Food Microbiology Exam (2)

What is the concept of Spontaneous Generation?

Disproven idea that life arises from non-living matter.

What does Germ Theory state?

Microbes cause diseases.

What are the steps of the Scientific Method?

Observation → Hypothesis → Experiment → Conclusion.

What is Taxonomy?

Classification of organisms (Domain, kingdom, etc.).

What is a Reservoir in terms of infectious diseases?

Where a pathogen naturally lives.

What is the Source of an infection?

Immediate origin of infection.

What is Food Infection?

Caused by consuming live microbes (e.g., salmonella).

What is Food Intoxication?

Caused by toxins produced by microbes (e.g., staphylococcus aureus).

Where are fungal pathogens typically found?

In soil, plants, and decaying matter.

What is Thermal dimorphism?

Ability to grow as yeast (warm) or mold (cold).

What is cutaneous entry?

Entry through cuts, abrasions, or wounds.

What does the respiratory tract allow entry for?

Inhalation of fungal spores from the air.

What is the gastrointestinal tract's role in pathogen entry?

Consumption of contaminated food or water.

How do pathogens enter through mucous membranes?

Early entry through mucosal surfaces during exposure to contaminated environments.

What characterizes systemic (opportunistic) entry?

Occurs in immunocompromised individuals, leading to systemic fungal infections.

What are Aflatoxins and where are they found?

Found in grains, peanuts; produced by Aspergillus; causes liver damage.

What is Ochratoxin and its targets?

Found in cereals, coffee (Aspergillus and Penicillium); targets kidney.

What gastrointestinal issues does Patulin cause?

Found in apples; causes gastrointestinal issues.

What affects the nervous system and where is it found?

Fumonisins; found in corn.

What is Deoxynivalenol (DON) and its effect?

Found in wheat; causes vomiting, gastroenteritis

What humidity level promotes mold growth in storage?

High water activity (aw > 0.7)

What temperatures accelerate mycotoxin production?

Warm temperatures (75-100°C) (25-30°C) accelerate production.

What storage condition encourages fungal growth?

Aerobic conditions

What increases the risk of mycotoxin buildup?

Longer storage

What makes grains more susceptible to mycotoxins?

Damaged or improperly harvested grains are more susceptible.

What are pre-harvest measures for mycotoxin control?

Use resistant crop varieties and apply fungicides when necessary.

What is critical during harvesting?

Harvest crops at the correct maturity stage.

What drying practice reduces moisture content for grains?

Drying: Reduce moisture content to below 13% for grains.

What temperature should products be stored at for safety?

Store products at low temperatures (< 10°C).

What is necessary for reducing moisture buildup during storage?

Ensure proper ventilation to reduce moisture buildup.

What kind of containers should be used for storage?

Use airtight, moisture-proof containers.

What should be done to remove contaminated grains?

Remove contaminated or damaged grains.

What physical methods can reduce mycotoxins?

Heat treatment (roasting), UV radiation, and irradiation can reduce mycotoxins.

What are some chemical methods for mycotoxin control?

Additives like organic acids (e.g., propionic acid) or preservatives (e.g., sulfites) can inhibit fungal growth.

What biological methods help in degrading mycotoxins?

Use of beneficial microbes to degrade mycotoxins.

What is the size range of viruses?

20-300 um. <0.2 um

What are the main structural components of viruses?

Capsids (protein coat), envelope (lipid layer), spikes (attachment).

What is the function of a capsid and envelope?

Protects nucleic acid when virus is outside host cell, aids in attachment to host cells, and assists with penetration of viral genome

What is a capsid composed of?

Proteins called capsomers that assemble into a protective shell around the viral nucleic acid.

What is an envelope composed of?

A lipid bilayer derived from the host cell membrane, containing proteins and glycoproteins.

What are spikes?

Protein structures on the surface of a virus envelope that facilitate attachment to host cells and play a role in the immune response.

What is the first step in virus multiplication?

Adsorption: The virus binds to host receptors.

How do enveloped viruses penetrate host cells?

Enveloped (fusion or endocytosis) and naked (endocytosis only).

What happens during fusion?

envelope fuses directly with host membrane by rearangement of lipids

What happens during endocytosis?

Entire virus penetrates and is enclosed in a vacuole or vesicle

Where do DNA viruses replicate?

DNA viruses replicate in the nucleus.

Where do RNA viruses replicate?

RNA viruses replicate in the cytoplasm.

What are the two methods of virus release?

Budding (enveloped) or lysis (naked).

What is the difference between latent and chronic infections?

Latent infections remain inactive for a period and can reactivate later, while chronic infections persist over a long time with continuous virus replication.

What are potential food sources of viruses?

Potential food sources of viruses include raw or undercooked seafood, fruits and vegetables contaminated by fecal matter, and unpasteurized dairy products.

How can viruses be controlled in foods?

