Lecture 11: Food Microbiology Flashcards
1) Give examples of microbes in food
2) What helps produce cheese?
1) Molds help us make soy sauce, beer and wine fermentation, bacteria make air pockets and holes in swiss cheese
2) Bacterial lactic acid production
1) Why does food go bad?
2) What are the two types of factors of microbial growth in foods?
1) Food goes bad because of microbes; for example, milk curdles (proteins coagulate) while going bad and pH decreases. This allows molds and yeast to take over.
2) Intrinsic and extrinsic
1) List the intrinsic factors of microbial growth in foods
2) List the extrinsic factors of microbial growth in foods
1) Intrinsic: Composition, physical, and biological state
2) Extrinsic: Temperature, relative humidity, gasses, contaminating microorganisms
1) How does temperature and heat affect microbial growth? How can atmosphere be changed to affect growth?
2) Give 2 examples of foods with antimicrobial activity
1) Low temperature and low humidity decrease growth. CO2 can be injected into packaging to prevent growth during shipment.
2) Fruits and vegetables have coumarins (antimicrobial) and spices are antimicrobial
Describe the 3 Genome Watch articles discussed in class
1) -omics: for example, metabolomics, lipidomics (study metabolism pathways), proteomics (study proteins) was used to study lactobacillus (beneficial bacteria) in bee guts
2) CRISPR-CAS
3) Those with COVID-19 had a limited amount of immunomodulatory bacteria; made their symptoms more severe
Describe the 6 Research Highlights articles discussed in class
1) Gut flora impact on obesity in IBD
2) Phage in the Pseudomonas strain can make proteins that protect phage DNA and form crystalline droplets that coat the host cell
3) Increased CO2 emission of soil bacteria grown in “global warming” conditions (vs control)
4) Necro signaling: Dying bacteria can secrete signals to living cells to warn about antibiotics
5) Virus causes host to attract mosquitos; but can be reversed
6) COVID-19 loss of smell; does not infect olfactory cells but changes their surface
What are some examples of specific intrinsic factors for microbial growth on food?
1) Food composition
2) pH
3) Physical structure
4) Availability of water
1) Low pH of food leads to what kind of microbial growth? 2) What about high pH?
1) Low leads to yeasts and molds
2) High leads to bacteria
How is the physical structure of food altered when we eat?
Grinding, mixing, etc increases surface area
What protection against microbial growth do fruits and vegetables have?
Spillage microorganisms have enzymes that protect
How does water affect food spoilage? What else can affect food spoilage?
There is less spoilage if 1) dry or 2) add sugar or salt
Give 9 examples of methods used to control food spoilage
1) Filtration
2) Low-temperature
3) High-temperature
4) Water availability
5) Ultra-high temp pasteurization
6) Chemical-based preservation
7) Radiation
8) Microbial product-based inhibition
9) Packaging
Define filtration and low-temperature
Filtration: removes microbes from liquids
Low temperature: slows but doesn’t kill
1) Give 2 examples of high temperature controlling microbes on food
2) How can water availability control microbes on food?
1) High temperature: pasteurization, canning
2) Water availability: drying vs storing in liquid
________ microorganisms prefer a dry environment
________ microbes grow best under osmotic conditions
-xerophilic; -osmophilic
1) Is ultra high temperature pasteurization shelf-stable? What does it kill?
2) What is chemical-based preservation closely regulated by?
1) Shelf-stable, kills bacteria
2) The FDA
1) When is radiation effective at controlling microbes? What does it use?
2) Give 2 examples of microbial product-based inhibition
Radiation: effective for moist foods (radappertization); also use electron beams
Microbial product-based inhibition: bacteriocins (nisin) and bacteriophage spray
Describe how packaging can control microorganisms on food
Through a ‘modified atmosphere’ (60% CO2 or high-O2)
1) Are molds unicellular or multicellular?
2) What can molds make?
3) What can molds cause?
4) How do molds reproduce?
5) What do molds secrete?
1) Can adopt multicellular arrangement
2) Can make filaments (fuzzy)
3) Cause allergies
4) Reproduce through spores
5) Secrete enzymes
Yeast: single-celled, can cause infection if immunocompromised, reproduce through mitosis (budding), fermentation of sugars into CO2 plus alcohol.
1) Are yeast single-celled or multicellular?
2) What can yeast cause? When?
3) How do yeast reproduce?
4) What do yeast do to sugar?
1) Single-celled
2) Can cause infection if immunocompromised
3) Reproduce through mitosis (budding)
4) Fermentation of sugars into CO2 and alcohol.
What are the two types of food related disease? Describe them.
