STORAGE STABILITY OF THIAMIN AND RIBOFLAVIN IN A DEHYDRATED FOOD SYSTEM

Abstract

The storage stability of thiamin mononitrate and riboflavin in a low moisture dehydrated model food system was determined as a function of water activity, moisture content and storage temperature. Fortification of the model system was at a level of 25% RDA per 100 g. The model system was equilibrated at water activities below, at and above the calculated water activity corresponding to the monomolecular moisture content for the adsorption isotherms. Thiamin retention was approximately 100% after eight months storage at temperatures from 20–37°C and a_w 0.1 to 0.65. Retention of thiamin in the model food system was only 10–20% at 45°C with an a_w from 0.40–0.65. Riboflavin retention was approximately 100% after eight months storage at 10 to 20°C with an a_w of 0.1 to 0.65 and at 30°C, with an a_w of 0.1 to 0.40. At 37°C the loss of riboflavin increased with increasing water activity. The rate of riboflavin destruction dramatically increased in the model system packaged in an oxygen permeable container. A similar effect was not observed in the thiamin study. The stability of thiamin and riboflavin was unaffected by the addition of vitamins A or C.