Food Science Flashcards
A human consumes on average ____ lbs of food per day
1.5 lbs per day
Name the bacterial growth phases
Lag - adapt to environment
Log - exponential growth, doubling in numbers every few minutes
Stationary - nutrients depleted, equal death and growth
Decline/Death - running out of nutrients or being poisoned by their own waste products, they die off.
The goal of food preservation is to extend which phase of bacterial growth?
Extend the lag phase
What are the bacterial growth factors?
FATTOM Food Acidity Time Temperature Oxygen Moisture
What are the three temperature zones of bacteria?
Thermophillic - 113-158F
Mesophillic - 59-112F
Psychrophillic - 35-50F
What is thermophillic spoilage
Spoilage by thermophillic bacteria which can survive foods that are just slightly under cooked.
What is flat sour spoilage?
When bacteria that thrive inside canned foods do not produce gases but instead produce lactic acid.
Cans will not appear swollen. Food will have a sour taste.
Found in:
Low acid foods
Facultative Bacteria
Bacteria commonly found on canning machines
In sugars and starches used for canning
Bacillus coagulans is an example of what type of spoilage?
Flat Sour Spoilage
What is thermophillic anaerobe spoilage
bacteria survives an anaerobic state and produces h2S gas, Hydrogen gas, CO2 as it ferments. Forms lactic acid.
Not poisonous, but produces resistant spores that are heat activated.
Clostridium thermosaccarolyliticum.
Only a problem if cans are stored in very hot environment. They often burst.
What is the sulfide stinker bacteria?
Clostridium nigrificans.
Found in low acid canned foods.
result of undercooking.
bacteria produce H2S gas and discoloration of food product.
What is mesophillic spoilage - give three bacteria examples.
bacteria that grow at room temperature rage.
clostridium botulinum
clostridium sporogenes
clostridium putrifaciens
they produce CO2 and H gas.
Cause canned products to swell or buldge.
undercooked food products.
What is psychrophilic spoilage
Bacteria that can grow at colder temperatures.
Foods can spoil in freezers that are not cold enough.
optimal freezer temp is 0F
At 0F all the water in food product is iced and the bacterial has no available water for growth.
What is pH?
The relative alkalinity or acidity. It’s based on the hydrogen ion concentration within a solution.
Bacteria commonly involved in food borne illness tend to grow at what pH range?
4.6 to 7
Typically food items w/ a pH less than _____ can be excluded as a potentially hazardous food
less than 4.6
Examples of high acid foods 4.5 and below
Apples, grapefruit, grapes, limes, oranges, peaches, pears, pineapple, plums
Examples of medium acid foods 4.5-5.5
Tomatoes, bananas, beets, squash, watermelon
Examples of low acid foods 5.5 and higher
peas, spinach, corn, beans, asparagus, brussel sprouts, cabbage, carrots, celery, onions, potatoes
What does sous vide mean?
“sue-veed” is a French term that means “excluding the air from the product”.
commonly known as vacuum packing.
makes for a great environment for anaerobic bacteria.
What is oxidation-reduction food preservation
In vacuum packing when a small amount of air with chemicals is added to counteract the negative anaerobic environment.
oxidants such as nitrates and permanganates are used.
This creates an environment in which neither anaerobes or aerobes can survive.
Most bacteria that cause food borne illness tend to grow in what temperature range?
41 to 135 (the temperature danger zone)
Water activity (Aw) must be at what level to support bacterial growth on food?
.85 or higher (the scale is 0 to 1.0)
What type of food do bacteria typically require?
nutrients such as proteins and carbohydrates
What is the Aw for the following foods
fresh meat/fish/poultry Fruits/veggies Cheese Cured Meat Jams/Jellies Cereal Sugar
fresh meat/fish/poultry .99 Fruits/veggies .98 Cheese .97 Cured Meat .90 Jams/Jellies .82 Cereal .15 Sugar .20
Which pathogen is the most moisture durable? Tested to be able to grow at .86 Aw
staph aureus
The ideal moisture level for most bacteria is between?
