This document discusses microorganisms that can inhabit or contaminate food, including bacteria, viruses, fungi, algae, and parasites. It explains that food microbiology studies microbes that cause food spoilage or illness in order to enhance food production and prevent disease. Various microbes are described, including their structures, modes of reproduction and growth, and potential risks if consumed. Intrinsic and extrinsic factors that influence microbial growth in foods are also outlined.

1. MICRO-ORGANISMS IN FOOD
SHREYA PRASAD
Assistant lecturer
IHM Bhubaneswar

2. WHY STUDY FOOD MICROBIOLOGY?
 Provide Clean, Safe, Healthful Food to Consumer
• Food Permits Growth
• Control of Microbial Growth
 Prevent Food Spoilage
 Prevent Food-borne Illnesses
 Food Preservation and Production

3. FOOD MICROBIOLOGY
 The study of the microorganisms that inhabit,
create, or contaminate food, including the study of
microorganisms causing food spoilage.
 Goals
- to use microorganism to enhance or produce new
food products (e.g. fermentation, cheese and wine
making)
- to study disease/spoilage-causing
microorganisms and their prevention

4. 1. BACTERIA
 are minute unicellular plant-like microorganisms.
 The length of a bacterial cell is about 1um and
smaller than this in diameter.
 Bacteria are classified according to the shapes of
their shells.

5.  Reproduce by cell division.
 Some bacteria cannot tolerate oxygen (anaerobes)
and some require oxygen for growth (aerobes).

6.  BACTERIAL GROWTH-
EXPONENTIAL GROWTH

7. VIRUS
 Extremely small ranging from 25-250um in size.
 They replicate inside a living cell using its host cells
metabolism.
 There are no of ways by which viruses may be transmitted
most common of this is via direct or distance contact i.e. from
host to host.
• by touching or through a short distance in the air. Indirect
transmission may occur.
• by the bite of certain infected insects (vector)
• by water and food (vehicles)
 There are a variety of ways in which viruses May enter foods.
1. Primary when the food product already contains virus at the
time of slaughter or harvest or
ii.
2. Secondary when it occurs during processing, storage or
distribution of food.

8.  STRUCTURE OF VIRUS

9.  VIRAL GROWTH

10. FUNGUS- YEAST
 Yeast are unicellular plants(fungi) widely distributed
 In nature and they grow well in a slightly acid
medium in the presence of sugar and water.
 The individual cell length is about 10um and the
diameter is about 1/3rd of this size.
 Used for for leavening of bread and to bring about
fermentation of food usage they can be harmful to
foods if they bring about undesired fermentation.

11.  YEAST REPRODUCTION

12. FUNGUS- MOULDS
 Molds are multicellular filamentous fungi having a
fuzzy or cottony appearance often they grow in
foods. They are larger than yeast. They are strictly
aerobes and require oxygen for growth and
multiplication.
 MOULD REPRODUCTION- SPORE FORMATION

13.  Moulds frequently thrive under conditions of acidity
or of osmotic pressure. Those are inhibitory to most
bacteria.
 That is why they are found on jams and jellies
moulds require less free moisture for growth than
yeast and bacteria the absence of bright light and
presence of stagnant air favour their rapid
development.

15. ALGAE
 Most algae live in fresh or sea water where they
can either be free-floating or attached to the
bottom. Some algae can grow on rocks, soil or
vegetation as long as there is enough moisture.
 All algae contain chlorophyll and do photosynthesis.

16.  Some algae produce toxins. Can enter the food
chain through shellfish or fish. In some cases, in
paralysis and even death. The risk of illness is
highest when algal blooms form in sea or fresh
water.

17.  Cyanobacteria (formerly called blue-green algae)
also form extensive blooms in fresh water in the
right climatic conditions and can kill any animals
that drink it.

18. PARASITES
 Ingestion of raw or semi-cooked food by humans
can lead to infection by parasites. Food like pork,
beef, lamb, shellfish, vegetables act as vehicles for
infection.
 The organism contaminated food when raw human
excreta are used for crops. Infected water-poor
hygiene also spread the parasite. Cooking kills
most of these parasites.

21. Factors affecting growth
of Micro-organism in food
Intrinsic
pH value
Moisture
contains(water
activity)
Nutrients
contain
Anti-microbial
constituents
Biological
structure
Extrinsic
Temperature of
storage
Relative
humidity of the
environment
Presence and
concentration
of gases
Presence and
activities of
micro-organism

22. FACTORS AFFECTING MICROBIAL GROWTH
 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.

23.  Extrinsic factors- Are factors external to the food
that affect microbial growth. They include:
 Temperature of storage,
 Presence and concentration of gases in the
environment
 Relative humidity of food storage environment.