Development of iron and vitamin D3 fortified low-fat synbiotic yogurt as a potential substrate for Lactobacillus acidophilus and Bifidobacterium lactis: evaluation of physicochemical and sensory Properties during the storage time

Fortification of foods including yogurt is one of the most important processes to compensate for the deficiency in some minerals and vitamins. This study aimed to determine the effect of fortification of low-fat synbiotic yogurt samples with iron (25 mg Fe/kg) and vitamin D3 (1000IU) on physicochemical (pH, acidity, viscosity, and syneresis) and sensory properties of prepared yogurts during 21 days of storage at 4 °C. As well, the viability of probiotic bacteria and changes in vitamin D3 and iron content of prepared yogurt samples were evaluated during the storage time. According to the results, the counts of probiotic bacteria in fortified yogurts were significantly higher compared to the control sample during the storage time. As found, fortification of yogurts with iron and vitamin D3 in combination had led to increase acidity and decrease pH values of the samples significantly. However, no remarkable changes were observed in the viscosity and syneresis values of the fortified yogurts compared to the control sample at the end of the storage time. Although iron and vitamin D3 content of fortified yogurts decreased over time, their content was efficient in experimental yogurts at the end of the expected shelf life. As well, the sensory analysis showed no significant differences in fortified samples in comparison to the unfortified yogurt sample which was indicated that it was a suitable vehicle for iron and vitamin D3.