.90-.99
What are the two most important factors in regards to FATTOM bacterial growth
Time and Temperature
What is ptomaine poisoning
a term to describe food borne illness prior to the discovery of bacteria. it was though that certain alkaloids produced by decaying food is what caused food borne illness
Hot foods must cool from ______ to ______ within __ hours and then from ______ to ______ within __ hours
135 to 70 in 2 hours
70 to 41 in 4 hours
Foods prepared at room temperature must be cooled to _____ in ___ hours
41 in 4 hours
What are methods of properly cooling food
cut large mass into smaller pieces
increase surface area by using shallow pans
do not fully cover products during cooling (keeps the heat in)
use stainless steel for cooling (plastic retains heat longer)
ice baths
cooling wand/ice paddles
adding ice as an ingredient
blast chillers (expensive units)
steam-jacketed kettles - cold water circulates. good for the first part of cooling
How should shallow pans be arranged in a walk in cooler for cooling?
never on top of one another. they should be separated so cool air can cover as much surface area as possible
Hot holding temperature should be _____ and above
135 and above
Does hot holding destroy bacteria?
No it just slows their growth
What types of equipment can be used for hot holding?
steam table, baine marie, steam cabinets and sometimes a broiler on a stove
Is there a time limit to hot holding?
No but usually the food quality is degraded after so long
Cold holding temperature
41 and below
Does cold holding kill bacteria?
No it slows their growth
What are some methods of food preservation that are based on available water in foods
sun drying salting smoking mechanical drying freeze drying
How does smoking preserve food?
by increasing the sodium content making less water available. It’s a short term preservation method. a couple of days to a few weeks.
How does freeze drying work?
frozen products are placed into a vacuum where heat is applied which causes sublimation (water goes from solid ice to gas phase). Because of the vacuum the water vapor is removed from the product.
What are the pro’s and con’s to freeze drying
pros: taste of food is not altered, can easily be rehydrated. product is very light weight.
cons: vitamin c and carotene are destroyed
freeze drying usually results in what Aw
.06
What are cans made of today?
steel with a resin (bpa) coating to fill in any microscopic holes.
sometimes there is a layer of steel but the steel has a tendency to react with acidic foods
When did the US stop using lead soldered cans?
1991
What are the steps in canning (green beans)
- sort to eliminate damaged or spoiled product
- washed/soaked in cool water
- blanched with hot steam or water (helps remove air pockets)
- cooked for 35 mins to a pressurized temperature of 240F to kill botulism spores
- cooled in cold water
- Water or broth is added to the can
- filled can is now “exhausted” by reheating to eliminate air or gas
- can is covered, sealed and cooled
What are some common problems with canned foods
undercooking prior to canning
improperly cooling which causes hydrogen gas to form inside
damaged cans
storing cans in high heat (over 100F)
What is a food additive
any substance that—directly or indirectly—becomes a component or otherwise affects the characteristics of any food. This definition includes any substance used in the production, processing, treatment, packaging, transportation or storage of food.
other e.g. color modifiers, flavor enhancers, nutritional supplements, moisture controllers, chemicals to alter physical characteristics etc.
Many food additives have been found to be ______________
carcinogenic or toxic
What is GRAS
Generally regarded as safe
Are food additives on the GRAS list?
most are not
What is DES
diethylstillilotral aka DES white. Is an odorless, crystalline powder that use to be given to roosters to decrease their sex drive and fatten them up.
it was found to be toxic and carcinogenic.
use is now banned.
What was food dye #8 used for?
to mark inspected meat products. Was found to be carcinogenic
What is aminotruazole
a weed killing agent that when consumed by livestock was present in their meat. Found to be carcinogenic
What are nitrates and nitrites used for?
As a common food additive to help preserve meats and meat products such as bacon and sausages.
to stop the growth of botulism
How do meat processors hide spoiled meat be preventing it from browning?
They add sodium nitrate which prevents the oxidation of myoglobin, thus keeping the meat red.
aka “dynamiting” making it look fresher than it is
What are nitrosamines?
A byproduct that is formed when humans ingest nitrates or nitrites. It is considered a carcinogen.
What can cause blue baby syndrome?
When a baby consumes nitrates and they are reduced to nitrites which blocks the oxidation of hemoglobin.
