Abstract
Iodine deficiency remains a major nutritional concern worldwide, and fermented dairy products are considered promising vehicles for iodine fortification. However, the chemical form of iodine may influence the physicochemical and microbiological stability of fermented dairy systems. This study aimed to compare potassium iodide and iodocasein as iodine sources for the fortification of a fermented dairy product and to evaluate their effects on product quality and iodine retention during refrigerated storage. Three formulations were produced: a control sample without iodine fortification and samples fortified with potassium iodide or iodocasein at a level of 25 µg iodine per 100 g of product. Samples were stored at 4 ± 1 °C for 7 days. Changes in pH, titratable acidity, syneresis, viscosity, viable counts of starter lactic acid bacteria, iodine retention, and sensory properties were evaluated during storage. The results showed that the iodine source significantly affected product stability. The potassium iodide-fortified sample exhibited greater post-acidification, increased syneresis, lower viscosity, and a more pronounced reduction in viable lactic acid bacteria during storage. In contrast, the iodocasein-fortified sample maintained physicochemical and microbiological characteristics closer to the control and demonstrated higher iodine retention. Fortification at the studied level did not significantly affect the basic composition or amino acid profile of the product. The findings indicate that iodocasein can improve iodine stability while preserving the quality characteristics of fermented dairy products, supporting its potential application in the development of iodine-enriched functional dairy foods.