Food Processing Unit Operations Multiple Choice Questions on “Contact Equilibrium Separation Process – Equipment Used for Extraction ”.
1. What are the classifications of extraction equipment?
a) By gravity
b) By centrifugal forces
c) By centrifugal forces and size of the particle
d) By centrifugal forces and gravity
Answer: d
Clarification: Classification of extraction equipment is based on centrifugal forces and gravity, the methods used for bringing together and separating the phases and is sub-classified according to type of contact.
2. What is basic principle behind packed towers?
a) By gravity
b) By centrifugal forces
c) By centrifugal forces and size of the particle
d) By centrifugal forces and gravity
Answer: a
Clarification: Packed columns always have nozzles for the initial distribution of each phase and droplets are present. Thus packed towers are considered as droplet extractors.
3. What are the main factors considered for the operation of extraction column?
a) Droplet size, axial dispersion
b) Droplet size distribution, axial dispersion
c) Droplet size, droplet size distribution
d) Droplet size, droplet size distribution and axial dispersion
Answer: d
Clarification: The main factors considered for the operation of extraction column are droplet size, droplet size distribution and axial dispersion. Axial dispersion follows from different phenomena like turbulence or differences in the droplet sizes, and results in lower column efficiency.
4. What are methods for regeneration of solvents?
a) Rectification
b) Evaporation
c) Crystallization
d) Rectification, evaporation, crystallization
Answer: d
Clarification: Rectification, evaporation, crystallization are the methods for regeneration of solvents. By these processes the pure products are produced and the solvent can be recycled in the extraction process.
5. Which of the following statements about centrifugal extractors are correct?
Statement 1: Discrete stages can be recognized.
Statement 2: The applied centrifugal force causes the two phases to move radially in countercurrent mode.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: a
Clarification: In centrifugal extractors no discrete stages can be recognized. The principle of this design is to introduce the heavy phase close to the axis of a rotating container, while the light phase is introduced close to the periphery. The applied centrifugal force causes the two phases to move radially in a countercurrent mode in such a way that the heavy phase is moved to the periphery and the light phase to the rotation axis.
6. What is the purpose of extraction?
a) Separate an organic substance from a mixture
b) Separate an inorganic substance from a mixture
c) Separate both organic and inorganic substance from a mixture
d) Separate dust from a mixture
Answer: a
Clarification: Extraction is the recovery of a substance from a mixture by bringing it into contact with a solvent, which dissolves the desired material. It is a suitable method for separating organic substance from a mixture.
7. What are the methods of extraction used?
a) Pressing
b) Distillation
c) Solvent extraction
d) Solvent extraction, distillation method, pressing
Answer: d
Clarification: Extraction is the initial step for separating the desired natural products from the raw compounds. Some of the examples are distillation, solvent extraction, sublimation and pressing. These are divided according to the compound to be extracted and the extraction principle.
8. What is percolation extraction?
a) A method of extraction by gravity
b) A method of extraction by filtration
c) A method of extraction by sedimentation
d) A method of extraction by distillation
Answer: b
Clarification: The active compound from a product is derived through percolation method.The solvent is passed over a bed of substance which helps in the liquid extract, and this liquid extract is then recirculated through the bed for a period of time.
9. What advantages does the Soxhlet extraction have over other extraction processes?
a) Complete extraction and high efficiency
b) Complete extraction and small solvent dosage
c) Small solvent dosage and complete extraction
d) Small solvent dosage, high efficiency and complete extraction
Answer: d
Clarification: The advantage of Soxhlet extraction is that it can be extracted multiple times. Compared with the other extraction method, it has small solvent dosage, high efficiency and complete extraction.
10. What solvent is used in phytonics extraction process?
a) Hydrofluorocarbon -134a
b) ammnia
c) CFCs
d) Alcohol
Answer: a
Clarification: The Phytonics process uses a novel non-toxic solvent based on hydrofluorocarbon -134a, having a boiling point of – 25°C and a vapor pressure of 5.6 bar at ambient temperature. It is mainly used in the extraction of plant materials.