2. Food spoilage means the original
nutritional value, texture, flavor of the
food are damaged, the food become
harmful to people and unsuitable to eat.
3. • Food spoilage can be the result of:
– Insect damage
– physical injury
– Enzymatic degradation
– Microbial activity
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4. Effects of food spoilage
Changes in nutritional value
• Decomposition of proteins , carbohydrates,
vitamins
Changes in organoleptic features
• Color , flavor , taste, unpleasant odor.
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5. Spoilage Signs
• Odor:
– Breakdown of proteins (putrefaction)
e.g. “rotten egg” smell
• Sliminess
- Primarily due to surface accumulation of microbial cells
and also be a manifestation of tissue degradation
• Discoloration
– Mould on bread, blue and green mould on citrus fruit
and cheese
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6. • Souring
– Production of acid
e.g. sour milk from production of lactic
acid
• Gas formation
– Meat becomes spongy
– Swollen or bubbling packages and cans
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10. Microbial spoilage of food
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•Bacteria, yeasts and moulds are the major causes of food
spoilage.
•They produce various enzymes that decompose the various
constituents of food.
•Moulds are the major causes of spoilage of foods with
reduced water activity.
e.g dry cereals and cereal product
•Bacteria spoil foods with relatively high water activity such
as milk and products.
11. Sources of microorganisms in food
The primary sources of microorganisms in food
include:
1. Soil and water
2. Plant and plant products
3. Food utensils
4. Intestinal tract of man and animals
5. Food handlers
6. Animal hides and skins
7. Air and dust
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12. SPOILAGE OF MEAT
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• Raw meat is subject to spoilage by its own
enzymes and microbial action.
• Excessive autolysis can cause souring
• Factors involving spoilage include
– The greater gut load of animal
– The physiological condition of the animal during
slaughter as like fever, excited or fatigued.
– Rapid cooling
14. SPOILAGE OF FISH
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•Spoiled by autolysis, oxidation or bacterial
activity.
•Under aerobic conditions Change in colour
of meat pigments
• Red colour, green , brown or grey.
• Off odours and Off tastes
16. SPOILAGE OF EGGS
•Cracks, leaks, stained or dirty spots on exterior
and blood clots, bloodiness, translucent spots
in the interior are all signs of spoilage
•Pseudomonas, certain coliform bacteria. Proteus spp,
Aeromonas, Serratia, Sporotrichum all cause rots in eggs.
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18. Vegetables
•Vegetables are a good substrate for yeasts, moulds or
bacteria
•It is estimated that 20% of all harvested fruits and
vegetables for humans are lost to spoilage by these
microorganisms.
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19. Soft rot
a. One of the most common types of bacterial spoilage.
b. caused by Erwinia carotovora
• Softening can also be caused by endogenous enzymes
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20. Mould spoilage
a.In vegetables where bacterial growth is not favored ,
moulds are the principal spoilage agents.
b.Most moulds must invade plant tissue through a
surface wound such as a bruise or crack.
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21. Fruits
•Like vegetables, fruits are nutrient rich substrates but the pH of
fruits does not favor bacterial growth. As a result, yeasts and
moulds are more important than bacteria in the spoilage of
fruits.
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22.
23. Fermented products
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Beer
•Spoilage in packaged beer is often due to
growth of the yeast Saccharomyces
diastaticus, which grows on dextrins that
brewers yeast cannot utilize.
•In either case, spoilage by yeasts results in
the development of turbidity, off flavors and
odors.
25. Wines
•Candida valida is the most important spoilage yeast in
wine
This reduces the acidity of the wine and adversely
affect wine flavor.
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26. SPOILAGE CAN LEAD TO…
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Food Poisoning
•When someone gets sick from eating food or
drink that has gone bad or is contaminated.
•There are two kinds of food poisoning:
poisoning by toxic agent or by communicable
agent.
27. FOOD PRESERVATION
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•Food preservation is the process of treating and
handling food ,with an aim to stop or slow down its
spoilage while maintaining its nutritional value, texture,
and flavour.
•Food preservation methods either kill microbes or
prevent their growth.
28. How to reduce food spoilage
• Remove expired or spoiled food
• Store food in the right parts of your
refrigerator
• Prevent mould growth in the refrigerator
• Keep some foods separate to prevent
spoilage
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