Microogranisms are the most important cause for what?
food spoilage
Gram-positive bacteria keep/do not keep stain?
keep
What is the major method for bacterial reproduction?
binary fission
The time laspe from one cell division to the next is called _____?
generation time
Fungi cannot use the sun for energy...instead fungi secrete digestive enzymes into their environment. What happens next
this breaks down the organic material and they absorb the resulting nutrients
Molds are fungi consisting of filamentous structures called?
hyphae.
A good example of mold is the black bread mold_____
Rhizopus
Reproduction of mold occurs primarily through?
production of asexual spores
Yeasts are also fungi T/F
They are multi celled or single celled?
Reproduction of yeasts occurs primarily by?
budding
Yeasts can be helpful such as the process for making?
wine, leavening bread
What happens during the lag phase?
microbes do not increase there might even be a slight decrease
During the log phase what happens?
cells begin rapied cell division
what happens during the stationary phase?
there is no net increase, meaning the same amount of cells reproduced also die off
what happens during the decline phase?
cells begin dying because of waste materials and depletion of nutrients
what does pH stand for? What is the range?
potential hydrogen / 1-14
Values less than 7 are?
acidic
In general, molds can grow in more acidic conditions than yeasts? T/F
True False
True
Yeasts can grow at lower pHs than most bacteria? T/F
True False
True
Bacteria can grow as low as what pH?
pH 4 and as high as pH 11
Fruits are relatively acidic?
True False
True
Spoilage of fruits is usually due to?
molds and yeasts
Meats usually have a pH close to neutral so they are spoiled by____
bacteria
Explain the fermentation process
nonharmful bacteria break down carbs in food to lactic acid
what is bound water?
held by large molecules in the food, therefore cannot be used by microorganisms
What is free water?
water available to microorganisms for their metabolic activities
fresh fruits and vegetables usually have an aW of?
.97-.99
dry cereals usually have an aW value of
.10-.20
Bacteria usually require of a high aW for growth and reproduction...what is that range?
.96-.99
Halophilic (salt loving) bacteria may grow as low as what aW
.75
What are the three ways to decrease aW?
dried/dehydrated, freezing, addiing sugar/salt
Egg whites contain what antimicrobials?
lysozyme, conalbumin, avidin, and ovomucoid
Milk contains what antimicrobials?
lysozyme, lactoferrin and lactoperoxidase
Which gram stain bacteria are more affected by suc inhibitors?
gram positive
Microbial flora refers to what?
microorganisms found in food
Streptococci in milk may grow in milk and convert lactose/milk sugar into lactic acid...what does this do?
drops the pH and allows steptococci to grow but inhibits other bacteria
After streptococci reach a high level in milk they inhibit themselves, but allow another bacteria to grow. What is that bacteria?
Lactobaccilli
Psychrophiles
Mesophiles
Thermophiles
name the temp ranges
P- grow at low temp 68- 77 M - grow at moderate temp grow best 98 range 68-110 T - grow at high temps 113-160
Psychrotroph grows best win?
low and moderate temps
Second largest cause of food spoilage is?
enzymes
What are the two types of enzymes?
food enzymes and microbial enzymes
If the enzyme phospatase is found in milk it means
the pasteurization for the milk is poor
What causes rancidity?
hydrolysis or oxidation
Common deteriotative conditions in meat are?
flavor, odor, texture, or appearance
Flavor conditions in meats include
rancidity, putrefaction, souring and gassing
Most of the rancidity problems in meats are caused by____
reaction of oxygen with unsaturated fats or oxidative rancidity
explain putrefaction
spoilage where bacteria metabolize meat proteins or free amino acids
Where is putrefaction commonly found?
in canned meats with bacon
Anaerobic bacteria sometimes metabolize carbohydrates in meat products causing ______
production of organic acids such as lactic acid
Lactic acid in meats creates what?
sour flavor
Souring gasses are usually found in what meat products?
fresh meats, bacon, ham, sausage, and canned meats
What are the three types of greening?
green core, green rings, surface greening
Green cores usually occur in?
