Food microbiology 2 + industrial microbiology Flashcards
What is food poisoning/intoxication
Caused by microbial toxins in food. Symptoms appear quickly
What is food infection
Organisms are ingested with the food and multiply in the host. Symptoms take longer to develop. Illness may be due to tissue invasion, production of toxins or both
Top 10 causes of food-borne diseases
- Leaving cooked foods at room temperature
- Lapse of 12 h or more between preparation and consumption
- Colonized/ infected persons handling food
- Inadequate reheating
- Improper hot holding
- Contaminated raw food/ingredients
- Foods from unsafe sources
- Improper cleaning of equipment
- Cross contamination -raw to cooked
- Inadequate cooking
What diseases do e.coli cause, how many people and by what foods
Food infection
63000 per year
Meat, especially ground meat, raw vegetables
What diseases do salmonella cause, how many people and by what foods
Food infection
1,340,000 per year
Poultry,meat,dairy, eggs
What diseases do clostridium cause, how many people and by what foods
food poisoning and food infection
248,000
Meat and vegetable held improper storage temperature
How botulism happen
A food poisoning, ingestion of the neurotoxin produced by Clostridium botulinum
What does botulism cause and the mortality rate
10% mortality
Causes flaccid paralysis, respiratory or cardiac failure
Symptoms of botulism
Difficulty swallowing, double vision, breathing difficulty, paralysis
Botuslism will take place
1-2 days
Clostridium botulinum is anaerobe/aerobe
Anaerobe
What is the precaution for Clostridium botulinum and canning
Home canning -> insufficient temperature to kill the spores
Processed foods that are not reheated (non-acid canned vegetables , slices meats)
Spores germinate, growth, toxin produced
Temperature and botulism toxin
Toxin is destroyed by heating (80C, 10 min). Properly cooked foods are safe to eat; it destroys the toxin, not the organisms
What organisms accounts for 40% of food poisoning cases
Staphylococcal
What toxin is secreted by Staphyloccocus aureus
Enterotoxin
Enterotoxin stability
Relatively heat-stable -> 30 min at 100C , 16H at 60 C and still going to be alive
How can you get S.aureus
20-30% of humans are colonized by S.aureus (skin and upper respiratory tract). It is easily transferred to food where it can grow and produce the toxin. Symptoms appear quickly (1-6h):nausea,vomiting, diarrhea
S.aureus are associated with what kind of food
Prepared in large quantities and then, left at room temperature (banquet,picnic,airline, meals). Halotolerant-> can grow on salted sausages,etc.
What can be done to prevent S.aureus poisoning
Keep cold food and hot food hot.
Adequate sanitation/hygiene
Did we know all strains of salmonella enterica?
No, only a fraction.
S.enterica can infect
Mammals, birds and reptiles
How salmonella enterica progresses
Contaminated food drink-> bacteria travel to small intestine, adhere to lining; begin life cycle
In severe cases, bacteria break through intestinal wall to bloodstream; can be deadly if not properly treated
Who can get a severe case of Salmonella enterica
Infants, elderly, people with impaired immune systems
What is salmonellosis
when salmonella grows in the intestinal tract
What system does Salmonella uses
two injectisome systems
Most common strains of salmonella
eteritidis
Typhimurium
How Salmonella enterica transmitted
Different routs: water, processing of different types of food
How many organisms of Salmonella enterica are needed to cause disease and what should happen before ingestion
10^5-10^8
It must multiply in the food before the food is eaten
Symptoms of Salmonella enterica are caused by
Invasion and destruction of the intestinal epithelium
S.enterica is associated with
Uncooked or slightly cooked foods, or cooked foods that were cross-contaminated
What helps against S.enterica
Good sanitation practices against cross-contamination.
Cooking kills S.enterica
Symptoms of S.enterica
Nausea, vomiting, fever diarrhea, abdominal cramps
Why it is difficult to find E.coli O157:H7
Fecal coliform but does not grow at 44.5C; escape detection by standard fecal coliform methods
What is EHEC
E. coli strain that causes a severe intestinal infection in humans
What is the effective dose of EHEC
less than 100 microorganisms
How does EHEc infect humans and what does it do
Food infection, attaches to the intestinal mucosa and produces an AB-type exotoxin: Shiga like toxin that inhibits protein synthesis
What is the effect if Shiga toxin
The toxin damages the underlying tissues-> causes bloody diarhea (hemorrhagic colitis)
The toxin travels through the blood stream and destroys cells in the kidney-> causes hemolytic uremic syndrome, can result in acute renal failure and death
How EHEC can be killed
By cooking
What are the aims of food processing and preservation
- Prevent or delay decomposition by microorganisms (spoilage)
- Destroy pathogens or inhibit their growth
- Prevent or delay self-decomposition by enzymes present in the food
How can food processing be achieved (6)
- Refrigeration and freezing
- Heating (pasteurization)
- Canning
- Reducing water availability
- Irradiation
- Chemicals
What are the enzymes of refrigeration and freezing?
