ArticlePDF Available
Ricardo Bartosik*
National Institute of Agricultural Technologies (INTA), Ruta 226 km 73,5 (7620), Balcarce,
Buenos Aires Province, Argentina
*Corresponding author's e-mail:
The silo-bags are a hermetic type of storage widely adopted. This paper summarizes the
results of the effect of silo-bag storage on the commercial quality of corn, soybean,
wheat, sunflower, malting barley, canola and beans. The effect of the modified
atmosphere on insect population and storage fungi, and recommendations for proper
storage conditions in the silo-bags are also presented.
Overall, when dry grain is stored in silo-bag, the CO2 ranges from 3 to 10% and the O2
from 18 to 10%. The degree of modification of the interstitial atmosphere increases with
the grain m.c. and temperature having typical CO2 concentration of 15-25% and O2 of 2-
5% for wet grain.
There are few reports of insect presence in silo-bags. Analysis of data indicates that
unfavorable environmental conditions negatively affect insect development. Thus, storage
in silo-bags under the analyzed climate conditions help to maintain grain without notable
insect populations.
When grain is stored in silo-bags at m.c. that would allow for mold development, the
mold activity is lower compared with that of normal atmosphere storage conditions.
Additionally, grain temperature inside the silo-bag is mainly affected by the ambient
temperature. Silo-bags have a high heat exchange rate with the air and soil (double
surface/volume ratio than regular bins), so no heat damage is observed, even when wet
grain is stored in temperate weathers.
The overall results indicate that dry grain (equilibrium relative humidity below 67%) can
be stored in silo-bag for more than six months without losing quality (measured as
percentage of mold damaged grain, test weight, germination, fat acidity, and nutritional
and organoleptic parameters, among others). When grain m.c. increases, commercial
quality could be maintained for up to six months in winter time, to less than three months
in summer time. In all cases, maintaining the airtightness of the bag is a key factor for
successful storage. A monitoring system for silo-bags based on measuring CO2
concentration was also developed.
Key words: hermetic storage, modified atmosphere, storage, quality, cereal, oilseeds
The silo-bags are a hermetic type of storage made with a plastic bag, with the shape of a tube,
of 60 m long and 2.74 m diameter. The plastic cover is made of three layers (white outside
and black inside) with 235 µm of thickness.
Each bag can hold approximately 200 tonnes of grain and with the available handling
equipment is very easy to fill. The new generation of high capacity combines found in the
Bartosik R (2012) An inside look at the silo-bag system. In: Navarro S, Banks HJ, Jayas DS, Bell CH, Noyes RT,
Ferizli AG, Emekci M, Isikber AA, Alagusundaram K, [Eds.] Proc 9th. Int. Conf. on Controlled Atmosphere and
Fumigation in Stored Products, Antalya, Turkey. 15 – 19 October 2012, ARBER Professional Congress Services,
Turkey pp: 117-128
silo-bag system is the ideal partner, since the loading capacity of the bagging machine is
basically limited to the transportation capacity between the combine and the place where the
bag is filled. Several companies also developed machineries to unload the plastic bag
transferring the grain directly from the silo-bag to the truck or wagon with a high capacity
(more than 180 tonnes/h).
Argentina is the country in which the silo-bag was developed for storing dry grains.
Since mid 1990’s when it was introduced, the silo-bag system gained rapid adoption in the
agricultural and industrial sector. Each year, more than 40% of the total production of the
country is stored in the silo-bags (more than 40 million tonnes in year 2011).
Due to the successful experience in Argentina, the silo-bag system is now being adopted
in more than 40 countries worldwide, from countries with tropical weather (i.e. Sudan) to
countries with cold weather (i.e., Russia).
There was an important development regarding to the bagging (loading) and unloading
equipment. The operating capacity of the loading and unloading equipment is higher than 180
tonnes/h. Fig. 1 shows a picture of a typical loading and unloading equipment.
Fig. 1- Images of loading (left) and unloading (right) machines.
Environment and Relationships
Fig. 2 shows a diagram of the main factors affecting the ecosystem of the silo-bag and the
relationship among them. Based on this model, the respiration of grains, fungi, insects and
other microorganisms present in the grain ecosystem consume the O2 and generate CO2, heat
and water. The respiration process also consumes the grain energy sources (starch, oil or
protein), which could be quantified as dry matter loss (DML).
The respiration rate is affected by grain type and condition, m.c., temperature, storage
time, and O2 and CO2 concentrations. These last two factors make a difference between the
respiration rate of grains in regular storage structures and hermetic structures.
The temperature of the grain depends on the initial grain temperature (this effect is less
important as the storage period increases), the effect of the sun radiation, the heat release from
the respiration process, and the transfer of heat with the air and soil. The grain m.c. depends
on the initial grain m.c., the entrance of moisture from the outside (through openings after a
rain event into broken or poorly sealed silo-bags), and the moisture released from the
respiration process. Additionally, due to the day and night temperature differential, some
moisture condensation can occur in the top grain layers resulting in a localized spot of wetter
For any particular time, the CO2 and O2 concentration in the silo-bag depends on the
balance between respiration (consumption of O2 and generation of CO2), the entrance of
external O2 to the system, and the loss of CO2 to the ambient air. The movement of gases in
and out of the silo-bags depends on the gas partial pressure differential and the permeability
of the system (through openings in the plastic cover, or through the natural permeability of the
plastic material to the gases).
