nutritionist: fardus fuad rageh

1. PREPARED BY NUTRITIONIST FARDUS FUAD RAGEH
INTRODUCTION TO FOOD MICROBIOLOGY

2. CHAPTER 1
INTRODUCTION TO FOOD MICROBIOLOGY
 Food supply consists basically of plants and animals
or product derived from them, it is understandable
that our food supply can contain microorganism in
interaction with food.
· These microorganisms use food supply as a source of
nutrients for their own growth.
These will cause 2 possibilities: Either – Result in
deterioration of food (“spoil”)
OR
These interactions between microorganisms and food
give beneficial to human

3. How microorganisms can cause
deterioration of the food?
 When they utilize the nutrients of the
food, it involved
changes in the food compound like
synthesis a new compound
• that cause spoiling of the food or
produced enzymatic changes and
contributing off flavour by mean of
breakdown of product.

4. How to prevent deterioration of the food
by microorganisms?
· Minimize the contact between microorganisms and food
· Eliminate microorganisms from foods
· Understand about preservation of the food
What are the importance of microorganisms in food?
Good (desirable) Bad (undesirable
· Food bioprocessing
· Food biopreservation·
Probiotics
· Food borne disease·
Food spoilage

5. GOOD (DESIRABLE)
Food bioprocessing
· Foods produce by using biological process. In this process,
food-grade microorganisms are used to produce different
types of fermented food using raw materials from animal and
plant sources (this process known as “starter culture”).
· Besides, microbial enzymes are also being used to produce
food and food additives.
Food biopreservation
· Is a food biological preservative by using antimicrobial
metabolites (taken from certain microorganisms in order to
control pathogenic and spoilage microorganisms in foods).
Probiotics
· Is a concentrated supplement of beneficial live cells of
bacteria (friendly bacteria) culture taken orally intended to
improve our health by promoting our body’s natural immunity
and improving digestion system.

6. BAD (UNDESIRABLE)
Food borne disease.
· Is a disease cause by consumption of contaminate during
various stage of handling between production and
consumption by many pathogenic microorganisms (bacteria,
molds and viruses).
Food spoilage.
· Is a condition of contaminate food due to:
Growth of microorganisms in food
OR
The action of microbial heat stable enzymes
· Microorganisms used food supply as a source of nutrients by
their own growth.
· Spoilage leads to wastage of food and economic loss.

7. Causes of food spoilage
•(a). Growth and activity of microorganisms
Bacteria, yeasts and molds are
microorganisms that cause food spoilage.
They produce various enzymes that
decompose the various constituents of food.
•(b). Enzyme activity: Action of enzymes
found inherently in plant or animal tissues
start the decomposition of various food
components after death of plant or animal.
•(c). Chemical reactions: These are reactions
that are not catalysed by enzymes.,e.g.
oxidation of fat

8. Microbial spoilage of food
Bacteria, yeasts and molds are the major
causes of food spoilage.
They produce various enzymes that
decompose the various constituents of food.
Molds are the major causes of spoilage of
foods with reduced water activity e.g dry
cereals and cereal product
Bacteria spoil foods with relatively high
water activity such as milk and products.

9. Sources of microorganisms in food
The primary sources of microorganisms in food
include:
1. Soil and water
2. Plant and plant products
3. Food utensils
4. Intestinal tract of man and animals
5. Food handlers
6. Animal hides and skins
7. Air and dust

10. Factors affecting microbial growth in
food
Intrinsic factors:
These are inherent in the food. They include:
 Hydrogen ion concentration (pH),
moisture content,
nutrient content of the food,
antimicrobial substances ad
biological structures.

11. PROBIOTICS
Definition:
Probiotic is a concentrated supplements of beneficial live bacteria
culture taken orally intended to improve our health. It is a friendly
bacteria which play vital role in keeping us fit and healthy.
Probiotics means “for life”
The good friendly bacteria are good because they promote the
body’s natural to keep our body fit and to help our digestion.

12. Advantages
1. By increasing the absorption of mineral and vitamins and it also can
improve digestion system especially of milk product t.
In our food, only vitamins that properly absorbed and digested are
useful. Probiotics also improve lactose intolerance.
2. Taking probiotics can support out immune system which is fight bad
bacteria and infection in keeping scope from breaking down.
•It produced antimicrobial substances that can deter various bad
bacteria. It is so important because many of the
disease begin in the intestinal tract.
3. Produced specific protein that act as antigen and stimulates the
immune system.
4. Increase the absorption of calcium, important mineral in the
prevention of osteoporosis.

13. Cont…………
5. Preventing intestinal tract infections that are cause by
Candida spp. and Helicobacter pylori.
6. Normalising bowel elimination problems and promoting
regularity.
7. Clean the colon and improve constipation.
8. Fights pathological moulds, yeast, fungus, viruses, parasites
and bacteria.
9. Stimulates β─ lymphocytes and related antibody production.
10. Supporting healthy liver function.
11. Alleviating bowil wind and bloating
12. Assisting in cholesterol management.

