Mid-Infrared Spectroscopy Coupled with Chemometrics: A Tool for the Analysis of Intact Food Systems and the Exploration of Their Molecular Structure-Quality Relationships - A Review Romdhane Karoui,* ,† Gerard Downey, ‡ and Christophe Blecker † Gembloux Agro-Bio Tech, Department of Food Technology, University of Lie `ge, Passage des De ´porte ´s, 2, B-5030 Gembloux, Belgium, and Teagasc, Ashtown Food Research Centre, Ashtown, Dublin 15, Ireland Received March 14, 2010 Contents 1. Introduction A 2. Infrared Spectroscopy - Overview of Theory and Principles B 2.1. Sample Presentation B 3. Multivariate Statistical Analysis of IR Spectral Data D 4. Application of IR Spectroscopy to Food Analyses D 4.1. Dairy Products D 4.2. Meat and Meat Products H 4.3. Fish K 4.4. Edible Oils L 4.5. Cereals and Cereal Products M 4.6. Sugar and Honey Q 4.7. Fruit and Vegetables Q 4.8. Coffee U 4.9. Identification of Bacteria in Different Food Systems V 5. Conclusions and Perspectives W 6. References W 1. Introduction Public interest in food quality and methods of production has increased significantly in recent decades, due in part to changes in eating habits, consumer behavior, and the increased industrialization and globalization of food supply chains. 1 Demand for high levels of quality and safety in food production obviously requires high standards in quality assurance and process control; satisfying this demand in turn requires appropriate analytical tools for food analysis both during and after production. Desirable features of such tools include speed, ease-of-use, minimal or no sample preparation, and the avoidance of sample destruction. These features are characteristic of a range of spectroscopic methods including the mid-infrared (MIR). While it is true that near-infrared (NIR) spectroscopy has achieved greater uptake by the food industry, 2 reported applications of MIR in this sector have increased over the past decade or more. Foods represent significant analytical challenges. They are highly complex, variable and can be found in a number of different physical states: these include solids, dilute solutions, emulsions, foams, highly visco-elastic forms, and glassy states. This has obvious consequences for the analytical tools and strategies that must be developed for analysis of these * To whom correspondence should be addressed. E-mail: karouiromdhane@ yahoo.fr. † University of Lie `ge. ‡ Ashtown Food Research Centre. Dr. Romdhane Karoui obtained his Ph.D. in Food Science in 2004 from Blaise Pascal University (Clermont-Ferrand, France) and his accreditation to supervise research in 2009. He has a long-term scientific experience in the fields of spectroscopic methods, and in the application of multivariate statistical methods. During the past 10 years, his research is focused on chemometrics with applications in the area of spectroscopy, food technology, and process analysis. He is the author of 60 peer-reviewed scientific papers and more than 35 proceedings, book contributions, and reviews. Professor Ge ´ rard Downey obtained his Ph.D. degree in 1997 and a D.Sc. from Queen’s University Belfast in 2005 for his contribution to NIR research. His main research interests lie in the application of fingerprint spectroscopic techniques (mainly near-infrared and mid-infrared) and multivariate data analysis to the rapid and nondestructive measurement of food quality. He has participated widely in EU research projects, and has authored or coauthored 97 peer-reviewed papers, 88 technical publications, and 10 book chapters. Chem. Rev. XXXX, xxx, 000–000 A 10.1021/cr100090k  XXXX American Chemical Society