The heterogeneous distribution of food constituents influence physical and chemical stability are discernible using electron spin resonance spectroscopy, time domain nuclear magnetic resonance, and three dimensionally using magnetic-resonance imaging (MRI). Constituents such as starch, protein, and water molecules tend to be organized as physically distinct and interdispersed domains, each with characteristic physiochemical and rheological properties. Depending on the particular molecular environment, reactions such as crystallization, oxidation-reduction, or crosslinking can take place, which are generally undesirable. The localized viscosity of these domains is discernible using electron spin resonance spectroscopy and a labeled spin-probe and using time domain nuclear magnetic resonance spectroscopy to determine T₂ relaxation times and diffusion coefficients for water molecules. An understanding of how domains are organized, how to classify domains exhibiting similar properties, and how to determine dynamic changes in the characteristics of domains is crucial to enhancing food stability. MRI, relying on C-13, and proton resonances, can provide a three-dimensional image of these domains; can determine localized regions of distinct glass-transition temperatures; and can map temperature during Ohmic heating of model foods during processing. The results will provide information on the inhomogeneities in viscosity and their effects on the structural and kinetic factors that control the physicochemical stability and microbiological stability of food systems.

 

Reference

Doona CJ, Baik MY: Journal of Cereal Science 45(3): 257, 2007

 

key words

Food science; Proteins; Magnetic resonance spectra; Images and image processing; Food processing;

Citizenship:  Open to U.S. citizens and permanent residents

Level:  Open to Postdoctoral and Senior applicants