Grain type and condition
Moisture content
Storage time
and CO
Factors affecting respiration
Moisture through
plastic perforations
Sun radiation
Dry matter
Oxygen enters
permeability or
dioxide exits
Exchange of heat with
the air and soil
Moisture condensation
and migration
Moisture condensation
and migration
Grain type and condition
Moisture content
Storage time
and CO
Factors affecting respiration
Moisture through
plastic perforations
Sun radiation
Dry matter
Oxygen enters
permeability or
dioxide exits
Exchange of heat with
the air and soil
Moisture condensation
and migration
Moisture condensation
and migration
Fig. 2- Section diagram of the silo-bag showing the main factors affecting the grain
ecosystem, the relationship among them and with the external environment.
Bartosik et al. (2008a) indicated that the grain temperature at the surface showed the
distinctive pattern of the ambient air temperature, reaching its maximum at noon and
minimum during the early morning ( 3). The daily temperature oscillation decreased with
the grain depth, being not noticeable after 0.7 m depth. It was also demonstrated that the
average grain temperature in the silo-bags followed the pattern of the average ambient
temperature through the season.
In a field experiment, silo-bags with wheat were set up during the summer time with
grain temperatures close to 40°C. The silo-bag was able to dissipate the heat in the grain to
the ambient air and the soil in a couple of months, reducing the grain temperature to less than
17°C by early May (Fig. 3). This could be explained with the relation volume/surface, which
is substantially lower for silo-bags (0.7 for a 200 tonnes silo-bag) than for a regular bin of
similar storage capacity (1.27 for a 7 m diameter and 9 m height bin of 200 tonnes capacity).
On the other hand, soybean and corn, harvested during the fall and winter, were able to
maintain the temperature below 17°C until early November. Similar results were reported by
Barreto et al. (2012) simulating the effect of ambient conditions on wheat silo-bags
temperature in different regions of Argentina.
Jan-01 Feb-01 Mar-01 Apr-01 May-01 Jun-01
Temperature ºC
Fig. 3-Temperature pattern at different grain depths (top, middle and bottom) during storage
of wheat in a silo-bag from January to June. Source: Bartosik et al. (2008).
Effect of Grain Moisture Content
Since the silo-bag is made of a hermetic plastic cover, no moisture variation should be
expected during storage, unless rainwater enters to the bag through openings. Gaston et al.
(2009) mentioned that the temperature differential between the top layer and the rest of the
bag caused migration of moisture from the core of the grain mass to the top layer, and, to a
lesser extent, to the bottom layer. Moisture migration can lead to m.c. rise in some grain
layer, increasing the risk of grain spoilage (and grain quality deterioration) in localized areas
of the silo-bag. Up to the present, it is not clear the magnitude of the moisture stratification
process during storage in the silo-bag. Gaston et al. (2009) considered that grain m.c., grain
temperature, grain temperature fluctuation magnitude and storage time affect the magnitude
of m.c. stratification.
Darby and Caddick (2007) reported moisture stratification during storage of dry barley
       -punctured silo-bags. This stratification
increased m.c. in the peripheral layer up to 13% over winter, but remained dry over summer
   ain could be stored in perfect condition
for up to 6 months. On the other hand, Ochandio et al. (2009) did not find m.c. stratification
in 12% m.c. barley silo-bags, even after 1 year of storage.
Respiration of Biological Components
Grain, insects, fungi and other microorganisms respire, consuming grain constituents and O2
from the environment, and releasing to the interstitial environment CO2, water and heat.
Grain type, m.c., temperature, storage time and O2 and CO2 concentrations affect the
respiration rate. Most of the factors influencing respiration in silo-bags could be modeled.
However, there are no correlations available for predicting respiration rate of grains stored
under hermetic conditions (oxygen depleting environments). In order to further improve the
modeling of modified and controlled atmospheres it is necessary to generate suitable
correlation for predicting respiration in O2 restricted environments.
The transfer of gases between the inside and outside of the silo-bag depends on the gas partial
pressure differential and the effective permeability of the silo-bag to gases (permeability of
the plastic layer film and perforations). While the permeability of the plastic cover could be
measured or estimated based on the characteristics of the plastic material (most of the silo-
bags are made of similar materials and have similar thickness), the permeability due to
perforations is more difficult to estimate since the size, shape, location and number of
perforations differ substantially among different silo-bags.
Plastic Cover
The permeability of the silo-bag plastic cover depends on the thickness and material
composition, both set by the manufacturing process. The silo-bag is made of a three layer
plastic of 230 to 250 µm thickness, black inside and white outside. The plastic layers are a
mixture of high density (HDPE) and low density polyethylene (LDPE). The plastic layer has a
differential permeance to O2 and CO2. For a silo-bag with an average thickness of 240 µm,
Abalone et al. (2011) estimated that the permeance to O2 was 4.06× 10-4 m3d-1m-2atm-1 and to
CO2 was of 1.34× 10-3 m3d-1 m-2 atm-1.
Perforations in the plastic cover increase the exchange rate of gases between the inside and
the outside. Simulations were performed by Abalone et al. (2011) to explore the effect of
structural damage of the silo-bag. It was shown that even a small perforation can significantly
change the evolution of gas composition, from 1 percentage point for one perforation of 1 mm
diameter per linear meter of a silo-bag, to more than 5 percentage points for one perforation of
10 mm diameter.
The effect of number of perforations on gaseous composition was also investigated.
