality in many prepared food products. These thermal properties are counterparts of the TAG profile in oils and fats [12]. There are a great number of studies that discussed the thermal behavior of low free fatty acid crude palm oil [13], refined, bleached, and deodorized (RBD) palm oil, RBD palm olein, and RBD palm stearin [10]. However, this study intended to highlight the physicochemical properties of Malaysian high free fatty acid crude palm oil and to analyze the thermal behavior of Malaysian high free fatty acid crude palm oil which is, to the best knowledge of the researcher, no similar study has been carried out so far.
MATERIALS AND METHODS Sample Malaysian high free fatty acid crude palm oil (HFFA-CPO) was obtained from Sime Darby oil refinery, Selangor, Malaysia.
Apparatus and Chemicals Wij’s solution, n-hexane, sodium hydroxide (NaOH), potassium iodide (KI) solution, sodium thiosulphate (Na2S2O3), potassium hydroxide(KOH), hydrochloric acid (HCl), acetic anhydride, pyridine, 95% v/v ethyl alcohol were purchased from Sigma-Aldrich
Chemical Analysis Acid value, iodine value, saponification value, unsaponifiable matter and hydroxyl value of Malaysian high free fatty acid crude palm oil were determined by adopting the methods by Salimon et al [14].
Physical Analysis Moisture content of the HFFA-CPO was determined using a Moisture Analyzer model AND MX-50. The colour was identified using a LovibondTintometer Model F/10508. Brookfield model RV DV-I+ (U.S.A) Spindle of SO5 was used for viscosity analysis. The oil refractive index was measured using a refractometer at 26.5 °C according to the specific gravity of the oil sample. All The physical properties analyses were performed according to AOCS official methods and PORIM test method [15] .
Fatty Acid Composition A Gas Chromatography (Shimadzu GC-17A) equipped with a capillary column BPX 70 (30m×0.25mm×0.25m) and the FID detector was used to identify the fatty acid composition (FAC) of HFFA-CPO. The column temperature was set at 120 °C with a regular increase of about 3 °C per minute for 57 minutes. However, the detector as well as injector temperature were programmed at 280 °C and 260 °C, respectively. Nitrogen gas was utilized as the gas carrier with a flow rated of0.3 mL/min. By using base-catalysed transesterification, fatty acid methyl ester (FAME) was prepared adopting the procedure of Salimon et al [14]. The peaks were identified by comparing its retention time with the authentic standards.
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Triacylglycerol composition By using HPLC from Waters model 1515 supplied with evaporative light scattering detector (ELSD) and equipped with an auto-injector and Spherisorb C18 column, (150mm×4.8μm×3mm), TAG of HFFA-CPO was identified by confirming with Salimon et al [14]. The mobile phase was a combination of acetone: acetonitrile (63.5:36.5), programmed at flow rate of 1mL/min. The sample was dissolved in 10 mL of the acetone: acetonitrile mixture before 20 mL of the sample was injected into HPLC with total running time of about 50 min. TAG peaks were identified based on the retention time of available commercial TAG standards. The relative composition percentage of TAG peaks were evaluated from all peaks appeared after 8 minutes (retention time of the first TAG peak appeared).
Thermal behavior Thermal properties of HFFA-CPO were investigated using a differential scanning calorimeter (DSC 822e Mettler Toledo calibration) to obtain the melting and crystallization curves. DSC analysis was carried out according to Salimon et a l[14]. Sample was weight into the 49 mL sealed aluminium pan ranged from 3 mg to 5 mg. The samples were put in an oven for 30 min, in the freezer for 90 min and then at room temperature for 48 hours. Then, the HFFA-CPO was put at 5 °C and was used directly to run at -60 °C to 60°C to -60 °C with heating rate 10°C.
RESULTS AND DISCUSSION Physicochemical properties Comparison with the standard Malaysian crude palm oil (Table 1) is prominent that the HFFA-CPO have higher FFA content and therefore, higher acid value. The difference of moisture content is also apparent, while other properties vary slightly. The result shows that the average value of FFA % and acid value for HFFA-CPO are 9.4±0.1 % and 21.3±0.1 respectively. It can be hypothesized that weathering and climatic conditions with exposure to heat and moisture may have caused the major difference in FFA %, acid value and moisture content, as well as prolonged storage time. FFA is an important quality indicator as it is related to the level of oil deterioration. ‘Rotten oil’ is not suitable for the food industry for it is inedible, thus its usage is only limited to non-food applications. Malaysian palm oil mills are restricted to the standard level of below 5% FFA content to ensure high quality palm oil [16]. Fats & oil unsaturation is measured according to the iodine value, where higher iodine value indicates higher degree of unsaturation [5]. The iodine value of the HFFA-CPO measured in this study was 50.6±0.2 mg/g which denotes its high content of unsaturated fatty acids in it. Somehow, the iodine value of HFFA-CPO and the standard CPO is compatible (Table 1). Similarly, saponification value of HFFA-CPO was 203.1±0.1 mg/g and also compatible with a range of typical crude palm oil. The average molecular weight of TAG for HFFA-CPO was 828.7 g/mol. The unsaponifiable matter showed quite a huge gap with the standard CPO. As it resembles the total quantity of substances present in oil or fat, it is an essential parameter that determines its selection of use in the industry. The total quantity of unsaponifiable matter of HFFA-CPO was recorded as 0.7±0.1% which was high compared to the Malaysian crude palm oil standard. HFFA-CPO was observed as semi-solid at room temperature and orange-red in colour, with viscosity detected at 52cp. The refractive index of HFFA-CPO at 28°C was 1.4669.
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TABLE 1. Physicochemical properties of HFFA-CPO Parameter FFA% Acid value mg/g Iodine value (Wijs) mg/g Saponification value mg/g Unsaponifiable matter % Average molecular weight g/mol Hydroxyl value mg/g Specific gravity g/ml Refractive index at 28°C Moisture content Viscosity (28°C)cp Colour at 28°C
HFFA-CPO 9.4±0.1 21.3±0.1 50.6±0.2 203.1±0.1 0.7±0.1 828.7 43.4±0.2 0.878 1.4669 0.6 % 52 50 R – 40 Y
CPOMS a
