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Title:	The development method for the analysis of fatty acids in vegetable fats and bakery products by using gas chromatography
Authors:	Talal Ahmed Salem Omar (P51603)
Supervisor:	Jumat Salimon, Professor Dr.
Keywords:	Fatty acids Gas chromatography Essential fatty acids
Issue Date:	30-Oct-2014
Description:	Minyak dan lemak dalam pemakanan harian merupakan sumber utama asid lemak (FAs) perlu dalam tubuh manusia. Namun begitu, kesedaran yang tinggi terhadap pengambilan makanan yang mengandunggi FAs trans dan cis wujud disebabkan oleh kesan buruk terhadap manusia. Oleh itu, kaedah penentuan secara tepat kandungan FAs dan asid lemak trans (TFAs) amat diperlukan bagi tujuan pengawalan dan perlabelan kandungan nutrien dalam sampel pemakanan berlemak. Pada fasa permulaan daripada penyelidikan ini, metodologi pengesteran metil yang digunakan dalam analisis FAs telah dinilaikan, dan kemudian tiga prosedur metilasi telah dicadangkan dan dikaji untuk mengatasi masalah pada kaedah tersebut untuk meningkatkan kepekaan dan ketepatan analisis. Selanjutnya, kaedah pengenalpastian dan penentuukuran kandungan FAs and TFAs dalam sampel makanan berlemak secara kromatograpi gas (GC) berasaskan kepada pengekstrakan lipid dan penterbitan menggunakan mangkin bes diikuti oleh trimetilsilil-diazometana (TMS–DM) telah dibangunkan. Selepas pengoptimuman, cadangan prosedur dibangunkan yang terdiri daripada ekstraksi lemak oleh heksana dan metilasi menggunakan NaOCH3 diikuti dengan TMS-DM pada 60°C, dengan kehadiran butylatedhydroxytoluene (BHT), kemudian diekstraksi oleh FAMEs dua kali dengan heksana, kaedah ini kelihatan yang paling memuaskan bagi menyediakan FAs untuk kuantifikasi GC. Kaedah yang dicadangkan telah dinilaikan dan divalidasi terhadap sembilan individu dan campuran pelbagai jenis FAs, termasuk TFAs, menggunakan dua teknik kuantitatif (piawai dalaman titik tunggal dan titik berganda), dan keputusan bagi faktor tindak balas, kelinearan, kepekaan, had pengesanan (LOD), had kuantifikasi (LOD), kepersisan dan ketepatan telah dibentangkan. Secara keseluruhannya, keputusan didapati tepat, sensitif (nilai-nilai cerun adalah sama, kira-kira 0.22), linear pada julat kepekatan dikaji, nilai pekali korelasi adalah lebih tinggi daripada 0.99 untuk semua FAs yang dikaji. Julat nilai LOD diperolehi ialah 0.03-0.09 μg/mL, dan pelbagai LOQ adalah 0.1-0.2 μg/mL bagi sasaran FAs. Tambahan pula, untuk menunjukkan kesesuaian kaedah yang dicadangkan, ia telah digunakan bagi penentuan kuantitatif kandungan FA dalam pelbagai lemak makanan sayur-sayuran dan sampel minyak (iaitu, marjerin, lelemak dan lemak adunan) dan pelbagai jenis produk bakeri seperti biskut, kek, biskut, roti keropok dan wafer. Kaedah ini juga telah divalidasi ke atas sampel sebenar dan kepersisan (%RSD) serta peratusan pemulihan (%R) semuanya telah ditentukan. Berdasarkan keputusan yang diperolehi, nilai R dari semua sampel didapati hampir 100%, kebolehulangan adalah di antara 0.32% dan 3.88%, dan nilai kebolehasilan semula RSD adalah di antara 1.03% dan 5.60%. Dalam fasa terakhir, kaedah ini telah dibandingkan dengan kaedah yang berdasarkan asas-pemangkin diikuti dengan kaedah asid-pemangkin (KOCH3/HCl), dan analisis statistik telah digunakan untuk mengkaji perbezaan yang signifikan (P=0.05) antara kedua-dua kaedah. Secara umum, keputusan membuktikan bahawa kaedah yang dicadangkan boleh dipercayai, tepat dan persis untuk analisis sasaran FAs memandangkan ia telah menunjukkan keberkesanan yang lebih tinggi dalam analisis cis/trans FA tak tepu berbanding dengan kaedah klasik. Oleh itu, ia boleh menjadi kaedah yang berkesan untuk menganalisis lemak sayuran dan minyak dalam campuran kompleks produk makanan untuk memantau tahap rendah FAs dan TFA, dan boleh digunakan untuk kajian nutrisi dan perubatan.,Fats and oils in human diets are the main sources of essential fatty acids (FAs) for the body. However, there is a mounting concern about intake of foods containing trans and cis FAs due to their deleterious effects on humans. Thus, the accurate detection of FAs and trans fatty acids (TFAs) is needed to control and correct nutrition labeling in dietary fat samples. During the initial phase of the present research, most methyl esterification methodologies used in FAs analysis were evaluated, and then three methylation procedures were proposed and studied for overcoming the shortcomings of those methods and improve the sensitivity and accuracy of the analysis. Accordingly, a method for the separation, identification and further quantification of FAs and TFAs in food fats by gas chromatography (GC) based on the extraction of lipid and derivatization using base catalyzed followed by (trimethylsilyl)-diazomethane (TMS)-DM was developed. After optimization, the proposed developed procedure, comprising lipid extraction by hexane and methylation using NaOCH3 followed by TMS-DM at 60°C, in the presence of butylatedhydroxytoluene (BHT), then extraction of FAMEs twice with hexane, seemed the most satisfactory method of preparing FAs for GC quantification. The proposed method was evaluated and validated to nine of individual and mixtures of different types of FA standards, including TFAs, using two of quantitation techniques (single- & multiple- point internal standard) , and the results for response factors, linearity, sensitivity, limit of detection (LOD), limit of quantitation (LOQ), precision and accuracy were presented. Overall, the results were found to be accurate, sensitive (the slope values were similar, approximately 0.22), linear over the concentration range studied and the coefficient of determination values were higher than 0.99 for all the FAs studied. The LOD values obtained ranged from 0.03 to 0.09 μg/mL, and the range of LOQ was from 0.1 to 0.2 μg/mL for the target FAs. Furthermore, in order to demonstrate the applicability of the proposed method, it was applied to the quantitative determination of the FA content in different vegetable food fats and oils samples (i. e., margarines, shortenings and blended fats) and various kinds of bakery products such as biscuits, cakes, cookies, crackers breads and wafers. The method was also validated on the real samples by determining the precision (RSD%) and the recovery percentage (R %). Based on the results obtained, the R-values from all the samples were revealed to be close to 100%, repeatability RSD ranged between 0.32% and 3.88%, and the reproducibility RSD values ranged between 1.03% and 5.60%. In the final phase, the method was compared with the method which was based on base-catalysed followed by an acid-catalysed method (KOCH3/HCl), and the statical analysis was used for evaluating the significant differences (P=0.05) between the two methods. In general, the results proved that the developed method is reliable, accurate and precise for the analysis of FAs since it has showed higher effectiveness in cis/trans unsaturated FA analysis than the classic methods. Thus, it could be an effective tool for analyzing vegetable fats and oils in complex mixtures of food products for monitoring the low levels of FAs and TFA, and can be applied to nutritional and medicine studies.,PhD
Pages:	229
Call Number:	QD79.C45O464 2014 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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