HUNGARIAN JOURNAL OF INDUSTRY AND CHEMISTRY Vol. 46(2) pp. 33–36 (2018) hjic.mk.uni-pannon.hu DOI: 10.1515/hjic-2018-0015 COMPARISON BETWEEN STATIC AND DYNAMIC ANALYSES OF THE SOLID FAT CONTENT OF COCONUT OIL VINOD DHAYGUDE *1 , ANITA SOÓS1 , ILDIKÓ ZEKE2 , AND LÁSZLÓ SOMOGYI1 1Department of Grain and Industrial Plant Technology, Szent István University, Villányi út 29–43, Budapest, 1118, HUNGARY 2Department of Refrigeration and Livestock Products Technology, Szent István University, Ménesi út 43-45, Budapest, 1118, HUNGARY The objective of this work was to compare the physical and thermal characteristics of two coconut oils and their blends which were observed by the results of differential scanning calorimetry (DSC) and pulsed nuclear magnetic resonance (pNMR). Fat blends composed of different ratios (fully hydrogenated coconut oil / non-hydrogenated coconut oil: 25/75, 50/50 and 75/25) were prepared and examined for solid fat content. The solid fat content of samples was determined as a function of temperature by pNMR. The DSC technique determines the solid fat index by measuring the heat of fusion successively at different temperatures. DSC calculates the actual content of solids in fat samples and how it changes throughout the duration of heating or cooling. A characteristic curve is constructed by the correlation of enthalpies. Based on our results, it is clear that both DSC and pNMR techniques provide very practical and useful information on the solid fat content of fats. DSC is dynamic and pNMR is static. A difference in the values of the solid fat indexes of samples was observed which may be due to a fundamental difference between the two techniques. These data can be used by food manufacturers to optimize processing conditions for modified coconut oil and food products fortified with coconut oil. Keywords: solid fat content, solid fat index, pNMR, DSC, and Coconut oil 1. Introduction Nowadays, a proper understanding of the crystallization and melting properties of coconut oil systems is essential to increase the number of applications in the food indus- try. Coconut oil is considered as a multi-component mix- ture of various triglycerides which determines the physi- cal properties that affect the structure, stability, flavor as well as sensory and visual characteristics of foods [1]. Modification of the properties of solid fat has received much attention in research recently because of its impor- tance during the processing and production of new food products. The crystallization and melting properties of modified fat used as a shortening in bakery products are critical [2]. The crystal networks present in modified fat strongly enhance its texture, stability and acceptance of fatty-food products. An essential aspect of the industrial manufacture of edible oils and fats is the ability to measure the physical and thermal properties of the materials such as melting and crystallisation profiles, solid fat content (SFC), solid fat index (SFI) and enthalpy. Nuclear magnetic resonance (NMR) spectroscopy and differential scanning calorime- try (DSC) are easier to implement and faster techniques than dilatometry which is time-consuming and inaccurate *Correspondence: vinod.dhaygude05@gmail.com [3]. NMR has been widely used for the analysis of food materials such as dairy products, fats and oils, in addi- tion to wine and beverages. Over the past two decades, DSC has been increasingly utilised for the thermody- namic characterisation of edible oils and fats as well as the SFI determination of food fats. Considering the significant scientific and practical im- portance of the physical properties of coconut oil from a few studies, the solid fat content determined by NMR and DSC methods was investigated and the obtained results compared. Ultimately, this research study is beneficial to the food industry which continues to reformulate many products. 