Engineering Questions with Answers - Multiple Choice Questions
Fermentation Technology MCQ’s – Yeast Handling in Brewery
The yeast cake is stored in the refrigerator at _________
a) 5 – 7°C
b) 2 – 4°C
c) 6 – 8°C
d) 8 – 10°C
Explanation: The yeast cake is stored in the refrigerator at 2 – 4°C. The yeast is pressed and skimmed on a plate and frame filter to recover entrain beer. Yeast cake is transferred to clean metal bins and then stored in the refrigerator at 2 – 4°C.
Which of the following difficulty arises when yeast is stored as a pressed cake?
a) Pressure control
b) Foam control
c) Dissolved oxygen control
d) Temperature control
Explanation: The problem of storing pitching yeast as a pressed cake is difficulty in the control of temperature. Yeast has poor thermal penetration and is coupled with exothermy due to the basal metabolism of yeast.
Prolonged storage of yeast as a cake may lead to _________________
Explanation: The excessive or prolonged storage of yeast as a pressed cake may lead to autolysis and excessive heat generation due to difficulty in temperature control. To avoid this problem, it is better to store the yeasts in thin sheets.
Which of the following is not an advantage of storing yeast as a slurry?
a) The risk of infection is controlled
b) Transportation via pumping
c) Attemperation is simple
d) It is a cheap technique
Explanation: The installation of yeast storage tanks and the plant is an expensive undertaking and not cheaper. There are many advantages to store yeast as a slurry. Since the yeast is contained within a vessel, the risk of contamination or infection is less. The yeast is stored in liquid form and hence the transportation can be facilitated via pumping. The most important advantage is that the attemperation is simple than that of storing as a pressed cake.
The yeast storage is made of _____________
d) Stainless steel
Explanation: The yeast storage or collection vessel is constructed from stainless steel, with mechanical agitation and dished ends. The set-up helps or assists the circulation of slurry and facilitates good draining.
The attemperation in slurry form is assisted by ______________
Explanation: The attemperation in the slurry form is assisted by the provision of the mechanical agitator. The attemperation is the control of maximum temperature which is achieved by mechanical agitator which is used for mixing the objectives of different phases and promotes good homogeneity.
What is the function of the microbiological filter?
a) Preventing the larger molecules to pass
b) Control of attemperation
c) Maintenance of hygiene
d) Maintaining water supply
Explanation: The function of the microbiological filter is to maintain the hygiene conditions since the hygiene is of paramount importance. A microbiological quality filter along with a dedicated CiP is provided on the gas exhaust main.
The rheological properties of yeast slurry fit in ___________
a) Bingham pseudoplastic rheology
b) Dilatant rheology
c) Casson body rheology
d) Pseudoplastic rheology
Explanation: The rheological properties of yeast slurries fit in Bingham pseudoplastic fluid rheology. It was concluded by Lentini et al. in 1992. The apparent viscosity decreases with the agitation rate.
Which of the following bacteria is responsible for the development of potential carcinogens?
a) Lactobacillus acidophilus
b) Enterobacter agglomerans
c) Obesumbacterium proteus
d) Pediococcus halophilus
Explanation: Obesumbacterium proteus is a bacteria which is responsible for the formation of potential carcinogens ATNCs during fermentation. There is a need to reduce bacterial loading to maintain product quality and safety.
Who proposed the use of polymyxin B?
Explanation: Lyon in 1956 proposed the use of polymyxin B. The use of polymyxin B persisted and provided the residual protection from bacterial contaminants throughout the fermentation and even beyond it.
Which of the following antibiotics is suitable for the use in dairy industries?
d) Bacteriocin nisin
Explanation: Bacteriocin nisin is suggested as a safer alternative as compared to the advantages of other antibiotics. Nisin has been widely used in the dairy and canning industries and exhibits activity against a wide spectrum of bacteria and Gram-positive species.
Who studied the effects of acid washing on 16 yeast strains?
a) Fernandez et al.
b) Simpsom and Hammond
Explanation: Simpsom and Hammond in 1989 studied the effects of acid washing on 16 different strains of yeasts including both lager and ale types. The use of ammonium persulphate had no effect but scanning with electron microscopy revealed the alterations to the yeast cell surface.
The pH of the combination of ammonium persulphate and phosphoric acid is more effective than acid lower pH lower than 2.2.
Explanation: The pH of the combination of ammonium persulphate and phosphoric acid is 2.8 which is more effective than acid lower pH lower than 2.2. It was reported by Simpson in 1987 that the oxidizing agent, ammonium sulphate can be used in conjunction with phosphoric acid to be more effective.
Tyrothricin is an anti-oxidant.
Explanation: Tyrothricin is an antibiotic that is used as an alternative to acid treatment. The use of tyrothricin was proposed by Gray and Kazin in 1946. It was protective in providing protection throughout fermentation.