This set of Food Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Fermented Dairy Products: Kefir, Parameters & By-Products”.
1. Which of the following is fermented by both, lactic acid bacteria and yeast?
a) Kefir
b) Yogurt
c) Salami
d) Cider
View Answer
Explanation: Kefir has a starter culture containing both lactic acid bacteria and yeast. Yogurt and salami need only lactic acid bacteria and the presence of yeast may indicate contamination. Cider needs yeast fermentation only, hence, lactic acid bacteria may cause spoilage.
2. Kefir starter cultures are an example of __________
a) Commensalism
b) Symbiotic relationships
c) Parasitism
d) Competition
View Answer
Explanation: The starter culture for kefir is kefir grains. These grains consist of a symbiotic culture of yeast and lactic acid bacteria. These organisms are surrounded by a matrix of proteins, lipids and polysaccharides.
3. Kefiran is a _________
a) Lipid-soluble disaccharide
b) Water-soluble disaccharide
c) Lipid-soluble polysaccharide
d) Water-soluble polysaccharide
View Answer
Explanation: Kefiran is a water-soluble polysaccharide found in the matrix of kefir grains. It has equal proportions of glucose and galactose residues.
4. Water kefir is also called _______
a) Matzoon
b) Shubat
c) Tibicos
d) Boza
View Answer
Explanation: Tibicos used a similar starter culture as used in kefir, which is a symbiotic culture of yeast and bacteria. Tibicos grains can be found as granules on certain species of cacti.
5. While making cheese, a lot of milk constituents are removed in ________
a) Whey
b) Rennet
c) Koumiss
d) Fat
View Answer
Explanation: When rennet or an acid is added to milk for casein to coagulate, the curds (milk solids) separate from the liquid. This liquid is called whey. It contains all the soluble components of milk. It contains 5% lactose too.
6. Milk is ________ before fermentation to prevent the milk fat from separating out.
a) Pasteurized
b) Homogenized
c) Curdled
d) Heated
View Answer
Explanation: A homogenizer breaks down big fat globules into smaller ones. This increases the stability of the product, increases the viscosity of milk and improves the quality in general.
7. Antimicrobials should be added when processing milk.
a) True
b) False
View Answer
Explanation: Milk contains natural antimicrobials which actually hamper the fermentation process. Agglutinins and the lactoperoxidase-isothiocynate system are the natural antimicrobials. Agglutinins can cause the clumping of the cells of the starter culture, whereas, the lactoperoxidase-isothiocynate system can inhibit them. The clumping of cells slows down their metabolism and growth thereby stopping the fermentation process.
8. Bacteria metabolize glucose to _________ when there is a lack of lactose.
a) Maltose
b) Sucrose
c) Fructose
d) Galactose
View Answer
Explanation: During the production of cheese, lactobacilli convert the glucose to galactose only when there is a lack of lactose. This extra galactose can accumulate and discolor the cheese or can affect the flavor.
9. Bacteria that produce ________ on glucose fermentation are called homofermentatives.
a) Maltose only
b) Galactose only
c) Lactic acid only
d) Lactate, carbon dioxide and ethanol
View Answer
Explanation: Homofermentatives produce lactic acid as the main product of glucose fermentation. Hence, they are able to produce twice as much energy as the heterofermentatives. Heterofermentatives produce equal quantities of lactate, carbon dioxide and ethanol.
Sanfoundry Global Education & Learning Series – Food Microbiology.
To practice all areas of Food Microbiology, here is complete set of Multiple Choice Questions and Answers.
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