Dr Kamal E M Elkahlout Food Microbiology 2 Sources of microorganisms in food amp Important Bacterial Groups in Foods 2 Sources of microorganisms in foods 3 The internal ID: 617358
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Slide1
1
Food Biotechnology
Dr.
Kamal
E. M.
Elkahlout
Food Microbiology
2
Sources of microorganisms in food
&
Important Bacterial Groups in FoodsSlide2
2
Sources of microorganisms in foods
Slide3
3
The
internal
tissues of healthy plants (fruits and vegetables) and animals (meat) are essentially sterile.
Raw and processed (except sterile) foods contain different types of molds, yeasts, bacteria and viruses.
Microorganisms get into food from natural sources and external sources. Slide4
4
Natural sources for foods of plant origin
Surfaces of fruits, vegetables and grains and damaged tissues and pores in some tubers (e.g. radish and tubers).
Natural sources for foods
of
animal origin
Skin, hair, feathers, gastrointestinal tracts, urinogenital tract, respiratory tracts and milk ducts (teat canals) in animals producing animals.Slide5
5
An understanding of the sources of microorganisms in food is important to:
develop methods to control access of some microbes in food.
develop processing methods to kill them in food.
Determine the microbiological quality of foods.
Setup microbiological standards and specifications of food and food ingredients.Slide6
6
Pre dominant microorganisms in plants (fruits and vegetables).
Internal tissues are sterile except for few porous vegetables and leafy vegetables.
Some plants produce natural antimicrobial metabolites that limit the presence of microorganisms.
Fruits and vegetables harbour microbes on their surfaces and microbe presence depends on their type, soil condition, water used and air quality. Slide7
7
Molds and yeasts
Lactic acid bacteria
Bacteria from the genera:
Pseudomonas, Alcaligenes, Micrococcus, Erwina, Bacillus, Clostridium and Enterobactor.
Pathogens especially of enteric types (
Salmonella, Escherichia coli, Campylobacter, Shigella, Cyclospora, Giardia
can be present if the soil is contaminated with untreated sewage. Slide8
8
Factors contributing to increase in microbial numbers
Diseases of the plants.
Damage of the surface before (during and after harvest).
Long delays between harvesting and washing.
Unfavorable storage and transport conditions after harvesting and before processing can greatly increase the microbial numbers.Slide9
9
Reducing microbial loads in foods of plant origin
Proper methods used during growing (such as use of treated sewage or other types of fertilizers).
Damage reduction during harvesting.
Quick washing with good quality water to remove soil and dirt.
Storage at low temperature before and after processing. Slide10
10
Are carriers and can carry pathogens such as
Salmonella
spp., pathogenic
Escherichia coli,
Campylobacter jejuni, Yersinia enterocolitica
and
Listeria monocytogenes
Laying birds – suspect of carrying
Salmonella enteritidis
in ovaries and contaminating yolk during ovulation.
Fish and shellfish carry normal microflora in the scales, skin and digestive tracts. Carry pathogens such as
Vibrio parahaemolyticus, Vib vulnifus.
Pre dorminant microroganisms in animals birds, fish and shellfishSlide11
11
Contamination of foods of animal origin during production and processing:
Milk – contaminated with fecal materials on the udder surface
Egg shells – contaminated with fecal material
Meat- contaminated with the intestinal contents during slaughtering
Enteric pathogens from fecal materials common are
Staphylococcus
aureus
, Micrococcus
spp
, moulds and yeasts.Slide12
12
Reduction in microbial load – foods of animal origin
Effective use of husbandry of live animals and birds:
- good housing
- avoid overcrowding
- supply of uncontaminated water
Testing animals and birds for pathogens and culling the carriers-to reduce the incidence of pathogenic microorganisms in food.
Cleansing carcasses with good quality water.
Careful hair, feather removal and digestive, urinogenital and respiratory organs.
Proper sanitation during slaughtering and processing.
Proper cleaning of the udder before milking and after milking.
Eggs should be collected soon after laying and washed and stored as per recommended procedures.
Fish and marine products should be harvested from unpolluted waters. Observe proper sanitation during processing. Use ice for storage
.Slide13
13
Sources of microorganisms
Air
Microorganisms are present in dust in air
Do not grow in dust but are transient and variable depending upon the environment
Their level is controlled by the degree of
humidity, size and level of dust particles,
temperature and air velocity and resistance of microorganisms to dryingSlide14
14
Dry air with low dust content and higher temperature has a low microbial level.