Viruses can be controlled in foods through proper cooking, pasteurization, and good hygiene practices to prevent contamination.

What are the characteristics of poliovirus?

Naked capsid, resistant to acid, bile, and detergents. Transmitted through fecal-oral route

What is the pathogenesis of poliovirus?

Adhere to mucosal receptors in throat and intestine, multiply and shed in feces and throat. Can leak into blood, cross into certain nerve cells. Most infections short-term, mild non-specific symptoms: fever, headache, nausea, sore throat.

What are the symptoms of poliovirus?

90%: Asymptomatic

5%: Minor symptoms: headache, malaise, sore throat

2%: Nonparylytic polio: invade meninges/CNS, spasms and muscle pain

3%: Paralytic polio: Invade spinal cord/motor cortex of brain, limits nerve impulse, symptoms depend on ID, age/health, can cause paralysis in limbs or respiratory tract

How can poliovirus be treated?

Artificial ventilation for respiratory failure, physical therapy, support

How can poliovirus be prevented?

Vaccination with inactivated poliovirus vaccine (IPV) or oral poliovirus vaccine (OPV) to induce immunity and prevent transmission.

What foods are associated with Hepatitis A virus?

Shellfish, raspberries

What is the pathogenesis for HAV?

Affects digestive tract. Multiplies in the small intestine, enters blood, and is carried to the liver. Viruses shed in feces. Flu-like symptoms may occur, leading to jaundice.

How can HAV be prevented and controlled?

Sensitive to formalin, chlorine, and UV. Sewage treatment, hygenic food handeling, adequate cooking of shellfish

How can HAV be treated?

There is no specific antiviral treatment, but can be prevented by vaccination

What are the characteristics of norovirus?

May cause 90% of all viral gastroenteritis. Transmitted by fecal-oral route: food, water, fomites. Raspberry cakes, soft cheeses.

What is the pathogenesis in norovirus?

Highly infectious. infects the epithelial cells of the small intestine, leading to inflammation and disruption of the intestinal barrier. This results in gastrointestinal symptoms such as vomiting and diarrhea.

What cooking temperature helps inactivating viruses like Norovirus?

Cook foods to appropriate temperatures (e.g., 85-90°C

What are the characteristics of rotavirus?

Non-enveloped, unusual double-stranded RNA genome transmitted through fecal-oral route. Globally prevalent in areas with poor sanitation

What are the symptoms of reovirus?

Mild respiratory infection, enteritis

What is the pathogenesis of rotavirus?

most common cause of infantile gastroenteritis. Primary cause of death from diarrhea in young children worldwide, leading to severe dehydration and electrolyte imbalances.

How can rotavirus be treated?

Treatment focuses on hydration and electrolyte replacement. Vaccination is also effective in prevention.

How do animals affect meat spoilage?

Lymph (red meat): embedded in fat, especially high in bacteria

GI tract: fecal contamination, in air, get on surface of dressed carcass

How does the environment affect meat spoilage?

Hide in hair/feathers, hooves: get in during incisions, transferred during removal

Handlers: microbes on gloves

Stick knife: should be sterile

Containers: nonsterile containers (primary source)

Storage and circulating air, transportation

Why do ground meats have higher numbers of microbes?

have higher numbers of microbes due to the increased surface area exposed to contamination and the mixing of bacteria from different cuts during processing.

What are common spoilage microbes in fresh meat?

Common spoilage microbes include bacteria such as Pseudomonas, Lactobacillus, Staphylococcus, Micrococcus, and Clostridium, which can lead to off-odors and spoilage. Fruity, rancid, bitter, slime, color changes. Vacuum packed: Lactobacillus (anaerobic). Yeast: Candida. Molds: Penicillium, Mucor, Cladosporium. Refrigerated: psychrotrophs, Pseudomonas

How can spoilage be detected in fresh meat?

through sensory evaluation, including off-odors, discoloration, and changes in texture. Additionally, microbial testing can identify the presence of spoilage organisms. Organoleptic changes.

How can shelf-life be determined in fresh meat?

Extract Release Volume (ERV) is a measurement used to assess the shelf life by evaluating the moisture and fat content, indicating the potential for spoilage.

What is sliminess in fresh meat spoilage?

Gray slime, LAB, Enterococcus, yeast.

What is souring in fresh meat spoilage?

underneath casings; bacteria produce acids from sugar fermentation

Lactobacilli, Enterococci (Gram +)

From milk solids

What is greening in fresh meat spoilage?

1) H2O2: vacuum packed: after anaerobically stored meat is exposed to air, peroxide —> green oxidized pigment, Lactobacillus, Enterococci, Weissella

2) H2S: fresh red meats in gas impermeable/vacuum packed, pH >6.0, 1-5C

H2S reacts with Fe2+ in myoglobin —> green precipitate

Pseudomonas and Schewanella

What are common spoilage microbes in poultry?

