Factors affecting the Formation of Elaidic acid in Syrian Edible Oils during Frying with Home Conditions
Rania Matar*, Mayssam Salami, Zaid Al Assaf.
Department of Analytical and Food Chemistry, Faculty of Pharmacy, Damascus University, Syrian Arab Republic.
*Corresponding Author E-mail: raniamatar1983@gmail.com
ABSTRACT:
Trans fatty acids formed in edible oils during the heating process are proved to have harmful effects on health including coronary heart disease infant neurodevelopment and growth, and childhood allergies. The main objective of this work was to study the effect of different factors (heat, moisture, time and pressure) on Elaidic acid formation in fried food and edible oils during frying in the home kitchen. Three types of locally consumed edible oils (corn oil, sunflower oil, and soybean oil) produced in Syria, were used for frying. First, the formation of trans fatty acid in oils during heating to several temperatures (180°C, 200°C, 210°C, 220°C) was examined, then the effect of repeated frying process during frying at 180°C, fat and moisture content in fried food, and the effect of pressure cooker on the fatty acid composition of the oils and the oils extracted from the fried food samples were investigated by gas chromatography (G.C) equipped with a Mass spectroscopy (MS). Results showed no effect of fat and moisture, frying period, or pressure on the decrease of Oleic acid and formation of Elaidic acid with a temperature less than 240°C, therefore fried foods prepared in home kitchen don’t have any impact on the dietary intake of Elaidic acid.
KEYWORDS: Edible oils, Elaidic acid, fried food, pressure cooker, GC-MS.
INTRODUCTION:
During the frying process, oils are repeatedly used at elevated temperatures under the atmospheric oxygen and receive maximum oxidative and thermal abuse. Many chemical reactions such as hydrolysis and oxidative or thermal degradation occur in the structure of the oil. Because of some physiochemical changes, new compounds arise in the oil depending on the frying conditions such as heating temperature, heating period, pressure, and the content of fat and moisture in food.
Fried foods absorb these compounds during the frying process(2,4-6). In general, frying might be a reason for the formation of trans fatty acids which have undesirable effects on human health(5).
Typically, common edible oils are the main sources of unsaturated fatty acids especially Oleic acid (9 cis C18:1) which is the most present unsaturated fatty acid(7,8), while Elaidic acid (9 trans C18:1), the trans isomer of Oleic acid is not found in crude oil or could be found in small amount formed during the purification processes(9) . According to several studies, The majority of Elaidic acid can be found in partially hydrogenated oils, shortening, margarine, cookies, snack food, and fried food as a result of heat treatments such as deodorization, cooking, frying depending on different parameters such as temperature and length of treatment (10-12).
In contrast to the effect of cis and essential fatty acids that have significant benefits in human body(13,14), high contents of trans fatty acid in foods are of concern for human health, due to their ability to promote several chronic diseases such as coronary heart disease, insulin resistance and allergic reactions. An increase of the blood levels of LDL cholesterol (LDL) and Triglycerides (TAGs) and a decrease of the level of HDL cholesterol (HDL) can be observed. There is further evidence for effects in connection with sudden cardiac death and systemic inflammation(15). Trans fatty acid compared with their cis analogues gave rise to higher insulin levels in the blood at the same blood sugar level which indicates that trans fatty acid produces increased insulin resistance(16). A rise in allergic diseases has also been observed upon the high ingestion of these fatty acids(17). Additionally, the high consumption of trans fatty acid during pregnancy has been associated with effects on intrauterine development(18). Based on these observations, WHO recommends that the trans fatty acids consumptions should be less than 1% of the total daily energy intake(19).
This study aims to investigate by GC(20) the production of Elaidic acid in frying oils and fried foods during frying in the home kitchen conditions, which makes approximately 80-90% of the total trans fatty acid in foods(21-23).
