Application of Portable and Benchtop Mid-Infrared Spectrometers in Profiling Composition and Quality of Edible Oils
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Application of Portable and Benchtop Mid-Infrared Spectrometers in Profiling Composition and Quality of Edible Oils THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Michael J Wenstrup Graduate Program in Food Science and Nutrition The Ohio State University 2013 Master's Examination Committee: Dr. Luis Rodriguez-Saona, Advisor Dr. John Litchfield Dr. Michael Mangino Copyrighted by Michael J. Wenstrup 2013 Abstract The application of infrared spectroscopy techniques to problems in the food and beverage industry has yielded many novel methods. With the increase in computational power, multivariate analysis has brought the unique properties of mid-infrared (MIR) systems to the forefront. The distinct, high intensity MIR absorption bands are well-suited to authentication, classification and quantification of components in complex matrices. This technique has been applied to a variety of food systems, with particular success in the analysis of edible oils. Methods for trans-fat determination, monitoring of oxidative indices, and discrimination of adulterated oils represent only a few of the developments in field of oils. The objective of this study was to utilize MIR spectroscopy in the analysis and characterization of products and processes related to edible oils. A temperature- controlled, ZnSe ATR sampling accessory was used with a benchtop FT-IR system to monitor oxidative changes in frying oils under the influence of a patented anti-oxidation device. In addition, reference methods for free fatty acids (FFA), anisidine value (AV), and color were used to monitor oil stability. FT-IR combined with chemometrics showed differences between control and treatment, with discrimination provided by regions associated with fatty acid hydrolysis and oxidation products. As compared to the control treatment, the anti-oxidation technology decreased the rate of FFA and aldehyde formation, as well as showing a marked effect on total color difference (ΔE). Overall, our results showed that a patented induction device slows the rate of lipid degradation, ii resulting 7-20% reduction in formation rate of key quality parameters and significantly longer utilization of frying oil. Omega-3 dietary supplements have been linked with health benefits due to their contents of EPA and DHA. The concentration of these active components in fish is highly variable; species, catch location, environment, season and processing parameters are all factors in determining the ratio of fatty acids found in the oil. Our objective was to characterize the composition of commercial Omega-3 dietary supplements using mid-infrared spectroscopy, gas chromatography, and chemometrics. Twenty-nine fish body oil (FBO), cod liver oil (CLO), and flaxseed supplements were purchased from retailers. Fatty acid composition of oils, determined by GC-FAME, encompassed a wide range of fatty acid profiles and delivery methods. Mid-infrared spectral data was collected on portable infrared systems and the spectra were used to classify supplements using SIMCA, a pattern recognition technique. In addition, PLSR was used to correlate the spectra with GC-FAME results. SIMCA analysis allowed for tight clustering of fish oil supplements into distinct classes, dependent upon the source and processing. Discriminating power showed a strong influence of the 1038 cm-1 band, which is typically associated with C-O stretching vibrations. PLSR generated multivariate models with high correlation (R ≥ 0.99) between the infrared spectrum and fatty acid composition, and SECV of 1.74 and 1.89 for EPA and DHA, respectively. Our results indicate that ATR FT-IR spectroscopy combined with pattern recognition analysis provides for rapid, robust screening and characterization of edible oils. iii Acknowledgments Thank you to all of my co-workers and labmates for their guidance and for helping me keep my sanity. Thank you to my committee members, Drs. Litchfield and Mangino, and to my advisor, Dr. Rodriguez-Saona. iv Vita June 2007 .......................................................…………………….Centerville High School June 2011…………………………………..B.S. Biochemistry, The Ohio State University January 2012 to present ................................Graduate Research Associate, Department of Food Science and Technology, The Ohio State University Fields of Study Major Field: Food Science and Nutrition v Table of Contents Abstract ............................................................................................................................... ii Acknowledgments.............................................................................................................. iv Vita ...................................................................................................................................... v Table of Contents ............................................................................................................... vi List of Tables ..................................................................................................................... ix List of Figures ..................................................................................................................... x Chapter 1: Literature Review ............................................................................................. 1 1.1 Lipids in Food ........................................................................................................... 1 1.2 Chemical Reactions of Lipids in Food Systems ....................................................... 2 1.2.1 Thermal Degradation .......................................................................................... 2 1.2.2 Lipid Oxidation................................................................................................... 3 1.2.3 Maintaining Oil Quality...................................................................................... 6 1.3 Infrared Spectroscopy ............................................................................................... 8 1.3.1 Near-Infrared Spectroscopy ................................................................................ 9 1.3.2 Mid-Infrared Spectroscopy ............................................................................... 10 1.4 Chemometrics and Multivariate Analysis ............................................................... 15 vi Chapter 2: Effect of a Novel Induction Food-Processing Device in Improving Frying Oil Quality............................................................................................................................... 18 2.1 Abstract ................................................................................................................... 19 2.2 Introduction ............................................................................................................. 19 2.3 Materials and Methods ............................................................................................ 22 2.3.1 Frying Protocol ................................................................................................. 22 2.3.2 Sample Collection............................................................................................. 23 2.3.3 Fatty Acid Profile ............................................................................................. 23 2.3.4 Oil Quality Metrics ........................................................................................... 24 2.3.5 Fourier Transform Mid-Infrared Spectroscopy ................................................ 25 2.3.6 Multivariate Analysis ....................................................................................... 25 2.3.7 Statistical Analysis ........................................................................................... 25 2.4 Results and Discussion ............................................................................................ 26 2.4.1 Fourier-Transform Infrared Spectroscopy ........................................................ 27 2.4.2 Monitoring Oxidative Indicators ...................................................................... 33 2.5 Conclusions ............................................................................................................. 37 Chapter 3: Application of a Portable Infrared Spectrometer for Characterization of Omega-3 Dietary Supplements ......................................................................................... 39 3.1 Abstract ................................................................................................................... 40 vii 3.2 Introduction ............................................................................................................. 42 3.3 Materials and Methods ............................................................................................ 45 3.3.1 Sample Preparation ........................................................................................... 45 3.3.2 Fatty Acid Profile ............................................................................................. 45 3.3.3 Fourier Transform Mid-Infrared Spectroscopy ................................................ 46 3.3.4 Multivariate Analysis ....................................................................................... 47 3.4 Results and Discussion ............................................................................................ 51 3.4.1 Characterization