Campylobacter, Ancietobacter (feathers), Moraxella (feathers), Pseudomonas (low temp), Candida yeast (antibiotics)

Why does breast meat of poultry spoil differently than the leg?

Breast meat has a lower fat content and higher protein concentration, making it more susceptible to spoilage from bacteria and fungi, while leg meat contains more fat, which can inhibit microbial growth.

What are the origins of spoilage in seafood?

Fresh, marine, warm, cold: Finfish, shellfish, mollusks

Inner tissue is sterile

Shucking, peeling, breading

Frozen seafood have less microbes

dried/salted fish (low aw); fungal spoilage

What types of microbes are in seafood spoilage?

Major bacteria: Areomonas, Pseudomonas, E.coli, Salmonella, Shewanella, Vibrio

Tropical fish (Gram +): more bacteria —> mesophiles: Aeromonas, Pseudomonas

Cold water fish (Gram -): fewer bacteria —> psychrotrophs: Bacillus, Micrococcus.

Where is most microbiota located in fish?

gills, outer slime layer, intestines

What is the most susceptible part to spoilage in finfish?

gills

What are the mechanisms of spoilage in finfish?

NO carbohydrates

More lipids = more rancid

Nitrogen compounds broken down first into simple volatile compounds (Rapid spoilage)

What are the four stages of finfish spoilage?

1. 0-6 days after death: Bacteria population shift, no odor

2. 7-10 days after death: Bacteria growth evident, slightly fishy odor

3. 11-14 days after death: Rapid bacteria growth, Strong fishy odor, spoilage noticeable, slime formation

4. 15+ days after death: Bacteria numbers stationary, proteolysis, extremely slimy skin, offensive odor

What are the mechanisms of spoilage in shellfish?

Shrimp, lobster, crayfish

Filter Feeders: microbiota varies based on water quality

Psuedomonas, Acinetobacter dominate… Proteus, Moraxella, Shewanella

Spoilage fermentative due to glycogen

Quality decreases as pH decreses from 6.2-5.2

Potent proteolytic enzymes break down protein

Tissue softening, volatile off-odors

What is the nonclimacteric state in produce?

A state where fruits and vegetables do not continue to ripen after harvest, Citrus, strawberries, beans, lettuce

What is the climacteric state in produce?

A state where fruits and vegetables continue to ripen after harvest, producing ethylene gas. Examples include apples, bananas, and tomatoes.

What are the spoilage mechanisms in produce and grains?

Bacteria are first spoilers

yeast and molds

Degradative enzymes: Pectinase, celulase, Protease, phosphatidase, and dehydrogenase

Why does fresh-cut produce have a higher microbial load?

Fresh-cut produce has a higher microbial load due to increased surface area and potential contamination during processing, handling, and storage. The cutting process can also damage tissues, making it easier for microorganisms to enter.

What is soft rot?

A type of decay in fruits and vegetables caused by bacteria and fungi, resulting in a mushy texture and foul odor.

Pectinase: early spoilage bacterial enzyme breaks down “cement” between plant cells

Pseudomonas, Bacillus

What happens during pre-harvest of produce?

Fungi invades strawberry blossoms —> gray mold

Fungi invades lenticles of apples —> lenticel rot

Fungi invades banana epidermis

What happens during post-harvest of produce?

Bruised/damaged product

Stem of pineapple, neck rot of onions

What are common spoilage organisms of Vegetables?

Gram +: Leuconostoc, Streptococci, LAB Corynebacteria

Staphylococcus (food handlers)

Coliforms

Erwina and Pectobacterium “bacterial soft rot”

What is the average moisture content and carb content of fruits?

moisture content: 85%

Carb content: 13%

What type of spoilage occurs in fruits?

Fungal spoilage, such as mold growth and yeast fermentation, often leading to soft rot and decay. Except pears:/apples: fire blight (Erwinia) —> pH too low to support bacterial growth

What pathogens are present in fruits and vegetables?

C. botulinum spores germinate, produce toxin: RTE Produce

Salmonella invade/internalized plants: sprouting on alfalfa, tomato plants

E. coli from soil gets in produce (apples) that have fallen on ground

Cantelope: warm from fields, washed in dirty water, bacteria penetrates pores —> cold temp may have closed pores preventing bacterial invasion

Contaminated water: Listeria, viruses, Vibrio

How can low acid prevent spoilage in fruit and vegetables?

heat treatment enough to destroy C. botulinum spores, but not more heat-resistant spores

How can high acid prevent spoilage in fruits and vegetables?

if pH < 4.6, not heated enough to inactivate all spores

How can sporeformers be controlled in fruits and vegetables?

Limit initial load, choose appropriate thermal treatment for storage, cool rapidly, chlorinate cooling water, use GMP

Screen raw materials for heat-resistant fungi

How can produce be preserved?

By using methods like canning, freezing, drying, or pickling to inhibit microbial growth and enzyme activity. Temperature control most effective