Slow or inhibit growth of microorganisms
What happens at -20C? (Aw)
At -20C the aw can reach 0.82. Most organisms cannot grow
What happens once the temperature is persmissive? ( again warm)
Viable microorganisms will resume growth
What cycle affect the quality of the food (ice crystals)
Freeze/thaw
What is cereulide
Toxin produced by B.cereus (spore-forming)
The action of cereulide
Attacks the mitochondrion, compromises membrane potential and oxidative phosphorylation
The result of the action of cereulide
Eventually leads to cell death (apoptosis)
Acute emetic agent (causes vomiting)
especially toxic for liver and pancreas (beta cells)
The aim of pasteurization
Reduce the number of microorganisms to delay spoilage and to eliminate pathogens
Pasteurization is done for what products
Dairy, liquid egg products, alcoholic beverages, fruit juice
Three methods of pasteurization for milk
Long temperature long time (LTLT)
High temperature short time (HTST)
Ultrahigh temperature (UHT)
Describe the conditions for LTLT
30 min, 62.8C, bad taste(ice cream and cheese)
Describe the conditions for HTST
HTST: 15 sec, 71.7C (milk for drinking)
Describe the conditions for UHT
2 sec, 141C (long shelf life at room temperature, virtually sterile)
Time AND TEMPERATURE required for pasteurization are affected by
The amount of fat, sugar and protein
Can raw milk be used for something in Quebec?
For cheese making
Aim of canning
Seal the food from the outside world and heat the container to kill most, if not all, of the microorganisms. It creates an aerobic environment
Temperature for canning
100 C for acidic food
Up to 121C for low-acid food
What is 12D process
Temperature and time of exposure must be sufficient to kill 10^12 spores of Clostridium botulinum
In canning, there is should be a balance between
Food safety, nutritional value and taste of the food
Drying: aim
Prevent microorganisms from growing by inhibiting water availability
Types of drying
- Sun dried
- Hot air dried
- Freeze-drying (lyophilization)
How can be reducing of water achieved in drying
Adding salt or sugar: increases the osmotic strength of the surrounding solution
Does drying kill microorganisms?
Not necessarily. Just inhibits their growth
What is the aim of irradiation?
Reduce contamination of fresh product by pathogen and spoilage organisms
Dosage of irradiation can be adjusted to
- Kill all microorganisms (radappertization)
- Kill specific microorganisms (radicidation)
- Reduce overall contamination (radurization)
What are some concerns about irradiating the food?
Possible radioactive contamination, production of toxic or carcinogenic compounds, altered nutritional value, production of off-flavor
Aim of chemicals and other treatments
Control growth of microorganisms (usually selected microorganisms )
What are chemicals generally recognized as safe (GRAS) and where they are used
Nitrite: prevents outgrowth of C.botulinum
Sulfites: wine industry, inhibits growth wild yeasts
Nisin: bacteriocin produced by lactococcus lactis. Present in cheeses made with lactococcus lactis. Effective against many gram-positive organisms , including lactic acid bacteria
What is bacteriohage for food
FDA has approved a cocktail of bacteriophages against listeria monocytogenes
What is produced during exponential phase
Primary metabolites: alcohol
What is produced at the end of growth, near or at the stationary phase
Antibiotics
Major products of Industrial microbiology
- Antibiotics
- Enzymes
- Food additives
- Chemicals
- Alcoholic beverages
What vessel is used for industrial growth of microorganisms
Chemostat
In industrial microbiology, fermentation refer to
Any large-scale microbial process (aerobic or anaerobic)
What is controlled in chemostats
- Temperature
- Nutrients
- pH
- Dissolved oxygen
What stains are not suitable for industrial use
wild-type industry
What two types of stains are used in industry
Mutant strains that overproduce the desired metabolites; deregulated mutant with respect to desired metabolic pathway. Leads to large scale production of the compound
-Genetically modified organisms. Genes are cloned into and expressed in bacteria or yeasts. Can control expression to synthesize as much ( or as little) product as required
What mutant strain is used in industry and is very useful and for what
Very useful to produce AAs (Corynebacterium sp.)
What is produced with genetically modified strains
Human insulin and a variety of enzymes (e.g. rennet)
What is somatotrophin
_human growth factor
-Deficiency causes heredity dwarfism
What can be corrected with human somatotrophin drugs
Can correct stunted growth in children
How do we get somatotrophin drug
Recombinant human somatotrophin gene cloned and expressed in bacteria
Bovine somatotrophin: how it is related to cows
An average dairy cow begins her lactation with a moderate daily leve of milk production. This daily output increases until, at about 70 days into the lactation, production peaks. From that time until the cow is dry, production slowly decreases. This increase and decrease in production is partially caused by the count of milk-producing cells in the udder. Cell counts begin at a moderate number,increase during the first part of the lactation, then decrease as the lactation proceeds. Once lost, these cells generally do not regrow until the next lactation.
Administration of rBST or BST prior to peak production, in cows that are well-fed, slows the rate at which the number of mammary cells decreases, and increases the amount of nutrients directed away from fat and toward the mammary cells, leading to an extension of peak milk production. The effects are mediated by the insulin-like growth factor (IGF) system, which is upregulated in response to BST or rBST administration in well-fed cows
Insulin produced by what type of cells and where
In pancreas by beta-cells
Why it is necessary to do insulin injections
To preserve glucose homeostasis and for survival-> to lower blood sugar levels
Insulin was the first ___
Human protein to be produced by bacteria
What can be done to a plant with bacteria
Plants can be genetically engineer herbicide or insect resistance into a crop plant
example of herbecide
Glyphosate (roundup) kills plants by inhibiting amino acid synsthesize
How can be resistance to Glyphosate
- Take gene from Glyphosate resistant bacteria
- Modify for expression in plants
- Clone (transfer) into crop plant,
- End result: crop plant is resistant can use glyphosate to kill weeds
How can you develop resistance to insects in plants
- Introduce genes encoding bacterial toxin that is toxic to insect into the plant
- Plants produce the toxin
- Insects that come into contact with plant ingest toxin and die
Example of plant toxin to insects
Bt toxin is very toxic to moths and butterflies (but not mammals)
