Storage stability and quality assessment of milk fortified with iron and zinc nanoparticles

This study investigated the refrigerated storage stability and microbial safety of pasteurized and homogenized toned milk (8.5% SNF, 3% fat) fortified with iron (Fe) and zinc (Zn) in nanoparticulate and bulk ionic forms (10.40 mg Fe and 5.01 mg Zn per 165 mL). Microbial quality (standard plate counts, psychrophiles, and coliforms) and physicochemical attributes (pH and titratable acidity) were monitored during storage at 4 °C. Results showed that nano-fortified milk exhibited lower microbial loads, delayed psychrophile growth, absence of coliforms, and greater pH stability compared with bulk-fortified and control samples. Although titratable acidity was slightly higher in fortified groups than in controls, nanoparticle fortification produced the most favorable stability profile. These findings demonstrate that Fe and Zn nanoparticles enhance microbial safety and physicochemical stability without compromising product quality, supporting their potential use in fortified dairy products to address micronutrient deficiencies.