FOOD THAT INFLUENCE MICROBIAL GROWTH IN FOOD .

FOOD MICROBIOLOGY

1. SUBJECT INCHARGE : SUBJECT INCHARGE :
SUBMITTED BY:
SUGASHINI RATHINAM
III Bsc., Microbiology,
Department of Microbiolog
VIAAS, Sankagiri.
SUBMITTED BY:
SUGASHINI RATHINAM
III Bsc., Microbiology,
Department of Microbiolog
VIAAS, Sankagiri.
Affiliated to Periyar University, Salem ; Recognised Under Section 2(f) & 12(B) of the UGC Act, 1956 )
TITLE :FACTORS THAT INFLUENCE MICROBIAL GROWTH TITLE :FACTORS THAT INFLUENCE MICROBIAL GROWTH
SUBJECT:FOOD MICROBIOLOGYSUBJECT:FOOD MICROBIOLOGYSUBJECT:FOOD MICROBIOLOGY
Dr.R.DINESHKUMAR
ASSISTANT PROFESSOR,
DEPARTMENT OF MICROBIOLOGY,
VIAAS, SANKARI .
Dr.R.DINESHKUMAR
ASSISTANT PROFESSOR,
DEPARTMENT OF MICROBIOLOGY,
VIAAS, SANKARI .

2. FACTORS THAT INFLUENCE MICROBIAL GROWTH

3. SYNOPSIS:SYNOPSIS:
H
Introduction
Type of factors
Intrinsic Factors :
1.Hydrogen ion concentration
2.Moisture content
3.Nutrient content
4.Antimicrobial constituents
5.Biological structure
Extrinsic Factors :
1.Temperature of storage
2.Relative Humidity of environment
3.concentration of gas in environment
Conclusion
Reference

4. Introduction:Introduction:
Since our food are of plant and animal orgin ,it is worth while to consider
characteristics of plant and animal tissue that affect the growth of microorganisms.
The plant and animals that serve as food sources have all evolve mechanisms of d
against the invasion and proliferation of microorganisms and some of these rem
effect in fresh food.

5. The factor of plant and animal tissue that are an inherent
part of the tissue are refferd to as intrinsic factor.
Or in other word intrinsic factor are related to the food
properties
There are five types :
1.Hydrogen ion concentration
2.Moisture content
3.Nutrient content
4.Antimicrobial Substance
5.Biological Structure
Intrinsic factors

6. Hydrogen ion concentration:
It has been well established that most microorganisms
grow best at pH values around 7.0(6.6-7.5),while few grow
below .
Bacteria tend to be more fastidious in their relationship to
pH than molds and yeast ,with the pathogenic bacteria
being the most fastidious.
For example :
1.Bacteria :6.8-7.5 pH
2.Molds : 1.5 -11.0pH
3.yeast : 1.5 - 8.5 pH

7. Food type Range of pH values
Beef 5.1 -6.2
Chicken 6.2 -6.4
Milk 6.3 -6.8

8. The effect of moisture is in terms of water
activity ,the amount of free water in a food
medium.
The amount of free ,water is important for
growth of microorganisms .
If there is lack of this free water microbes will
not grow.
Measure =aw
Moisture content :

9. Organisms Aw
Hallophilic bacteria 0.75
Xerophillic molds 0.61
Osmophilic yeasts 0.61
A single
vector

10. Nutients content of the food
Microbsrequire,protein,carbohydrates,lipids,water
,energy,nitrogen,sulphur,phosphorus,vitaminsand
minerals for growth.
Various foods have specific nutrients that help in
microbial growth.
Food such as milk ,meat and eggs contain a number of
nutrients that are required by microorganisms.
These food are hence susceptible to microbial spoilage
.

11. Nutrients Rice Millet
Energy 0.001 414
Moisture 6 11
Protein 12.5 9
G.corn yam Garri
394 373 384
12 76 14
15 7.3 1.2
Fat 0.2 5
Carbohydrates 0.2 83
Calcium 12 50
3.2 6.6 0.4
76 86 94
26 10.4 45

12. Antimicrobial substance:
The stability of some food against attack by microorganisms is due to
the presence of cert naturally occurring substances that have been
shown to have antimicrobial activity .
Some species are known to contain essential oils that posses
antimicrobial activity.
Among these are Eugenol in cloves ,allicin in garlic,and thymol in
oregeno.
Cow's milk contain several antimicrobial substance include
lactoferrin,conglutin , casein.
The hydroxcinnamic acid derivatives found in
fruits,vegetables,tea,mollasses,and other plant source.

13. It inhibit microbial growth.
Various food have inherent antimicrobial substance that pre
microbial attack.
Inhibitors :
1.Zactinin in milk
2.Anti coliform in milk
3.Lysozyme in egg white
To stop growth

14. Biological Structure
Natural covering of some food provide excellent protection
against the entry and subsequent damage by spoilage
organisms .
In this category are such structure as the tests of seeds,the
outer covering of fruits ,the shell of nuts ,the hide of animals
and the shell of eggs .
Once cracked of course,nutmeats,are subject to spoilage by
molds.
The skin covering of fish and meats such as beef and pork
prevent the contaminated and spoilage

15. Egg have shell and inner
membrane that prevent yolk
and egg white from
infection.
Unshelled walnut has a longer
shell life than Shell once
because their hard shell
protect them from light and
heat .

16. Extrinsic factors:Extrinsic factors:
The extrinsic factors of food are those propertie
of the storage environment that affect both foo
and their microorganisms.
Those of greatest important to the welfare o
food borne organisms.
1.Temperature of storage
2.Relative humidity of environment
3.Presence and concentration

17. Temperature:
The growth of microorganisms is affected by
environmental temperautre
Various Microbes are able to grow at certain
temperature and not others.
It classified into three types .
1.psychrophilic
2.Mesophillic
3.Thermophillic

18. Psychroplilic :
Grow at =10°C-20°C in unfrozen media.
These bacteria can cause food spoilag
at low temperature .
Moulds of general of penicillin ,Mucos

19. Mesophillic :
Grow at =25°C-40°C
Optimum temperature =37°C
Not grow in below 5°C to above 45°C
Most of pathogenic bacteria belong to
this group.

20. Thermophillic :
Grow at above 45°C
Optimum temperature=50°C-70°C
Growth of some bacteria occur at 80°C
Bacteria in this group are mainly spore formers
and are of importance in the food industry
especially in processed foods.

21. Chimeric
Plantibodies
Concentration of gases in environment:
This relates to the presence and concentration
of gases in the food environment.
Various microorganisms require for growth
either high oxygen tension (aerobic),low oxygen
tension (micro aerobic )or absence of oxygen
(anaerobic).
Some microorganisms may grow either in high
oxygen tension,or in the absence of oxygen.

22. Food affected by various group:
Anaerobic or facultative anaerobes spore
former are most likely to grow in canned food.
Microaerophilic bacteria are most likely to grow
in vacuum packed food since they have low
oxygen tension.
Aerobic bacteria are likely to grow on the
surface of raw meat.
Aerobic molds will grow in inscifficiently dried
or salted products.

23. Relative Humidity:
Relative Humidity 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.

24. Conclusion:
Food spoiled due to physical,chemical,and
microbial degradation with their
metabolites .
Storage of food is an important .

25. Reference:
Modern Food microbiology James M.JAY
Fourth Edition

26. Thank you ??????