Spring 2026 Exam 1 Study Guide (FOS4222/5225C)

These flashcards cover key concepts from the Spring 2026 Exam 1 Study Guide for FOS4222/5225C, focusing on microbiology, bacterial growth, and food safety.

Robert Koch's major contributions to microbiology include conducting __.

his germ theory, developing vaccines, and establishing postulates.

The three postulates established by Koch state that __.

specific pathogens cause specific diseases, pathogens can be isolated and grown in pure culture, and pathogen introduction causes the same disease.

Food microbiology deals with __.

food safety, spoilage, preservation, and pathogens.

Not all microbes are harmful. Some beneficial microbes are used in __.

fermentation and enhancing food flavor.

Food quality refers to __.

attributes like taste, appearance, and freshness, which may be different from food safety.

Intrinsic factors affecting bacterial growth in foods include __.

pH, moisture, nutrients, and water activity.

Extrinsic factors affecting bacterial growth involve __.

temperature, time, pressure, and humidity.

Water activity (aᵥ) is the measure of __.

the amount of free water available for microbial growth.

Bacteria classified as psychrophiles grow at __.

low temperatures, such as those found in a refrigerator.

Obligate aerobes require __ for their growth.

oxygen to survive.

A facultative anaerobe prefers __ but can also grow without it.

oxygen.

Aerotolerant anaerobes can tolerate __ but do not require it.

oxygen.

An obligate anaerobe finds oxygen __ and cannot survive in it.

toxic.

Binary fission refers to __.

the method by which prokaryotes multiply.

The four phases of bacterial growth include lag, log, __, and death phases.

stationary.

During the lag phase, bacteria are in a __ mode as they adapt to their environment.

resting.

In the log phase, cells double at a __ rate due to abundant nutrients.

constant.

The stationary phase is characterized by __ in numbers of dying and dividing cells.

equalization.

The death phase of bacterial growth occurs when __ exceed growth replenishment.

toxin effects.

VBNC state in bacteria means _.

viable but non-culturable.

Persister cells are defined as bacteria that can __ under stress.

enter dormancy but can later recover.

Biofilm formation leads to __ in microbial communities.

increased resistance to removal.

Buffers in culture media help to __.

stabilize pH changes during bacterial growth.

Selective media is designed to __.

only allow certain bacteria to grow.

Differential media allows for __.

the identification of bacteria based on color change.

General media culture serves to ___ bacterial viability.

assess.

Enrichment media is used to ___ bacterial load.

increase.

MPN stands for __.

most probable number.

CFU refers to __.

colony-forming units.

Incubation temperature for total coliforms is __.

35 °C.

Fecal coliforms are incubated at __.

44.5 °C.

Spoilage in food can result from __.

high concentrations of molds or bacteria.

Autolysis refers to the __.

enzymatic breakdown of cells.

Spoilage is subjective, as it heavily relies on __.

consumer perception.

The danger zone for food temperature is between __.

40°F and 140°F.

SSOs are organisms that contribute to the __ of food.

spoilage.

Water activity is significant because it affects __.

microbial growth and survival.

The primary function of pectinase in spoilage is to __.

break down pectin in plant cell walls.

Ground meat poses a higher microbial risk because it has undergone __.

more processing and exposure.

The primary spoilage bacteria in fresh fish include __.

Pseudomonas spp.

Chemical spoilage in meat includes excessive amounts of __.

hydrogen sulfide and biogenic amines.

True or False: Fresh fruits and vegetables are nearly ideal for microbial growth due to their nutrient-rich environment.

True.

Ripening in fruits can be accelerated by __.

exposure to ethylene gas.

Dried fruits have lower __ compared to fresh fruits, making them less susceptible to spoilage.

water activity.

Psychotropic microorganisms in milk can affect its __.

flavor and quality.

Raw milk typically has a bacterial load of __.

up to 5 log CFU/ml.

Yeasts tend to grow in environments with __ conditions.

low pH and high lactose concentrations.

Controlled spoilage in dairy products is beneficial because it utilizes __ to inhibit harmful bacteria.

lactic acid bacteria.

Bacillus cereus poses risks in dairy due to its __ ability.

spore-forming.

Lactoferrin in milk acts as a natural __.

antibiotic.

Pasteurization effectively reduces microbial loads to _ CFU per ml in Grade A milk.

less than 4.3.

Low pH helps protect __ in fruit juices.

against most bacterial growth.

The primary spoilage microorganisms in fresh juice are __.

LAB and molds.

Biogenic amines can cause __ and safety concerns in seafood.

intoxication.

Cold storage is crucial for slowing __ in perishable foods.

spoilage.

True or False: Cooking food only kills actively growing bacteria.

True.

The preservatives used in modified atmosphere packaging (MAP) are __.

CO2, N2, and O2.

Comminuted products like sausages have __ shelf lives due to processing.

limited.

High-risk foods like molluscan shellfish can concentrate __.

pathogens due to their filter-feeding habits.

The major source of spoilage microorganisms in muscle foods includes __.

processing and the environment.

Cleaning routines in milk production must limit contamination from __.

soil and animal contact.

Spoilage-associated defects in meat can lead to __.

unpleasant odors and textures.

