Mathematical Approach for Estimation of Alginate-Iron Salt Solutions Viscosity at Various Solid Concentrations and Temperatures

Alginate has been widely used in the pharmaceutical industries as tablet binder and disintegrant, release agent and controlled release drug delivery system. Whereas in the food industries, alginate is generally employed as thickener, emulsifier, stabilizer, texturizer, formulation aid, firming agent, flavor adjuvant, and surface-active agent. As one of the important raw materials in the functional food preparation, iron is hard to manage due to its vulnerability to oxidization, degradation and possesses a strong unique aroma. Considering its superior coating and release properties, alginate gel can be the best choice to preserve iron from various undesirable effects. Unfortunately, there has been lack information in the published literature to estimate the effect of temperature, concentration, and stirring time on the mechanical properties of alginate. Although many mathematical models have been developed based on these factors to predict the viscosity of the alginate-Fe solutions used as feed in spray drying application, no clear information have been reported for their accuracy. This study aims to examine four physical models for their suitability in estimating alginate-Fe solution viscosity, namely the Walther, Mark Houwink, Vogel – Tamman – Fulcher (VTF), and Intrinsic models. Prior to model validation, alginate-Fe solutions containing alginate: Fe (2:1) mass ratio were prepared. They were heated to desirable temperatures (30°, 45°, 60°, and 75°C), stirred for various stirring times (0 to 60 minutes), and subjected to viscosity measurement. The results exhibited that the viscosity of alginate-Fe solution with 5% alginate concentration stirred for 15 minutes at 30°C reached 320 cP. Whereas the viscosity of Alginate-Fe solution with 1% (m/m) concentration at the same temperature and stirring time was only 250 cP. This observation suggested that a higher alginate solution concentration leads to a higher the viscosity. As expected, a higher temperature and longer stirring time resulted in the decline of the Alginate-Fe solution viscosity. Although the proposed models demonstrated the similar trend, it can be concluded that the Walther model was proven to be the most accurate model used for the prediction of the Alginate-Fe solution viscosity compared to the other models as shown by its highest R2 value, which was 0.987.