Journal of Agricultural Science and Technology B 6 (2016) 67-71
doi: 10.17265/2161-6264/2016.02.001
D DAVID PUBLISHING
Cereal Storage Techniques: A Review
Hatice Pekmez
Naci Topçuoğlu Vocational School, University of Gaziantep, Gaziantep 27000, Turkey
Abstract: Cereal grains are stored to preserve the product from storing to consuming without any quality loss. The choice of the
most suitable and economical store has great importance on storage period of cereals under consideration of climate conditions, types
of grain and transportation facility. The aim of present study was to give information about different cereal storage methods and
discuss the most preferable technique for stock keepers. There are five main storage methods for the cereals, i.e., bulk storage,
storage in underground pit, storage in bags, storage in sheds and storage in silos. Each has many advantages and disadvantages.
Grains are usually preserved as bulk stack in horizontal stores. Nowadays, the storage underground is not preferred in cereal industry.
For long-term storage period, cereals are unfavorable when stored as bulk in bags. Location, moisture content and sufficient
ventilation are important factors for cereals stored in sheds. The most preferred storage technique in plants is to keep the products in
silos. Steel and galvanized silos are the most common ones when compared with the others. In recent years, convention of storage
techniques for grains has been advanced with the innovations, such as aeration, refrigerated storage, modified atmospheric storage
and hermetic storage systems.
Key words: Storage of cereals, bulk, underground, bag, shed, silo.
1. Introduction is to protect the quality of grains, prevent grain losses
and conserve the product in a proper way [2].
Cereal grains, such as wheat, corn, rye, oat, rice,
Post-harvest loss caused by climatic region, country,
etc., are important nutritional and energy sources for
crop, infrastructure and methods of storage is a major
humans. They must be stored, transported and
problem for cereal safety. Safe grain harvest and
conveyed using methods that preserve their quality.
storage play a crucial role to prevent losses caused
Storage varies with the length of time ranging from
mainly by weevils, beetles, moths and rodents [5].
short-term storage on farm for drying to long-term
Before storage of cereals, there are many protectional
storage for strategic reserves. That is, storage can
points from damages, such as harvesting of crops on
occur on farm or at large commercial facilities [1].
time, drying of crops on farm without waiting, setting
Loss in stored grains is nearly 20% of the whole
of new and old crops separately, cleaning of crops
production due to population increase globally, a huge
from foreign materials, careful selection of storage site,
demand for the cereals and improper storage
storage structure and suitable fumigation of empty
conditions [2, 3].
store.
Microbial, pest, enzymatic activities, mechanical
During storage period, proper aeration of grains,
effects, foreign matter damages and heat problems,
regular inspection of grain stock, cleaning and
which result in quality loss in grains during storage,
fumigation of stored grains need to be performed,
can be prevented by right storage methods using
because these requirements have great importance on
proper machine and equipment [4]. Up to today, many
the safe and scientific storage [5]. The store chosen
storage methods have been used for ages. However
appropriately must satisfy the grain to be kept dry,
traditional or modern method, the aim of storing grain
kept at a uniform temperature and protected from
insect, rodents and birds [6]. There are many
Corresponding author: Hatice Pekmez, assistant professor,
research fields: cereal technology, starch properties, ozonation, researches and applications for storage of cereals.
and drying technology.
68 Cereal Storage Techniques: A Review
Nowadays, new technology development in this area bulk storage, sealing and aeration play an important
has been providing easier control of store, more role. Aeration may be ambient or refrigerated on base
effectiveness for stored grains and more stable of the requirement. Thus, improved storage structures
conditions during storage period. The present article is and scientific storage of grains in form of warehouses
the review of the different cereal storage techniques are the need of the hour to strengthen traditional
and structures, the newly developed methods, their means of storage with modern inputs and to provide
advantages and disadvantages during storage period cheaper storage facility to farmers as well as to
and discussion about preferable types by stock prevent enormous storage losses [5].
keepers. As traditional or modern, there are five main
storage methods for the cereals, i.e., bulk storage,
2. Main Storage Techniques
storage in underground pit, storage in sack, storage in
The grain production has increased all over the warehouse and storage in silo. Each has many
world over last decades, as the grain is the essential advantages and disadvantages during storage period of
consumer goods for human and modulating economy. grains.
That is, grain production is the key part of the
2.1 Bulk Storage
economic and social development. A grain stored
properly must be equivalent to a grain produced. Grains can be stored and preserved as bulk in both
During storage, significantly qualitative and vertical and horizontal warehouses [7]. In this method,
quantitative losses occur due to several factors, such the surface of bulk stack cereals (wheat, barley, rye,
as environmental factors (temperature, moisture oat, corn, chickpea and lentil) is levelled properly. It is
content of grains, pH, humidity, etc), type of storage possible to store more grain on unit area. It also
structure used, length and purpose of storage, method facilitates the control of grain samples easily, has less
of storing grains, and biological factors (insects, pests, labor cost and provides the time-saving.
microorganisms and rodents). Nowadays, the grains
2.2 Storage Underground
are stored using the improved methods, such as in
bags, silos, sheds, containers and even in piles on the Underground pits are claimed to keep grain without
ground managed as man-made ecosystems [3]. damage for many years. The pits keep grain cool, and
Traditionally, there are two approaches employed some of them are relatively airtight. Grain on top and
for grain storage: temporary storage and long-term around the sides can however often be mouldy [8]. In
storage methods [5]. this method, hay, stalk, polyethylene, apron, etc., are
Under temporary storage, aerial storage, storage on placed both under and also on the cereal before
the ground or on drying floors and open timber covering with soil. This technique provides the grain
platforms which is normally done at farm level, are not to contact with air, i.e., oxygen (O2) during storage
followed, whereas under long term storage methods, period. However, the weather conditions and the
storage baskets (cribs) made exclusively of plant position of ground should be considered carefully not
materials, calabashes, gourds, earthenware pots, jars, to be exposed to any damage on cereals. Nowadays,
solid wall bins, and underground storage can be the storage underground is not preferred in the cereal
employed [5]. industry.