1) Food-borne infections: ingestion of pathogen-grown-invasion/ toxin production (food poisoning) (toxins made in body)
2) Food intoxications: results from microbial growth in food products (toxins made in food)
Name 6 food-borne microbes
1) Salmonella
2) Norovirus
3) Campylobacter
4) Toxoplasma
5) E. coli 0157
6) Listeria
What is the incubation period, symptoms, and food sources of Salmonella?
Incubation: 8-48 hours
Symptoms: Gastroenteritis (diarrhea, fever, vomiting).
Food source: Fruits, vegetables, poultry, eggs, cheese
What is the incubation period, symptoms, and food sources of Norovirus?
Incubation: 12-48 hours (‘cruise ship virus’)
Symptoms: Diarrhea, fever, nausea
Food source: Produce, shellfish, salad, sandwiches
What is the incubation period, symptoms, and food sources of Campylobacter?
Incubation: 2-5 days
Symptoms: Diarrhea, fever, cramps
Food source: Poultry, contaminated water
What is the incubation period, symptoms, and food sources of Toxoplasma?
Incubation: 1-3 weeks
Enlarged lymph nodes, headaches, myalgia.
Food source: Raw meat, contaminated water (& cat litter box)
What is the incubation period, symptoms, and food sources of E. coli 0157?
Incubation: 1-10 days
Symptoms: Severe diarrhea, vomiting, HUS (hemolytic uric syndrome)
Food source: Contaminated water, raw milk/ fruit/ veggies, hamburger meat
What is the incubation period, symptoms, and food sources of Listeria?
Incubation: 3-70 days
Symptoms: Fever, stiff neck, confusion, myalgia
Food source: Deli meats, hot dogs, raw milk and dairy, soft cheese (survives in fridge).
1) Does food intoxication require growth of disease-causing microbes?
2) How fast do symptoms manifest?
1) Growth of disease-causing microorganisms not required
2) Symptoms manifest quickly
1) Where is Staphylococcus aureus (SA) normally found?
2) Describe when its growth and toxin production occurs and if it’s heat-stable
3) What are its symptoms and how fast do they manifest?
1) Introduced into food during preparation
2) Growth and toxin (heat-stable) production occurs as food sits out.
3) Nausea, vomiting, stomach cramps, and diarrhea as little as 30 minutes after you eat something (up to 2 hours).
1) Where is Clostridium perfringens found?
2) What does it do in its production of gut-toxin?
1) Growth in rewarmed meat dishes
2) Sporulation in gut-toxin production
1) Where is Botulinum found?
2) Describe its mortality
1) Growth in anoxic foods (canned goods) = toxin.
2) Toxin absorbed in gut = high mortality.
What are the two forms of Bacillus cereus?
Short form (emetic form) and long form (diarrheal form)
Name the 2 forms of Bacillus cereus and describe their heat stability, incubation times, and symptoms
1) Emetic form: Toxin heat-stable, 1-6 hours, vomiting, and cramps
-Fried rice, sprouts, cucumbers
2) Diarrheal form: Toxins heat-labile, 8-16 hours, diarrhea and cramps
What are the 4 places in which food can be contaminated?
1) Production: spraying fields with contaminated water, contamination before harvest
2) Processing: using contaminated water to wash
3) Distribution: being left in warm weather before distribution
4) Preparation: being contaminated by a human in the kitchen
What are 3 traits found in the ideal food-borne pathogen detection method?
1) Specificity and sensitivity
2) Speed
3) Simplicity.
Describe the 3 levels of food-borne pathogen testing and when each happens
1st level: Testing to prevent (before it leaves farm)
2nd level: Testing to protect (prior to consumption)
3rd level: Testing to recover (determine origin of an outbreak)
True or false: It can take a lot of time to detect pathogens
True
Microbes are involved in what 3 aspects of food?
Safety, quality, and nutrition
Name 4 types of groups that may respond to a food-borne pathogen outbreak
1) Local agencies
2) State agencies
3) CDC
4) Federal regulatory agencies: FDA, USDA’s Food Safety and Inspection Service (FSIS), etc
How can lactic acid bacteria (LAB) be used? (5 ways).
Describe each.
1) Mesophilic fermentation: Lactococcus lactis used to make milk richer; buttery flavor.
2) Thermophilic fermentation: S. thermophilus and L. bulgaricus
3) Probiotic: live microorganisms, which when administered in adequate amounts, confer a health benefit for the host
4) Microbial dietary adjuvants: immunomodulation, control of diarrhea, anticancer, Crohn’s disease
5) Ethanolic fermentation: wine, beer, etc
What temperatures do mesophilic and thermophilic lactic acid fermentation take place at?
1) Mesophilic: 20-30C
2) Thermophilic: 45C