Wheat at 13% m.c. and 25°C stored in a completely airtight silo-bag reached a CO2
concentration of 6.5% and a O2 concentration of 12%. One perforation of 3 mm diameter per
meter of silo-bag reduces the CO2 concentration to 4.5% and increases the O2 concentration to
15%, while 5 perforations per meter resulted in a decrease in the CO2 concentration to 1.5%
and an increase in the O2 concentration to 19.5% (Abalone et al., 2011).
Oxygen and Carbon Dioxide Concentration
The CO2 and O2 concentration in any given time is the result between the respiration rate
(depletion of O2 and generation of CO2) and the gas exchange rate with the outside (entrance
of O2 and exit of CO2). Gas concentration data were measured over time for different grains
and storage conditions (m.c.) ( 4). Typically, for dry grains, the O2 concentration
equilibrates between 10 and 18%, while the CO2 concentration equilibrates between 3 and
10%. For wet grains (equilibrium relative humidity higher than 67%) the O2 concentration
drops to 2 to 5%, while the CO2 rises to 15 to 25%. In some cases, with exceptionally wet
grain, the CO2 concentration can reach values as high as 70% (O2 close to 0%).
Silo-bags would act as a typical modified atmosphere system when the grain is wet
enough to hold biological activity that would consume the O2 at a higher rate than O2 is
entering to the bag from the outside through the plastic cover. Under this situation the O2
concentration will drop below the limit at which aerobic respiration starts to be limited. This
observation is in agreement with Darby and Caddick (2007) in their comprehensive report
made about silo-bags in Australia.
Fig. 4-O2 and CO2 concentration during storage of dry (a) and wet (b) grains in silo-bags.
Adapted from Bartosik et al. (2008). Legends: solid line, CO2; dashed line, O2
The temperature also has a positive effect on the biological activity, but the interaction
with m.c. shows that the effect of temperature is higher in wet grain storage than in dry grain
storage ( 5). This would imply that dry grain would not hold significantly different
biological activity in winter or summer, but storing wet grain could be substantially more
challenging (affected by biological activity) in summer than in winter time.
Fig. 5- Predicted evolution of O2 and CO2 concentrations during storage from summer
(January 1) to winter (July 30) for different initial storage temperatures of grains. Initial grain
moisture content: a) 12% w.b; b) 13% w.b; c) 14%w.b. Initial grain temperature- -
 
Effect on Quality
The storage of dry wheat (12.5% m.c.) during 6 months in a silo-bag resulted with no
substantial reduction in the test weight, neither affecting the baking quality parameters (loaf
volume, gluten %, w, etc). When 16.4% m.c. wheat was bagged in January the average grain
temperature was of 42°C. The combination of high m.c. and high temperature resulted in a
substantial decrease on most of the quality parameters evaluated. Test weight decreased from
78.7 to 77.3 kg/hl, although this decrease did not change the commercial grade of the wheat.
Additionally, all the baking quality parameters were negatively affected, making this wet
wheat not suitable for flour milling purposes.
The grain bagged at 14.8% m.c. resulted with a slightly higher test weight after 150 days of
storage, while the percentage of damaged kernels increased by 1.3 percentage points (the
initial percentage of damaged kernel was greater than 3%). The wet corn samples (19.5%
m.c.) resulted with a reduction in the test weight of 2 kg/hl, and a substantial increase of the
damaged corn faction of 4.4 percentage points.
The soybean bagged at 12.5% m.c. did not substantially modify the test weight and oil
percentage of the samples after 150 days. On the other hand, the oil acidity index and the
germination were, slightly affected. The wet soybean samples (15.6% m.c.) did not result in
effect on the test weight and the percentage of oil, but resulted with an increase in the oil
acidity index from 1.7% to 2.3%.
Malting barley stored dry (below 12% m.c.) for a storage period from 6 to 12 months did not
have negative effect on the germination (always remained above 98%). In one study including
56 silo-bags, only 2 resulted with germination test values of 94%, and one with values of
86%. The protein content typically did not change during storage, being the highest change
observed of 1 percentage point after 6 months of storage (Ochandio et al., 2009; Cardoso et
al., 2010; Massigoge et al., 2011).
When sunflower was bagged at 8.4% m.c. no reduction in oil composition was observed,
while the oil acidity index slightly increased from 0.9 to 1.4%. This increase in the oil acidity
index did not affect the commercialization standard grade of sunflower, since the oil acidity
index limit for the argentine standard is 1.5% until August 31, and 2% thereafter. Thus,
storage of dry sunflower (below 11% m.c.) is a safe practice, since the industrial quality
parameters were not affected after 150 storage days. Storing of wet sunflower (16.4%)
resulted in a reduction of oil composition of 1.3 percentage points (from 47.0 to 45.7%) after
150 storage days, and a more substantial increase in the oil acidity index (0.9 to 3.9%).
The r.h. in the interstitial air of canola remained below 50% along the entire storage period
(canola m.c. of 6%). The m.c., foreign matters and fat values remained unchanged throughout
the storage period. The fat acidity increased during storage in 0.7 % points, reaching a final
value of 1.4%, but did not represent a commercial quality loss (Ochandio et al., 2010).
When seeds are stored with low m.c. (equilibrium r.h. below 67%), no substantial reduction in
the germination was observed for wheat (Bartosik et al., 2008a) and barley (Ochandio et al.,
2009; Cardoso et al., 2010; Massigoge et al., 2010). In the case of soybean it was observed
that when the initial germination values were low, there was a substantial decrease of this
parameter during storage, even for m.c. as low as 12.5% (Bartosik et al., 2008a). Additional
data showed that when the initial germination value was high (i.e., above 95%), the soybean
seed viability did not change during storage when the m.c. was below 12.5%. However, when
the seed was stored at a m.c. higher than 12.5%, the number of samples in which a reduction
in the germination was observed increased.
