Unit 1 Food Microbiology and Chemistry Flashcards
What causes the most food spoilage?
microorganism
What are spherical-shaped bacteria called?
cocci
What are rod-shaped bacteria called?
bacilli
If you start with 1,000 bacteria, how many will you have after 10 minutes?
2,000 bacteria
What conditions can endospores resist?
heat, cold, drying, and many disinfectants
What do fungi secrete to meet their metabolic needs?
digestive enzymes
What is the mass of hyphae called that makes up a mold colony?
mycelium
How do yeasts reproduce?
budding, where a smaller new cell is pinched off from a larger existing yeast cell
Which is the time lapse from one cell division to the next called?
Generation time
Which process is the forming of the endospore during bacterial growth?
sporulation
What prominent factors have an impact on microbial activity?
food, acid, time, temperature, oxygen, and moisture (FATTOM)
What do cranberries have a relatively high concentration of?
benzoic acid
What becomes the dominant microorganism as the pH drops in foods?
yeasts and molds
What does a pH value of 7 represent?
neutral
In what pH condition do molds grow better in?
acidic
What most often causes meat spoilage?
bacteria
What happens during fermentation that affects the pH level?
nonharmful bacteria break down carbohydrates in food to lactic acid
What is one of the most important environmental conditions influencing microbial growth?
temperature
What are the three temperature groupings of microorganisms?
psychrophilic, mesophilic, and thermophilic
Psychrophilic microorganisms grow relatively well at what temperature range?
relatively low temperatures
Mesophilic microorganisms grow relatively well at what temperature range?
moderate temperatures
Thermophile microorganisms grow relatively well at what temperature range?
relatively high temperatures
What is a psychrotroph?
grows best at moderate temperatures but also can grow at low temperatures
What are the four bacterial growth phases?
- lag
- log
- stationary
- decline
During this phase, there is no increase in the number of bacterial cells
Lag phase
What happens during the log phase of bacterial growth?
Bacteria grow logarithmically or very rapidly
In what bacterial growth phase does the reproductive rate equal the death rate of bacterial cells?
Stationary phase
What bacterial growth phase begins when cells start dying because of the accumulation of waste materials and depletion of nutrients?
Decline phase
What microorganisms can live and grow in the presence of free oxygen?
aerobic microorganisms
What microorganisms can grow only in the absence of oxygen?
anaerobic microorganisms or anaerobes
What are the two ways water exists in foods?
“bound” and “free” water
Which water is held by large molecules in the food and, therefore, cannot be used by microorganisms?
Bound water
Which water is available to microorganisms for their metabolic activities
Free water
What is the measurement of the availability of water for chemical reactions and microbial metabolism in food called?
“water activity” (Aw)
What is a halophilic bacteria?
(salt-loving) bacteria
What are the three methods typically used to lower Aw?
Foods are:
1. Dried or dehydrated
2. Frozen
3. Adding solutes (salt or sugar)
What does a microorganism at optimum temperature for growth provide?
For the microorganism to grow at lower Aw values
What substance is a catalyst that breaks down substrates such as carbohydrates, fats, and proteins in foods?
Enzymes: either enzymes from the food itself or enzymes from microorganisms in the food
What food process are beneficial enzymes involved in?
ripening fruits and vegetables
What items in the food industry inhibit enzymes in foods?
Preservatives, antibiotics, inhibitors, poisons, and insecticides
What does it indicate if phosphatase is found in milk?
The efficiency of the milk pasteurization was poor
What are carbohydrates and proteases used for in the baking industry?
Converting proteins to amino acids for improving the dough in baking
What are some examples of undesirable microorganism changes?
If bacteria like Staphylococcus aureus, Salmonella typhimurium, Clostridium perfringens, or Clostridium botulinum are allowed to grow in foods, people consuming them may get sick
Besides microbial flora and natural inhibitors, which other prominent factor has an impact on microbial activity?
Nutrients
Which chemical can be added to food to adjust the potential hydrogen (pH)?
acetic acid or citric acid
Which describes facultative microorganisms?
Microorganisms that can grow with or without oxygen in the environment
Which describes the water activity value of a food?
Total availability of water in a food for chemical reactions.
What are the favorable temperatures for Salmonella growth?
40 to 115ºF (4−46ºC)
How soon after the ingestion of Salmonella contaminated foods will illness symptoms occur?
6 and 72 hours, with an average of 12 to 36 hours
What are the symptoms of a streptococcal infection transmitted through food?
red sore throat, high fever, and vomiting
What is a common inhabitant of the intestinal tract of cattle, swine, sheep, chickens, turkeys, and other animals such as dogs, cats, rodents, and monkeys?
