Chapter 2: Food Microbiology Flashcards
Microbial population show a characteristic type of growth pattern, called?
exponential growth
little or no apparent growth for a period following the initial contact between the microbes and the environment
length of this phase varies with the condition of the microorganisms and the nature of the environment
stage 1: lag phpase
microorganisms are growing and dividing at the maximal rate
constant growth rate is observed
cells are in their healthiest state
stage 2: log phase (exponential phase)
no net increase or decrease in cell number
accumulation of wastes that are toxic and nutrient depletion
stage 3: stationary phase
decline in the number of viable cells
rate of death exceeds rate of growth
many of the numbers essential for survival are no longer available
stage 4: death phase
characteristic of the growth substrate
intrinsic factors
microorganisms require this type of moisture
free/available water
free water may be expressed as
water activity (aw)
amount of free or available water in a product, which can affect its shelf life, safety, and quality. It is measured on a scale from 0 (completely dry) to 1.0 (pure water)
water activity (aw)
ratio of the water vapor pressure over a food at equilibrium with the atmosphere above it to the water vapor pressure at the same temperature
water activity (aw)
aw of water is?
aw = 1.0
aw of a completely dehydrated food (e.g. crackers and powdered products)
aw = 0
Most bacteria, yeasts, and molds cannot grow. This is important for food preservation
aw = 6
an organism that grows in high concentration of salt
halophiles
salt tolerant organism
haloduric
organisms that can grow over a fairly wide range of Aw or solute concentrations
osmotolerant
aw of fresh foods
0.99
organic and inorganic compounds found in any substrate provide energy that supports microbial existence
release of energy consists of oxidizing one compound and reducing another
oxidation-reduction (redox) potential (Eh)
require positive Eh values
aerobes
will not start to grow until the redox has reached a critical maximum, much lower than facultative aerobes
anearobes
requires negative Eh values
anaerobes and facultative anaerobes
microorganisms need these nutrients to survive (conspim)
carbon, oxygen, nitrogen, sulfur, phosphorous, iron, magnesium
Water activity where yeasts can grow at lower aw levels compared to bacteria
aw = 0.88
Antimicrobial constituent in cloves, cinnamon, and sage
eugenol
Antimicrobial constituent in cinnamon
cinnamic aldehyde
Antimicrobial constituent in sage and oregano
thymol
Antimicrobial constituent in garlic
thymol
Antimicrobial constituent in mustard
allyl isothiocyanate
Antimicrobial constituent in eggs and milk
lysozyme
Antimicrobial constituent in milk
lactoperoxidase
imposed from outside
extrinsic factors
organisms with a narrow temperature range for growth
constant temperature
sa isang temperature lang makaka-survive (either cold or hot)
stenothermal
organisms growing from environments with greater natural variation of temperature
eurythermal
microorganisms that can grow at subzero to 20C with optimum at 10-15C
psychrophiles
psychrophiles are microorganisms that can grow at what temperature
subzero to 20C
optimum at 10-15C
microorganisms that can grow at and below 7C with optimum at 20-30C
psychrotrophs
psychrotrophs can grow at what temperature
at and below 7C
optimum at 20-30C
microorganisms that can grow at 20-45C with optimum at 30-40C
thrive best at rom temp and are more common spoilage organisms
mesophiles
mesophiles are. microorganisms that can grow best at what temperature
20-45C
optimum at 30-40C
microorganisms that can grow at and above 45C with optimum at 55-65C
cause of spoilage in thermally processed foods
when they multiply, they produce spores that are heat-resistant
thermophiles
thermophiles are microorganisms that can grow best at what temperature
at and above 45C optimum at 55-65C
two main gases that affect microbial activity
oxygen and carbon dioxide
Must have oxygen to survive and grow
obligate aerobe
Can grow with or without oxygen. They prefer oxygen but can switch to anaerobic processes if oxygen is absent.
facultative anaerobe
organisms that can grow in the absence of oxygen
anaerobes
some aerobic microorganisms that require only low levels of oxygen (2-10%) for growth
microaerophilic
The oxygen level is typically reduced, while carbon dioxide is increased to slow down respiration and ripening. The environment is tightly controlled to ensure stability throughout storage.
controlled atmosphere (ca)
A method where the concentrations of gases (mainly oxygen, carbon dioxide, and nitrogen) are continuously monitored and adjusted to maintain a precise atmosphere over time.
controlled atmosphere (ca)
The atmosphere inside the package is modified (typically by reducing oxygen and increasing nitrogen and carbon dioxide) to slow down spoilage. The modified atmosphere is passive, relying on packaging materials to maintain the gas composition.
Modified Atmosphere (MA) Storage
A one-time adjustment of the gas composition in a sealed package or container, without ongoing control or monitoring. Once the package is sealed, the atmosphere inside is not actively controlled further.
