18A-26 |
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Y. YOU and R. D. Ludescher. Dept. of Food Science, Rutgers, The State Univ. of New Jersey, 65 Dudley Rd., New Brunswick, NJ 08901-8520 Molecular mobility in amorphous food materials plays a key role in controlling physical and chemical properties that correlate with food stability and shelf life. Luminescence from optical probes provides spectroscopic characteristics such as lifetime and emission energy that are specifically sensitive to molecular mobility of the local environment. We have recently demonstrated that the triplet probe erythrosin B can be used to explore molecular mobility and dynamic heterogeneity in amorphous solid sucrose. However, widespread use of luminescence to measure molecular properties in real foods will require introducing molecular probes such as erythrosin into the food matrix. We thus need to analyze how variations in local concentration of probe as well as the presence of the dispersing solvent affect the spectroscopic measurements of food properties (erythrosin B is poorly soluble in water and thus must be introduced via an organic solvent). Emission energy of erythrosin B was measured from 5 to 100C in thin films of amorphous sucrose at various probe and solvent (dimethyl formamide, DMF) concentrations using excitation at 500 nm and emission over the range from 520-750 nm. Lifetime was determined using excitation at 530nm and emission at 680nm over the same temperature range. Our results showed that variations in probe concentration over the range from 0.00005-0.0001 probe:sucrose molar ratio and 10-fold variations in the amount of DMF used to disperse the probe, did not affect the shape of the emission spectra, the emission energy, or the measured lifetimes of erythrosin B in amorphous sucrose. The luminescence technique thus appears to be immune to variations in probe concentration and the presence of the solvent used to introduce the probe, and thus should be useful in making measurements of molecular properties in actual foods doped with spectroscopic probes.
Session 18A, Carbohydrate: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |