DIFFERENT MICROBES IN FOOD AND THEIR EFFECTS

1. MICROBIAL SPOILAGE OF FRESH AND
PROCESSED FOODS

2. CONTENTS
• Causes of spoilage.
• Classification of foods by ease of spoilage.
• Factors affecting kinds and numbers of microorganisms in
the food.

3. FOOD SPOILAGE
• It is a state in which food is deprived of it's good or effective
qualities. Deterioration or spoilage starts from the time food is
harvested slaughtered and results in undesirable changes in the
physical and chemical characteristics of food.

4. • Growth & activity of microorganisms such as bacteria,yeast& molds.
• Gain or loss of moisture.
• Reaction with oxygen & light.
• Physical stress or abuse.
• Insects and rodents.
• Inappropriate temperatures for a given food.
CAUSES OF FOOD
SPOILAGE

5. CLASSIFICATION OF FOODS BY EASE OF
SPOILAGE
• The shelf-life of food is greatly influenced by its moisture
content.
• On the basis of their stability during storage,foods can be
divided into 3 categories.
1. Non-perishable
2. Semi perishable
3. Perishable

6. STABLE OR NON-PERISHABLE FOODS
• These foods which do not spoil unless handled carelessly
include such products as sugar,floured dry beans.
• For these foods pick up moisture readily from the atmosphere
and may deteriorate.

7. SEMI-PERISHABLE FOODS
• Semi-perishable foods can be stored for a week to
a month at room temperature without any
undesirable change in flavour or texture.

8. PERISHABLE FOODS
• It includes most important daily foods that spoil readily.
• They have to be stored at refrigeration temperature, if their
shelf life is to be perishable.
• Ex.,meats,fish,poultry,milk,paneer,eggs,fruits&vegetables.

9. FACTORS AFFECTING KINDS AND
NUMBERS OF MICROORGANISMS IN
FOOD
• Contamination may increase number of microorganisms in the
food.Wash water may incorporate surface-taint bacteria in butter.
• Growth of microorganisms in or on the food obviously will increase
numbers of or the bio burden of microorganisms.
• Pretreatment of foods may remove or destroy some kinds of
microorganisms, change the proportions of those present or inactivate
part or all of the food enzymes and thus limit the number of spoilage
agents.

10. FACTORS AFFECTING GROWTH OF
MICROORGANISMS IN FOOD
• Associative growth: Association of microorganisms with each
other are involved in spoilage of most foods.
• Microorganisms are not always antagonistic to each other.
• These are sometimes mutually helpful are symbiotic.

11. Metabiotic:Both organisms mat be growing at the same
time,but more commonly one success the other.Most natural
fermentation of raw food illustrate metabiosis.

12. EFFECT OF ENVIRONMENTAL GROWTH
• Intrinsic parameters: The parameters of plant and animal
tissues that are inherent part of the tissues are referred to as
intrinsic parameter.

13. INHERENT ACIDITY
.Some foods have a low pH because of inherent
property of the food.
• Ex.,Fruits and vegetables.

14. BIOLOGICAL ACIDITY
• Some foods develop acidity from the accumulation of acid
during fermentation.
• Ex.,Egg white.

15. REDOX POTENTIAL
• Oxygen tension or partial pressure of oxygen about a food and
the O R potential or reducing and oxidizing power of the food
itself,influence the type of organisms which will grow and
hence the changes produced in food.

16. REFERENCE
• Sumati.R.Mudambi,Shalini.M.Rao and
M.V.Rajagopal.2006.Foodscience,2nd Ed. New Age International (P)
limited,New Delhi.