Flashcards in Exam 2 Deck (79):
measurement based on the resistance in an electric circuit to the flow of alternating current
Direct Microscopic Count
DMC on filters has been simplified by the use of _________ _______ that bind to bacteria.
this method uses dyes and fluorescent microscopy to rapidly enumerate bacteria on a filter
Direct Epifluorescent Filter Technique
4 Advantages of DMC (including DEFT)
1. rapid and simple
2. morphology can be determined
3. repeatability is better than SPC
4. solid foods can be examined using the prefiltration step
5 disadvantages of DMC (including DEFT)
1. tiring to analyze
2. can’t tell live from dead cells
3. food parts sometimes look like cells
4. cells are usually not distributed evenly
5. different MO don’t stain equally
Way to make millions of copies of DNA from a single piece of DNA
Examples of foodborne infections
Difference between exotoxin and endotoxin
Botulism is also a ________ toxin
causes typhoid fever
Different strains of salmonella are classified by ________ and ________ antigens
3 epidemiological groups of Salmonella serovars
Those that only infect humans
Host adapted serovars
why is it no longer a risk after 1 year old?
Infant developes intestinal normal flora
where is it found?
needs higher source of AA
found in meats and gravy
How to prevent botulism?
Damage or injuries that make food undesirable for human consumption
In general what can cause Spoiled Food?
3 Basic types of Foof Spoilage
Taste and Odor
What can make food appear spoiled?
Visible Mycelia and Bacterial Colonies
cloudiness in liquid
Breakdown of heme or chlorophyll
What texture changes are seen on spoiled food?
soft rot due to enzymatic degredation
What causes changes to taste and color?
What can determine what organisms grow on the food and in the number that they do?
Evironment from where the food was taken
intrinsic factors of food
Packaging and storage conditions
Microflora of Whole fresh meat
What kind of organism is Pseudomonas?
Gram neg aerobic rod
Most perishable food?
What can be a source of contamination inside unprocessed meat?
Single most important factor for meat spoilage?
What temp can molds not grow on on meat surface?
5 C and below
Under what conditions do Pseudomonas, Acinetobacter and Moraxella spp. usually spoil fresh cut meat?
Refrigerator at high humidity
What organisms always spoil ground beef?
What concentration of Bacteria gives meat an odor and slimy look?
What is not broken down in all meat spoilage?
Primary protein structure
What do bacteria eat on meat?
What is different microbially between whole and ground beef?
Ground has higher microbial load
pH range of ground beef
What can inhibit C. botulinum in vacuum packed meat?
Vaccume packed meats are usually safe from pathogens with the exception of what organisms?
What gives away vacuum packed meat spoilage?
What causes meat greening?
H2O2 or H2S production
What organisms produces H2O2 or H2S in V meat packaging?
the H2O2 oxidant reacts with what in V packed meat? to form what?
What organism makes H2S in packed meat? Under O2 permeable packaging? Under O2 impermeable packaging?
What conditions cause H2S greening in vaccume packed meat?
above 6 pH
In H2S greening what does it react with? what does it form?
Specifically what causes off odors in meat?
Release of short chain fatty acids and volatile compounds like acetoin and H2S
Does raw or cooked meat have a higher pH?
which pathogen prefers cooked meat?
Pathogen that favors uncooked meat? pH of uncooked meat?
low nitrate levels in meat can favor what organism
high nitrite concentration in meat favors what organism?
most common type of organisms to spoil processed meat?
Which apparant type of processed meat spoilage means it shouldnt be eaten?
why are cured meats like ham and bacon resistant to spoilage?
smoking or brining ham
high fat - low water activity of bacon
What organisms do spoil cured meats? What genera?
How can advanced spoilage be determined in poultry?
the skin will fluoresce under UV because of pseudomonads
what occurs before slime buildup on poultry
What can be done to possible salvage poultry?
remove the skin
Fish have high _______ content but no carbohydrate
What is the microbial activity of fish heavily influenced by?
The quality of water from which the fish was harvested
In general, frozen fish products have ______ counts than fresh products.
location of bacteria on fresh fish?
why can crustacean spoilage occur more rapidly?
CHO and more free AA
microflora of vegetables
Gram + bacteria like LAB
What organisms get onto vegetables from handlers?
organisms that cause soft rot
how does polygalacturonase work?
hydrolyzes a 1,4 glycosidic bond in pectin which leads to softening
org which causes blue fruit rot
causes downy mildews in grapes
black rot on onions
causes sour rot and comes from harvestors
Raw milk flora can contain almost anything but what is present when it is properly handled?
what organisms makes temperature stabilizing enzymes im milk?
What does pasteurization kill/
Pasteurized milk used to be spoiled by LAB but now what is it spoiled by? what causes the curdling?
aerobic spore formes like Bacillus
what 3 factors of cheese inhibit growth except for surface molds
low water activity
molds that produce gas inside of cheese like swiss