Microbiology 11-Lecutre: Food Microbiology

1st semester: 22'-23'

ARTHROSPIRA

marketed as spirulina also known as

dihe in Africa or tecuitlatl in
Mexico,

ARTHROSPIRA

photosynthetic cyanobacteria,

sold as form food
supplement or food additive

why was chlorella coing as

single-cell protein or SCP

The protein
content of cyanobacterial and microalgal origin is
generally high

CHLORELLA

food supplement:

vitamin B12

beta carotene which is the
metabolic precursor of vitamin A.

QUORN

Fusarium venenatum

QUORN, why is it a meat substitute

protein quality
equivalent to conventional protein sources such
as eggs and cow’s milk.

QUORN

Fungi are also used as a source of food. The filamentous fungus

used as a meat
substitute

why does fusarium venenatum need to under go heat treatment

The nucleic acid content of crude microbial
biomass is too high for direct consumption of
humans.

cause elevated levels of uric acid

heat treatment to remove nucleic
acids. processed microbial biomass
predominantly consists of dead cells

FERMENTATION

controlled microbial growth and

enzymatic conversions of food components

benefits of

FERMENTATION

improves the shelf life, safety, and
organoleptic properties of food

agents of fermentation

yeast molds bacteria

Wine (Sugars to ethanol)

Saccharomyces cerevisiae

winemaking

fermentation of fruit
sugars by yeasts to produce ethanol.

two types of beer and their differences

Large beer - bottom fermentation and saccharomyces carlbergensis

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ale beer - top fermentation and saccharomyces cerevisiae

bottom fermentation

yeast at the bottom of the vessel at the end
of the fermentation process

7 to 10 degrees Celsius, and takes 7 to 12 days to finish due to the relatively slow fermenting capabilities of S. carlbergensis

top fermentation

a top yeast that rises to the surface of

an active fermentation, forming the yeast head.

18 to 25
degrees Celsius, for 5 to 7 days.

baker’s yeast

saccharomyces cerevisiae as leavening agent

saccharomyces cerevisiae as leavening agent

causes the bread to rise by
converting the fermentable sugars in the dough into
carbon dioxide and ethano

Cocao fermentation

Saccharomyces and Candida sp

Cocao fermentation process

production of ethanol,
secretion of pectinolytic enzymes, and
metabolization of citric acid. The process is
proceeded by bacteria, predominantly lactic acid
bacteria and acetic acid bacteria.

Surface mold-ripened cheeses

White molds covering the cheese

Penicillium camemberti

Internal mold-ripened cheeses

Penicillium roqueforti
which produces blue-veined cheeses.

Koji is a solid-state culture of

Aspergillus oryzae

Aspergillus oryzae

amylases
and proteinases which breakdowns the starch and
protein present in the substrate.

Vinegar

successive
fermentation of yeasts and acetic acid bacteria.

fish sauce

halophilic aerobic spore formers are the
predominant microorganisms in the production of
fish sauce.

lactic
acid bacteria.

the most utilized group of bacteria is

femrentation of LAB in sausages

Under the anoxic and high-salt cured
meat environment, they produce large amounts
of lactic acid that helps add flavor and prolong
the shelf life of sausages

fermented dairy products cheese buttermilk sourcream, using milk as a substrate

Lactococcus lactis subsp. cremoris/lactis

yogurt

Streptococcus thermophilus and Lactobacillus
delbreuckii subsp. bulgaricus are thermophilic lactic
acid bacteria

probiotics

ingested live microorgansisms that are beneficial to humans that poses no harmful response to humans and provide benefits

most known probiotic drink in Asian countries is

Lactobacillus casei strain Shirota

spoilage

unacceptable changes in flavor odor and other organoleptic properties of food

spoilage of protein rich foods such as fresh meat and poultry products, what causes their foul odor anf off color

ammonia,
hydrogen sulfide, indole, and amines

spoilage of protein rich foods such as fresh meat and poultry product

peptide chains broken down

most common bateria to cause spoilage of protein rich foods

Pseudomonas,

usually found at surface due to availability of oxygen, causes

characteristic slimy surface of
spoiled meat.