Molds and Mycotoxins
In grain ecosystems, the most important abiotic conditions that influence mold growth and
mycotoxins production are aw, temperature, and gas composition. Fungal species involved in
the deterioration of stored grain are obligate aerobes, but they can grow under conditions of
reduced levels of oxygen, and some species can tolerate high levels of CO2. Additionally,
modified atmospheres also had been reported to have control effect on mycotoxin production
at both, high CO2 concentration and low O2 concentration (Chulze, 2010).
Pacin et al. (2009) reported fumonisin in corn silo-bags. The contamination levels
recorded at the closing of the silo suggest that contamination with molds and fumonisins are
more dependent on the grain conditions at the moment of entrance to the silo bags than on the
duration of storage.
Castellari et al. (2010) indentified two potential producers of aflatoxins (A. flavus and A.
parasiticus) and a potential producer of fumonisins (F. verticillioides) in corn silo-bags with
m.c. from 14 to more than 20%, although toxins levels were not tested.
Most of the mold species typically present in grains cannot develop in environments
with r.h. below 67-65%, which corresponds with an equilibrium m.c. of 14% in wheat and
corn, 12.5% in soybean and 8-9% in sunflower. Under this storage condition in the silo-bag
the mold activity is basically stopped, and hence the mycotoxin production.
When storing grain at a m.c. that would support mold growth (equilibrium r.h. higher
than 67%), the mold activity and the mycotoxin production would be affected by the
atmosphere composition. If the grain is wet, thus the microbial activity would deplete the
oxygen rather quickly (few hours), preventing mold damage and mycotoxin production.
However, if the grain is slightly wet, the modification of the interstitial atmosphere would be
rather slow, and many days (and may be months) would be required to reach the level of mold
suppression. Under this condition mycotoxin production could be possible. Additionally, if
the grain is wet (high biological activity) but the silo-bag has a low airtight level (i.e., bad
sealing of the closing end, perforations, etc), oxygen will enter from the outside allowing
mold development and mycotoxin production. The relationship among grain m.c., the effect
on biological activity, the resulting CO2 and O2 concentration and how this affect the
mycotoxin production is yet not fully understood for typical silo-bag storage conditions and
more research is needed.
Insects in the Silo-bag
There are relatively few reports of insect infestation of grain stored in silo-bag. Massigoge et
al. (2010) reported that insects were observed in 10 barley silo-bags out of 56 monitored. The
wheat milling industry, which uses silo-bag for storing dry wheat, indicates that the presence
of insects is more frequent during summer time and in silo-bags filled with grain that has been
previously stored in regular bins (not coming from the field).
Conditions that Affect Insect Development in Silo-bags
The insect development in silo-bags is limited because: 1) most of the silo-bags are filled with
grain coming directly from the field. The presence of stored grain insects in the field is rather
scarce, depending on the ambient condition of the harvest time (temperature, r.h.), proximity
to storage structures, etc, but most of the time the grain comes form the field free of insects.
Additionally, during the harvest operation the grain passes through the combine, then to a
truck or wagon and then to the bagging machine, reducing the risk of infestation when
compared to grain stored at the elevators. 2) The plastic bag itself comes free of insects, in
comparison with regular bins which could be infested prior to the harvest. 3) Once the grain is
stored in the silo-bag, the plastic cover acts as a physical barrier, preventing the entrance of
insects. 4) The temperature of the grain inside of the silo-bag follows the average ambient
temperature throughout the year. Thus, in temperate and cold climates, during the fall and
winter the grain temperature will drop below the range of insect activity (15-17°C), reducing
substantially their development. 5) When grain is stored with m.c. above the mold activity
limit, the O2 concentration can drop below the 2% and the CO2 concentration can rise above
20%, creating a lethal environment for insects.
Based on these considerations, the most critical situation that would favor insect
development (and damage) in the silo-bags is when the bag is filled with previously infested
grain, the grain is stored over summer time (grain temperature between 25 and 30°C), and the
grain is too dry to create a lethal atmosphere for insects.
Phosphine Fumigation
Phosphine fumigation in silo-bags has been successfully implemented when insect control is
required. Cardoso et al. (2009) showed that applying aluminum phosphine pellets each 5 m
along the silo-bag with a dose of 1 g of PH3 (3 g of aluminum phosphide) per tonne was
sufficient to hold 200 ppm during 5 days in the almost entire grain mass. The critical point
was the closing end, where a re-application after 3-4 days was recommended. In a similar
study using a phosphine dose of 1.5 g m-3 in wheat, Ridley et al. (2011) found that complete
control of all life stages of R. dominica was achieved at all locations in the fumigated silo
Monitoring Grain Quality (CO2 Monitoring)
The respiration of the biotic components of the grain mass (fungi, insects, and grain) increases
CO2 and reduces O2 concentrations. Thus, the degree of modification of the gas composition
in the interstitial air could be related to the biological activity inside the silo-bag, and can be
used as a monitoring tool to detect early spoilage problems (Bartosik et al., 2008b). INTA
developed the CO2 monitoring technology with a private company (Silcheck, Lincoln,
Argentina). Trained personnel with a portable CO2 meter measures interstitial atmosphere
CO2 composition every 6 m along the bag, perforating the plastic cover with a needle (this
operation takes less than 10 min for the entire bag). The information is uploaded to a server
where the data are automatically analyzed and processed, a storage risk index is elaborated for
each environment of the silo-bag, and the storage condition of the silo-bag can be monitored
through internet. In case of detecting unsafe storage conditions, an automatic report is sent to
the owner of the silo-bag through e-mail, fax or by cell phone SMS.