Large sausages such as bologna
Green cores occur only when?
the meat is cut because the bacteria are aerobic
Cooking meats to an internal temp of____ during processing destroys greening microbes
160F
How soon is surface greening noticeable?
5 days after processing and sometimes not until two weeks
Slime is rarely a problem with vaccumm package meats? T/F
True False
True
What substance is produced in fish once it's killed?
trimethylamine - because of breakdown in fat or proteins in fish due to enzyme and bacteria (this is what causes the fishy odor
After death, ______in fish is broken down to lactic acid.
glycogen (lowers pH and preserves fish)
What are the common types of food preservation?
heat processing, refer/freezing, drying/dehydrating, fermenting, irradiating, controlled atmospheres, and smoking
What is the most used method for heat preservation?
heat
Agitation allows higher temps to be used during heating without harming the product? T/F
True False
True
Whats the difference between pastuerization and commercial sterilization?
pasteruziation is below 100C
List two types of milk pasteruization
held at 145F for 30 min or flash method 161F for 15 seconds
Blanching is used on _____ ; the process is what?
fruits and vegetables; foods pass thru water/steam of 190F-212F
What is blanching?
heat treatment usually applied to fruits and veg...to inactivate natural food enzymes
the best method of food preservation is what?
refer and freezing - does not effect tast texture nutrition value or other attributes
What is fermenting
chemical change of anaerobic breakdown of food brought by the use of enzymes or microorganisms
What are the 3 chemical changes made through fermentaion?
- acidulation of milk (cultured buttermilk) - oxidation of nitrogenous organic compounds (baker's yeast) - decomposition of starches and sugars into ethyl alcohol, carbon dioxide and organic acids (sausages and pickles)
Which type of food preservation increases nutritional value.
fermentation...adds riboflavin, B12 and precursor vitamin C
Lactic acid are used to produce what?
cucumbers into pickles, cabbage into sauerkraut, taro root into Poi. used on meats for salami sausage
Acetic acid bacteria can convert these foods into what?
wine,, cider, honey and other foods high in sugar into vinegar
what gas is used to ripen bananas?
ethylene
What are the food additives a food inspector must be aware of?
curing, dry curing, wet curing, sugar, nitrites/nitrates, sulfur dioxide/sulfites, sorbic acid/sorbates, propionic acid and propionates, benzoic acid/benzoates, ethylene oxide/propylen oxide
what is a wet cure also known as?
pickled (contains the same ingredients as a dry cure but has been put into a brine or solution)
What is the most common food wet cured?
meat - hams
What are the characteristics of under curing?
exhibit a brown or grayish-green
This use belongs to what preservative: added to foods to fix the color, and they only have limited inhibitory use. Most of the time they are mixed with other chemicals for curing foods such as meats
nitrites and nitrates
This use belongs to what preservative: Used to fix flavor and color of fruits and veg. They have limited inhibitory use against microbes. When dissolving sulfite salts in water, a sulfurous acid is formed that is used to inhibit yeasts, molds, and bacteria. This solution is used mainly in the wine industry as well as for dried fruits and veg
sulfur dioxed and sulfites
This use belongs to what preservative: _______ is an unsaturated fatty acid used to protect acid foods from mold and yeast growth. This acid is added to such foods as cheese, orange juice, fruit and fruit syrups, margarine, pickles and yogurt
sorbic acid/sorbates
What are the food packaging materials?
rigid metals flexible metals glass plastics cardboard laminates
What is a hermetic container?
impermeable to or not allowing the entry of gases and vapors. also protects food from moisture gain or loss and is essential for strict vacuum
What is a nonhermetic container?
also prevents entry of microorganisms, but is permeable to or allows the entry of gases. (cellophane, cardboard)