C. jejuni
What are the symptoms if a person is infected with C. jejuni?
nausea, abdominal cramps, headache, fever, and diarrhea which might be bloody if severe
What are the manifestations of Listeria monocytogenes?
Meningitis, abortion, prenatal septicemia, permanent mental deficiency, or death
Why is L. monocytogenes an important pathogen?
Its distribution in the environment, ability to survive for long periods of time under adverse conditions, and ability to grow while under refrigeration
What is a realistic and satisfactory positive control for an internal cooking temperature for pork products?
170ºF (77ºC)
What is the most common cause of foodborne intoxications?
Bacteria
How is the toxin produced from Staphylococcus organisms destroyed?
Nothing will destroy it
What causative agent lives in decaying matter, soil, lake silt, and is often found in animal intestinal tracts?
C. botulinum
Cooked meats and poultry have been the chief offender in foodborne illness outbreaks for what organism?
C. perfringens
What are the symptoms of C. perfringens foodborne illness?
Acute abdominal pain, gas, diarrhea, chills, and fever
In a refrigerated storage unit, what is the best control measure for cooling foods until the ideal temperature is reached?
Leave foods uncovered
Which disease is more common than both salmonellosis and shigellosis?
Campylobacter enteritis
Which toxin is considered “heat stable”?
Staphylococcal foodborne intoxication
Which toxin causes a descending symmetrical flaccid paralysis which may progress until there is complete respiratory paralysis?
Botulism
What factors must be present for a foodborne illness to occur?
An agent, a vehicle, a susceptible consumer, and an abuse of a food handling procedure
What factors determine the effect a food pathogen has on an individual?
The person’s size, age, present health, eating habits, and dose of the pathogen
How often should you exercise your bases foodborne illness investigation plan?
Annually
What organization develops a notification plan or recall roster in case of a foodborne illness outbreak?
MTF
What must be present first for a foodborne illness to occur?
Infective agent or pathogen
What should the patient interview identify after an outbreak of a foodborne illness?
A common meal or facility
After notification of a foodborne illness, when should a sanitary evaluation be conducted at a suspected facility?
Immediately after interviewing patients and finding a common facility, meal, or food
What two PH teams collect food samples after a foodborne illness?
Patient interview and collecting food sample team
Where can you get help investigating a foodborne illness, if you are overwhelmed?
AFIOH/SDE
On what form do you record food history for each individual interviewed?
AF Form 431
Which agent causes over 68 percent of foodborne illnesses?
bacterial agent
Which are the two types of samples collected during a foodborne illness outbreak investigation?
Human and food samples
What does the bacteria metabolizing sugars in foods produce?
Levans and dextrans
What conditions does flavor deteriorative include?
Rancidity, putrefaction, souring, and gassing
What causes rancidity in meats?
Hydrolysis or oxidation
What is putrefaction?
A type of spoilage where bacteria metabolize meat proteins or free amino acids
What causes a sour flavor in meat?
Anaerobic bacteria metabolize carbohydrates in meats causing lactic acid that brings down the pH and develops a sour flavor
How does the “greening” of meat occur?
Bacteria such as Lactobacillus viridescens produce hydrogen peroxide. Hydrogen peroxide is a strong oxidizing agent that degrades the meat pigment turning it green
How is the greening organisms destroyed during processing?
Cooking the meat to an internal temperature of 160F (71ºC)
Describe “green rings” as it pertains to meats
Green rings are similar to green cores except that the greening occurs in rings at varying depths within the meat
Why doesn’t surface greening occur in vacuum packed meats?
Since the bacteria are aerobic, surface greening usually does not occur on vacuum packaged meats while still packaged
How does slime appear on nonvacuum packaged meats?
In characteristic beads that are sticky to the touch and give off odors sometimes described as yeast-like
Why should meats with molds be discarded or trimmed?
Some molds produce carcinogenic substances known as aflatoxins that are extremely toxic
Hydrolysis or oxidation in meats is caused by
oxygen reacting with fats
Which causes putrefaction spoilage in meats?
Bacteria reacting with amino acids
Which produces aflatoxins
Mold
At 32ºF (0ºC) how long can fresh fish be kept?
Seven days
After death explain what causes the typical fishy odor in fish?
Trimethylamine: breakdown of the fat or proteins in the fish due to enzyme and bacterial action
Why does fish struggling before being caught cause the pH to be higher?
