Food spoilage is caused by changes in texture, smell, taste or appearance that make food undesirable for human consumption. The two most influential factors for stored grain spoilage are moisture and temperature. High moisture levels above 12% promote fungal and bacterial growth, while temperatures between 15-35°C allow insects to develop. Direct spoilage damages food through biological consumption, chemical reactions, or microbiological growth, while indirect damages result from inadequate storage facilities, transportation, or processing systems. Various control measures can be implemented including maintaining proper hygiene, stacking, disinfestation, and use of ecological, physical, or chemical techniques.

1. BY
ABARNA.A
2016015001
SPOILAGE MECHANISMS – DIRECT AND INDIRECT DAMAGES OF PERISHABLE AND
DURABLE COMMODITIES AND SPOILAGE CONTROL MEASURES IN STORAGE

2. FOOD SPOILAGE
 Food spoilage is a metabolic process that causes foods to be
undesirable or unacceptable for human consumption due to
changes in sensory characteristics.
 Spoiled foods may be safe to eat, i.e. they may not cause illness
because there are no pathogens or a toxin present, but changes in
texture, smell, taste, or appearance cause them to be rejected.

3. Spoilage mechanisms

4. The effect of temperature
and moisture on stored grains
 The most influential factors in the storage of grains is moisture and
temperature.
 Grains containing less than 12% moisture and pulses with less than
10% moisture can be stored for food purposes indefinitely.

5.  High moisture content in grain of over 12% causes damage to
the seeds because it promotes diseases.
 At 13 to 15% moisture levels some fungal spores begin to grow,
other species of fungi require 16 – 23%.
 Aerobic bacteria require 20% to grow.

6. Temperature
 In considering temperature for safe grain storage system the
following important points are to be kept in mind.
1)Mites do not develop below 5°C nor insect below 15 °C.
2)Most of storage fungi do not develop below 0 °C.
3)The effect of temperature on an organism can be
correlated with amount of grain moisture.

7. Chemical reactions
 Chemical reactions take place in the presence of atmospheric oxygen
and sunlight.
 Two major chemical changes, which occur during the processing
and storage of fruits and vegetables, are lipid oxidation and non-
enzymatic browning which deteriorate sensory quality, colour and
flavour .
 Lipid oxidation is influenced by light, oxygen, high temperature and
the presence of iron and copper, and water activity.
 Control of these factors can significantly reduce the extent of lipid
oxidation or rancidity in foods.

8.  Non-enzymatic browning is one of the major causes of
deterioration which takes place during frying, cooking, storage
of dried and concentrated foods through Maillard, caramelization
and ascorbic acid oxidation.

9. Food spoilage microorganism
 Yeast
 Molds
 Bacteria

10. Yeast
 Yeasts are a subset of a large group of organisms called fungi
that also includes molds and mushrooms.
 They are generally single-celled organisms.
 They often colonize foods with a high sugar or salt content and
contribute to spoilage of maple syrup, pickles.
 Fruits and juices with a low pH are another target, and there are
some yeasts that grow on the surfaces of meat and cheese.

11. Molds
 Molds are filamentous fungi that do not produce large fruiting
bodies like mushrooms.
 They are well adapted for growth on and through solid
substrates, generally produce airborne spores, and require
oxygen for their metabolic processes.
 Most molds grow at a pH range of 3 to 8 and some can grow at
very low water activity levels (0.7–0.8) on dried foods.
 Spores can tolerate harsh environmental conditions but most are
sensitive to heat treatment.

12. Spoilage due to insects, pests and
rodents
 The main categories of foods subject to insects and pest attack
are fruits, vegetables, grains and their processed products.
 Warm humid environment promote insect growth, although most
insects will not breed if the temperature exceeds above 35°C or
falls below 10°C.
 The products of insect and pests activities such as clumped-
together food particles and holes can also reduce the food value.

13. Types of damages
 Direct damages
 Indirect damages

14. Direct damages
PRIMARY CAUSES OF LOSS
Biological : Consumption of food by rodents, birds, monkeys and
other large animals causes direct disappearance of food
Chemical : Many of the chemical constituents naturally present in
stored foods spontaneously react causing lose of colour, flavour,
texture and nutritional value

15.  Biochemical reactions: A number of enzyme-activated reactions can
occur in foods in storage giving rise to off-flavours, discolouration
and softening.
 Mechanical: Bruising, cutting, excessive pooling or trimming of
horticultural products are causes of loss.
 Physical: Excessive or insufficient heat or cold can spoil foods
 Microbiological, mechanical and physiological factors cause most of
the losses in perishable crops.