What are direct additives
those that are added to a food for a specific purpose in that food.” For example, using phosphates in meat and poultry products to retain moisture and protect the flavor.
What are indirect additives?
those that become part of the food in trace amounts due to its packaging, storage or other handling
e.g. BPA
What is MSG
monosodium glutamate - a flavor enhancer and meat tenderizer
made from beet glucose that has been decomposed by bacteria and ferments MSG
many are allergic
caused cancer in lab rats
“Chinese restaurant syndrome”
What is EDTA
ethylene diamine tetra acetate
food additive to prevent botulism growth.
it’s a sequestering agent (ties up certain minerals)
can contribute to food discoloration
What are sulfites used for?
an additive to preserve freshness and prevent discoloration. it stops the enzyme reaction in fruits and vegetables
illegal for restaurants to add.
What is TSP?
trisodium phosphate
preservative in some fruits which injures the cell wall
What is calcium propionate used in?
a preservative used in breads
Name a metal that can be added as a food preservative
silver
What three risk factors are checked for food additives
carcinogenic factors
toxicity
side effects
an additive can still be used if it falls into one of the three categories
What is foodborne illness?
any syndrome resulting from the ingestion of food
What are the three classifications of foodborne illness?
foodborne intoxication
foodborne infections
toxin-mediated foodborne infection
What is foodborne intoxication
illness caused by eating food containing poisonous chemicals or toxins (either chemically or bacteriologically produced)
What are three e.g. of foodborne intoxication
staph aureus
bacillus cereus
clostridium botulinum
What is a foodborne infection
an illness caused by eating food containing live pathogenic organisms
What are three e.g. of bacteria that cause foodborne infection
salmonella typhi
campylobacter jujeni
listeria
What is a toxin-mediated foodborne infection
an illness caused by eating food containing live pathogenic organisms that reproduce within the intestines and produce a toxin which makes one ill
What are three e.g. of toxin-mediated foodborne infections
e coli 0157 h7
clostridium perfringens
shiga-toxin producing e coli
While interviewing a potential foodborne illness you should find out the food eaten within the last_____ hours prior to the onset of symptoms
72 hours
Where do most foodborne illness occur?
In the home
Chemical food poisonings usually have (fast/slow) onset of symptoms
fast
the following chemicals can cause chemical food poisonings how…
arsenic cadmium lead sodium fluoride Freon bleach copper
arsenic - insecticide residual cadmium - lemonade leached containers lead - ceramics, insecticides sodium fluoride - insecticide Freon - leaky air conditioning units bleach - spill or accidental use copper - old soda beverage dispensers
What is PSP
paralytic shellfish poisoning
a type of chemical food poisoning (foodborne intoxication)
the toxin is Gonyaulax c. which is very potent.
The shellfish carry this toxin after consuming dinoflagellates (ocean algae) during red tide summer season
cooking does not destroy
can cause paralysis or death
What is scromboid poisoning
a chemical food poisoning (foodborne intoxication)
scromboid species that are held at improper temps will have bacteria that produce histamines (the toxin)
symptoms include burning peppery taste, rash, dizziness, cramps etc.
cooking does not kill
What is a histamine
a toxin produced by scromboid fish held improperly
What are some of the scromboid species (name 6)
tuna, mackerel, bonitos, swordfish, bluefish, skipjack
scromboid poisoning has also been found it which species that are not part of the scromboid family
mahi-mahi, marlin, sardines
What percentages of fat are in regular, lean and extra lean hamburger meat
regular - not more than 30%
lean grade - no more than 22%
extra lean grade - no more than 15%
Fresh beef should be….
bright red in color firm and elastic to touch (spring back) light fresh odor marked for USDA inspection received at 41 or below
Fresh pork should be…
pink in color firm and elastic to touch light fresh odor marked for USDA inspection received at 41 or below
Fresh poultry should be…
almost white with no dark discoloration no noticeable odor flesh should NOT be sticky marked for USDA inspection received at 41 or below
Fresh fish should be…
bright red gills clear eyes Firm and elastic to touch no fish odor received between 32 and 41 packed on ice should not be slimy, skin should reflect light
Shellfish include…
oysters, clams and mussels