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Monitoring Flavor Quality, Composition and Ripening Changes of Cheddar Cheese Using Fourier-Transform Infrared Spectroscopy

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Monitoring Flavor Quality, Composition and Ripening Changes of Cheddar Cheese Using Fourier-Transform Infrared Spectroscopy MONITORING FLAVOR QUALITY, COMPOSITION AND RIPENING CHANGES OF CHEDDAR CHEESE USING FOURIER-TRANSFORM INFRARED SPECTROSCOPY DISSERTATION Presented in Partial Fulfillment of the Requirements for Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Anand S. Subramanian, M.S. ***** The Ohio State University 2009 Dissertation Committee: Approved by Dr. Luis E. Rodriguez-Saona, Advisor Dr. W. James Harper _______________________ Dr. V.M Balasubramaniam Advisor Dr. David B. Min Food Science and Nutrition Graduate Program Copyright by Anand Swaminathan Subramanian 2009 ABSTRACT Cheese flavor develops during the ripening process, when complex changes take place, leading to the formation of flavor compounds, including amino acids and organic acids. However, cheese ripening is not completely understood, making it difficult to produce cheese of uniform flavor quality. Currently, cheese characteristics are determined using sensory panels and chromatography, which are expensive, time- consuming, and laborious. The objective was to develop a rapid and cost-effective technique based on Fourier-transform infrared spectroscopy (FTIR) for simultaneous analysis of cheese composition and flavor quality and identify some of the biochemical changes occurring during ripening. Cheddar cheese samples were obtained from a cheese manufacturer, along with their composition, age and flavor quality data. The samples were powdered using liquid nitrogen and water-soluble compounds were extracted using water, chloroform and ethanol. The extracts were analyzed by reverse phase HPLC for 3 organic acids, GC-FID for 20 amino acids, and FTIR to collect the mid-infrared spectra (4000-700 cm-1). The collected spectra were correlated with flavor quality and composition data to develop classification models based on soft independent modeling of class analogy (SIMCA) and regression models based on partial least squares (PLS). The infrared spectra of the samples were well defined, highly consistent within each sample and distinct from other samples. All the cheese samples formed well separated clusters based on their flavor quality (fermented, unclean, low flavor, sour, good, etc.) in SIMCA classification plot. The PLS models showed excellent fit with coefficient of correlation (r-value) >0.83 and could simultaneously determine the pH, ii moisture, fat, salt, age, 20 amino acids and 3 organic acids in less than 20 min per sample. The estimated standard errors of prediction were less than 5%. Absorptions from amino acids, organic acids and short-chain fatty acids (1800-900 cm-1) were found to be very important factors influencing the models. Lactic acid, glutamic acid, leucine, asparagine, phenylalanine and valine are some of the compounds that exhibited significant changes during ripening. This method shows great promise as a rapid tool for simultaneous analysis of cheese characteristics, which can save time, labor and operational costs for the industry and cheese research. iii Dedicated to My parents M. Subramanian and S. Savithri Thank you for your love, support and encouragement. iv ACKNOWLEDGEMENTS I thank my parents and my brother, whose support and encouragement were instrumental to all my achievements throughout my academic life. My heartfelt thanks to Veena, whose patience, support and motivation during every step of my Ph.D. and help with my experiments and dissertation, greatly helped me achieve this and more. I sincerely thank Dr. Luis Rodriguez-Saona for his intellectual support, enthusiasm, believing in my capabilities, eagerly extending help whenever needed and supporting me not only with my research and academic activities but also several extracurricular activities. I wish to thank Dr. W. James Harper for his insightful suggestions, discussions and thoughts that helped in steering my research in the right direction. I am also grateful to Dr. David B. Min and Dr. V.M. Balasubramaniam for serving in my research committee and providing their valuable comments to improve my research. Thanks to my colleagues Annegret Männig, Cecilia Shiroma-Kian, Nathan Baldauf, Francisco Parada-Rabell and Jian He for their help at various stages of my Ph.D. Special thanks to my lab mate Geng Chen for his help with my experiments. I am thankful to my friends Raghupathy Ramaswamy and Mallikarjuna Rettiganti for their support and help with my academic and non-academic activities. v This research was supported by grants from Ohio Agricultural Research and Development Center (OARDC), Midwest Advanced Food Manufacturing Alliance (MAFMA; USDA Cooperative State Research, special grant number 2006-34328-17149) and DairiConcepts LP (Springfield, MO). I particularly thank Kris Clements of DairiConcepts for his support and involvement in the project. I wish to express my gratitude to the Department of Food Science and Technology for providing the opportunity to pursue my Ph.D., and financial assistance. I also thank the department staff for their help with activities related to my Ph.D. studies. vi VITA December 06, 1980 ........................................Born – Chennai, India 1998 – 2002....................................................B.Tech. Food Process Engineering, Tamil Nadu Agricultural University. 