Selected spin probes for the electron spin resonance study of the dynamicsof water and lipids in doughs

New water-soluble and lipid-soluble spin probes suitable for the ESR invest igation of the physical states and interactions of components of dough have been developed. This paper reports some preliminary findings on the suitab ility of these probes for this type of investigation. Rotational correlatio n times have been measured for the spin probes in water, dough, oil, and a starch/water mixture. An increase in rotational correlation time of the spi n probe corresponds to an increase in microviscosity of the medium. Changes observed in correlation times of the water-soluble spin probes in doughs a nd in water/starch mixtures clearly correspond to a gelatinization process when the mixtures are heated above 60 degrees C. These irreversible changes , clearly important in the baking process, were monitored by following the change of mobility of a spin probe in doughs over a wide temperature range. The similarity of the results from the two sets of experiments suggests th at the phenomenon of the increase of correlation Limes with temperature in doughs is attributable to the starch component. The lipid-soluble spin prob e was found to be located preferentially in the lipid phase of the dough.