Physicochemical Properties and Oxidative Stability of Milk Fortified with Spray-Dried Whey Protein Concentrate–Iron Complex and In Vitro Bioaccessibility of the Added Iron

In the present study, spray-dried whey protein concentrate–iron (WPC–Fe) complex was prepared using a laboratory-scale spray drier under the optimized conditions of inlet temperature 180 °C, flow rate 2.66 mL/min and total solids 15% with the objective to make iron compatible with food products. In order to remove the free iron from the bound iron, standardised method involving centrifugation and ultrafiltration was employed. Further, the retentate was subjected to spray drying to produce WPC–Fe complex. Milk fortified with WPC–Fe complex (γ(iron)=15 mg/L) showed non-significant difference in heat stability, rennet coagulation time, colour estimation, curd tension, viscosity and sensory attributes as compared to control milk. In vitro bioaccessibility of iron and induction period of the fat from milk fortified with WPC–Fe complex were found to be slightly higher (p<0.05) than that of milk fortified with iron alone. Therefore, milk can be fortified with up to 15 mg/L iron in the form of WPC–Fe complex without significantly affecting its physicochemical properties.