2. Experimental 2.1 Materials In this research study, Barco coconut oil was used as a source of non-hydrogenated coconut oil (NHCO) which was kindly provided by Mayer’s Kft. in Budapest. The fully hydrogenated coconut oil (FHCO) was obtained from local industry in Hungary. Blends of NHCO and FHCO were mixed in 25:75, 50:50 and 75:25 (w/w) pro- portions. The blends were melted and maintained at 80 ◦C for 30 mins to erase crystal memory. Subsequently, mailto:vinod.dhaygude05@gmail.com 34 DHAYGUDE, SOÓS, ZEKE, AND SOMOGYI Table 1: Fatty acid composition (%) of NHCO, FHCO and their blends. Fatty acid FHCO FHCO:NHCO NHCO (%) 75:25 50:5 25:75 C6:0 0.1 0.225 0.35 0.475 0.6 C8:0 1.9 3.175 4.45 5.725 7 C10:0 2.7 3.4 4.1 4.8 5.5 C12:0 53.3 51.425 49.55 47.675 45.8 C12:1 0.1 0.075 0.05 0.025 − C14:0 21.3 20.675 20.05 19.425 18.8 C16:0 10 10.025 10.05 10.075 10.1 C18:0 10 8.25 6.5 4.75 3 C18:1 trans 0.03 0.0575 0.085 0.1125 0.14 C18:1 cis 0.3 2.0 3.7 5.4 7.1 C18:2 trans − 0.02 0.05 0.08 0.11 C18:2 cis 0.1 0.5 0.9 1.3 1.7 C20 0.1 0.1 0.1 0.1 0.1 Other 0.02 0.03 0.05 0.065 0.08 all blends and pure samples of fat were stored in a refrig- erator at 10 ◦C until use. 2.2 Methodologies Static analysis The static analysis of the solid fat con- tent was conducted by pulsed nuclear magnetic resonance (pNMR) apparatus (Bruker Minispec 300, Bruker GmbH, Germany) according to the official method Cd 16b-93 of the American Oil Chemists’ Society (AOCS) [4]. The solid fat content was measured at 5 ◦C, 10 ◦C, 15 ◦C, 20 ◦C, 25 ◦C and 30 ◦C. Three parallel measurements were conducted and average values reported (Fig. 1). Ad- ditionally, these SFC values were converted into percent- ages where the initial value was considered to be 100 %. These percentage SFCs were compared with the SFIs. Dynamic Analysis Dynamic analyses of the samples were studied by DFC according to AOCS official method Cj 1–94 [4]. Samples of nearly 20 mg were loaded onto the middle of the aluminum pans using a small spatula and hermetically sealed by an empty pan that served as a reference. Samples were cooled to 0 ◦C at a rate of 1 ◦C min−1 and maintained at this temperature for 10 mins. The heating of blends and pure samples of oil was performed until a temperature of 80 ◦C was achieved at the same rate as for the cooling. The samples were maintained at 80 ◦C for 30 mins. The cooling process started after this period and the rate of cooling was 1 ◦C min−1 until the temperature reached −20 ◦C. Before being heated again to ambient temperature, the samples were maintained at this temperature for 10 mins. After that, heating commenced once more at a rate of 5 ◦C min−1 up to 20 ◦C at which point calorimetric measure- ments ended. Three parallel measurements were taken and the average thermogram was reported. The SFI of fat is expressed as a function of temper- ature. The numbers of solids in the samples of oil in re- lation to the temperature were estimated on the basis of the calorimetric results. Areas of the thermograms were Figure 1: Solid fat content profiles of two coconut oils and their blends. calculated and correlated with the percentage of solids in the samples. 3. Results and Discussion 3.1 Fatty acid composition Samples were characterized by their fatty acid composi- tion (see Table 1). The dominant fatty acids in the sample of coconut oil were lauric acid (C12:0) 45.8-53.3 % and myristic acid (C18:0) 18.8-21.3 %. The NHCO exhibited a higher percentage of medium-chain fatty acids and a lower percentage of unsaturated fatty acids. The FHCO was rich in polyunsaturated fatty acids (PUFA) and mo- nounsaturated fatty acids (MUFA). 