Development of a high shear wet granulation regime map for the controlled agglomeration of heat sensitive amorphous food powders

If not controlled, temperature and humidity may induce caking of amorphous food powders that can be a major issue during food granulation. Caking must be avoided because it results in the permanent loss of material and process failure. The impact of key process parameters to achieve controlled particle agglomeration by avoiding caking in a High Shear Granulator was assessed across a range of Maltodextrins. Findings reveal that increasing impeller speed, batch size and run time promoted the rate of heat generation in the system. The resulting increase in bed temperature was found to impact the different Maltodextrin powders to varying extents depending on the powder T_g, with high DE Maltodextrins showing greater sensitivity to temperature increases. This study also highlighted that high DE Maltodextrins require less water for effective granulation. This behavior correlated with the rate at which the water binder's viscosity increases as it incorporates Maltodextrin during granulation. High DE Maltodextrins demonstrated slower viscosity rises with increased solid composition than low DE counterparts, producing binder systems that remains mobile and adhesive at higher solid contents, thereby facilitating more efficient granulation. A parameter $k_{\mu }$ was modelled to reflect this relationship. The parameters (T- T_g) and $\left(L/S\right)/k_{\mu }$ were then used to produce a caking regime map for the High Shear Granulation system. This regime map delineates an optimal region for controlled agglomeration and a region where a high likelihood of caking occurs. The threshold of this caking region was set at a T-Tg of 40 °C and $\left(L/S\right)/k_{\mu }$ value of 0.0325.