Characterizing the pH-Dependent Release Kinetics of Food-Grade Spray Drying Encapsulated Iron Microcapsules for Food Fortification

Iron deficiency is the primary cause of many widespread nutritional diseases including anemia, pregnancy complications, and infant mortality. Release kinetics of iron premixes to be mixed with food items like salt, rice, and tea is a key research objective of many globally active iron fortification efforts. Iron release kinetics of microcapsules of two reverse-enteric coating materials (chitosan and Eudragit EPO) encapsulating various amounts of ferrous sulfate (10–40% of total other solids) were done at three pH values (1, 4, 7) for 2 hours. Chitosan and Eudragit microcapsules contained 2.8–5.3% (w/w) and 1.7–9.6% (w/w) iron, respectively, depicting higher iron loading capacity of Eudragit microcapsules. More than 90% iron was released from most samples within 30 min under stomach conditions (pH 1) and less than 15% iron was released in 2 h under ambient conditions (pH 7), showing suitability of both chitosan and Eudragit EPO as reverse-enteric coatings for iron encapsulation. In terms of reverse-enteric behavior (RE), Eudragit EPO (RE = 2.4) was found to be slightly better than chitosan, suggesting the use of fillers in future research. Higuchi model and Hixson-Crowell model were found to best fit the data, suggesting a transport phenomenon governed by both (a) the diffusion process through the coating material and (b) the dissolution phenomenon resulting in decrease in size of the capsules. Results from this study shall provide guidance for technology development aspects of various food fortification initiatives and an understanding of the iron release from these fortificants during the food preparation and digestion stages.