spoilage of protein rich foods in vacuum-packaged refrigerated meat

“deep
tissue” or “bone taint” caused by psychrophilic,
psychrotrophic, or psychrotolerant clostridia

clostridia spoilage

proteolysis of protein

spoilage of protein rich foods in vacuum-packaged refrigerated meat , characterized by what

muscle softening,

large
amounts of hydrogen sulfide gas which may
cause blown package which is shown in the
image, and

release of offensive odors and
exudate,

while the initial pinkish red meat
becomes green

spoilage of foods rich in carbohydrates (AEROBIC)

Micrococcus.

spoilage of foods rich in carbohydrates (anaerobic)

Fermentative microorganisms may be yeasts,
lactic acid bacteria, coliforms, propionibacteria,
and clostridia.

uncontrolled growth of LAB in milk

causes the souring of milk due to the utilization
of the milk sugar, lactose.

spoilage of foods rich in carbohydrates processes invovled

hydrolysis of sugars to CO2 nand H20

femrnentation

spoilage of foods rich in carbohydrates (sucrose to dextran)

Leuconostoc mesenteroides

hydrolyzes sucrose and synthesizes a glucose
polymer known as dextran

gummy and slimy polymer

spoilage of foods rich in carbohydrates (bread process known as ropiness)

Bacillus subtilis

amylase in the core of bread

amylase can
hydrolyze starchy materials into sugars

spoilage of high fat food known as lipolytic spoilage

microorganisms that break down lipids into fatty acids
and glycerol.

short-chain fatty acids from
triglycerides results to rancid flavor and odor

why are

Dairy products are the common target of lipolytic

because milk is an excellent
medium for lipase production.

why odes vegetables go soft when spoiled

caused by
pectinolytic microorganisms such as
Pectobacterium

Pectobacterium carotovorum

Pectin

provides structural integrity to fruits and vegetables

Pectobacterium

production of pectinases that hydrolyzes
the pectin

Once the outer plant barrier has been
destroyed, fruits and
vegetables are susceptible to further
degradation by other microorganisms

reasons for spoilage of canned goods

underprocessing, inadequate cooling,
contamination of the can due to leakage from
the seams, and preprocess spoilage.

microorganisms involved in spoilage of canned goods

sporeformer bacteria

Flat sour spoilage

flat can, no vacuum

Geobacillus
stearothermophilus and Bacillus coagulans

food is sour due to production
of acids

“rotten egg” _odor

sulfide spoilage microorganisms.

sulfide spoilage

hydrogen sulfide gas produced is absorbed by
the product which reacts with the iron present,
that results to the blackened color due to the
iron sulfide precipitate.

\
Desulfotomaculum nigrificans

Swelling or bursting of cans

indicators of canned food spoilage and this
is an indication of excessive gas production
by microorganisms.

spoialge of canned goods: swelling, indicated by

souring, cheesy, or butyric odors

thermophilic anaerobes,

Thermoanaerobacterium
thermosaccharolyticum

spoialge of canned goods: swelling, indicated presence indicated by putrid odors due to production of ammonia

putrefactive anaerobes

such as Clostridium
putrefaciens

Acidic fruits are commonly spoiled by

molds due to ability of these microorganisms to
grow in low pH

spoilage of fruits is charaxterized by

the appearance of
cottony growth on the surface of the food with
varying colors

blue mold rot i in fruits

Penicillium
expansum

gray mold rot in fruits

Bortrytis cinerea

common cause of spoilage in
fermented foods.

Yeasts

Yogurt spoilage

S. cerevisiae., Kluyveromyces,
Pichia, and Candida

pink discoloration of sauerkraut, yeast spoilage

Rhodotorula species

softening and bloating of olives and pickles, yeast spoilage

Saccharomyces, Debaryomyces, Pichia,
Candida, and Rhodotorula.

