Application of Fourier-transform Infrared (FTIR) for Quality Control of Swiss Cheese THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Ni Cheng Graduate Program in Food Science and Technology The Ohio State University 2013 Master’s Examination Committee: Dr. W. James Harper, Advisor Dr. Luis E. Rodriguez-Saona Dr. Sheryl. Barringer Copyrighted by Ni Cheng 2013 Abstract Swiss-type cheese has many problems in its manufacturing. Split and variability are two most important problems in Swiss cheese. And traditional cheese grading is time consuming and costs a lot. The objective of this study was to find indicators for split formation and to show the sources of quality variability. Rapid classification of graded cheese has also been studied. Swiss-type cheese samples were obtained from different factories for study on split, variability and grading, respectively. Fourier-transform infrared spectroscopy (FTIR) was used in different parts of this study. FTIR collects the mid-infrared spectra (4000-700cm-1), and the resulting wave numbers formed, were used to monitor water extracts of Swiss-type cheese during manufacture, in defective cheeses and in different grades of cheese. Soft independent modeling of class analogy (SIMCA) was used to develop different classifications with infrared spectra. This study has shown that FTIR, coupled with water extraction, was a useful tool to monitor changes occurring in Swiss cheese making, for split formation and cheese ii variability. FTIR showed that band 1639- 1612 cm-1, 1158-1151cm-1, 1485-1493cm-1, which belong to the amide I and II of protein degradation compounds, might be characteristic bands for split formation. Lactic acid degradation may also be a factor for split formation. For variability in Swiss cheese, FTIR showed different patterns amount different factories and within a single factory (at different manufacturing stages, from vat to vat, and from batch to batch). Based on Taylor’s sensory study (Taylor, 2013) on the same 15 cheeses from five different factories, FTIR could be a promising method to study flavor variability in Swiss-type cheese. FTIR data showed different indicators for flavor variability both within a factory and among different factories. FTIR was also a possible method for rapid cheese grading. iii Dedicated to My parents B. Cheng and Z. Li Thank you for your love iv Acknowledgments I would like to thank my parents, whose love, support and encouragement are unreserved and unconditional. I also would like to thank my Aunt Rachel Cheng and Uncle Lin Hao, for taking care of me in the USA. I would like to thank Dr. W. James Harper for his wisdom suggestions and thoughts that helped in guiding my research and thesis. I am grateful to Dr. Luis E. Rodriguez- Saona for his generous support and help. I would like to Dr. Sheryl Barringer for being as my committee member. I would like to thank my lab members, Cheryl Wick, Taehyun Ji , Kaitlyn Taylor, Feifei Hu, Hardy Castada and Matt Gardener for their help and encouragement. I would like to thank Ting Wang and all people in Dr. Rodriguez-Saona’s lab, for their helps for my experiments. I would like to extend my gratitude to all my friends within and without Food Science program, who lightened up my life in Columbus, Ohio. v I am thankful to my dear friends Xiaoxue Hu, Yan Huang, Qian Li and Danny Yang for their understanding and always send me positive energy. I wish to thank the faculty and staff in department for their help related with my Master studies. I also want to thank the Swiss Cheese Consortium for providing cheese samples. vi Vita June 2007 .......................................................Chongqing Yucai School, P.R.China 2011................................................................B.S. Food Science and Engineering, The Beijing Forestry University, P.R.China 2011 - Present ...............................................Master Food Science, Department of Food Science and Technology, The Ohio State University Fields of Study Major Field: Food Science vii Table of Contents Abstract ............................................................................................................................... ii Acknowledgments................................................................................................................v Vita .................................................................................................................................... vii Fields of Study .................................................................................................................. vii Table of Contents ............................................................................................................. viii List of Tables .................................................................................................................... xii List of Figures .................................................................................................................. xiv Introduction ..........................................................................................................................1 Chapter 1: Literature Review ...............................................................................................3 1.1 Swiss-type Cheese ......................................................................................................3 1.2 Swiss-type Cheese Manufacture ................................................................................4 1.2.1 Starter Cultures and Two Major Fermentations ..................................................6 1.2.2 Eye Formation in Swiss-type Cheese ..................................................................7 1.2.3 Swiss-type Cheese Flavor ....................................................................................9 1.3 Defects of Swiss-type Cheese ..................................................................................10 1.3.1 Split Defect of Swiss-type Cheese .....................................................................11 viii 1.3.1.1 Factors Contributing to Splits Defect ............................................11 1.3.1.2 Techniques for Evaluation or Prediction of Split or Eye Formation ....................................................................................................................12 1.4 Fourier-transform Infrared Spectroscopy (FTIR) ....................................................12 1.4.1 History ...............................................................................................................12 1.4.2 FTIR Spectrometer Mechanism.........................................................................13 1.4.3 Principle of Attenuated Total Reflectance (ATR) .............................................15 1.4.4 Principle of Reflection Fourier-transform Infrared Microscopy .......................16 1.4.5 Advantages and Disadvantages of FTIR ...........................................................18 1.4.6 Application of FTIR in Cheese Analysis ...........................................................19 1.5 Analysis of Infrared Spectra .....................................................................................20 Chapter 2: Fourier-transform Infrared Methodology .........................................................22 2.1 Sample preparation for FTIR ...................................................................................22 2.2 ATR-FTIR Spectroscopy Conditions .......................................................................23 2.3 Microscopy-FTIR Reflectance Conditions ..............................................................24 2.4 Spectra Analysis .......................................................................................................24 2.5 Multivariate Analysis ...............................................................................................26 Chapter 3: Monitoring Water Soluble Compounds of Swiss-type Cheese during Manufacturing Using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) ................................................................................................28 ix 3.1 Abstract ....................................................................................................................28 3.2 Introduction ..............................................................................................................29 3.3 Material and Method ................................................................................................30 3.3.1 Swiss-type Cheese Samples...............................................................................30 3.3.2 Methods .............................................................................................................33 3.4 Result and Discussion ..............................................................................................33 3.4.1 Classification of All Four Manufacturing Stages of Swiss-type Cheese ...........33 3.4.2 Classifications of Individual Cheeses at Each of the Four Stages ....................36 3.4.3 Classification of At Cut Swiss-type Cheese Based on Blind, Eye and Split Areas ...........................................................................................................................47 3.5 Conclusion. ...............................................................................................................53 Chapter