Effect of high shear granulation process parameters on the production of granola cereal aggregates

Granola is an aggregated cereal food product which can be used as a breakfast cereal or snack comprised of ingredients such as cereals, nuts and honey. A high shear mixer granulator was used to produce granola in a wet granulation process followed by oven drying. The aim was to investigate the effect of granulation parameters; impeller speed, binder addition rate and wet massing time on key granola physical properties. Experiments were carried out at impeller speeds of 150, 200 and 300 rpm during binder addition and wet massing. Binder addition rates of 0.22, 0.33 and 0.65 g s−1 and wet massing periods of 6, 9 and 12 min were applied respectively. The granola was then dried on an oven at 160 °C for 10 min. Granule size distribution and granule strength were measured using a digital image analyser and texture analyser respectively. Regarding the process variables, the agglomeration behaviour was found to vary greatly with impeller speed. Granules formed at low impeller speed were found to have low apparent density. The results enabled the optimal ranges of impeller speeds, liquid binder addition rate and the wet massing time to be established for this system, thereby aiding the manufacturing process in terms of controllability and reproducibility.