This document discusses food spoilage, defined as changes in food that make it inedible or unsafe through physical, chemical, or microbial deterioration. Food spoilage can be caused by natural decay through moisture loss, enzyme action, or contamination by microorganisms. Enzymes present in food can cause oxidation, browning, and ripening through chemical changes. Proper food handling, adequate storage conditions and separation of foods can help prevent spoilage from inadequate quality, supervision, storage or cross-contamination. Maintaining appropriate refrigeration and dry storage helps control spoilage from microbial growth or moisture loss.

1. By:
Dr. Waleed Foad
MSc.Public Health in Nutrition
Clinical Nutrition Specialist
European Society of Gastrointestinal Endoscopy (ESGE)
Member of the American Society of Nutrition
Email: wfoad@outlook.com

2. Food Spoilage
 Definition: Changes in food, through physical, chemical,
enzyme deterioration or micro-organism growth, that lead to
the food becoming damaged, inedible or unsafe if eaten.
 The food has visible signs of deterioration which makes it
appear unpalatable or unpleasant.
 The rate of deterioration depends on a variety of factors.
 Contaminants may be already present in the food, e.g.
salmonella in chicken or transferred to the food by humans,
flies, rodents and other pests.

3. Conditions that could lead to
Food Spoilage
1. Inadequate quantity of Food purchased (than
required).
2. Inadequate quality of food and food ingredients
purchased
3. Inadequate supervision of incoming Food items.
4. Inadequate supervision of Food-handling
personnel.
5. Inadequate storage conditions and/or equipments.

4. Inadequate storage conditions
and/or equipments
Examples:
 Dry storage: Irregular inspection and maintenance of Storage
areas, which leads to insanitary conditions. E.g.. Rodents,
insects,....etc.
 Frozen storage: failure to maintain refrigerators and freezers in
good operating conditions.
 Inadequate storage separation of different food items (e.g.
Meats & vegetables, raw and cooked, frozen and dry,....etc)

5. Storage or Cross-contamination?

6. Causes of food spoilage
Food spoilage is caused by two main factors, namely;
 Natural decay in foods:
 Definition: Natural process that leads to spoilage of food
as a result of:
 Moisture loss and/or
 The action of enzymes present naturally in the food.
 Contamination by micro-organisms e.g. Yeast, Bacteria
(Previously Discussed)

7. Natural decay in food
Moisture loss
 Mostly occurs in fruit and vegetables which contain large
amounts of water.
 Fruits and vegetables continue to respire after harvesting
and therefore lose water through their leaves and skin.
 The vegetable or fruit shrinks in size, its skin becomes
wrinkled.
 Moisture loss occurs in other foods like meat, fish, cheese,
due to evaporation of water from the surface.

8. Natural decay in food
Enzyme action in the food
 Through the action of enzymes presents in the food.
 They speed up chemical changes that result in loss of flavor,
color and texture.
 As enzymes are mainly composed of protein, they are
sensitive to heat. They are active in temperatures found in a
kitchen on a warm sunny day.
 They can remain very slightly active at very low
temperatures such as those found in the freezer. This is why
there is a limit to the time food can be stored in a freezer.

9. Natural decay in food
Enzyme action in the food
 The activity of these enzymes stops when they are heated
above 70 oC.
 The activity of enzymes in food makes it easier for the
micro-organisms responsible for food spoilage to enter the
food.
 Such enzymes speed up the process of decay by breaking
down the tissues and components of the food in the various
ways such as: Oxidation, Browning and Ripening.

10. Natural decay in food
Enzyme action in the food
 Oxidation:
 When food comes into contact with oxygen, the enzymes
cause the destruction of certain nutrients e.g. vitamin c,
thiamine and carotene.
 Browning :
 Enzymes cause browning in certain foods the moment they
are exposed to air. When you cut or bruise food such as apple,
the exposed surface will discolor and turn brownish due to the
activity of enzymes.
 Ripening.

11. Natural decay in food
Enzyme action in the food
 Oxidation:
 Browning :
 Ripening:
 Enzymes are involved in that process in certain foods such as
fruits and vegetables.
 Unripe bananas for example contain starch which is gradually
converted to sugars, until the banana becomes very sweet, and
its skin color changes from green to yellow. Eventually, the
skin color changes to dark brown and it is no longer fit to be
consumed.

12. Natural decay in food
Enzyme action in the food
Browning and Ripening:

13. Reasons for keeping food items
from spoilage
 Saving Food: Deterioration may cause food to be wasted
 Saving Health: Contaminated food can cause illness and in
severe cases, food poisoning
 Saving Money
 Saving nutritive value
 Storing food items for lean seasons.

14. Food Spoilage

15. For Further Support:
Dr. Waleed Foad
Email: wfoad@outlook.com