This set of Enzyme Technology Multiple Choice Questions & Answers (MCQs) focuses on “Large Scale Use of Enzyme – Application of Lactases in Dairy Industry”.
1. There is a need for low lactose milk in the world.
a) True
b) False
View Answer
Explanation: There is a need for low lactose milk in the world for the following reasons:
• Presence of lactose makes it unsuitable for adult population in areas where there was no diary industry traditionally.
• Presence of lactose intolerance in new-born which may be noticed at birth. By feeding such kids lactose containing milk may result severe tissue dehydration, diarrhea and even death.
• Lactose low solubility which result in crystallization at 4˚C which prevents its use in concentrated whey syrups as they have unpleasant sandy texture and are prone to microbial spoilage.
• Disposal of whey containing lactose is expensive due to its high biological oxygen demand.
2. Lactose is hydrolyzed to β-galactosidase by _________
a) rennet
b) pullulanase
c) lactase
d) papain
View Answer
Explanation: Lactose is hydrolyzed to β-D-galactose by lactase which is a β-galactosidase. Rennet is an enzyme used to hydrolyze casein in milk and in used in cheese making. Papain is a proteolytic enzyme used in meat tenderization. Pullulanase cleaves only α-1,6-links to give rise to straight-chain maltodextrins.
3. What does X represent in the equation?
Lactose \(_{\overrightarrow{x}}\) β-D-galactose + glucose
a) Protease
b) Lactase
c) Glucoamylase
d) Cellulase
View Answer
Explanation: in the equation above ‘X’ represent lactase enzyme. The equation shows the hydrolysis of lactose to β-D-galactose and glucose. Lactase is a β-galactosidase enzyme. Proteases hydrolyzes proteins to shorter peptides. Glucoamylase hydrolyzes starch to glucose. Cellulase breakdown cellulose to glucose by hydrolysis reaction.
4. Which of the following micro-organisms do not produce lactase?
a) Trichoderma reesei
b) Kluyveromyces fragilis
c) Aspergillus Niger
d) Aspergillus Oryzae
View Answer
Explanation: Trichoderma reesei is used to produce cellulase in large scale and not in production of lactase. Kluyveromyces fragilis, Aspergillus Niger, Aspergillus Oryzae are used to produce lactase commercially. Lactases are subject to varying degrees of product inhibition by galactose and also show significant transferase ability and produces b-1, 6-linked galactosyl oligosaccharides.
5. Which lactase preparation is suitable for milk treatment?
a) Aspergillus Oryzae
b) Kluyveromyces fragilis
c) Aspergillus Niger
d) Bacillus acidopullulyticus
View Answer
Explanation: Lactase produced from Kluyveromyces fragilis has an optimum pH of 6.5-7 and hence is suitable for use in milk treatment. Lactase preparation from Aspergillus Oryzae and Aspergillus Niger has an optimum pH of 4.5-6 and 3-4 respectively and hence is more suitable for whey hydrolysis. Bacillus acidopullulyticus is used in the production of pullulanase which cleaves only α-1, 6-links are to give straight-chain maltodextrins.
6. Which is not application of the use of lactase in industries?
a) Production of ice-creams
b) Production of sweetened flavored milk
c) Meat tenderization
d) Production of condensed milk
View Answer
Explanation: Lactase is a β-galactosidase enzyme which hydrolyzes lactose to galactose and glucose Meat tenderization is done by papain which is a proteolytic enzyme, and not lactose. Lactose is used in the production ice-creams, sweetened flavored milk and condensed milk.
7. Lactase is used in production of __________
a) skimmed milk
b) high conversion syrups
c) high maltose syrups
d) cheese
View Answer
Explanation: Lactase hydrolyzes lactose to galactose and glucose. When lactase is added to milk or liquid whey and left for about a day at low temperatures about 50% of the lactose gets hydrolyzed to give a sweeter product which will not crystallize if condensed or frozen. This allows the use of wasted whey to replace it to skim milk powder which used in traditional ice cream recipes. It also improves the ‘scoopability’ and creaminess of the product.
8. Which of the following lactase is used?
a) Cheese making
b) High maltose syrups production
c) High conversion syrups production
d) Long life sterilized milk
View Answer
Explanation: Lactase is used in smaller amounts in long life sterilized milk in order to produce inexpensive lactose reduced product. Rennet is used in cheese production. For the production of high maltose and high conversion syrups, β amylases are used.
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