Storage of Grains

Grains (rice, wheat, maize, and pulses) are staple foods that feed billions of people around the planet. When these grains are harvested, that is far from the end of the story. Grains are highly susceptible to pests, moisture, fungi, and spoilage when stored improperly. These threats can wipe out a farmer’s hard work and a nation’s food security. The storage of grains is, therefore, not just a logistical concern but a critical aspect of agricultural sustainability and economic stability.

Storage options have moved dramatically from traditional systems of mud bins or jute sacks for grain storage to bulk grain storage using huge silos. Storage systems have changed with times, technologies and demands for grains. Modern and inventive forms of storage today, like hermetic storage of grains and the cold storage of grains, allow for safer and longer-lasting grain preservation, especially for high-value or perishable crops. The importance of storage of grains, ranging from a small farm to a national grain reserve, lies in ensuring that food can stay edible, nutritious, and available to eat at any time of the year.

1.0Importance of Storage of Grains

Proper storage of food is one of the most important aspects of keeping food quality, reducing waste, and making food available for the times we may need it. Here are some reasons why food storage matters: 

• Prevents Wastage: Proper storage decreases spoilage through pests, humidity, and microbes, preventing loss of both food and finance.
• Cost-Effective: Proper storage costs less than the costs associated with food spoilage or shortages.
• Supports Food Security: In India, the Food Corporation of India (FCI) purchases grain and stores it in the large warehouses to meet the needs of a growing population. 
• Extends Shelf Life: The longer you keep them fresh and preserve the nutritional value, especially with perishable items such as meat and dairy that need refrigeration.
• Ensures Year-Round Supply: Storage allows seasonal crops to be distributed evenly throughout the year, stabilising supply and prices.
• Essential in Emergencies: Stored food acts as a safety net during natural disasters, famines, or supply chain disruptions.

2.0Types of Storage of Grains

Traditional Storage of Grains

Across rural India, the traditional storage of grains is still very much practised, especially by small farmers. These structures, simple in design, testify to the older and extremely capable knowledge of the region's climate and availability of materials.

• Bukhari
  A Bukhari is a cylindrical grain store made from mud or mud coupled with bamboo. It is raised on wooden or masonry plinths so that it may prevent mud and pest attacks to some degree. Bukharis are thus commonly used for paddy, wheat, maize, Bengal gram, and sorghum. The capacity of Bukharis varies from 3.5 to 18 tonnes, while smaller sizes are also made very commonly.
• Morai
  Southern and eastern India accommodates Malay structures that hold the shape of inverted cones raised over wooden or brick pillars. They keep grains such as maize, sorghum, and paddy, with capacities similar to that of Bukharis.
• Mud Kothi
  Mud Kothis stand rectangular and are clay bins found across rural households. They can store grains and seeds, with a capacity ranging from 1 to 50 tonnes.
• Kothar
  Kothar is a wooden box-like structure that is placed on wooden pillars and is further roofed using thatch or tiles to protect the grains from rain and sun. Having a 9 to 35-tonne capacity, it is well-suited for the bulk storage of grains such as wheat, maise, and paddy.

Modern Storage of Grains

Contemporary techniques for the economic storage of grains include many new and advanced ideas, an emphasis on bulk-handling grain preservation and mechanisation of their storage systems.

Silos

Silos are tall, cylindrical structures from steel or reinforced concrete used for bulk storage of grains. Silos are employed in both government and private situations, and can be described as:

• Shallow bins: Plane of rupture meets the surface before the opposite wall.
• Deep bins: Plane of rupture strikes the opposite wall first—e.g., vertical silos.

Key technical terms:

• Angle of Repose: The natural slope angle formed by piled grains, indicating flowability.
• Plane of Rupture: Surface where stored grain pressure causes sliding within the bin.

Cold Storage of Grains
Cold storage is used for temperature-sensitive grains such as pulses and seeds. Maintaining a lower temperature (2–15°C) restricts microbial activity to extend the period of viability.

Warehouses/Sheds
Large-scale sheds or warehouses, often constructed from steel and concrete, are utilised by agencies such as the FCI. These structures are cost-effective and facilitate hermetic storage of grains with protection from rodents, birds, and moisture. Advanced facilities also feature drag-chain conveyors for efficient handling of grains.

3.0Key Factors Influencing the Storage of Grains

Even when postharvest handling is implemented effectively, approximately 10% of unprocessed dry food grains are damaged or lost each year, which is a significant concern in a country that prioritises food security. Grains deteriorate due to both biological (biotic) and environmental (abiotic) factors, and understanding how to control these factors is crucial for managing grain deterioration.    

Biological Threats to Grain Storage

Living organisms pose the most direct threat to stored grains:

• Insects and Pests: Over 100 species of insects, including the rice moth, the Indian meal moth, the flour beetle, etc., attack stored grains (wheat, rice, barley, maize, pulses), reducing both weight and quality.
• Rodents and Weeds: Rodents destroy grain stock rapidly and contaminate storage areas, while weed residues may harbour harmful insects.
• Fungal Contamination: Moulds, such as Aspergillus and Penicillium, not only contribute to grain deterioration but can produce mycotoxins, which render food unsafe for human or animal consumption. Furthermore, mycotoxins are not only relatively heat resistant, but cannot be purged.

Environmental Factors Affecting Grain Quality

Non-living, or abiotic, elements also impact grain condition:

• Temperature Fluctuations: Elevated temperatures can cause grains to "sweat," encouraging fungal growth. Improper storage temperatures accelerate spoilage.
• Humidity and Airflow: Moist conditions encourage mould and pest activity. Maintaining proper aeration prevents heat buildup and condensation inside storage structures.

Tip: Use natural airflow or mechanical ventilation to stabilise temperature and prevent moisture accumulation.

The Moisture Factor

Moisture is a major culprit in grain damage. Wet grains are prone to:

• Fungal infections
• Discoloration
• Nutrient loss

Modern electronic moisture meters help monitor and maintain optimal moisture levels before and during storage.

4.0Types of Grain Storage Damage

Direct Damage
Loss of nutrients, hollow kernels, an unpleasant odour, spoilage, and, ultimately, loss, caused by insect(s) feeding on the grain.

Indirect Damage
Loss of grain due to human consumption of infested or contaminated grain. This loss can lead to foodborne illness, parasitic infection, and other health issues in humans.