PARAMETERS THAT AFFECT MICROBIAL
GROWTH

intrinsic parameters

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\
Extrinsic parameters

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Extrinsic parameters

dependent to the food itself, but rather to the storage environment that affect both the foods and microorganisms

intrinsic parameters

pH, moisture content, nutrient content, oxidation reduction potential, antimicrobial constituents, and biological structures.

food preservation

prevent or delay microbial activities in food., takes advantages of both intrisinc and extrinsinc aparameters

process of food preservation

1. direct removal of
microorganisms through washing and filtration
2. keeping out microorganisms by employing
aseptic techniques and effective food
packaging,
3. killing microorganisms by application
of heat and chemicals
4. inhibiting growth of
microorganisms by low temperature storage

Hurdle technology

Controlling multiple factors to
prevent growth of microorganism

when a
microorganism fails to conquer a “hurdle”, they
are either inhibited or destroyed.

microbial stressors of hurdle technology

lowering acidty and aw

lowered water activity in hurdle technology

causes the microbial cell to use energy to accumulate compatible solutes

that prevents osmotic stress

acidic conditions in hurdle technology

cause the cells to use more energy to pump out protons. These activities result to microbial cells diverting the energy needed for biosynthesis into maintenance of homeostasis, and hence, cell growth is inhibited.

When the energy demand for
maintenance of homeostasis exceeds the
energy-producing capacity of the cell, the
microorganism dies.

Foodborne infection

involves the ingestion of food
contaminated with pathogenic
microorganism.

microorganisms grow in the intestinal tract

invade the tissues or produce
toxins which leads to the onset of the disease

most common cause of foodborne

Salmonella, Campylobacter,
enterohemorrhagic Escherichia coli, Listeria,
and Vibrio.

enteric Salmonella and its two species

facultatively anaerobic, Gram-negative, rod belonging to the family Enterobacteriaceae.

\
S. bongori and
S. enterica. S. enterica

serovars of s enterica

2600 serovars that causes most of salmonellosis.

Typhoidal Salmonella

typhoid and
paratyphoid fever

highly
adapted to human reservoirs.

non-typhoidal serovars

causes inflammation of the stomach or the intestinal surface.

apted to both humans
and animals

Campylobacter

most common bacterial cause of human gastroenteritis,

spiral-shaped bacteria with 17 species

Campylobacteriosis,

watery or
bloody diarrhea, fever, abdominal cramps, and
vomiting that lasts for 5 to 7 days.

most common species to cause
campylobacteriosis

Campylobacter jejuni and Campylobacter coli

main reservoir of Campylobacter

poultry,
and consumption of raw or undercooked meat is
the common cause of infection.

most important
STEC serotype in relation to public health

E. coli O157:H7

e coli that is the most common cause of food borne infections that prodces shiga toxin

Shiga toxin-producing E. coli or STEC,

damages the intestinal wall
which causes bloody diarrhea

characterized by acute
renal failure, hemolytic anemia, and
thrombocytopenia or low blood platelets

hemolytic uremic
syndrome or HUS.

can cross
intestinal, brain, and placental barriers and can
cause meningitis, encephalitis, abortion,
neonatal infection, and septicemia.

Listeria monocytogenes

Consumption of contaminated dairy products and
ready-to-eat products are the main source of

Listeria monocytogenes

Vibrio species

leading

cause of human bacterial disease associated with
the consumption of seafood.

toxigenic Vibrio cholerae

causative agent of cholera, is
commonly found in water and food contaminated by
the infected persons

causes vibriosis

Vibrio parahaemolyticus and V. vulnificus

toxico infection

occurs when ingested bacteria first colonize the
mucosal surface and then produce exotoxins in
the intestine

produced during toxicoinfection can
induce negative effects on the local cells or
tissues, and in some cases, toxins enter blood
stream and induce disease

cholera toxin

produced by
Vibrio cholerae

heat-labile and heat-stable toxin
produced by

entero-toxigenic E. coli

enterotoxin

from Clostridium perfringens.

Human noroviruses

estimated to be responsible for over 95% of
non-bacterial gastroenteritis outbreaks.

attributed to ready-to-eat foods
handled by infected food handlers

Viral hepatitis

auses inflammation of the
liver, may also be transmitted through food

what causes

Viral hepatitis

Hepatitis A and E which are trransmitted through

fecal-oral route.