MATERIAL AND METHOD:
Chemicals, reagents and Instruments:
Oleic acid methyl ester and Elaidic acid methyl ester were purchased from Larodan Sweden, and were used to confirm the retention times and mass spectra for peak identification, as well as to determine the concentrations of Oleic acid and Elaidic acid in samples tested. Methanol, potassium hydroxide, hydrochloric acid and n-Hexane were obtained from FLUKA. A rotary-evaporator (Stuart) was used to evaporate the solvent after Soxhlet extraction. Gas chromatography (GC) equipped with a Mass spectroscopy (MS) was used for the specific analysis of the trans fatty acids in the extract
Samples:
For the present study, three kinds of Syrian edible oils (corn oil, sunflower oil, and soybean oil) produced in Syria, were collected from local supermarkets. And three types of food were selected for frying process (chicken, potato and aubergine).
Elaidic acid and oleic acid content in crude oils before heating processes:
Edible oils may contain a small amount of trans fatty acids (0-1 %) that could be produced during the purification processes. To estimate the contents of Oleic acid and Elaidic acid in crude oils, three samples of commercially available edible oils (corn oil, sunflower oil, and soybean oil) were analyzed before heating processes using GC-MS.
Formation of Elaidic acid in heated edible oils:
In order to estimate the formation of Elaidic acid in edible oils during heating, edible oils samples were heated without food to several temperature (180°C, 200°C, 210°C, 220°C), after four hours of heating, Elaidic acid formation was investigated using GC-MS.
Formation of Elaidic acid during the frying process:
The formation of trans fatty acid in oil during the frying process with home conditions has also been investigated in this study which depended on the frying period, pressure and the content of fat and moisture in fried foods.
Effect of fat and moisture content in food:
Foods vary in their content of moisture and fat, which could affect the amount of trans fatty acids formed during frying process. The different food samples (chicken, potato and aubergine) which differ in their content of fat and moisture were fried in sunflower oil at 180°C. after every seventh frying operation in the same frying oil of each type of food, fried food samples were subjected to an oil extraction process with n-hexane using a soxhlet extraction system, then Elaidic acid in the frying oil and oils extracted from fried food were analyzed using GC-MS.
The effect of frying period:
Potatoes were fried in sunflower oil at 180°C separately for different time periods (5, 7, 10, 15, 20 min), fried potatoes samples were subjected to an oil extraction process with n-hexane using a soxhlet extraction system, and Elaidic acid content of the extracted oils was determined.
The effect of pressure:
Chicken samples were fried in sunflower oil using household pressure cooker which causes a pressure, high temperature (240°C) and less time (10min) during frying process. Elaidic acid in the frying oil and oils extracted from fried chicken was analyzed using GC-MS.
These processes were repeated twice using corn oil and soybean oil as frying oils.
Determination of Elaidic acid content in frying oil and oils extracted from fried food:
Soxhlet extraction method:(24,25)
A homogenized sample (5g) was weighed into a cellulose extraction cartridge and the soxhlet apparatus containing the cartridge was fitted to a distillation flask containing 150ml of n-hexane and a few anti bumping granules. Sample were extracted for 220 min (30-40 cycles/h). At the end of the extraction, the solvent was removed using a vacuum rotary evaporator.
Esterification method:(24,26)
0.2g of frying oil (or 150mg of oil extract from fried food by soxhlet) was put into test tube and dissolved in 2.4ml of n-hexane, an aliquot 0.6ml of (2mol/l) methanolic potassium hydroxide solution was added. The tube was capped and shaken for 20 s and allowed to boil for one minute in water bath at 70°C. Then, 1.2ml of (1mol/l) hydrochloric acid was added and gently stirred. Next, 3ml of n-hexane was added and the upper phase containing the fatty acids methyl esters was decanted and dissolved in n-hexane to 10ml and 0.5 ϻl of the obtained solution was injected into the GC-MS.