3.2 Solid fat content according to NMR The composition of fatty acids and triacylglycerols (TAG) would contribute to the percentage of solid fat par- ticles in liquid oil at various temperatures. The SFC pro- files of the original fats and their blends at temperatures ranging from 5 ◦C to 30 ◦C are presented in Fig. 1. The SFC profile of NHCO exhibited low values of 81.06 %, 69.70 %, 54.61 %, 34.54 %, 25.86 % and 0.17 % over the temperature range of 5 ◦C – 30 ◦C because of the concentration of fatty acids. In the case of FHCO, the solid fat content was high at 90.49 %, 81.28 %, 69.29 %, 54.15 %, 48.30 % and 4.46 % over the same temperature range. The SFC profiles of blends changed following the addition of FHCO to NHCO. An increase in the maxi- mum values of SFC was also observed by Ribeiro et al. following the addition of fully hydrogenated soybean oil to soybean oil [5]. This can be explained by the changes in the composition of triacylglycerols of the blends. At 5 ◦C, the blends exhibited SFCs ranging from 84.94 % to 90.02 %, which decreased non-linearly until melting completely at 30 ◦C. During the blending, the concen- tration of TAGs with high melting points increased and subsequently the SFC values of blends were modified. In all blends, the SFC values at 30 ◦C were almost identical to the SFC of the FHCO. Hungarian Journal of Industry and Chemistry STATIC AND DYNAMIC ANALYSES OF THE SOLID FAT CONTENT OF COCONUT OIL 35 Figure 2: Melting profiles of two coconut oils and their blends. Table 2: Thermal properties of NHCO, FHCO and their blends. Sample Max. Peak temperature Enthalpy (◦C) (J/g) FHCO 24.61 80.24 75:25(w/w)FHCO:NHCO 24.30 76.21 50:50(w/w)FHCO:NHCO 23.96 63.44 25:75(w/w)FHCO:NHCO 23.52 55.84 NHCO 23.27 46.38 3.3 Melting characteristics The melting profiles of NHCO in the presence of fully hydrogenated coconut are depicted in Fig. 2. The melt- ing behavior of the original oils and blends was charac- terized by only one endothermic peak. A similar ther- mal behavior of coconut oil and hydrogenated coconut oil was observed by one major peak in various studies [6, 7]. Components with the lowest melting points tend to melt first and represent the most unsaturated triglyc- erides, while components with higher melting points that represent the most saturated triglycerides melt later. Sim- ilarly, results showed that NHCO started melting first compared to other samples because of its higher con- tent of unsaturated triglycerides. The addition of FHCO to NHCO did not alter the melting behavior but as the content of FHCO was increased, the peaks according to the melting profiles of blends shifted towards the high- melting temperatures (Fig. 2). This melting profiles provided an indication of the amount of crystallized fat and the occurrence of polymor- phic transitions. The thermal characteristics of the original oils and their blends are shown in Table 2. No significant differ- ences were observed between the values of onset temper- ature (Ton) and peak temperature (Tp) in addition to the enthalpies of NHCO and FHCO. Ton ranged from 15.60 ◦C to 20.50 ◦C while Tp ranged from 23.27 ◦C to 24.61 Figure 3: Solid fat index profiles of two coconut oils and their blends. ◦C. Melting enthalpies of NHCO following the addition of FHCO increased from 46.38 J/g to 80.24 J/g (see Table 2). 3.4 Solid fat index (SFI) The solid-liquid ratio in fats expressed as solid fat con- tent is determined from the melting curves that result from DSC by partial integration. The heat flow into or out of samples of fat was measured as they were heated and cooled isothermally. The estimation of the SFIs of samples is dependent upon the onset and final tempera- tures of melting. The SFI profiles of all samples calcu- lated by melting thermographs are shown in Fig. 3. Non- hydrogenated coconut oil exhibited a characteristic steep slope and a rapid decrease in the percentage of solids at 20 ◦C. This ratio of solids to liquids decreases differently in these blends of fat as the temperature rises and is at its minimum for all blends at around 30 ◦C (see Fig. 3). 