Bacterial growth occurs in four phases: lag, log (exponential), stationary, and death. Bacteria multiply most rapidly during the log phase. The six conditions that influence bacterial growth are: food, acidity, temperature, time, oxygen, and moisture. There are three main types of food hazards - biological, chemical, and physical. Biological hazards include bacteria, viruses, parasites, and toxins. Chemical hazards stem from toxic metals, pesticides, and cleaning chemicals. Physical hazards are foreign objects that contaminate food such as glass or metal shards. Proper food handling and sanitation can help reduce these food safety risks.

1. Bacterial Growth

2. 1) Bacterial growth - is the division of one
bacterium into two daughter cells in a
process called binary fission
2) Binary Fission – the reproduction of the
cell or a one cell divided into two equal
parts
3) Lag Phase - bacteria adapt themselves to
growth conditions. It is the period where
the individual bacteria are maturing and
not yet able to divide.

3. 4) Log Phase – “exponential phase” growth is
very rapid, doubling in numbers in every few
minutes
5) Stationary Phase - the growth rate slows
as a result of nutrient depletion and
accumulation of toxic products. This phase
is reached as the bacteria begin to
exhaust the resources that are available to
them.
6) Death phase- bacteria run out of
nutrients and die.

4. pH – potential of Hydrogen. A measure of
the acidity or alkalinity of a solution,
numerically equal to 7 for neutral
solutions, increasing with increasing
alkalinity and decreasing with increasing
acidity. The pH scale commonly in use
ranges from 0 to 14.

5. 4 Phases of Bacterial Growth

6. 6 Conditions Bacteria Multiply

7. F - Food
Protein foods Carbohydrates

8. A - Acidity
acidic alkaline
7
• Very acid (below 4.6) will not support the growth of
bacteria
• pH (4.7 to 9.0 ) is the best for the bacteria to grow
and multiply.
Meat, milk , fish are in this range.
• Disease causing bacteria grow best at the pH 4.6 to
7.0

9. Alkaline Foods Acidic Foods
Alkaline – Fruits,vegetables Acidic - corn, meat, beans,
Very Alkaline - Bananas fish, fowl, grains, coffee,
plums, prunes, distilled
Chocolate, mineral
water
water, potatoes, spinach,
water melon Very acidic – Eggs, liver,
gravy, wine, yogurt, sour
cream, fermented foods
and aged cheeses

10. T - Temperature
• Temperature Danger Zone - temp.
range 41F-140F (5C-60C). Food
borne bacteria grow and reproduce.
• Temperature Abuse –foods that
have not been to a safe temperature
or kept at the proper temperature
Psychrophilic bacteria – grow within
the temperature range of 32F(0C) –
70F (21C) (spoilage organisms)

11. • Mesophilic bacteria – grow at temp.
70F(21C) – 110F(43C)
• Thermophilic bacteria – grows best
above 110F (43 c)
Cold foods, must be stored 41F or
below
Hot foods, must be held at 140F
(60C) and above

12. T - Time
• Under ideal conditions, bacterial cells can
double in number every 25 minutes to 30
minutes.
• Pathogens starts to multiply in four hours
at the Temp. Danger Zone

13. O - Oxygen
Bacteria differ in their oxygen
requirement.
Anaerobic bacteria – cannot survive
when oxygen is present bec. it is toxic
to them.
 Anaerobic bacteria grow well in
vacuum packaged foods or canned
foods where oxygen is not available

14. Aerobic bacteria – need oxygen to
grow
Facultative anaerobic bacteria – can
grow with or without free oxygen but
have a preference
Microaerophilic organisms – can
survive in a very little amount oxygen,

15. M- Moisture
Moisture is important factor in bacterial growth.
The amount of water available for bacterial
activity.
Water Activity level – is the measure of the
amount of water that is not available for
bacterial to grow. ( 0- 10)
Potentially hazardous foods (PHF) – foods
that have a water activity level of .85 or
higher

16. TYPES OF FOOD HAZARDS

17. Test your knowledge (true / false)
1. Fish that has been properly cooked will be safe
to eat
2. Cooking can destroy the toxins.
3. Copper utensils can cause illnesses when
used to prepare acidic foods
4. Cleaning products may be stored with
packages with foods
5. Most biological toxins found in seafood, plants
and mushrooms occur naturally , are not
caused by the presence of microorganisms.

18. FOODBORNE HAZARDS – refers to
biological, chemical, or physical that can
cause illness or injury when consumed
along with the food.
Types of Food borne hazards:
4) Biological Hazards
5) Chemical Hazards
6) Physical Hazards

19. 1) Biological Hazards
• Biological contaminants – caused by
microbial contaminants such as bacteria,
viruses, parasites, fungi and biological
toxins.
 pathogens spread mostly by foodhandlers
 unsanitary facilities and equipment
 pests

20. 3 Types of Biological Toxins
1) Seafood Toxins
b) Ciguatera Toxin – fish that have eaten algae
containing toxins (amberjack, barracuda,
grouper, snapper). Odorless and tasteless
cooking do not destroy toxins.
c) Scombroid toxin – histamine caused by
bacteria, they are time temp abused. ( bluefish,
mackarel, swordfish, mahi mahi).
d) Shellfish toxin – caused by algae they eat.
(mussel, clams, scallops)

21. 2. Plant toxins – natural part of plants
3. Fungal Toxins – poisonous mushrooms
***cooking and freezing will not
destroy the toxins ***

22. 2) Chemical Hazards
 Caused by chemical substances like toxic
metals, pesticides, cleaning products,
sanitizers, lubricants
 Utensils and equipment containing toxic
metals ( lead, copper, brass, zinc,
antimony and cadmium) – can cause a
toxic metal poisoning when combined with
acidic foods

23. What to do?
 Store chem. Away from foods, utensils
and equipment used for foods
 Clear labels and stored away from food
 Measure correctly
 Wash hands afterwards
 Wash fresh fruits and vegetables
 Monitor pest control operators
Metal containers – use only NSF and
UL labeled

24. 3) Physical Hazard
• A foreign object that accidentally find its
way to the food such as a piece of glass,
hair, fingernails, dirt, metal shavings,
staple wires

25. What to do?
 Store toothpicks, etc. below food
 Shields on lights
 Clean can openers
 Remove staples, etc. in receiving area away from
food
 Avoid temp equipment fixes that could fall off
 Use hair restraints
 No nail polish, jewelry
 No pencils behind ears
 Only approved food containers for storage
 Never re-use single use containers

26. Where are the hazards?