This document discusses food spoilage, which is the process by which food deteriorates to the point of being inedible or having reduced quality of edibility. Spoilage is caused by microbial and biochemical activities and is influenced by intrinsic factors like pH and nutrients, and extrinsic factors like temperature and humidity. Different foods like fruits, vegetables, cereals, milk, meat, fish, eggs and canned foods are subject to spoilage by various microbes under different conditions. Food preservation methods aim to stop or slow spoilage by killing microbes or preventing their growth in order to maintain food safety and nutrition.

1. By
NEETHU ASOKAN
PERIYAR UNIVERSITY

2. WHAT IS THE DIFFERENCE?

3. WHAT IS SPOILAGE?
• Spoilage is the process in which food deteriorates to
the point in which it is not edible to humans or its
quality of edibility becomes reduced OR
• Any change which renders a product unacceptable
for human consumption.
• Complex event in which a combination of microbial
and biochemical activities may interact.
• One of the major reason that led to preservation.

4. FACTORS DETERMINING THE SPOILAGE
• Microbial colonization depends on
– characteristics of product
– The way processed
– The way stored
• Factors are characterized into four:
– Intrinsic parameters
– Extrinsic parameters
– Modes of preservation and processing
– Implicit parameters

5. INTRINSIC PARAMETERS
• Physical, chemical and structural properties.
• Inherent in the food itself.
• Important factors include water activity,
acidity, redox potential, available nutrients and
natural antimicrobial substances.
EXTRINSIC PARAMETERS
• Factors in the environment where food is
stored
• Temperature, humidity and atmosphere
conditions.

6. MODES OF PRESERVATION AND PROCESSING
• Physical or chemical treatment
• Change characteristics of food product
• Determine the micro flora associated with the
product
IMPLICIT PARAMETERS OR MICROBIAL
INTERFERENCE
• These are the result of the development of
synergistic or antagonistic microbes
• It can be said as the destruction of one organism
by another species releasing H2 O2 , bacteriocin
and other di-acetyl compounds.

7. • Synergistic: Production or availability of
essential nutrients due to the growth of
certain organisms, which allow the growth of
another group which were otherwise unable
to grow.
• Antagonistic : Competition for essential
nutrients, changes in pH value or redox
potential or formation of antimicrobial
substances.

8. TYPES OF SPOILAGE
Two types of Spoilage:
• Microbial spoilage
• Non- Microbial
Based on rate of spoilage:
• Highly perishable
– Meat, fish, poultry, eggs, milk, most fruits and
vegetables.
• Semi perishable
– Potatoes, some apple varieties, nutmeats
• Stable or non-perishable
– Sugar, flour, dry beans

9. 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

10. • 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

11. • 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.

12. 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.

13. • 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.

14. 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

15. 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

16. 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

17. –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

18. • 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.

19. 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

20. SPOILAGE OF CANNED FOODS
• Chemical spoilage
– Hydrogen swell
– Discolouration of inside of the can
– Cloudiness of liquors
– Loss in nutritive value
• Biological spoilage
– Attacked by
• Thermophilic and
• Mesophilic bacteria

21. • Flat sour spoilage:
– Ends of can flatten due to souring
– Bacillus stearothermophilus
• TA spoilage:
– Thermophilic anaerobe
– Forms acid and gas
• Sulfide spoilage:
– Desulfotomaculum nigrificans
– Black colonies
• Clostridium spp:
– Putrefactive or proteolytic organisms
– Produce H2S,ammonia, indole,mercaptans
– CO2 and hydrogen cause can to swell.

22. 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.

23. 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.

24. 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

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