Fig. 6-a) CO2 concentration during storage of one silo-bag without storage problems (--)
and two silo---) with soybean at m.c. around 13.5%
(Source: Bartosik et al., 2008b). b) CO2 meter and internet report with visual information
showing in a color scale the storage risk index.
Recommendation for Successful Storage with Silo-bags
The overall results indicate that dry grain (equilibrium r.h. below 67%) can be stored in silo-
bag for more than six months without losing quality (measured as percentage of mold
damaged grain, test weight, germination, fat acidity, and nutritional and organoleptic
parameters, among others). When grain m.c. increases, commercial quality could be
maintained from three to six months in winter time, and from one to three months in summer
Silo-bags storing dry grain will not create a lethal environment for insects. However,
low temperatures during winter in temperate climates will affect insect development. Storing
grain at m.c. that can hold mold activity would create a lethal environment for insects, but the
storage time will be limited due to effects on grain quality. Phosphine fumigation in silo-bags
is a simple and effective insect control methodology.
Prior to set up the silo-bag, the site selection is a key factor. The piece of land should be
high and with a slight slope to avoid rain water accumulation that, potentially, could enter into
the silo-bag through perforations. A smoothing and leveling operation of the ground should be
done. The soil should not have materials that could damage the bottom of the silo-bag during
the filling operation, such as stones, residues of the crop, etc. Additionally, sites that are close
to trees should be avoided to place silo-bags, since falling branches can damage the bag.
Maintaining a high airtightness level is a key factor for successful storage. Good care
should be taken to maintain the plastic cover integrity during the bag filling operation and
during storage. It is also critical to make a proper sealing of the closing end. Thermo sealing
seems to be the most appropriated technique for ensuring a high airtightness level.
Place the silo-bags in pairs, leaving one open road for the unloading operation before
the next pair of silo-bags. With this configuration, any silo-bag could be unloaded at any time
(i.e., because a spoilage problem was detected), without having to unnecessary unload an
extra bag.
Set up a fence around the silo-bags to keep out the animals, either wild or domestics
(i.e., dogs and cats). The fence could be permanent, or made with electrified wires, such as
those used for cattle. The wires should be placed at different heights, according to the typical
animals of the location.
Some animals, such as birds and rodents, cannot be controlled by a fence. Thus, a
rodent monitoring and control program must be implemented. Keeping clean and mowing or
spraying herbicide in the silo-bag area will also help to prevent animal activity around the
The silo-bags should be periodically inspected. Any perforation should be properly
sealed immediately. Avoid probing the silo-bag, since the patches often get detached. It is
convenient to collect grain samples for quality control during the bag filling operation.
Monitoring of the grain storage condition should be done by measuring CO2 concentration,
since it does not affect the physical integrity of the bag.
Abalone R, Gastón A, Bartosik R, Cardoso L, Rodríguez J (2011) Gas concentration in the
interstitial Atmosphere of a wheat silo-bag. Part II: Model sensitivity and effect of grain
storage conditions. J Stored Prod Res 47: 276-283.
Bartosik R, Rodríguez J, Cardoso L (2008a) Storage of corn, wheat soybean and sunflower in
hermetic plastic bags. Proceedings of the International Grain Quality and Technology
Congress, July 15-18, Chicago, Illinois, USA.
Bartosik R, Cardoso L, Rodríguez J (2008b) Early detection of spoiled grain stored in
hermetic plastic bags (silo-bags) using CO2 monitoring. Proceedings of the 8th
International Conference Controlled Atmospheres and Fumigation of Stored Products,
from September 21-26, Chengdu, China.
Barreto A, Abalone R, Gastón A, Bartosik R (2012) Computer simulation of gas
goncentration in the interstitial atmosphere of a wheat silo-bag for typical agricultural
areas of Argentina. Presented at the 9th International Conference on Controlled
Atmospheres and Fumigation on Stored Products, October 15-19, Antalya, Turkey.
Cardoso L, Ochandio D, de la Torre D, Bartosik R, Rodríguez J (2010) Storage of quality
malting barley in hermetic plastic bags. Proceedings of the International Working
Conference on Stored Product Protection, June 27 to July 2, Estoril, Portugal.
Cardoso L, Bartosik R, Milanesio D (2009) Phosphine concentration change during
fumigation in hermetic plastic bags. Proceedings of the CIGR Section V International
Symposium, September 1-4, Rosario, Argentina.
Castellari C, Marcos Valle F, Mutti J, Cardoso L, Bartosik R (2010) Toxigenic fungi in corn
(maize) stored in hermetic plastic bags. Proceedings of the International Working
Conference on Stored Product Protection, June 27-July 2, Estoril, Portugal.
Chulze S (2010) Strategies to reduce mycotoxin levels in maize during storage: a review.
Food Additives and Contaminants 27(5): 651657.
Darby J, Caddick L (2007) Review of grain harvest bag technology under Australian
conditions. Technical report Nº: 105. CSIRO Entomology. Available at: Accessed in June 2009.
Gastón A, Abalone R, Bartosik R, Rodríguez J (2009) Mathematical modeling of heat and
moisture transfer of wheat stored in plastic bags (silo-bags). Biosystems Eng 104: 72-
Massigoge J, Cardoso L, Bartosik R, Rodríguez J, Ochandio D (2010) Almacenamiento de
cebada cervecera en silo bolsas. In Spanish: “Storing of malting barley in silo-bag”.
