The document discusses various types of microbial spoilage in fruits, vegetables, cereals, milk, meat, fish, and eggs, detailing the organisms responsible and the conditions leading to spoilage. It highlights the impact of microbial action, physical damage, and environmental conditions on food deterioration, as well as the potential health risks associated with spoiled food. Additionally, it emphasizes food preservation methods aimed at preventing spoilage and maintaining food quality.

1. R. Nisha
Department of Microbiology
Sacred Heart College (Autonomous)
Tirupattur.

2. WHAT IS THE DIFFERENCE?

3. SPOILAGE OF FRUITS AND
VEGETABLES
• The organism responsible for taints are acid tolerant
bacteria:
– Lactobacillus spp.
• Deterioration can be caused by action of animals, birds,
bruising, wounding, cutting, freezing, dessication or
other mishandling and growth of microorganisms;
environmental conditions, contact with spoiled foods.
• Microbial spoilage maybe due to:
– Plant pathogens acting on stems, leaves, flowers or roots
– Saprophytic organisms

4. • Types of spoilages:
– Baterial soft rot
• Caused by Erwinia carotovora, ferment pectins
• Pseudomonas marginalis, Bacillus and
Clostridium cause water soaked appearance, a
soft, mushy consistency and bad odour.
– Anthracnose
• Caused by Collectotrichum lindemuthianum.
• Spotting of leaves and fruits
– Black mold rot
• Caused by Aspergillus niger
• Dark brown to black masses of spores of the
mold termed as smut

5. • Rhizopus soft rot
– Caused by species of Rhizopus
– Soft and mushy rot
– Cottony growth of mold forms black spots of
sporangia covering the foods.
• Alternaria rot
– Caused by Alternaria tenuis
– Greenish-brown to brown black spots
• Fungal spoilage results in water soaked mushy
areas, brown or cream coloured areas. Rots of
juicy fruits result in leakage.

6. SPOILAGE OF CEREALS
• Moisture content above 12 to 13 percent may cause
spoilage of cereals
• Little moisture cause mold growth and high moisture
may cause growth of yeasts and bacteria.
• Microbial content, physical damage and temperature
are also some factors.
• Aspergillus, Penicillium, Mucor, Rhizopus, Fusarium are
some common molds; produce mycotoxins.
• Acetobacter spp, lactics and Coliforms, Micrococci and
Bacillus are some species causing spoilage.

7. • Cause flour dough to develop an odour of
acetic acid and esters
• Ropiness of bread is common in home baked
bread
– Caused by Bacillus subtilis, B. licheniformis and
other species
– Due to the capsulation of Bacillus ropiness occurs.
– First odour is evident, then discolouration and
finally softening of the crumb with stickiness and
stringiness.
• Red bread is caused by the pigmented growth
of Serratia marcescens. Molds such as
Neurospora sitophila and Geotrichum
aurantiacum can also cause red colouration.

8. SPOILAGE OF MILK
• An excellent medium
• Souring
– caused by Streptococcus lactis, Enterococci,
Lactobacilli, Micrococci
• Gas production
– caused by Coliform, Clostridium, Yeasts, Bacillus
• Proteolysis
– cause bitter taste, caused by Bacillus, Micrococcus,
Proteus, Pseudomonas, Flavobacterium, Serratia.
• Changes in colour and tastes

9. SPOILAGE OF MEAT
• 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

10. SPOILAGE OF FISH
• Spoiled by autolysis, oxidation or bacterial
activity.
• Under aerobic conditions
– Surface slime
• Caused by Pseudomonas, Moraxella, Alcaligens,
Lactobacillus, Streptococcus,
Leuconostoc,Bacillus,Micrococci.
– Change in colour of meat pigments
• Red colour, green,brown or grey

11. –Change in fats
• Rancidity
• Lipolysis
• Oxidation of fats
–Phosphorescence
• Photobactererium spp growing on meat
―Surface colours due to pigmentation
• Red spot caused by Serratia marcescens
• Chromobacterium gives a greenish blue colour
• Pseudomonas gives a bluish colour

12. • Micrococcus or Flavobacterium gives a yellowish
colour.
• Pencillium may cause greenish colour.
• Cladosporium may cause black colour
—Off odours and Off tastes
• Taints, Souring, stale flavour can be caused as a
result of bacterial and fungal growth.

13. 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, Acinetobacter, Alcaligens,
certain coliform bacteria. Proteus spp,
Aeromonas, Serratia, Sporotrichum all cause
rots in eggs

14. SPOILAGE CAN LEAD TO…
• 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.

15. HOW CAN WE PREVENT?
• FOOD PRESERVATION
• What is food preservation?
• 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.

16. Some methods are:
1. Boiling
2. Dehydration
3. Refrigeration & freezing
4. Canning
5. Using chemical preservatives
6. Using Salt, sugar, oil, or vinegar
7. Pasteurization

17. “Better pay the chef than the doctor!”