In continuous UHT processing of milk, direct steam injection (DSI) differs fundamentally from indirect tubular heating in that:
Options:
(A) Direct steam injection dilutes the milk with steam condensate, requiring subsequent vacuum flash cooling to remove the exact amount of added water
(B) Direct steam injection requires $10\times$ larger heat transfer surface area
(C) Indirect heating heats milk instantaneously within 0.1 seconds
(D) Direct steam injection cannot heat milk above $85^\circ\text{C}$
Answer Key:
A
Step-by-Step Solution & Explanation
In direct steam injection/infusion, culinary steam mixes directly with milk, condensing and introducing $\approx 10\%$ water. A downstream vacuum flash chamber instantaneously flashes off the exact equivalent mass of moisture, cooling the product while stripping off-flavors.