Proceedings of the IX Congreso Latinoamericano y del Caribe de Ingeniería Agrícola -
CLIA 2010 y XXXIX Congresso Brasileiro de Engenharia Agrícola - CONBEA 2010.
July 25-29, Vitória - ES, Brasil.
Ochandio D, Cardoso L, Bartosik R, de la Torre D, Rodríguez J, Massigoge J (2010) Storage
of canola in hermetic plastic bags. Proceedings of the International Working Conference
on Stored Product Protection, June 27-July 2, Estoril, Portugal.
Ochandio D, Rodríguez J, Rada E, Cardoso L, Bartosik R (2009) Almacenamiento de cebada
cervecera en bolsas plásticas herméticas. In Spanish: “Storage of malting barley in
hermetic plastic bag”. Proceedings of the X Congreso Argentino de Ingeniería Rural y
II del Mercosur (CADIR), September 1-4, Rosario, Argentina.
Pacin A, Ciancio Bovier E, González H, Whitechurch E, Martínez E, Resnik S (2009) Fungal
and fumonisins contamination in Argentine maize (Zea mays L.) silo bags. J Agric Food
Chem 57: 27782781.
Ridley A, Burrill P, Cook C, Daglish G (2011) Phosphine fumigation of silo bags. J Stored
Prod Res 47: 349-356.
... Permeable packages are those which allow a greater exchange of water vapour between the seeds and the atmospheric air, therefore, they are typically recommended for shorter storage times, however this packaging should preferably be located in dry places (Anankware et al., 2012). On the other hand, semipermeable packaging offers high resistance to water vapour exchange and therefore, the moisture content of the seeds in the initial stage of storage should be lower than recommended (Bartosik, 2012). However, waterproof packaging does not allow the exchange of water vapour the seeds and the ambient air, furthermore, it reduces the availability of oxygen inside the packaging. ...
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The use of silo and raffia bags for the temporary grain storage has been increasing in recent years. However, the methods for monitoring a stored product are limited to visual inspections and sampling. Thus, this research aimed to real‐time equilibrium moisture content monitoring to predict grain quality of corn stored in different conditions in silo and raffia bags using wireless sensor network prototype, Internet of Things (IoT) platform, and neural network algorithms. Experiments were conducted using corn grain with two initial water contents of 13% and 18% (w.b.), three storage environments with temperatures of 30, 23, and 17°C, and two types of packaging, that is, silo and raffia bags, for a 3‐month storage evaluation. During the monitoring of stored grain, variations in equilibrium moisture hygroscopic content were observed, which inferred changes in the corn quality. Water contents of 13% under a storage condition of 17°C showed the highest quality results, whereas storage in silo bags with water contents of 13% and 18% showed no differences at 23°C; however, at a temperature of 30°C, the grain suffered a high level of deterioration. The storage time influenced the reduction of grain quality for all factors. The physicochemical quality prediction results indicated a high coefficient of determination of the trained models, presenting itself as a promising perspective, mainly in developing embedded technologies for monitoring and predicting the qualitative variables of grain stored in silo and raffia bags. Practical Applications The application of sensor technology and the Internet of Thing (IoT) to monitor the temperature and relative humidity of intergranular air in real time for the determination of equilibrium moisture content became possible to predict the physical and physicochemical quality of grains stored in bag silos and raffia bags using artificial neural networks (ANN) algorithms. The results obtained were satisfactory and can replace the punctual sampling of the grains mass stored in hermetic packages. The application of a set of technologies possible to monitor the grain quality in real time and predict the grain storage time in bag and raffia silos to reduce losses.
... Permeable packages are those which allow a greater exchange of water vapour between the seeds and the atmospheric air, therefore, they are typically recommended for shorter storage times, however this packaging should preferably be located in dry places (Anankware et al., 2012). On the other hand, semipermeable packaging offers high resistance to water vapour exchange and therefore, the moisture content of the seeds in the initial stage of storage should be lower than recommended (Bartosik, 2012). However, waterproof packaging does not allow the exchange of water vapour the seeds and the ambient air, furthermore, it reduces the availability of oxygen inside the packaging. ...
Full-text available
Superior agricultural yields are obtained from seeds which have a high physiological potential, these are conserved in the post-harvest stage. Thus, it is crucial to implement post-harvest projects with appropriate technologies related to the equipment used and the control of operations. This article presents a review of the technical-kinetic developments in the area of the technology of processing post-harvest soybean seeds, with a particular focus on the evolution and current circumstances of the sector. The findings from this research reveal significant technological advances in the drying, processing and storage of seeds at different levels and in various areas of soybean production. In drying systems, temperatures of up to 40°C are recommended, while seed batches must remain static in drying chambers. When processing and standardizing seeds, it is recommended that low-moving equipment and abrupt contacts with mechanical systems, such as pneumatic and gravity separators, be employed to minimize dropping and contact with seeds. In soybean storage, the applications of technologies that can control temperature and relative humidity, and also maintain the storage moisture content in a hygroscopic balance are recommended. The storage of seeds in coated big bags and artificial cooling; a controlled and modified atmosphere serve to preserve essential seed qualities. This review concludes that over the years, there has been a reduction in the cumulative losses due to post-harvest processes.
