Fortification of yogurt with nano and micro sized calcium, iron and zinc, effect on the physicochemical and rheological properties

- Fortification of a dairy products with minerals.
- Nanoparticles and micro-minerals were incorporated to yogurt.
- Nanoparticles fortification improve syneresis compared to micro-minerals.
- Nanoparticles fortification does not alter the flow properties of yogurt.
- Nanoparticles fortification enhances the consistency and firmness of yogurt.

Yogurt is a highly consumed dairy product, regarded as healthy. The objective of this study was to fortify a set-type yogurt with two levels of iron oxide, zinc oxide, and calcium phosphate nanoparticles. Minerals were also used to make a comparison between nano and micro-sized minerals, to determine their effect on the physicochemical and rheological properties during 28 days of storage. The pH decreased while acidity increased in all samples during storage. Density and moisture did not show differences between samples, or during storage. Color parameters showed variations in iron-fortified samples, whereas an increase in net color change through storage was recorded for all samples. Syneresis increased significantly in micro-mineral samples, being lower in nano-fortified ones; during storage the separation significantly increased in all samples. The Herschel-Bulkley flow model fitted well the non-Newtonian behavior of the yogurt. The yogurts fortified with calcium and zinc nanoparticles increased their consistency and firmness concerning to the other samples, both parameters decreased during storage in all samples; yield stress and flow index did not significantly change during storage. In vitro digestion analysis of the yogurt with nanoparticles showed more solubility than micro-minerals, for the three minerals. In general, nanoparticles showed advantages over conventional fortification.