Modernly, warehouses are scientific storage
2.3 Storage in Bag
structures especially constructed for the protection of
the quantity and quality of stored products. Under For long-term storage period, some types of cereals
Cereal Storage Techniques: A Review 69
(rice, flour, legume, etc.) are unfavorable for bulk cost and less time for storage. Steel silos (Fig. 1) [10]
storage, so they are put into bags (sacks) for keeping and galvanized silos are the most common used stores,
quality. The moisture content of cereal is the critical because they are more resistant and easier controlled
factor on this technique. If the moisture content in when compared with the others. Wheat, barley, rye,
cereal is increased, the number of sacks in cereal stock oat, etc., could be stored conveniently both in concrete
is decreased. In this method, it is easy to number the and steel silos.
sacks and to take sample from each sack, but it is
3. Advanced Storage Methods
difficult to control the products as they are in bags.
Besides, less amount of cereals are stored on unit area Storage technologies for grains have been advanced
when compared to the bulk storage technique. This with innovations on the main systems, such as
method is also more expensive due to high labor cost aeration, refrigerated storage, modified atmospheric
and more time-consuming causing to easier rodent storage, hermetic storage systems in many developed
damages. countries [3].
2.4 Storage in Warehouse (Shed) 3.1 Grain Aeration
Sheds are commonly used by bulk handling The most common non-chemical alternative for
companies, but require careful site preparation, labour storage of cereals is the use of aeration systems during
for handling large tarp covers and machinery to move the winter [11]. Aeration is supplied by the forced
grain on and off the grain stack. Effective treatment of movement of ambient air of suitable quality, or
insect infestation is difficult in sheds and bunkers. For suitably conditioned air, through a grain bulk for
on-farm storage, grain in bags may be a more suitable improvement of grain storage. It is an acceptable
short-term alternative [9]. For the storage in practice to reduce the commodity temperature and is
warehouse, the determination of location, control of achieved by using mechanical aeration by means of
moisture content and supplement of sufficient aeration fans. This system is suitable especially for low humid
of cereals are important factors. The cereal and cereal environment. On commercial scale, forced aeration
products could be stored as bulk stack and also in plays important and effective role to preserve grains [3].
sacks in this technique. The damage from insects is
the most common problem in warehouses.
2.5 Storage in Silo
The most preferred storage technique in plants is to
store the grain in silos. It has many advantages due to
less labour cost and less time-consuming depending
on easy discharge and conveying of cereals and
keeping hygienic conditions during these processes.
As the silos are vertical, more products are stored on
the unit area. There are three types of silos made of
wood, concrete and steel. Wood silos are not suitable
for preservation, as they are susceptible to fire and
favorable for the insect surviving. Concrete silos are
ideal to store cereals, as they are required less labor Fig. 1 Inside of steel silo [10].
70 Cereal Storage Techniques: A Review
In the study of silo automation control system with insects and other aerobic organisms in the grain or the
fuzzy logic controller, the grain can be stored at grain itself to generate the modified atmosphere by
appropriate temperature and humidity [12]. reducing O2 and increasing CO2 concentrations
through respiratory metabolism. Respiration activity
3.2 Refrigerated Storage
of the living organisms creates an atmosphere
The main objective of refrigerated aeration in the containing about 1%-2% O2 and about 20% CO2.
summer time is to achieve temperatures of less than Insect control success due to the hermetic storage
18 °C to reduce insect activity [11]. In this method, treatment is comparable to conventional fumigants
ambient air is cooled and then passed over the bulk (over 99.9% kill), and losses due to insect activity are
grains via existing aeration system. The initial minimal. Low O2 and high CO2 environment kills
investment for refrigerated storage system is insect and mite pests, and prevents aerobic fungi from
comparatively higher, but together with the growing [3].
dehumidified air method, it could provide answers to
4. Conclusions
the practicability of aeration for safe commercial
storage in tropical climates [3]. In this way, cold The choice of the most suitable and economical
centered silo design has been studied [13]. storage method has great importance on storage period
of cereals to prevent deterioration caused by physical,
3.3 Modified Atmosphere Technology
chemical and biological factors. In cereal industry,
In warm climates, for cereal grain stored in bags or among the main storage methods (bulk storage,
in bulk, a new gaseous application technology, storage underground, storage in bags, storage in
modified atmospheres, has successfully replaced sheds), the most preferred storage technique is to store
fumigants [11]. Modified atmosphere (MA) and in silo, especially made from galvanized steel due to
controlled atmosphere (CA) treatments have been less labour cost, time-saving, easy discharge, storing
proved not only to control insects but also to preserve more products on unit area, conveying of cereals
the quality of the commodity with no residues after under hygienic conditions during the processes and
treatment. They offer alternative to the use of also easy transportation. When the silos are advanced
conventional residue producing chemical fumigants with temperature, humidity, pressure control and
for controlling insect pests attacking stored grain, aeration systems to maintain the constant conditions,
oilseeds, processed commodities and some packaged the effectiveness and period of traditional grain
foods [3, 14]. An integrated pest management (IPM) storage would increase amazingly and result in
control program could be integrated for insect demanding by stock keepers.
monitoring, aeration in winter, chilling with
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