Gas chromatography mass spectrometry analysis:
GC–MS analysis was carried out using an Agilent 6890 gas chromatograph with a 5973 MS detector equipped with 60 m×0.25 mm, i.d. 0.25μm/MS DB-WAX capillary column (Agilent). Helium was used as the carrier gas at a flow rate of 0.58 ml/ min with a split ratio of 30:1, and the sample size was1.0 μL. The following temperature program was used: injector temperature 230°C, initial column temperature 100°C (held 5 min), temperature ramp 10°C/min to 240°C and held at this temperature for 10min. The total run time was 30 min. the injection was performed manually. Data acquisition was realized in the scan mode (range 40-400 m/z). The fatty acids were identified by comparing their retention times and mass spectral data to the mass spectral data obtained by analysis of standard fatty acids methyl esters solution under the same conditions.(27)
RESULTS AND DISCUSSION:
Elaidic acid and oleic acid content in crude oils:
Prior the heating process, corn oil and soybean oil contained 25.54(g/100g) and 21.35 (g/100g) Oleic acid, respectively. and 0.04 (g/100g) and 0.06 (g/100g) Elaidic acid, respectively. While sunflower oil did not contain Elaidic acid and contained 31(g/100g) of Oleic acid.
Elaidic acid formed in oils during heating to several temperatures:
Results shown in table (1) indicate no significant changes in the percentage of fatty acids in oils as result of heating even after four hours of heating at different temperatures ranging from 180°C to 220°C. Therefore there is no heat effect on the formation of Elaidic acid in edible oils at temperatures lower than 220°C. Our results are in accordance with previous studies that reported the formation of only small amount of trans fatty acids in vegetable oils during continuous heating at 180°C(28-30). Other studies also proved that heating oils to temperatures less than 200°C has no significant effect on the production of trans isomers of unsaturated fatty acids.(31)
Elaidic acid formed in oils during frying process:
Effect of moisture and fat:
Results in table (2) show that the difference in content of fat and moisture did not affect the composition of oil's fatty acids during the frying process even after repeating the frying process several times using the same oil. The fatty acids composition of the fried food was consistent with that of the frying oil. These results agree with the results of other studies that have proven that repeated frying process would not have a large effect on trans fatty acid increase in frying oil. (32)
Table (1) Elaidic acid and oleic acid percentage before and after four hours of heating at different temperatures
|
|
Before heating at room temperature |
180°C |
200°C |
210°C |
220°C |
|||||
|
Oleic acid % |
Elaidic acid % |
Oleic acid % |
Elaidic acid % |
Oleic acid % |
Elaidic acid % |
Oleic acid % |
Elaidic acid % |
Oleic acid % |
Elaidic acid % |
|
|
Sunflower oil |
31.4 |
0 |
31.02 |
0 |
31.65 |
0 |
30.98 |
0 |
31.28 |
0 |
|
Corn oil |
25.54 |
0.04 |
25.23 |
0.04 |
24.95 |
0.038 |
25.62 |
0.04 |
25.51 |
0.04 |
|
Soybean oil |
21.35 |
0.06 |
21.62 |
0.06 |
21.65 |
0.06 |
21.24 |
0.058 |
21.29 |
0.06 |
Table (2) composition of sunflower oil's fatty acids before and during the frying process(area%)
|
Fatty acid |
Crude Sunflower oil |
After seventh frying operation |
|||
|
sunflower oil (frying oil) |
Potato |
Aubergine |
Chicken |
||
|
Palmetic acid |
6.76 |
6.9 |
6.82 |
6.92 |
6.89 |
|
Linolic acid |
59.17 |
60.32 |
59.62 |
60.52 |
60.28 |
|
Oleic acid |
31.4 |
32.02 |
31.65 |
32.11 |
31.99 |
|
Elaidic acid |
0 |
0 |
0 |
0 |
0 |
|
Stearic acid |
2.71 |
2.76 |
2.73 |
2.77 |
2.76 |
Table (3) effect of frying period on Elaidic acid and Oleic acid percentage in fried potatoes:
|
|
5min |
7min |
10min |
15min |
20min |
|||||
|
Fried potatoes |
Oleic acid % |
Elaidic acid % |
Oleic acid % |
Elaidic acid % |
Oleic acid % |
Elaidic acid % |
Oleic acid % |
Elaidic acid % |
Oleic acid % |
Elaidic acid % |
|
31.02 |
0 |
31.5 |
0 |
31.24 |
0 |
30.98 |
0 |
31.35 |
0 |
|
Effect of frying period:
Results presented in table (3) show that frying to a constant frying temperature (180°C) do not lead to trans fatty acids formation no matter how long the heating period lasts. The fatty acids composition of the fried potatoes was consistent with that of the frying oil.