16. Indirect damages
 SECONDARY CAUSES OF LOSS
They are usually the result of inadequate or non-assistant capital
expenditures, technology and quality control
 Inadequate harvesting, packaging and handling skills.
 Lack of adequate containers for the transport and handling of
perishables.
 Storage facilities inadequate to protect the food.
 Transportation inadequate to move the food to market before it spoils.

17.  Inadequate refrigerated storage.
 Inadequate drying equipment or poor drying season.
 traditional processing and marketing systems can be responsible
for high losses.
 Bumper crops can overload the post-harvest handling system or
exceed the consumption need and cause excessive wastage.

18. Examples
 Spoilage of milk and fish
gas production, change in color and tastes, change in fats
 Spoilage of canned fruits
1) chemical spoilage – discolouration of inside of the can,
loss in nutritive value
2) biological spoilage attacked by thermophilic and
mesophilic bacteria

19. Control measures in storage
 Preventive
 Curative

20. Hygiene and sanitation
 Many factors responsible for food grain losses in storage can be
minimized by maintaining hygiene and sanitation.
 Before storing ensure that food grain must be dry(8-10 %) , clean
cool , wholesome , free from obnoxious odour.
 Storage structure should neat and clean and air tight.

21. There are different sanitation measures which can be adopted:
a) Threshing floor should be clean, free from insect infestation, away
from vicinity of village.
b) Harvesting machines, threshing machines and means of transport
should be cleaned before use.
c) Cleaning of storage structures, receptacles and godowns by:-
 Removing dirt, rubbish etc.
 Closing of cracks, crevics, holes, walls etc.
 Closing of rat burrow with broken glass pieces and mud.
white washing the storage structure
d) Bags used for storage should be treated with insecticide

22. Proper stacking
 Stack bags properly on dunnage (wood/plastic) 0.5 metre away
from wall and floor in the lines keeping 0.5 metre between two
lines and 0.2 metre open space towards the roof.
 Don’t stack more than 10 bags vertically.

23. Disinfestation of storage containers,
structures and stores
 Clean and disinfest empty used gunny bags by dipping in boiled
water and drying under sun.
 Treat gunny bags by dipping in cypermethrin 0.01% or
fenvalerate 0.01% or malathion 0.1% for 10 minutes and dry.
 Treat walls and surfaces by malathion(50 EC) or
fenitrothion(50EC) using any of insecticide in one litre of water .
 Fumigate with aluminium phosphide @ 21-30 gram.

24. Curative measures
 There are different curative measures :-
1. Ecological
2. Mechanical
3. Physical
4. Cultural
5. Botanicals
6. Chemical
7. Biological
8. Engineering
9. Other methods

25. Ecological measures:
Safety of stored grain from pest depends upon:-
a) Storage temperature
b) Grain moisture content
c) Available of oxygen
a) Storage temperature:-
 Temperature range 25-35°c increase insects development
 Temperature above 40°c and below 15°c retards
reproduction and development of insects
 Temperature above 45°c and below 10°c kills the insects.

26. b) Grain moisture content:
 10% moisture content escapes grains from insects.
 12-16% moisture content increase seed deterioration.
c) Availability of oxygen:
 Reduction in oxygen level stops multiplication of insects.
 Oxygen can be reduced by adding CO2 and N2.

27. Mechanical measures:
These are diff. practicable mechanical measures:-
a) Screening:
 Screening or sieving out reduces insects attack by
removing broken and cracked grains.
 Screenings should be destroyed immediately.
 Bags used for carrying screenings should not used
again unless disinfested.

28. b) Grain protection devices:
 TNAU Insect Probe Trap
 TNAU Pitfall Trap
 Indicator Devices
 UV Light Trap for Grain Storage Godown.

29. Cultural control measures:-
a) Splitting of pulses:
Store pulses after splitting because some insects like pulse beetle
C. chinensis prefer whole grains not broken.
b) Parboiling of paddy:
Parboiled rice is least susceptible to insect attack as compared to
raw rice because of hard glutenized outer layer.

30. Chemical control measures:-
 Most popular and most effective.
 Malathion 50 EC spray over bags in ratio 1:100 @ 3 l/100 m².
 Fumigation with ethylene dichloride and carban tetrachloride @
1l for 20 quintals of grains or 30 l/ 100 m³ of space with
exposure period of 4 days.
 Aluminium phosphide @ one tablet(3 g) per metric tonnes or 25
tablets/100m³ of space with exposure period of 7 days.

31. Engineering control measures
Air-tight storage- food grains kept in air tight sealed structure
remains insect free because grains and insects respires and
release CO2.

32. Reference :
 ecoursesonline.iasri.res.in
 www.pelagiaresearchlibrary.com
 Textbook of post harvest technology of cereals, pulses
and oilseeds, A chakraverty.
 Textbook of unit operations of agricultural processing,
KM sahay,KK singh.