2003 – 2005....................................................M.S. Agricultural and Biological Engineering, Pennsylvania State University. 2005 – Present................................................Ph.D. Food Science and Nutrition, The Ohio State University. PUBLICATIONS Subramanian, A., Harper, J. W, ad Rodriguez-Saona, L. E. 2009. Rapid prediction of composition and flavor quality of Cheddar cheese using ATR-FTIR spectroscopy. J. Food Sci. 74(3): C292-C297. Subramanian, A., Harper, J. W, and Rodriguez-Saona, L. E. 2009. Cheddar cheese classification based on flavor quality using a novel extraction method and Fourier transform infrared spectroscopy. J. Dairy Sci. 92:87-94. Subramanian, A., and Rodriguez-Saona, L. E. 2008. Fourier Transform Infrared (FTIR) Spectroscopy. Pages 145-178 in Infrared Spectroscopy for Food Quality Analysis and Control. D. W. Sun, ed. Academic Press, New York, NY. FIELDS OF STUDY Major Field: Food Science and Nutrition vii TABLE OF CONTENTS ABSTRACT........................................................................................................................ ii ACKNOWLEDGEMENTS................................................................................................ v VITA................................................................................................................................. vii LIST OF TABLES............................................................................................................. xi LIST OF FIGURES .......................................................................................................... xii CHAPTER 1 ....................................................................................................................... 1 LITERATURE REVIEW ................................................................................................... 1 1.1 CHEDDAR CHEESE............................................................................................... 1 1.1.1 Cheddar Cheese Manufacture............................................................................ 3 1.1.2 Cheddar Cheese Ripening.................................................................................. 5 1.1.3 Biochemical Changes during Ripening ............................................................. 6 1.1.3.1 Metabolism of Lactose, Lactate and Citrate ............................................... 6 1.1.3.2 Lipolysis and Catabolism of Free Fatty Acids............................................ 8 1.1.3.3 Proteolysis and Catabolism of Amino Acids.............................................. 9 1.1.4 Factors Affecting Ripening and Flavor Development..................................... 13 1.1.5 Cheddar Cheese Flavor.................................................................................... 15 1.1.5.1 Component Balance Theory ..................................................................... 15 1.1.5.2 Contribution of Volatile Phase.................................................................. 15 1.1.5.3 Contribution of Aqueous Phase ................................................................ 16 1.1.6 Monitoring Cheese Ripening and Flavor......................................................... 17 1.2 FOURIER-TRANSFORM INFRARED SPECTROSCOPY ................................. 19 1.2.1 Brief History .................................................................................................... 19 1.2.2 Fourier-Transform Mid-Infrared Spectroscopy ............................................... 20 1.2.3 Construction of FTIR Spectrometers............................................................... 21 1.2.4 Collection of Spectra........................................................................................ 23 1.2.5 Advantages and Limitations ............................................................................ 26 1.2.6 Chemometric Analyses of Spectroscopic Data................................................ 27 1.2.6.1 Principal Component Analysis ................................................................. 27 1.2.6.2 Soft Independent Modeling of Class Analogy (SIMCA) ......................... 28 1.2.6.3 Partial Least Squares Regression (PLSR)................................................. 29 viii 1.2.7 Cheese Analysis
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