The microbial population can vary due to pre-harvest conditions such as __.

water, insects, and fertilizer.

Ethylene gas plays a role in initiating __ in fruits.

ripening and spoilage.

Molds like __ are common on grains.

Aspergillus.

Factors such as temperature and water quality are crucial in determining __ in fish.

microbial load.

Cooling food quickly post-cooking is important to minimize __.

bacterial growth and spoilage.

What role do spoilage organisms play in food safety?

Spoilage organisms can indicate the breakdown of food quality, leading to potential safety risks.

How does temperature influence bacterial growth in food?

Temperature affects the rate of microbial growth, with specific ranges promoting or inhibiting bacteria.

What is the significance of lactic acid bacteria in food preservation?

Lactic acid bacteria can help preserve food by lowering pH and inhibiting spoilage organisms.

What are the common indicators of food spoilage?

Indicators include off odors, discoloration, and changes in texture.

How does fermentation contribute to food preservation?

Fermentation can create an acidic environment that inhibits harmful bacteria.

What temperature range is considered safe for food storage?

Food should be stored below 40°F to minimize bacterial growth.

Why is monitoring water activity important in food safety?

It helps predict microbial growth potential and spoilage risks.

How do preservatives work to inhibit spoilage?

Preservatives can disrupt microbial metabolism and decrease moisture availability.

What types of bacteria are most commonly responsible for foodborne illnesses?

Common culprits include Salmonella, E. coli, and Listeria.

What is the impact of packaging on food shelf life?

Packaging can protect food from contamination and extend shelf life by limiting exposure to air and moisture.

What are the primary types of bacteria found in food?

The primary types include pathogenic bacteria like Salmonella, spoilage bacteria such as Pseudomonas spp. and Shewanella, and beneficial bacteria like Lactic Acid Bacteria (LAB).

Where do pathogenic bacteria such as Enterobacteriaceae typically grow in food?

Pathogenic bacteria like Enterobacteriaceae grow in protein-rich foods such as meat, poultry, and dairy products.

Which specific spoilage bacteria are commonly found in dairy products?

Spoilage bacteria in dairy products include Pseudomonas spp., Bacillus spp., and various Lactic Acid Bacteria (LAB) such as Lactococcus and Leuconostoc.

What environmental conditions support bacterial growth in food?

Warm temperatures, moisture, and nutrient-rich environments support bacterial growth, especially for Bacillus spp. and Vibrio spp.

What is the significance of psychrotrophic bacteria like Pseudomonas spp. in food spoilage?

Psychrotrophic bacteria like Pseudomonas spp. can spoil food even at refrigeration temperatures, particularly in dairy and meats.

What are the indications of bacterial spoilage in food?

Signs of bacterial spoilage include off odors, sliminess, discoloration, and changes in texture due to biofilm formation.

How can bacteria such as Serratia marcescens in contaminated food affect human health?

Contaminated food with bacteria like Serratia marcescens can cause foodborne illnesses, resulting in symptoms like nausea, vomiting, and diarrhea.

What are the different forms of Lactic Acid Bacteria (LAB) used in food preservation?

Forms of LAB used in food preservation include Lactobacillus and Streptococcus, which can inhibit spoilage through acid production.

How do VBNC (viable but non-culturable) bacteria impact food safety?

VBNC bacteria can survive under stress without growing, making them undetectable yet potentially harmful in contaminated food.

Where are persister cells typically found and what is their role?

Persister cells can be found in biofilms and are characterized by their ability to survive harsh conditions, posing challenges for food safety and preservation.

What are enzymes and their role in food?\n\n

Enzymes are biological catalysts that speed up chemical reactions in food, influencing flavor, texture, and preservation.\n\n

What types of enzymes are commonly involved in food processing?\n\n

Common types include proteases, amylases, lipases, and pectinases, each targeting different components in food.\n\n

What are biogenic amines and how are they formed?\n\n

Biogenic amines are organic compounds formed from the decarboxylation of amino acids, often produced by microbial action during spoilage.\n\n

What are the potential health effects of biogenic amines in food?\n\n

Biogenic amines can cause intoxication and allergic reactions, leading to symptoms such as headaches, flushing, and gastrointestinal issues.\n\n

How does autolysis occur in food products?\n\n

Autolysis is the self-digestive process where cells break down their own components, often occurring in food during spoilage or fermentation.\n\n

What factors influence autolysis in food?\n\n

Factors include temperature, pH, and the presence of enzymes, which can accelerate or delay the autolytic process.\n\n

Which enzymes are involved in autolysis?\n\n

Proteolytic enzymes, lipases, and amylases are commonly involved in autolysis, leading to the breakdown of proteins, fats, and carbohydrates.\n\n

How can controlling autolysis benefit food preservation?\n\n

Controlling autolysis can help maintain food quality, extend shelf life, and prevent off-flavors by managing enzyme activity.\n\n

What role do pectinases play in food processing?\n\n

Pectinases help in breaking down pectin in fruits, aiding in juice extraction and improving texture in fruit products.\n\n

Why is monitoring enzyme activity important in food safety?\n\n

Monitoring enzyme activity is crucial to prevent undesirable spoilage and maintain food quality during storage and processing.