Modified Atmosphere (MA) Storage
killing, inhibition, or removal of all microbes that may cause disease
used in inanimate objects
disinfection
an agent that kills microbes but may also be harmful to human tissue
disinfectant
general terms for an agent that kills microbes or inhibits their growth
antimicrobial agent (ama)
low moisture and temp, high concentration of sugar and acid stimulates growth of _____
molds
high moisture and temp, high concentration of sugar and acid stimulates growth of _____
yeast
a process that kills or removes all forms of microbial life situation, results to complete absence of live microorganism whether in spore or vegetative form
sterilization
sterilization that requires the use of water is known as
wet sterilization
do not require the use of water
done to a point where there is dehydration and oxidation enough to destroy the bacterial cells
dry heat sterilization
use of AMAs of substances that can prevent cell growth or even lead to cell death is suggested for disinfection and sterilization
chemicals
radiation that can destroy intracellular structure of microorganisms are those with short wavelengths like the x-rays and the gamma rays
irradiation
a microbial product or derivative that kills or inhibits growth of a susceptible microbe
antibiotic
separation of microbial contamination from liquid
filtration
causes the formation of thymine dimmers in DNA that inhibits DNA replication
raditation
results from ingestion of pathogen-contaminated food
food-borne infection
results from ingestion of foods containing performed microbial toxins
food-borne intoxication
beneficial microbes: yeast fermentation in bread
or baker’s year is most useful in bread production
Saccharomyces cerevisiae
causes gluten network to expand
co2
formed after thorough kneading of flour, water, and yeast mixture
gluten network
a beverage made from malted barley and water and flavored with the female flower of the hop plant
beer
yeast added to the wort (mashed mixture of water, barley, and hops)
considered as the “top” yeast of the fermentation vessel in beer making
saccharomyces cerevisiae
bottom yeast in making beer
saccharomyces carlsbergensis
ingredients of beer
water
malt barley
yeast
flavored with the female flower (hop plant)
results from the alcoholic fermentation of glucose and fructose contained in grapes and other fruits by yeast
wine
used to facilitate fermentation of grape and other juices
saccharomyces cerevisiae, var. ellipsoides
this type of wine derive its color from the red soluble pigment of the grape skin
fermentation temp: 20 ℃ to 32 ℃
red wines
the skins and pulp of the grape are removed from the juice before fermentation begins
the temp of fermentation is lower than red wines (10-15C)
white wine
bacteria utilized for the conversion of alcohol to acetic acid
allowed to grow aerobically on the surface of wine to produce malt vinegar
genus acetobacter
products such as: cheese, butter, yoghurt, pickled vegetable products like sauerkraut (pickled cabbage), atchara, cucumber are from the fermentation of
acetic acid and lactic acid fermentation
mold used for camembert cheese ripening
penicillium camemberti
mold used for blue cheese ripening
p. roqueforti
an organism able to grow at low temp
ex: food stored in the refrigerator
psychrotrophs
an organism capable of growth at high temp
ex: foods kept warm for extended periods of time
thermophiles
microbes that grow in acidic environment, responsible for spoiling products
ex: pickles, mayonnaise, and certain fruit juices
acidophiles
infectious agent having a simple acellular organization with a protein coat and a single type of nucleic acid, lacks independent metabolism and reproducing only within living host cells
smallest known living organisms
ex: poliomyelitis, hepatitis a, viral gastroenteritis
virus
organisms that resembles the characteristics of a virus and bacteria
contains both DNA and RNA, have typical bacterial cell walls
cannot be cultivated outside of living cells = obligate parasites
rickettssiae and chlamydia
associated in the tissue of arthropods
ex: fleas, lice, ticks, and mites
transfer to humans or other animal is via bites from these blood-sucking arthropods
rickettsiae
concern rickettsiae the causative agent for q-fever, can be excreted in the milk of an infected cow
can be trasnferred by a respiratory pathway in aerosols of infected dust and via the bite of tick
coxiella burnettii
concern chlamydia is the causative agent transmitted to human in aerosols from infected poultry
chlamydia
organism intermediate to virus and fungi in size
unicellular or multicellular prokaryotic organism
bacteria
bacteria shape
spherical
cocci
bacteria shape
rod-shaped
bacilli
bacteria shape
helical
spirilla
bacteria shape
curved
vibrios
diverse group of organisms that may be unicellular or made up of tubular filaments (hyphae) and lacks chlorophyll
ex: yeast, mushrooms, molds
fungi
multicellular and filamentous form of fungi on almost any substance used for food
seen on stable bread, cheese, fruit
musty odor and destroy the fresh flavor of food
molds
molds produce a poisonous toxin called
mycotoxin
a collective name for single-celled organism important in brewing and bread making
contamination if food created a slime on the surface, bubbles, and an alcoholic smell or taste
yeasts
group of simple plants with unicellular reproductive structure
posses the green photosynthetic pigment, chlorophyll a
algae
algae concerned associated with marine “red tides”
pyrrophyta/dinoflagellates
unicellular eukaryotic microorganisms that lack cell walls
protozoa
protozoa concerned in food microbiology
entamoeba hystolytica
referred to as parasites
food- and water-borne helminthic infection is a common problem in situations with poor hygiene
helminthic eggs and larvae
parasites found in game or pork
trichinella spiralis
referred to as cod fish worm or seal worm
found in fish
anisakis spiralis
microbial population show a characteristic type of growth pattern called
exponential growth
little or no apparent growth for a period following the initial contact between the microbes and the environment
becomes acclimated to their environment
length of this phase varies with the condition of the microorganisms and the nature of the environment
stage 1: lag phase
microorganisms are growing and dividing at the maximal rate
constant growth rate is observed
the chemical and physiologic properties of the population are most uniform
cells are in their healthiest state
stage 2: log phase (exponential phase)
no net increase or decrease in cell number
characterize by accumulation of wastes that are toxic and nutrient depletion
stage 3: stationary phase
decline in the number of viable cells
rate of death exceeds the rate of growth
factors essential for survival are no longer available
stage 4: death phase
