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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.

SUMMARYPoor absorption of iron from food and oral iron formulations results in extensive use of high-dose oral iron, which is not tolerated. Disposal of whey, a byproduct of the cheese industry, causes environmental pollution. Whey proteins have the ability to bind significant amount of iron, thereby reducing its chemical reactivity and incompatibility with other components in foods. To make iron compatible with food, it was complexed with whey protein concentrate (WPC). After complexation, centrifugation and ultrafiltration techniques were utilised to eliminate the insoluble and free iron from the solution. To enable the availability of whey protein concentrate–iron (WPC–Fe) complex in the powder form, spray drying technique was used. Optimized spray drying conditions used for the preparation were: inlet temperature 180 °C, flow rate 2.66 mL/min and solution of total solids 15%. The complex was observed to be stable under different processing conditions. The in vitro bioaccessibility (iron uptake) of the bound iron from the WPC–Fe complex was significantly higher (p<0.05) than that from iron(II) sulphate under simulated gastrointestinal conditions. WPC–Fe complex with improved iron bioaccessibility could safely substitute iron fortificants in different functional food preparations.

In this study, spray-drying process was optimized to produce whey protein concentrate-iron (WPC-Fe) complex with the aim of making iron compatible with food products. WPC-80 and FeSO 4 complex formation was achieved using centrifugation (to remove insoluble iron), ultrafiltration (to remove unbound iron), and spray-drying. Spray-drying of WPC-Fe complex solution was carried out at inlet temperature, flow rate, and total solids (TS) ranging from 126.3°C to 193.6°C, 0.63 to 9.87 ml min −1 , and 1.59% to 18.40%, respectively, as generated by central composite rotatable design. The optimum operating condition for WPC-Fe complex production was 180°C inlet drying temperature, 2.66 ml min −1 flow rate, and 15% TS content. At this optimized condition, moisture content, yield, and solubility were observed to be 4.19%, 8.21 g 100 ml −1 , and 87.53% which were comparable with the predicted values, viz. 4.11%, 8.29 g 100 ml −1 , and 87.63%, respectively. The spray-dried WPC-Fe complex generated could be used in foods as an organic fortifier to reduce the menace of iron deficiency. ARTICLE HISTORY

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