A microencapsulation-based technology platform has been developed for salt double fortification with iron and iodine, aiming to address two globally prevalent micronutrient deficiencies simultaneously. Specifically, ferrous fumarate was microencapsulated into a form of salt grain-sized premix, and then added into iodised salt. The earlier process involved fluidised-bed agglomeration followed by lipid coating. To improve physico-chemical properties of the iron premix, the use of cold-forming extrusion for agglomerating and microencapsulating ferrous fumarate was investigated and optimized in this study, leading to optimal formulations and operation parameters. Grain flours were suitable for forming an extrudable dough incorporating high percentages of ferrous fumarate. All extruded iron particles, regardless of binders used, were rich in iron and had excellent iron in vitro digestibility. The extruded iron particles formed the basis of the final, microencapsulated iron premixes with desired particle size (300-700 µm), and other physical, chemical, nutritional, and organoleptic properties suitable for salt fortification.
An extrusion-based encapsulation process has been developed for making salt grain-sized iron premix for salt fortification. The first step of extrusion agglomeration process has been studied and reported previously. The focus of this study is on the optimisation of the colour-masking and polymer coating steps. Several colour-masking techniques and polymer encapsulants were investigated at various encapsulation levels. Salt samples prepared by blending the resulting iron premixes with iodised salt retained more than 90% of the original iodine and more than 93% of the ferrous iron after 3 months storage at 35°C and 60% relative humidity (RH). Hydrophilic coatings such as hydroxypropyl methyl cellulose (HPMC) offered more protection at the 10% encapsulation level compared to other coating materials studied. All iron premix formulations exhibited high particle density, good bioavailability and acceptable organoleptic properties. The process using the most effective formulations and optimised operation parameters is ready for pilot scale testing and field studies.
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