... Alternatively, the low-cost technique of naturally increasing the concentration of CO2 in the packaged bag through respiration of the commodity has also been proven to be effective in both mold and pest control [7] [8]. Hermetic bags, however, which are often made of 2-3 layers of (~250 μm thick) polyethylene plastic [9], are prone to the exchange of gases like O2, CO2 and water vapor over extended storage times due to their finite permeability coefficient and, perforations that may occur during storage and handling can cause significant quality degradation with time [10]. Integrity inspections and headspace analysis are hence frequently required for their quality estimation. ...
Dry food commodities like grains and pulses can be stored safely for several years under controlled storage conditions. The equilibrium moisture content of the packaged grain is one of the most important parameters required to be monitored and controlled for extended safe storage. This paper presents a single element dual-polarized sensing tag based on an annular slot antenna operating at two closely spaced resonant frequencies for radar cross-section-based monitoring of relative humidity in hermetically packaged food commodities. One of the resonant frequencies is functionalized for sensing while the other acts as a built-in reference, mitigating the effects of environmental loading. A polyvinyl alcohol coated interdigitated capacitor, integrated onto the antenna is used as a capacitive transducer for the sensing element. Laboratory scale measurements were carried out using the saturated salt solution method. Results show that the proposed sensor can be used for monitoring a wide range of humidity conditions.
... Under well sealed conditions, the resulting modified atmosphere has important benefits for seed conservation, including reducing or controlling insect activity (Bera, Sinha, Singhal, Pal, & ;Navarro, 2012), reducing fungal activity (Lorenzo et al., 2020;Samapundo, De Meulenaer, Atukwase, Debevere, & Devlieghere, 2007;Taniwaki, Hocking, Pitt, & Fleet, 2009), and minimizing seed viability deterioration (Chiu, Chen, & Sung, 2003;Groot, de Groot, Kodde, & van Treuren, 2015). Due to the mentioned benefits and the development of flexible packaging (plastic liners) at affordable cost, hermetic storage systems have attracted attention in recent years in different regions of the world, in particular in Africa and South East Asia with the use of individual bags (up to 100 kg) for family consumption (PICS™, SuperGrainbag™ and AgroZ) (Baributsa & Ignacio, 2020), and in South America with the use of silo bags of more than 200 t capacity (Bartosik, 2012). ...
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The dynamics of oxygen (O2) and carbon dioxide (CO2) concentrations were characterized in corn (Zea mays L.) seed hermetically stored in glass jars at 15, 25 and 35 °C and 14.3, 16.5 and 18.3% moisture content. Gas concentration curves were modeled with linear and exponential correlations and the respiration rate was calculated for each temperature and MC combination as storage time progressed and O2 was consumed. Three predictive respiration models were proposed: Model I, dependent on temperature and MC, and Model IIA, dependent on temperature and oxygen (fitted for each MC level), and Model IIB, dependent on temperature, MC and O2. All models were validated with two independent sets of experimental data. Respiration rate increased with MC and temperature, and it appeared that O2 concentration affected respiration only after a critical limit of about 1% was reached. The values of respiration rates obtained in this study were from 1.36 to 823.76 mg O2 kgDM−1 d⁻¹ and from 0.83 to 1265.62 mg CO2 kgDM−1 d⁻¹. Respiration rate substantially increased for aw conditions greater than 0.85, presumably due to the onset of the embryo's metabolic activity and the activation of the facultative microorganisms. Literature data was provided to support this observation. Based on this study, Models I and IIB could be indistinctly used in simulation models for predicting O2 and CO2 evolution of hermetically stored seed. However, model IIB provides the advantage of attenuation of the respiration rate as O2 is depleted.
The effects of glyphosate (GLY)-based and glufosinate ammonium (GA)-based herbicides (GBH and GABH, respectively) and polyethylene microplastic particles (PEMPs) on Scinax squalirostris tadpoles were assessed. Tadpoles were exposed to nominal concentrations of both herbicides (from 1.56 to 100 mg L⁻¹) and PEMPs (60 mg L⁻¹), either alone or in combination, and toxicity evaluated at 48 h. Acetylcholinesterase (AChE), carboxylesterase (CbE), and glutathione-S-transferase (GST) activities were analyzed at the three lowest concentrations (1.56, 3.12 and 6.25 mg L⁻¹, survival rates >85%) of both herbicides alone and with PEMPs. Additionally, the thermochemistry of the interactions between the herbicides and polyethylene (PE) was analyzed by Density Functional Theory (DFT). The median-lethal concentration (LC50) was 43.53 mg L⁻¹ for GBH, 38.56 mg L⁻¹ for GBH + PEMPs, 7.69 for GABH, and 6.25 mg L⁻¹ for GABH+PEMPs. The PEMP treatment increased GST but decreased CbE activity, whereas GBH and GABH treatments increased GST but decreased AChE activity. In general, the mixture of herbicides with PEMPs increased the effect observed in the individual treatments: the highest concentration of GBH + PEMPs increased GST activity, whereas GABH+PEMP treatments decreased both AChE and CbE activities. DFT analysis revealed spontaneous interactions between the herbicides and PE, leading to the formation of bonds at the herbicide-PE interface, significantly stronger for GA than for GLY. The experimental and theoretical findings of our study indicate that these interactions may lead to an increase in toxicity when pollutants are together, meaning potential environmental risk of these combinations, especially in the case of GA.
