Evaluation of iron valence state alterations in thermally processed liquid model systems

Abstract

A glucose glycine liquid model system fortified with 24 ppm of iron as either ferrous sulfate, ferric orthophosphate or ferric orthophosphate + 110 ppm ascorbic acid was thermally processed as 240, 250 and 260°F for 3, 6, 9, 12 and 15 minutes. Levels of elemental, nonelemental, soluble, total ionic and ferrous iron were measured for the model systems at each processing parameter. Data from the iron profiles were evaluated for the effect of iron salt; ascorbic acid; glucose and glycine, and processing temperature and time on changes in the iron chemistry during processing.

The ferrous sulfate model system resulted in significantly higher levels of soluble and ferrous iron. Soluble iron from the ferric orthophosphate model system increased significantly with the addition of ascorbic acid. The presence of glucose and glycine prevented formation of insoluble iron hydroxides during processing of the ferrous sulfate system, promoted solubilization and ionization of iron for the ferric orthophosphate system and restricted the enhancing effect of ascorbic acid on the ferric orthophosphate profile.

The interaction of the iron salt with the model system was stimulated by the application of heat. The insignificant correlation between process lethality values and the iron profile for each iron salt indicated that changes in the iron profile were time and temperature dependent. Kinetic parameters were calculated for all three model systems. The ferric orthophosphate iron profile was less sensitive to temperature change than either of the other two model systems. Evaluation of samples at sequential time intervals during the processing treatment allowed for a better understanding of the reaction mechanisms that occurred during processing which brought about a change in the iron profile of each model system.