Single droplet drying with stepwise changing temperature-time trajectories: Influence on heat sensitive constituents

Area of Science:

• Chemical Engineering
• Food Science
• Biotechnology

Background:

• Industrial spray drying optimization relies on empirical methods, with limited mechanistic understanding.
• Studying single droplet drying offers a pathway to enhance process comprehension.

Purpose of the Study:

• To develop and utilize a novel sessile single droplet drying platform.
• To simulate changing inlet and outlet air conditions representative of industrial spray dryers.
• To investigate the impact of temperature-time trajectories on enzyme inactivation during drying.

Main Methods:

• A new sessile single droplet drying platform was engineered.
• Two air streams were employed to mimic spray dryer inlet and outlet air conditions.
• Temperature measurements validated the imposed thermal profiles on drying droplets.
• Single droplets containing beta-galactosidase (an enzyme) and maltodextrin were dried under controlled temperature-time trajectories.
• Enzyme inactivation was quantified as a measure of thermal load.

Main Results:

• Accurate temperature measurements confirmed the ability to impose specific temperature profiles on single droplets.
• The 'locking point' was identified as a critical parameter in droplet drying.
• Air temperature before the locking point had minimal impact on beta-galactosidase inactivation.
• Elevated air temperatures after the locking point led to significant enzyme inactivation.
• A coupled drying and inactivation model successfully predicted beta-galactosidase inactivation.

Conclusions:

• The developed single droplet drying platform effectively simulates industrial spray drying conditions.
• The locking point is a key determinant of thermal stress and subsequent enzyme inactivation.
• Mechanistic modeling can accurately predict enzyme stability during spray drying, aiding process optimization.