(554e) Chemical Mapping of Sweeteners and Additives in Commercial Chewing Gums Using Imaging FTIR Spectroscopy

Chemical Mapping of Sweeteners and Additives in Commercial Chewing Gums using imaging FTIR Spectroscopy

Ramazan KIZIL,

Istanbul Technical University, College of Chemical and Metallurgical Engineering, Chemical Eng. Dept. Maslak, 34469 Istanbul-Turkey. Contact: kizilr@itu.edu.tr

Determination of the structural organizations of chemical constituents, such as lipids, proteins and carbohydrates, within a food at the microscopic level is expected to significantly contribute to the modern food technology whose prime interest lies in development of controlled processes and operations to preserve, transform and create or destroy food structure (Aguilera, 2001). Food microstructure analysis has an ultimate goal of understanding structural hierarchies, forming naturally or manufactured, from images that depict spatial arrangements and interactions of chemical compounds that form flavor, color, texture and nutritional value.  Developing new tool to correlation microstructure with food texture perception is expected to contribute to food industry in production of textually attractive food products (Wilkinson et al. 2000).

Vibrational spectroscopic tool such as Raman or infrared spectroscopy coupled with an optical microscope can be used to visualize structures in a form of image produced from chemical composition contrast. The technique is known to be chemical imaging and it is becoming a promising modality for diagnosis of cancer as a complimentary molecular histopathology tool. Another interesting application field of chemical imaging is pharmaceutical industry for which visualization of the distribution of active ingredients and excipients is prime interest.

Analyzing molecular vibrational transitions of atoms of a compound as a result of absorbance of IR radiation provides a strong basis for chemical structure determination of organic or inorganic substances. This analysis can be best performed by implementing a multiplexing detection of all wavelengths at the same time using a focal plane or linear array detectors. A classical FTIR system coupled to an optical microscope with a motion controlled stage and a multiplexing detector collects spectrum at a resolution set by the diffraction limit, which is around 5.5 micron for most commercial IR imaging systems.

Chemical imaging is a powerful tool for visualization of structure of a specimen from its functional groups in a form of chemical contrast map, representing the spatial distribution of chemical entities in the sample. FTIR provides the contrast necessary for enabling chemical structural imaging by means of the selectivity of vibrational absorption modes detected only at specific frequencies/energies. The spectrum at each pixel is referred to as fingerprint of chemical composition.

This talk covers experimental studies of determining the spatial distribution of sweeteners and additives in chewing gums to elucidate the chemical nature of developed microstructure in different brands. The samples were investigated in attenuated total internal reflectance (ATR) mode in order to obtain images at pixel resolution of 1.65 micron by oversampling approach and solid immersion lens (SIL) technology (Kazarian and Chan, 2010). Similar to oil immersion optics, ATR uses hemispherical Germanium element which has refractive index of 4.1. This allow to obtain images with 4 times enhanced resolution comparing to that of transmission or transreflectance modes of IR imaging. Three different brand commercial chewing gums were used to study microstructure imaging. ATR imaging necessitates a firm contact of the Ge element with the sample, so a little distortion of images due to contact pressure related stretch. Since all samples will be subjected to a similar stretch condition, the images offer a comparing realistic visualization of the microstructure. Chemical mapping strategy was followed to show the spatial distribution of sweetener and additives in the texture from their own molecular fingerprint. The main matrix was well represented in the images and inhomogeneous distributions of other components were mapped at a pixel resolution of 1.65 micron. The findings of the study and sensory evaluations suggests that controlling the microstructure can help improve the sensory quality and functional characteristics of chewing gums.

References:

Aguilera, J.M. 2005. Why food microstructure. Journal of Food Engineering. 67:3-11.

Kazarian, S.G., Chan, A. 2010. Micro-and macro ATR infrared  spectroscopic imaging. Applied Spectroscopy. 64:135A-152A.

Wilkinson, C., Dijksterhuis, B.G., Minekus, M. 2000. From food structure to texture. Trends in Food Science and Technology. 11:442-450.