Predorminant microbes in air include spores of
Bacillus spp. Clostridium spp.,
mold and Gram-positive bacteria (
Micrococcus spp and Sarcina
).
Microbial contamination in the air can be reduced by
removing the potential sources,
controlling dust particles in the air (using filtered air) using positive air pressure,
reducing the humidity level and installing UV light.Slide15
15
Soil
Soil contains several varieties of microorganisms
Microorganisms multiply in soil, their numbers can be very high (billions/ g)
Moulds, yeasts and bacteria genera (
Enterobacter, Pseudomonas, Proteus, Micrococcus, Enterococcus, Bacillus
and
Clostridium
) can get into foods from the soil.Slide16
16
Soil contaminated with fecal materials can be source of enteric pathogenic bacteria
Sediments where fish and marine foods are harvested can also be a source of microorganisms in those foods
Prevention - removal of soil (and sediments) and avoiding soil contamination are used to reduce microorganisms in foods
Slide17
17
Sewage
Sewage when used as fertilizer in crops can contaminate food with microorganisms.
Predominant types include enteropathogenic bacteria and viruses.
Major concern with organically grown foods and many imported fruits and vegetables where untreated sewage may be used as fertilizers.
Prevention
–
not to use sewage as fertilizers, or should be efficiently treated to kill the pathogens.
Wash foods following harvesting is importantSlide18
18
Water
Is used to produce, process and in some cases store foods.
Used for irrigation of crops, drinking by food animals.
Raising fishery and marine products.
washing foods, processing (pasteurization canning and cooling of heated foods).
washing and sanitation of equipment , processing and transportation facilitiesSlide19
19
Water is used as an ingredient in many processed foods thus can greatly influence the microbial quality of foods.
Wastewater can be recycled for irrigation
Chlorine-treated potable water should be used in processing, washing, sanitation and as an ingredient.
Although potable water does not contain coliforms and pathogens. It can contain other bacteria capable of causing food spoilage (including
Pseudomonas, Alcaligenes
and
Flavobacterium)
Improperly treated water can contain pathogen and spoilage microorganismsSlide20
20
Humans
Between production and consumption foods come in contact with people handling the foods.
people working in a food processing plant, handling foods at restaurants, catering services, retail stores and at home.
Improperly cleaned hand, lack of aesthetic sense and personal hygiene, dirty clothes and hair can be a major sources of microbial contamination in foods.
Pathogens such as
Staphylococcus
aureus
, Salmonella spp.
Shigella
spp.
Pathogenic
E. Coli
and hepatitis A can be human sources.
Slide21
21
Food ingredients
prepared or fabricated foods many ingredients or additives are included in different quantities.
Many ingredients can be a source of both spoilage and pathogenic microorganisms
various spices can possess very high populations of mold and bacterial spores.
Starch, sugar and flour might have spores of thermophilic bacteria. Slide22
22
ingredients should be produced under sanitary conditions.
and given antimicrobial treatments.
Setting up acceptable microbial specifications for the ingredients will be important in reducing microorganisms in foods from this sourceSlide23
23
Equipments
wide variety of equipment are used in
harvesting, transportation,
processing and storage of foods
microorganisms from air, raw foods, water and personnel can get into the equipment and contaminate foods.
Depending on environment and time,
microbes can multiply from low initial population to reach high level and contaminate large volumes of foodsSlide24
24
processing used continuously for a long period of time,
microorganisms resent initially can multiply and act as a continuous source of contamination in the product.
small parts, inaccessible sections and certain materials may not be efficiently cleaned and sanitized therefore can serve as sources of both pathogenic and spoilage microorganisms in foodSlide25
25
Small equipments such as cutting boards, knives, spoons due to improper cleaning can be source of cross-contamination
Salmonella, Listeria, Escherichia, Enterococcus, Micrococcus, Pseudomonas, Lactobacillus, Listeria
and yeasts and moulds can get into food from equipment
Proper cleaning and sanitation of equipment at prescribed intervals are importantSlide26
26
Miscellaneous sources
Several other sources of food contamination include :
Many types of packaging materials are used in food. (wrapping materials, containers).
Flies, birds, house pets and rodents.
proper microbiological standards (or specifications) for packaging materials are necessarySlide27
Important Bacterial Groups in FoodsSlide28
Lactic Acid bacteria
produce relatively large quantities of lactic acid from CHO's.
