Factors affecting the quality of cereal grains and their management

Factors affecting the quality of cereal grains and their management

Storage of cereals:

Many developing countries are facing post-harvest losses in the storage of different types of cereal grains. Damage and loss can vary among crop variety, the system of harvesting, processing, climate, insects, pests and handing, etc. Mainly quality loss of cereal grains occurs during storage. The prime objective of grain storage is to maintain its quality for a long period and to cope against conditions like starvation and crop failure. Moreover to prevent it from deterioration and other hazards including some biotic and abiotic factors. So appropriate management is required by monitoring all the factors affecting the quality of grains for their safe storage.

Grain Storage Principles:

High moisture and high temperature are responsible for deteriorating the quality of stored grains. These can alter further quality characteristics i.e. malting and baking quality and decline in germination as well. Insects and molds destroy the quality by feeding and laying eggs on grains. High moisture and temperature result in the development of insects and molds. The temperature should be maintained below 10°C to protect from both insects and molds. Moreover use fungicides and insecticides as well.  

Factors:

Once the grains are stored in containers, silos, bins, underground pits, etc. There is a high need to maintain the quality of grains. So proper management is required to maintain the quality of grains means better practices better would be the final yield. These four factors deteriorate the grain storability moisture content, temperature, initial condition of grains and insects, and mold growth/attack. All of these factors are somehow interrelated.

 Abiotic factors

·      Moisture Content:

Grains are a naturally low moisture commodity. So if the moisture is too high then the management practices or best aeration equipment will not protect it from spoiling. Moreover microorganisms including molds, fungi require moisture to grow so it is necessary to prevent moisture content from entering the storage area to protect the quality and increase the shelf life of grains. Moisture contents may vary depending upon the variety of cereals. Maintain the grain at a safe moisture level. Sitting time and ventilation system in the storage area are also important. Condensation of moisture is also a big problem as it will increase the moisture in the layers of grains that are stored at the edge wall of the store. In excessive humid conditions fungi Aspergillus spp will produce aflatoxins which deteriorate the grains making them unfit for human consumption. So storage grains should be alive so they will give off moisture and heat by respiration.   

·      Grain Temperature:

Temperature maintenance is crucial in the case of grains as the temperature is affected by many factors including the sun, outside air, radiations, heat generated both by grains and insects during respiration. Storing grains for both shorter and longer periods it is necessary to control the temperature by passing air through grains. So aeration is needed to lower the temperature and avoid mold growth. Vapor diffusion occurs in grains as the moisture moves from hot toward cold in the storage area. So if the grain is not properly cooled then moisture will enter and spoil the grain quality. Hence keep the grains at the proper temperature or concerning with the outside temperature.

·      Initial Condition of grains:

During storage quality of grain is not improved can only be maintained. So initially it’s important to assure that we are storing high-quality grains. Properly clean the storage area for the new lot. Firstly minimize the grain damage during pre-handling operations including harvesting and threshing to get better quality of final yield. So, the initial condition is also important in affecting the quality of grains.  

 Biotic factors

Cereal grains are also affected by biotic factors including some microorganisms (bacteria, fungi, yeast, and mold) insects and rodents, etc.  

·      Insects:

Insects cause post-harvest losses by damaging the grains. Some insects are beneficial as they attack other insects and pests while others are harmful i.e. Weevils (Rice weevil and maize weevil). Defected grains can be detected by the residues of insects. Insect infestation can further lead to mold problems as they have increased the moisture level in grains. They also cause quality losses through their excreta. Insects would not be problematic if grains are at safe moisture, low temperature, and in proper storage conditions. Use insecticides and other fumigants to get rid of this problem.

·      Rodents:

Different species including house mice, brown rats, and black rats are responsible for spoilage. They damage grains more by their droppings rather than by consuming. Control them by preventing their entry to storage areas. Biological control is also available to control rat damages. Trapping is mostly used to kill the rat.

·      Birds:

Like rodents birds also consume and contaminate the grains which result in quality losses of grains making them unfit for human consumption. Thus it’s important to prevent their access to the storage areas.

 Management Practices:

·      Moisture:

If grains have high moisture then they cannot be stored for a long period. Moisture moves inside the container or silo and develops mold growth. Proper aeration can help slow down the deterioration process in high grain moisture. If grains have more moisture than the set limit then dry them for long-term storage. However, operate the drying process by following all the specifications to avoid any misshaping (Hysteresis). Grains also lose their weight after moisture reduction.

·      Temperature:

Temperature maintenance is also necessary as aeration will reduce the temperature by cooling down the grains thus minimizing the deterioration in the quality of grains. Moreover, it will maintain the temperature difference which will ultimately stop the moisture migration.

·      Insects and chemical residues:

Using insecticides and fungicides sprays to control them. Use phosphine as it will leave minimal residues. Use Dischlorvos to treat infested grains. Good hygiene practices are an essential component while storing grains. This will ultimately increase the shelf life of grains.  

·      Inspection and Monitoring:

Stored grains should be inspected after time intervals. Visit the storage area frequently to inspect the insect or mold activity. This can be done by operating an aeration system for grains. If there is some insect activity is detected then fumigate it as soon as possible. Monitor grain regularly to keep the grains at optimum moisture and temperature conditions. If any problem is detected then correct it to avoid further deterioration in grains. Use the well-designed and proper storage system for the grains.