14. Side effect that occurs include:
a) Headache.
b) Diarrhea.
c) Bloating.
d) Constipation.
e) Production of intestinal gas.
Bacteria in the intestine
The variable and greatest number of bacteria lives in large intestine.
Lactobacillus acidophilus guard small intestine.
Bifidobacter protect large intestine.

15. Foods affected by various groups
Anaerobic or facultatively anaerobic
sporeformers are most likely to grow in canned
foods .
Microaerophilic bacteria are most likely to
grow in vacuum packed foods since they have
low oxygen tension, while
Aerobic bacteria are likely to grow on the
surface of raw meat.
Aerobic molds will grow in insufficiently dried
or salted products

16. Relative humidity
Relative humidiy is the amount of moisture in the
atmosphere or food environment.
Foods with low water activity placed at high humidity
environment take up water, increase their water activity
and get spoiled easily.
For example, dry grains stored in a environment with high
humidity will take up water and undergo mold spoilage.

17. Food preservation
•Food preservation is a process through which physical and
/or chemical agents are used to prevent microbial spoilage
of food.
•Food preservation aims at treating food in a manner to
prolong its storage life
•In food preservation, efforts are made to destroy
organisms in the food,or Increase the period taken by
microorganism to adapt to the food environment before
they start to spoil the food.

18. Food preservation principles
Two general principles are employed
in food preservation.
(1). Inhibition priciple
(2). Killing principle

19. (1). Inhibition principle
In this principle, food preservation is achieved by
inhibition of growth and multiplication of microorganisms.
The inhibition principle can be achieved by any of the
following methods:
(a). Reduction of water activity e.g. By drying and salting
(b). Reduction in pH e.g. by fermentation and addition of
acids.
(c). Use of preservatives, e.g. sodium benzoate
(d). Use of low temperatures (freezing)
(e). Smoking – which has a drying and preservative effect

20. Inhibition methods
Preservation of food by inhibition methods
does not necessarily imply the destruction
of organisms,
On removal of the inhibiting influence, the
food will undergo spoilage as the
microorganism present will grow and
multiply to cause spoilage.

21. Food preservation by lowering water
activity
Lowering of water activity can be achieved by:
Addition of high content of salt: Sodium chloride and
sometimes nitrats and nitrites
Addition of high content of sugar
Drying: sun/air drying; electrical drying or freeze
drying

22. The salting procedure
The salting procedure can be performed in four
ways:
1. Dry cure in which the meat or fish is rubbed
with salt
2. Pickling: The products are immersed in pickle
of brine, usually containing about 15% salt.
3. The injection cure: concentrated salt injected
to muscles
4. Direct addition method

23. Killing principle
In this principle, spoilage
microorganisms are destroyed (Killed) in
the food, and the food protected against
subsequent contamination by being
enclosed in an air tight container.

24. Methods employed to achieve the
killing principle
1. Heat treatment: through pasteurization or
sterilization
2. Irradiation with either ionizing or
electromagnetic radiation e.g Radiations
kill microorganisms by destruction of DNA
and by creating toxic reactive compounds in
a medium and in microbial cells
3. Use of gases: by use of ethylene oxide or
ozone. The gases destroy both vegetative
cells and spores.

25. Pasteurization
Is the process of heat treatment at
specific temperatures and times.
Pasteurization is aimed at destroying all
pathogenic microorganisms without
affection the nutritive value of the food.

26. Three methods of pasteurization
a. Low temperature long time (63oC for
30 min)
b. High Temperature short time (72oC for
15 seconds)
c. Flash method (80oC for 1-2 seconds)

27. Sterilization
Is the use of physical or chemical
means to destroy all microorganisms
that are present in the food.
Sterilization can be achieved by:
a. Heating at high temperatures,
e.g. 100-140oC
b. Irradiation:Irradiation kills
bacteria, spores, and insects as
well as inactivates enzymes.

28. Applications
In pratice, often a combination of
inhibition and killing principles and the
various methods are used depending on
the food type. e.g.
use of pasteurization and chilling of
milk,
lowering of water activity and low
temperature storage,
use of preservatives and low
temperature etc

29. Important terminologies on use of
heat in food preservation
D- value
Decimal reduction Time (D-Value)
Is the time required at any temperature to destroy 90%
of the spores or vegetative cells of a given organism.
The higher the temperature, the faster is the rate of
destruction and the shorter it takes to kill 90% of the
cells.
For example, D-value for Clostridium sporogenes in a
given food at 120oC is 1 minutes, at 115oC is 4 minutes,
at 110oC is 10 minutes.

30. Thank for your intension