The glycogen is depleted which is usually broken down into lactic acid that lowers the pH. With the glycogen depleted, fewer amounts of lactic acid are produced causing the pH to be higher
The glycogen in fish is broken down to lactic acid causing
lower pH, limiting bacterial growth
Explain the formation of an egg
1st: egg yolks are formed in the hen’s ovaries
2nd: the yolk passes down the hen’s oviduct where
layers of egg white are added
3rd: further down the oviduct the membranous tissue along with calcium
and minerals are added to form the shell.
How is knowing the formation of an egg helpful?
It helps to explain some defects of eggs
Why are shell eggs porous?
Allow gases to pass in and out of the egg
Which bacteria is found in the reproduction tract of chickens?
Salmonella enteriditis
Most organisms that affect the flavor of milk belong to what species and coliform?
Pseudomonas
Flavobacterium
Chromobacterium
Alcaligenes
What is some spoilage problems associated with soft serve ice cream?
Time between pasteurization and consumption, temperature abuse, and possible contamination
What is the most common spoilage organisms associated with cheese?
Molds, yeasts, and anaerobic spore formers that can oxidize lactate and various protein and fat products
What can cause gas production during cheese processing?
Using raw milk, inadequate heat treatment, and contamination after pasteurization, and slow acid
production by the starter bacteria such as Streptococcus lactis.
Which product does not usually have spoilage problems since there is not much time
between its pasteurization and freezing?
Hardened ice cream
Most vegetable spoilage is caused by
bacteria
Which is the predominant fruit spoilage organism?
Molds
Most organisms grow easily between which degrees Fahrenheit?
61 and 100
In thermal or heat processing most organisms start to die at which degrees Fahrenheit?
179
In thermal or heat processing temperatures of at least what will start to kill pathogenic bacteria?
140
Newer cans have which type of seam?
Top
A process using heat treatment to either eliminate pathogenic organisms or eliminate
other organisms to extend the product’s shelf life
pasteurization
temperature below 212 degrees F
pasteurization
temperature of or above 212 degrees F
sterilization
At which degrees Fahrenheit is milk kept for 30 minutes making it a holding method pasteurizing for milk?
145
At which degrees Fahrenheit is milk kept for 15 seconds making it a flash method pasteurizing for milk?
161
At which degrees Fahrenheit is milk kept for three seconds making it an ultra-high
temperature (UHT) pasteurizing for milk?
207
A heat treatment that is generally applied to fruits and vegetables primarily to inactivate the natural food enzymes.
blanching
Acetic acid usually lowers the potential hydrogen (pH) level in catsup, salad dressings, and
pickles to which level or below?
5.0
Which method is becoming more cost effective to use as a food preservation technique?
Irradiating
Which organization accumulates data and tries to find answers to very important questions
such as, “Will food irradiation create an environment in which microorganisms can adapt and
flourish?”
Food and Drug Administration (FDA)
Nitrates and nitrites are added to foods, such as meats, to
fix the color
any substance the intended use of which results or may
reasonably be expected to result directly or indirectly in its becoming a component or otherwise
affecting the characteristics of any food
food additive
Preserving food by adding salts or other substances to inhibit microbial growth. The process
alters the food’s color, flavor, texture, as well as susceptibility to microbes
Curing
Means the container is impermeable to or not allowing the entry of gases and vapors
Hermetic
Also prevents the entry of microorganisms, but is permeable to or allows the entry of gases
Nonhermetic
Which function or requirement must food containers meet to ensure foods are protected?
Protect against moisture, gas, odor, and light.
Most cans are made of
steel
Which metal has a lower chance for atmospheric corrosion and is easier to shape into cans?
Aluminum
Most common defect associated with cans
dents
Occurs when at least one side of a can is
flattened or collapsed
paneling
A can that appears normal but has little or no vacuum (critical defect)
flipper
Similar to the flipper, except one end of the can is always distended
Springer
Which type of critical defect occurs when both ends of a can are distended at the same
time?
Sweller
opposite of a paneled can
buckled
Which is not true of glass used in food packaging?
Must be treated, coated, or laminated to improve its protective qualities.
Which guide is used for food storage, determining shelf life and humidity requirements of
both perishable and semiperishable foods?
DODR 4145.19–R–1, Storage and Materials Handling
The long standing rule for proper food rotation is
first in, first out
Which happens to food when it’s stored in high levels of humidity?
Absorbs the water
Which happens to food when it’s stored in low levels of humidity?
dry out and shrink
Which is an indicator that a freezer has air leaking in or out of a door seal?
Ice around the door.
Refers to foods that are canned, dried, dehydrated, or otherwise processed to
the extent that the items may, under normal conditions, be stored without being refrigerated
semiperishable