Effect of pressure:
Results showed that frying using household pressure cooker did not affect the composition of oil's fatty acids during the frying process despite pressure and high temperature (250°C), even after repeating the frying process several times using the same oil.
The fatty acids composition of the fried chicken are shown in table (4), which were consistent with that of the frying oil.
Table (4) composition of fried chicken's fatty acids during the frying using household pressure cooker (area%)
|
|
First frying operation |
Seventh frying operation |
|
Palmetic acid |
6.82 |
6.78 |
|
Linolic acid |
59.52 |
59.35 |
|
Oleic acid |
31.61 |
31.53 |
|
Elaidic acid |
0 |
0 |
|
Stearic acid |
2.79 |
2.75 |
The formation of Elaidic acid in corn oil and soybean oil during frying was also not remarkable and matched the same level as that of sunflower oil, therefore introducing other oils as frying oils would not significantly change the percentage of Oleic acid and Elaidic acid in these edible oils.
CONCLUSION:
Based on the results obtained in this study, Frying with a heat temperature less than 240°C don't affect the composition of fatty acids in frying oil. So frying processes using edible oils with home kitchen condition don't have an effect on Elaidic acid formation in frying oil and fried food.
ACKNOWLEDGEMENTS:
The authors acknowledge the financial support received from Damascus University. Scientific assistance provided by Prof. Mounir Ataei (Faculty of Pharmacy, Arab international university) , D. Ghassan Abochama (Faculty of science, University of Damascus) and D. Wissam Zam ( Al Andalus university) is greatly appreciated.
CONFLICT OF INTEREST:
No conflict of interest to be declared.
REFERENCES:
1. Boskou G et al. Content of trans, trans-2,4-decadienal in deep-fried and pan-fried potatoes. Eur J Lipid Sci Tech. 2006; 108: 109–115.
2. Dobarganes C, Marquez-Ruiz G, Velasco J. Interactions between fat and food during deep-frying. Eur J Lipid Sci Tech. 2000; 102: 521–528.
3. Edna S J. An epidemiological survey to determine the prevalence of consumption of fast food among children and their knowledge regarding the food they eat. Asian J. Nursing Edu. And research.2013;3(4): 267-269.
4. Gertz C. Chemical and physical parameters as quality indicators of used frying fats. Eur J Lipid Sci Tech. 2000; 102: 566–572.
5. Karn S, Abraham RA, Ramakrishnan L. Assessment of trans fatty acid content in widely consumed snacks by gas chromatography in a developing country. Food Nutr Sci. 2013; 4: 1281–1286.
6. Saiprabha M M, Goswami-Giri A S. Composition and characterization of refined oil compared with its crude oil from waste obtained from mangifera indica. Asian J. Research Chem. 2011;4(9): 1415-1419.
7. Gargee Y, Srivastava H C. fatty acid composition and oil content of some safflower (Carthamus tinctorius L.) cultivars of Indian origin. Asinan J. Research Chem. 2013; 6(7): 634-636.
8. Nisreen A et al. isolation and ultra-purification of oleic acid extracted from olive oil using urea crystallization. Rrsearch J. Pharm. And Tech.2018; 11(2):624-627.
9. Corl B A et al. Trans-7, cis -9 CLA is synthesized endogenously by 9-desaturase in daily cows. Lipids. 2002; 37: 681–688.
10. Devinat G, Scamaroni L, Naudet M. Isomérisation de l’acide linolénique durant la désodorisaton des huiles de colza et de soja. Rev Franc Corps Gras. 1980; 27: 283–287.
11. Liu W H, Inbaraj B S, Chen B H. Analysis and formation of transfatty acids in hydrogenated soybean oil during heating. Food Chem. 2007; 104: 1740–1749.
