This set of Fermentation Technology Multiple Choice Questions & Answers (MCQs) focuses on “Yeast Propagation”.
1. Which of the following results in the formation of nitrosamines?
a) Lactobacillus sp.
b) Obesumbacterium sp.
c) Streptococcus sp.
d) Staphylococcus sp.
Explanation: Obesumbacterium species results in the formation of nitrosamines from which are carcinogenic in nature. Carcinogenic nitrosamines are formed from nitrites. They are the agents which may also cause cancer in human beings.
2. Hammond and Wenn reported the experiences of a brewery where one newly propagated yeast strain produced slow fermentation. This was due to inability of strain to utilize __________
Explanation: Hammond and Wenn in 1985 reported the experiences of a brewery where one newly propagated yeast strain produced slow fermentation. This was due to the inability of strain to utilize maltotriose. However, this effect was temporary and disappeared after 7 – 10 generations.
3. Which of the following is used for propagating or germinating cells or seedlings?
Explanation: Propagator is a container which is used for the propagation and germination of cells or seedlings. It is usually filled with earth or compost and is covered and heated. The new strains of yeast give poor performance due to poor propagation design and operation.
4. Which of the following is a very important requirement of a propagator?
b) Cycle time of propagation
c) Condition of yeast
d) Viability of yeast
Explanation: Hygiene is a very important requirement of a propagator. It is of prime importance and the design and operation of the plant must ensure that a pure yeast culture is generated.
5. Which of the following is not a requirement of a propagator?
a) Phenotype of yeast
b) Condition of yeast
c) Viability of yeast
d) Cycle time of propagation
Explanation: Phenotype of the yeast is not a requirement of a propagator. However, the propagator is concerned with the physiological condition of the yeast, viability of the yeast, the cycle time of propagation.
6. Who introduced the yeast propagators?
Explanation: The first yeast propagators were introduced by Hansen in 1883. All the propagation regimes basically consist of yeast culture sequence in progressively increasing volume.
7. The terminal stages in laboratory propagation uses ___________
a) Yeast extract
Explanation: The terminal stages in a laboratory propagation uses wort. However, the wort must be sterilized by autoclaving before use. The initial stages use yeast extract, peptones, and glucose.
8. What is the capacity of a stainless steel flask used in the terminal laboratory stage?
a) 20 liters
b) 30 liters
c) 25 liters
d) 15 liters
Explanation: The capacity of the stainless steel flask used in the terminal laboratory stage is 25 liters. The heavy gauge stainless steel is fitted with a number of ports passing through the top-plate assembly. However, the top-plate is removable for cleaning purposes.
9. The vessels in the brewery propagation are operated under _____________ bar pressure.
a) 1.0 – 2.0
b) 3.0 – 5.0
c) 0.5 – 1.0
d) 0.1 – 0.5
Explanation: The vessel in the brewery propagation are operated under 0.5 – 1.0 bar of top pressure. The vessels are made of stainless steel. After cleaning, the vessels are sterilized with the help of steam.
10. Who first described the application of dried yeast?
Explanation: Muller et al. in 1997 first described the application of dried yeast. Fels et al. in 1999 described its applications after Muller. These communications reported the results of fermentation trials at a scale of 300 hl.
11. The viability of dried yeast is ____________
a) 35 %
b) 50 %
c) 95 %
d) 65 %
Explanation: The viability of dried yeast is just 65 % compared with that of the typical value of 95% for usual brewing strain. However, it is necessary to rehydrate the dried yeast by suspending in the wort, prior to pitching, for 30 minutes at 20°C.
12. The reproduction in yeast is by ____________
a) Binary fission
Explanation: The reproduction in yeast is by budding. The budding is a type of asexual reproduction in which a small bud develops from yeast and grows into a daughter cell. The bud develops in a parent yeast and develops into an individual.
13. Dried yeasts do not require storage vessels.
Explanation: If dried yeasts are used in the fermentation, then there is no need for, or at least reduction in, storage vessels. This is the potential advantage of dried yeast.
14. Yeast propagation on wort generates the greater yield of the yeast.
Explanation: The propagation of yeast on wort limits the yield of the yeast because metabolism is always catabolite repressed. The yield of the yeast is obtained in a much greater amount if the yeast is grown under depressing conditions.
Sanfoundry Global Education & Learning Series – Fermentation Technology.
To practice all areas of Fermentation Technology, here is complete set of 1000+ Multiple Choice Questions and Answers.