Food Microbiology Mid-Term Study Guide: Key Concepts and Hazards

What is the maximum allowable standard plate count (SPC) for raw milk?

Raw milk must not exceed __________ SPC/ml.

What is the acceptable bacterial count and coliform limit in pasteurized milk?

Acceptable bacterial count and coliform limit in pasteurized milk.

Define somatic cells and explain their significance in milk quality testing.

Somatic cells are a measure of milk quality, indicating the health of the mammary gland.

Differentiate between aerobic, anaerobic, and facultative anaerobic bacteria.

Aerobic bacteria require oxygen, anaerobic bacteria do not, and facultative anaerobes can survive with or without oxygen.

List three intrinsic factors affecting microbial growth.

Intrinsic factors include pH, water activity, and nutrient content.

What are zoonotic pathogens?

Zoonotic pathogens are microorganisms that can be transmitted from animals to humans.

State three changes that make spoiled food unacceptable for human consumption.

Changes include off-odors, off-flavors, and visible mold growth.

What produces mycotoxins, and how can they enter humans?

Mycotoxins are produced by molds and can enter humans through contaminated food.

List three ancient methods of food preservation.

Methods include drying, salting, and fermentation.

Define oxidation and reduction.

Oxidation is the loss of electrons, while reduction is the gain of electrons.

What is water activity, and why is it important in food microbiology?

Water activity measures the availability of water for microbial growth; lower water activity inhibits spoilage.

What is the buffer capacity of food?

Buffer capacity refers to the ability of food to resist changes in pH.

Explain the difference between aerobic and anaerobic bacteria.

Aerobic bacteria require oxygen for growth, while anaerobic bacteria grow in the absence of oxygen.

Define extrinsic factors and give three examples.

Extrinsic factors are environmental conditions affecting microbial growth, such as temperature, humidity, and atmosphere.

What are psychrotrophs?

Psychrotrophs are microorganisms that can grow at refrigeration temperatures.

What are mesophiles?

Mesophiles are bacteria that grow best at moderate temperatures, typically between 20-45°C.

What are thermophiles?

Thermophiles are bacteria that thrive at high temperatures, usually above 45°C.

Explain the relationship between temperature and relative humidity in food storage.

Higher temperatures can increase the rate of microbial growth, while relative humidity affects water activity.

What are the two main atmospheric gases with antimicrobial properties?

The two gases are carbon dioxide and nitrogen.

What do high microbial counts in food indicate?

High microbial counts indicate potential spoilage and food safety risks.

List three consequences of high microbial counts.

Consequences include food spoilage, foodborne illness, and economic loss.

Name two fungi commonly found in meats.

Common fungi include Penicillium and Aspergillus.

Name two types of yeast found in meats.

Types of yeast include Saccharomyces and Candida.

Why are comminuted meats more contaminated than non-comminuted meats?

Comminuted meats have a larger surface area exposed to contaminants.

What microorganism is widely used as an indicator of food sanitation?

Escherichia coli (E. coli) is commonly used as an indicator.

State three control measures to prevent foodborne diseases.

Control measures include proper cooking, refrigeration, and hygiene practices.

Define cryogenic freezing.

Cryogenic freezing is a method that uses extremely low temperatures to freeze food quickly.

State two methods of thermal processing.

Methods include pasteurization and sterilization.

Describe two types of freezing methods and how each destroys microbes.

Quick freezing forms small ice crystals, while slow freezing can damage cells, both inhibiting microbial growth.

Provide one example of a parasite and one type of food associated with it.

Example: Trichinella spiralis associated with undercooked pork.

State three extrinsic factors affecting microbial growth.

Extrinsic factors include temperature, humidity, and packaging.

Explain how food preservation inhibits spoilage microorganisms.

Food preservation methods reduce moisture, alter pH, or create inhospitable environments for microbes.