12. Ledoux M, Juanèda P, Sèbedio J L. Trans fatty acids: definition and occurrence in foods. Eur. J. Lipid. Sci. Technol. 2007; 109: 891–900.
13. Manjula B et al. Role of omega fatty acids in human body. Asian J. Research Chem. 2009; 2(2):93-99.
14. Nutan M, Prakash M. Omega 3 fatty acds for women's health and happiness. International journal of advances in nursing management. 2016; 4(3): 309-313.
15. Mozaffarian D, Aro A, Willett W C. Health effects of trans‐fatty acids: Experimental and observational evidence. Eur. J. Clin. Nutr. 2009; 63: 5–21.
16. Bray GA et al. The influence of different fats and fatty acids on obesity, insulin resistance and inflammation. J Nutr. 2002; 132: 2488-91.
17. Weilandsk et al. Intake oftrans fatty acids and prevalence of childhood asthma and allergies in Europe. Lancet. 1999; 353: 2040– 2041.
18. Decsit, Koletzkob. Do trans fatty acids impair linoleic acid metabolism in children?. An Nutr Met. 1995; 39: 36– 41.
19. WHO. Diet, Nutrition and the preventation of chronic diseases. WHO Technical Report. 2003; Series 916.
20. Neelam V, Rakesh C. Electrchemical analysis of fatty acids obtained from the natural resource seed of perilla frutescens. Asian J. Research Chem. 2011;4(5): 705-707
21. Weggemans R M, Matsuoka A, Ushida K. Intake of ruminant versus industrial transfatty acids and risk of coronary heart disease-what is the evidence? Eur. J. Lipid Sci. Technol. 2004; 106: 390–397.
22. Kraft J et al. The conversion efficiency of trans-11 and trans-12 18:1 by Delta-9 – desaturation differ in rats. J. Nutr. 2006; 136: 1209–1214.
23. Stender S, Dyerberg J, Astrup A. High levels of industrially produced trans fat in popular fast foods. New Eng. J. Med. 2006; 354: 1650–1651.
24. Snežana Kravić et al. Determination of transfatty acids in foodstuffs by gas chromatography–mass spectrometry after simultaneous microwave-assisted extraction–esterification. J. Serb. Chem. Soc. 2010;75 (6): 803–812.
25. Rajabudeen E, Saravana G A, M. Padma S S. GC-MS analysis of the methanol extract of tephrosia villosa (L.) pers. Asian J. research chem. 2012; 5(11): 1331- 1334.
26. Vishwe P S et al. comparative study of biodiesel production from pure sunflower oil and waste sunflower oil. Research J. Pharma. Dosage forms and tech. 2013; 5(3): 171-173.
27. Yogeshwar R M et al. A sensitive and selective GC-MS method for the determination of process related genotoxic impurities in esomeprazole magnesium. Asian J. Research Chem. 2010; 3(2) :395-397.
28. Bansal G et al. Analysis of trans fatty acids in deep frying oils by three different approaches. Food chem. 2009; 116: 535-541.
29. Liu W H et al. Analysis ad formation of trans fatty acids in hydrogenated soybean oil during heating. Food chem. 2007; 104: 1740-1749.
30. Tsuzuki W et al. Cis/trans isomerization of triolein, trilinolein and trilinolenin induced by heat treatment. Food chem. 2008; 108: 75-80.
31. Morenomcmm et al. Determination of unsaturation grade and transisomers generated during thermal oxidation of edible oils and fats by FTIR. J Molec Struct. 1999; 482: 551– 556.
32. Tsuzuki W, Matsuoka A, Ushida K. Formation of trans fatty acids in edible oils during the frying and heating process. Food Chem. 2010; 123: 976–982.
Received on 18.04.2019 Modified on 21.05.2019
Accepted on 16.06.2019 © RJPT All right reserved
Research J. Pharm. and Tech. 2019; 12(11): 5451-5455.
DOI: 10.5958/0974-360X.2019.00945.4