This set of Fermentation Technology Multiple Choice Questions & Answers (MCQs) focuses on “Fermentation Biochemistry – Formation of Flavour Compounds”.
1. Which of the following metabolite does not impart flavour to beer?
a) Esters
b) Thiols
c) Carbonyls
d) Alcohols
View Answer
Explanation: Thiols does not impart flavour to the beer. Some aromatic alcohols, esters, carbonyls, and various sulphur-containing compounds are yeast metabolites that contribute to beer flavour. They are chemically diverse and includes organic acids and medium chain-length aliphatic alcohols.
2. Who reported flavours of more than 200 beer components?
a) Meilgaard
b) Ingram
c) Dombek
d) Rees
View Answer
Explanation: Meilgaard in 1974 reported the flavours for more than 200 beer components. He also reported that flavour thresholds varied to an enormous extent. Flavour is mainly influenced by the chain length of the molecule.
3. Which of the following is responsible for butterscotch flavour?
a) Dimethyl sulphate
b) Hydrogen sulphide
c) Diacetyl
d) Acetate
View Answer
Explanation: Diacetyl is responsible for imparting butterscotch or toffee flavour to the beer. It is also called as 2,3-Butanedione and is used to give butter-like or other flavours to the beer or other food products like popcorn.
4. Which of the following is used to give banana flavour?
a) Isoamyl acetate
b) Hydrogen sulphide
c) Dimethyl sulphate
d) Diacetyl
View Answer
Explanation: Isoamyl acetate is responsible to impart banana flavour to the beer. It is also called as isopentyl acetate and is a colourless liquid that is slightly soluble in water. It is a banana smelling ester which is used in many fragrance and flavour imparting departments in industries.
5. Which of the following is responsible for apple flavour?
a) Isoamyl acetate
b) Hydrogen sulphide
c) Dimethyl sulphate
d) Ethyl acetate
View Answer
Explanation: Ethyl acetate is responsible for imparting apple flavour to the beer and other food products. It is also used in glues, nail polish removers, decaffeinating tea and coffee. It is an inflammable solvent.
6. Which of the following has goat-like aromas?
a) Caprylic acid
b) Succinic acid
c) Malic acid
d) Formic acid
View Answer
Explanation: Caproic and Caprylic acid has an unpleasant smell responsible for goat-like aromas. It is also found in the milk of many mammals, coconut oil and kernel oil. Caprylic acid has antifungal, antiviral, antibacterial properties and is useful in the treatment of many infections like a vaginal yeast infection.
7. Which of the following acts as an osmoprotectant?
a) Glycogen
b) Glycerol
c) Acetic acid
d) Starch
View Answer
Explanation: Glycerol acts as an osmoprotectant. It contributes to the body and mouth-feel of beers at concentration 1-2 g/l. It also has a role in redox control. The elevated glycerol concentrations induce the cultivation of yeast with low activity of water.
8. Which of the following imparts rose flavour?
a) Isobutyl acetate
b) Isoamyl acetate
c) Phenylethylacetate
d) Caproate
View Answer
Explanation: 2-Phenylethylacetate is responsible for imparting rose flavour to the beer and other food products. It also imparts honey and apple aroma to the food products. It is found in many fruits and is colourless liquid.
9. Which of the following is responsible for aldehyde reduction?
a) ADH II
b) ADH I
c) ADH III
d) ADH IV
View Answer
Explanation: Alcohol dehydrogenase coded by ADH I is responsible for the reduction of aldehyde. The products of ADH II and ADH III, respiratory alcohol dehydrogenase, are not involved in the reduction of aldehyde.
10. Which of the following is an alternative to diacetyl for imparting a yellow colour to the beer?
a) 2,3-Pentanedione
b) 2,4-Pentanedione
c) 2,2-Pentanedione
d) 1,2-Pentanedione
View Answer
Explanation: 2,3-Pentanedione is used for imparting a yellow colour to the beer and other food products. It is used as an alternative if diacetyl is not available. Both are strong flavouring substances and impart butterscotch flavour to the compounds.
11. Sulphite acts as _______________
a) Oxidant
b) Anti-oxidant
c) Anti-inflammatory
d) Anti-aging
View Answer
Explanation: Sulphite acts as a natural anti-oxidants. They are added to fermenting alcohol beverages because it is more toxic to bacteria and molds than to yeast. In addition to that, it also acts as anti-oxidants in many food products.
12. Acetaldehyde is ___________ toxic to cells.
a) Less
b) Not
c) Highly
d) Moderate
View Answer
Explanation: Acetaldehyde is highly toxic to cells. It was reported by Jones in 1989. Its ability to form Schiff bases with amino acid residues leads to the inactivation of enzymes and also disrupts the synthesis of proteins and nucleic acids.
13. Oxygen is used for the synthesis of sterols.
a) True
b) False
View Answer
Explanation: Oxygen is required in the brewery fermentation to yeast to allow the synthesis of sterols and unsaturated fatty acids which are essential components of the membrane of yeast. Yeast is also capable to grow under strictly anaerobic conditions.
14. Steam beer is a bottom-fermented beer.
a) True
b) False
View Answer
Explanation: Steam beer is the top-fermented beer. It was originated in California, USA. It is prepared with bottom yeast at a relatively higher temperature. It is well-hopped beer with amber colour and highly carbonated.
Sanfoundry Global Education & Learning Series – Fermentation Technology.
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