Thermal, Structural, and Molecular Characterization of a Model Cereal-Milk Infant Formula: Impact of Ultrasound...

This study investigated the impacts of an ultrasound (US) pre-treatment applied to a liquid feed suspension prior to conventional spray drying to overcome the inherent stickiness and low yield challenges in a complex, carbohydrate-rich model cereal-milk infant and toddler complementary food formulation. The effects of US pre-treatment duration (30-90 s), spray dryer inlet temperature (150°C-180°C), and feed rate (7-12 mL/min) were evaluated using a full-factorial response surface design. The findings demonstrated that acoustic cavitation applied as a feed pre-treatment significantly reduced the viscosity of the suspension and improved subsequent atomization efficiency, which ultimately increased the powder recovery yield from approximately 12% to over 30%. Furthermore, the micro-structural modifications and improved fat encapsulation induced during the ultrasound pre-treatment step led to enhanced powder reconstitution properties, significantly increasing solubility. Microstructural and thermal evaluations revealed that the optimized processing parameters produced finer, less agglomerated particles that maintained an amorphous glassy state (T_g ranging from 17.5°C to 20.3°C) with preserved protein secondary structures. Notably, the accelerated drying kinetics resulting from the enhanced feed atomization limited the progression of the Maillard reaction, keeping advanced glycation products like HMF well within safe limits. Overall, this study highlights that an ultrasound pre-treatment is a highly effective, non-thermal feed-modification strategy to optimize process efficiency, physical stability, and nutritional integrity in the spray drying production of complex multi-component infant formulas.