Drying and Storage Engineering

Lesson 23. Causes of spoilage in storage

23.2 Heat

Causes

• Unsuitable storage structures (false location, insufficient shade and ventilation facilities, lack of heat insulation)

• Mass reproduction of storage pests and fungi

• Lack of aeration of store

• High moisture content of the grain

 Effects

• Losses in weight

• Losses in quality (nutritional value, germination power)

• Good conditions for pest development

• Condensation with subsequent development of fungi

Countermeasures

• Build suitable storage structures

• Provide shade for stores or silos (e.g. by means of wide eaves or shading trees)

• Keep temperatures as low as possible (aerate storage facility)

• Conduct treatments for pest control

• Store bags on pallets in order to improve aeration

• Maintain spaces of 1 m around all bag stacks

23.3 Moisture

Causes

• insufficient drying before storage

• High relative humidity

• Constructional faults and damage to the store (unsuitable materials, unsealed floor, walls and roof, holes, gaps, etc.)

• imbalances in temperature (e.g. day/night) in storage facility with subsequent condensation

• Produce stored on the floor or touching the walls

• Mass reproduction of pests

Effects

• Losses in quality

• Losses in weight

• Development of fungi and formation of mycotoxins

• improved conditions for the development of pests

• Swelling and germination of seeds

• Damage to storage structures

Countermeasures

• Dry produce sufficiently before storage

• Repair and seal storage facility

• Keep relative humidity as low as possible in storage facility (perform controlled ventilation)

• Store bags on pallets

• Maintain spaces of 1 m around all bag stacks

• Conduct pest control treatments

• Avoid temperature fluctuations (day/night) in store by means of shade and ventilation

23.4 Insect Pests

Causes of infestation

• introduction of infested lots
• Cross infestation from neighboring lots or stores
• Migration from waste or rubbish
• Hiding places in stores (cracks, fissures)
• Use of infested bags

Effects

• Losses in weight

• Losses in quality (impurities such as droppings, cocoons and parts of insects, reduction of nutritional value, reduction in germination power)

• increase of temperature and moisture

Countermeasures

• Harvest at the right time

• Choose tolerant varieties

• Keep means of transportation clean

• Remove infested cobs, panicles or pods before storage

• Ensure that produce is dry before storing

• Prevent pest introduction by checking for infestation before storing

• Clean the store daily

• Keep the temperature and relative humidity as low as possible (perform controlled ventilation)

• Prevent any pest infiltration by sealing the store (windows, doors, ventilation facilities; e.g. with the use of insect gauze)

• Repair any damage to the store immediately

• Store old and new lots separately

• Clean empty bags thoroughly and treat them against insects if necessary

• Perform pest control treatments

• Rotate stocks: 'first in first out'

23.5 Microorganisms

Causes of infestation

• High moisture content of stored produce

• High relative humidity in store

• Condensation

• Humidity and moisture produced by insects

Effects

• Loss of quality (smell, taste, colour, nutritional value, germination power)

• Formation of mycotoxins

• Slight loss of weight (mould)

• Further increase in temperature and moisture

• Further condensation

Countermeasures

• Dry produce sufficiently before storage

• Keep relative humidity as low as possible in storage facility (perform controlled ventilation)

• Store bags on pallets

• Maintain spaces of 1 m around all stacks

• Conduct pest control treatments

23.6 Rodents

Causes of infestation

• Penetration through badly closing doors, windows, ventilation openings, holes

• Lack of barriers

• Lack of hygiene in store and surrounding area (possible hiding and breeding places)

 Effects

• Loss of weight

• High losses in quality due to contamination of produce with faeces and urine

• Contamination of produce with pathogenic agents (typhoid, rabies, hepatitis, plague, etc.)

• Damage of material and facilities (bags, doors, electric cables)

Countermeasures

• Prevent entry of rodents by sealing store rat-proof

• Keep store and surrounding area clean

• Place traps

• Carry out rodent control measures

23.7 Birds

Causes of infestation

• Open or broken doors, windows, ventilation openings or roofs

Effects

• Losses in weight

• Damage to bags

• Contamination of stored produce with droppings and pathogenic agents

Countermeasures

• Bird-proof stores (carry out repair work, fit grilles or nets)

• Remove any nests of granivore birds from the store and surrounding area

23.8   References

1. A Text Book of Unit Operations Agricultural Processing by K.M Sahay and K.K.Singh.

2. FAO Corporate document Repository Produced by Agriculture and consumer Protection.

3. Sinha, R.N &Muir. Grain Storage: Part of a System. Avi Publisher.