Fruit juice (a heat sensitive material) can be concentrated in a __________ evaporator.

ANS:B - falling film

Fruit juice, being a heat-sensitive material, can be concentrated in a falling film evaporator. Falling film evaporators are suitable for processing heat-sensitive materials because they operate under vacuum conditions and allow for rapid and efficient evaporation of volatile components at lower temperatures compared to other types of evaporators. In a falling film evaporator, the liquid to be concentrated is fed onto the inner surface of vertical tubes, where it forms a thin film due to gravity. Heat is applied to the outer surface of the tubes, causing the liquid film to evaporate and concentrate. The thin film ensures a short residence time for the product at high temperatures, minimizing heat exposure and thermal degradation of heat-sensitive materials like fruit juice. Therefore, the correct option is: falling film.