Subtopic: Concentration and drying of liquid foods – evaporators, tray, drum and spray dryers
Question Statement:
In spray drying of heat-sensitive liquid foods such as milk and fruit juices, co-current airflow is predominantly chosen over counter-current airflow primarily because:
Options:
(A) The hottest drying air contacts the wettest droplets, keeping droplet temperature low due to evaporative cooling
(B) It completely eliminates the need for cyclone separators
(C) Counter-current airflow produces zero exhaust humidity
(D) Co-current flow prevents any moisture evaporation in the upper chamber
Answer Key:
A
Step-by-Step Solution & Explanation
In co-current spray drying, atomized droplets encounter the hottest drying air when their moisture content is highest. Rapid wet-bulb evaporation keeps droplet temperatures low, protecting heat-sensitive proteins, vitamins, and sugars from thermal denaturation.