This set of Food Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Thermal Deactivation of Microbes – Sterilization and Pasteurization”.
1. ________ milk has about 2% fat content.
a) Reduced fat
b) Soy
c) Skim
d) Almond
View Answer
Explanation: Reduced fat milk is obtained by centrifuging milk at high speeds following which it is heated to around 310.9 K to get rid od butter fat. Either that, or desired fat content is added to skim milk which has 0.5% fat.
2. The 2 methods of Pasteurization are LTLT and ______
a) KTHT
b) HTST
c) HTTT
d) LTHT
View Answer
Explanation: The LTHT method stands for Low Temperature Long Time and the HTST method stands for High Temperature Short Time. LTHT uses 336 K for 30 minutes and HTST uses 345 K for 15 seconds.
3. The HTST method is also called the Flash method.
a) True
b) False
View Answer
Explanation: The HTST method uses a high temperature for a shorter period of time. This causes thermal deactivation of microbes by subjecting them to a sudden thermal shock.
4. Which of the following enzymes is deactivated after Pasteurization?
a) Sulfurous acid
b) Polynucleotide Phosphorylase
c) Kinase
d) Alkaline Phosphatase
View Answer
Explanation: Milk naturally contains alkaline phosphatase. This enzyme is deactivated after successful Pasteurization. Therefore, the absence or presence of alkaline phosphatase in treated milk is often a test to check for Pasteurization.
5. __________ was credited with developing the method of heat processing.
a) Peter Durand
b) Leeuwenhoek
c) Nicolas Appert
d) Hooke
View Answer
Explanation: Nicolas Appert realized the value of heat when it came to food preservation. He sealed and immersed packed bottles of food in boiling water to get rid of the microbes.
6. Bacteria that are able to survive Pasteurization temperature are called _____
a) Halotolerant bacteria
b) Thermophilic bacteria
c) Thermoduric bacteria
d) Osmophilic bacteria
View Answer
Explanation: The bacteria that are able to withstand Pasteurization temperature of 72°C are called thermoduric bacteria. Halotolerant bacteria can survive high salt concentration whereas thermophilic bacteria grow and thrive at temperatures above 50°C. Osmophilic bacteria can grow at a relatively higher osmotic environment than other bacteria.
7. Processing of dairy and dairy products is done by using UHT. What is the full form of UHT?
a) Unit Heat Temperature
b) Unit High Temperature
c) Ultra Handy Temperature
d) Ultra High Temperature
View Answer
Explanation: Ultra Heat Temperatures are usually above 408 K. They are used to sterilize dairy and other dairy products. Due to the very high temperature, sterilization takes a very short time. This process can be called Ultra-Pasteurization. This is also called Sterilization.
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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