4. Discussion The results obtained from two methods exhibited a wide range of solid fat content values of the same samples. The values of SFC calculated from pNMR results were lower than values of SFI according to DSC where DSC is a dy- namic method and NMR is a static method. The values of the percentages of SFC for each blend at 15 ◦C calculated by DSC were 87.55 %, 88.38 % and 95.95 % (see Fig. 3) but 68.05 %, 68.83 % and 72.35 % when calculated by pNMR, respectively (see Fig. 4). DSC samples exhibited a sharp decline in their SFI or ratio of solids to liquids when heated from 15◦C to 25◦C, however, the SFC of samples according to NMR exhibited a gradual slope. DSC measurements of physical behavior were ob- served under controlled heating conditions. The results of DSC describe the whole melting process whilst be- ing heated. The NMR results indicate the statistical val- ues of solid fat content. The difference between the two measurements was possibly due to the time-dependent process concerning the development of crystal structure where SFI describes the status of the fat system and SFC 46(2) pp. 33–36 (2018) 36 DHAYGUDE, SOÓS, ZEKE, AND SOMOGYI Figure 4: Solid fat content (%) of two coconut oils and their blends. the solid status after stabilization. In addition NMR iden- tified state vise crystals at respective temperatures. The difference in values may be due to the method of tem- pering, the rate of heating or cooling, and the degree of accuracy. 5. Conclusion The results revealed that by combining FHCO with NHCO the melting behavior of blends of coconut oils was modified, leading to significant increments in the melt- ing point and in the maximum solid fat content. These two methods yielded more descriptive and clear informa- tion about melting behaviour by determining amounts of solids in the samples of coconut oil in relation to the tem- perature. Static and dynamic analytical methods showed a difference in the solid-to-liquid ratio of samples which may be due to fundamental differences. The blending of FHCOs with vegetable oils can produce valuable blends of fat of good consistency and with reduced or even in the absence of trans-isomers of unsaturated fatty acids suit- able for margarine. Acknowledgement This research was supported by the Doctoral School of Food Sciences at Szent István University. REFERENCES [1] Dayrit, F. M.: The properties of lauric acid and their significance in coconut oil. J. Am. Oil Chem. Soc., 2015 92, 1–15 DOI: 10.1007/s11746-014-2562-7 [2] O’brien, R. D.: Fat and oils formulating and processing for applications Boca Raton, FL CRC/Taylor & Francis, 2009, USA ISBN: 9781420061666 [3] Walker, R. C.; Bosin, W. A.: Comparison of SFI, DSC and NMR methods for determining solid- liquid ratios in fats. J. Am. Oil Chem. Soc., 1971 48, 50–53. DOI: 10.1007/BF02635684 [4] AOCS: Official Method Cd 16b-93 Solid fat con- tent (SFC) by low-resolution nuclear magnetic res- onance; in: Firestone, D. (ed.) Official methods and recommended practices of the AOCS. The Ameri- can Oil Chemists Society, 2005 , Champaign, USA. ISBN: 9780935315974 [5] Ribeiro, A.; Grimaldi, R.; Gioielli, L. A.; Gonçalves, L.: Zero trans fats from soybean oil and fully hydrogenated soybean oil: Physico- chemical properties and food applications. Food Research International, 2009 42, 401–410 DOI: 10.1016/j.foodres.2009.01.012 [6] Tan, C. P.; Che Man, Y. B.: Differential scanning calorimetric analysis of palm oil, palm oil based products and coconut oil: Effects of scanning rate variation. Food Chemistry, 2002 76, 89–102 DOI: 10.1016/S0308-8146(01)00241-2 [7] Shen, Z.; Birkett, A.; Augustin, M. A.; Dungey, S.; Versteeg, C.: Melting behavior of blends of milk fat with hydrogenated coconut and cottonseed oils. J. Am. Oil Chem. Soc., 2001 78, 387–394 DOI: 10.1007/s11746-001-0273-4 Hungarian Journal of Industry and Chemistry https://doi.org/10.1007/s11746-014-2562-7 https://doi.org/10.1007/BF02635684 https://doi.org/10.1016/j.foodres.2009.01.012 https://doi.org/10.1016/j.foodres.2009.01.012 https://doi.org/10.1016/S0308-8146(01)00241-2 https://doi.org/10.1016/S0308-8146(01)00241-2 https://doi.org/10.1007/s11746-001-0273-4 https://doi.org/10.1007/s11746-001-0273-4 Introduction Experimental Materials Methodologies Results and Discussion Fatty acid composition Solid fat content according to NMR Melting characteristics Solid fat index (SFI) Discussion Conclusion