Lactoccus, Leuconostoc, Pediococcus, Lactobacillus
and
Streptococcus thermopillus
Lactococcus
LeuconostocSlide29
Lactic Acid bacteria
Pediococcus
Lactobacillus
Streptococcus thermopilusSlide30
Acetic acid bacteria
bacteria that produce acetic acid.
Acetobacter aceti
.Slide31
Propionic
acid bacteria
bacteria that produce propionic acid and are used in dairy fermentation.
Propionibacterium freudenreichii
.Slide32
Butyric acid bacteria
bacteria that produce butyric acid in relatively large amounts.
Some
Clostridium spp
such as
Clostridium butyricum
.Slide33
Proteolytic
bacteria
those that are capable of hydrolyzing proteins, due to production of extracellular proteinases.
Species in genera
Micrococcus, Staphylococcus, Bacillus, Clostridium, Pseudomonas, Alteromonas,
and
Flavobacterium.Slide34
Proteolytic
bacteria
Staphylococcus
Micrococcus
Bacillus
Pseudomonas
Clostridium
FlavobacteriumSlide35
Lipolytic
bacteria
able to hydrolyze triglycerides due to production of extracellular lipases.
Species in genera
Micrococcus, Staphylococcus, Pseudomonas, Alteromonas
and
Flavobacterium.
AlteromonasSlide36
Saccharolytic
bacteria
able to hydrolyze complex CHO's.
Bacillus, Clostridium, Aeromonas, Pseudomonas
and
Enterobacter.
Aeromonas
EnterobacterSlide37
Thermophilic
bacteria
able to grow at 50°C and above.
Include some species from genera
Bacillus, Clostridium, Pediococcus, Streptococcus
and
Lactobacillus
.
PediococcusSlide38
Psychrotrophic
bacteria
able to grow at refrigerated temperatures (
5°C).
Pseudomonas, Alteromonas, Alcaligenes, Flavobacterium, Serratia, Bacillus, Clostridium, Lactobacillus, Leuconostoc, Carnobacterium, Brochothrix, Listeria,
Yersinia
and
Aeromonas
.
Alcaligenes
Serratia
ListeriaSlide39
Thermoduric
bacteria
able to survive pasteurization temperature treatment.
Include some species from
Micrococcus, Enterococcus, Lactobacillus, Pediococcus
,
Bacillus
(spores) and
Clostridium
(spores).
EnterococcusSlide40
Halotolerant
Bacteria
able to survive high salt concentrations (
10%).
Bacillus, Micrococcus, Staphyloccus, Pediococcus, Vibrio
and
Corynebacterium
.
VibrioSlide41
Aciduric Bacteria
:
able to survive at low pH (below 4.0).
Lactobacillus, Pediococcus, Lactococcus, Enterococcus
and Streptococcus
.
Osmophilic bacteria
:
can grow in a relatively higher osmotic environment than other bacteria.
Some species from genera
Staphylococcus, Leuconostoc
and
Lactobacillus
are included. They are much less osmophilic than yeasts and molds Slide42
Gas-producing bacteria
produce gas (CO
2
, H
2
, H
2
S) during metabolism of nutrients.
Leuconostoc, Lactobacillus, Propionibacterium, Escherichia, Enterobacter,
Clostridium
and
Desulfotomaculum
.
EscherichiaSlide43
Slime Producers
:
produce slime due to synthesis of polysaccharides.
Xanthomonas, Leuconostoc, Alcaligenes, Enterobacter, Lactococcus
and
Lactobacillus.Slide44
Sporeformers:
ability to produce spores.
Bacillus, Clostridium
and
Desulfotoaculum
spp.
They are divided into
aerobic sporeformers,
anaerobic sporeformers,
flat sour sporeformers,
thermophilic sporeformers
sulfide-producing sporeformers.Slide45
Coliforms:
includes species of
Escherichia, Enterobacter, Citrobacter
and Klebsiella and used as index of sanitation.
Fecal Coliforms:
mainly
Escherichia coli
. Also used as index of sanitation.Slide46
Enteric Pathogens:
includes pathogenic
Salmonella, Shigella, Campylobacter, Yersinia, Escherichia, Vibrio, Listeria
,
hepatitis A and others that can cause gastrointestinal infection.