Respiration of biotic components of the grain ecosystem generates self-modified atmospheres (oxygen reduced and carbon dioxide enriched) during hermetic storage. The effect of temperature, moisture content and modified atmospheres on the evolution of maize microbiota is not entirely known. In this study, corn grain samples were conditioned to different moisture contents (14.3, 16.5 and 18.4%) and hermetically stored in glass jars at 15, 25 and 35 °C. Grain samples were collected at different stages of modified atmosphere evolution of each experiment: T0 (O2: 21% initial concentration); T1 (O2: 10%); T2 (O2: 0%); T3 (CO2 maximum concentration stabilized). Microbiota was quantified with Petri dish counts using selective growth media for different microbial groups. Additionally, ethanol, acetic acid and lactic acid were measured for monitoring anaerobic activity. Results indicated that there was a high correlation between water activity (aw) and the time to reach anaerobiosis (R² of 0.85), the maximum CO2 concentration (R² of 0.86), and the reduction of filamentous fungi and bacterial counts during hermetic storage (R² of 0.72 and 0.48, respectively). A differential behavior of the hermetic storage was observed according to aw of the grain, and a general conceptual model is offered for its understanding. It was concluded that modified atmospheres reduced or inhibited microbial growth in stored corn, and that aw was the most influential factor in the time to reach anaerobiosis, maximum CO2 concentration, and the filamentous fungi and bacterial counts reduction during hermetic storage.
Silo bag technology is used for storing grains in a hermetic plastic structure. The major limitation of this structure is resistance to improper handling and external aggression, thus promoting pest incidence due to alterations in its internal atmosphere. In this study, we developed a biopesticidal silo bag consisting of a co-extruded three-layer film made of polyethylene and essential oil of Mentha piperita (7% w/w) in the inner layer. A film with the same structure but without essential oil was produced to be used as a control. The presence of the biopesticide in the silo bag was confirmed by FTIR-spectroscopy. Thus, mechanical, optical and chemical properties were evaluated. Diffusion coefficient of biopesticide from silo bag at 15, 25 and 35 °C was estimated as 6.4 ± 0.1 × 10⁻¹¹, 1.45 ± 0.17 × 10⁻¹⁰ and 1.30 ± 0.2 × 10⁻¹⁰ cm²/s, respectively. Finally, the biopesticide silo bag was tested against Rhyzopertha dominica, primary pest of stored grain, showing 100 % of mortality during the time assayed (7 days). Hence, the incorporation of biopesticide by co-extrusion technology (low-cost and efficient machinery) into the inner layer of a silo bag could help to replace synthetic pesticides and avoid manipulation of these in the field, preventing biotic infestation.
Alternatives to chemical fumigation, are being explored as the popular fumigants like methyl bromide and phosphine are being phased out for their ozone depleting nature and insect resistance, respectively. Vacuum hermetic storage has potential for storage of agricultural durable commodities without fumigants and can eliminate 99% of insect infestation. In present research, the vacuum hermetic storage was tested in field with assistance of sensors and compared with the conventional phosphine fumigated storage by grain quality assessment and interstitial atmosphere for six months. Relative humidity of the hermetic bags remained below 25%, whereas temperature followed the same pattern as of the ambient. Germination percentage, thousand kernel weight and besatz content did not change significantly (p > 0.05), whereas mould count and moisture content reduced over the storage time compared wheat stored in metal bin.
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The main destination of barley grown in Argentina is malt production. The main standard quality parameter for the malting industry is to maintain at least 98% germination percentage (GP). A typical operation is to harvest dry barley (around 12%) and store it in hermetic plastic bags, a temporary storage system of modified atmosphere, until end use in the malting industry. The objective of this study was to determine whether the typical Argentinean storage condition of malting barley in hermetic plastic bags produces a deleterious effect in its commercial and industrial quality. Two plastic bags filled each with 180 tonnes of malting barley were used for this experiment, one with 11% moisture content (m.c.) and the other with a range between 11 and 11.5% m.c. The experiment began immediately after harvest on December 27th (early summer) and lasted for five months. Carbon dioxide (CO₂) concentration, grain temperature, m.c., protein and GP were evaluated every 2 wk. GP did not substantially decrease during the entire storage period for both bags, but samples with higher m.c. had the lowest GP. The protein percentage remained stable throughout the entire evaluation period for both bags. The maximum value of CO₂ in the bag with 11% m.c. was 4.4%. The bag with the higher range of m.c. had a maximum CO₂ value of 13%, and this high concentration was associated to a small portion of spoiled grain, presumably due to rain water entering the bag through perforations in the plastic cover at the bottom of the bag. It was concluded that it is safe to store quality malting barley with 12% m.c. or less in hermetic plastic bags for five months.
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Due to the small size of the seed, canola ( Brassica napus or Brassica campestris ) offers different challenges in the harvest and the subsequent post-harvest operations. Often, in Argentina, farmers do not have enough permanent storage capacity so they overcome this deficit with the use of hermetic plastic bags (silobags). The objectives of this work were: 1) Determine the feasibility of the bagging and extraction processes of canola. 2) Monitoring the condition of canola by periodic measurement of carbon dioxide (CO2), temperature, moisture content (m.c.) and quality of the grain. Thirty tonnes of canola with initial m.c. of 6 % were stored in a silobag in the southeast of the Buenos Aires province, Argentina. The storage period was extended from November 2008 to November 2009. The variables measured every two weeks were CO 2 concentration, m.c. and grain quality parameters, such as foreign matters, fat acidity and fat content. The temperature and relative humidity (r.h.) of the interstitial air inside the bag and of the ambient air were also recorded with a frequency of one hour. It was observed that, even the size and characteristics of the canola seeds, it was possible to perform the bagging and extraction operations of canola seeds without problems. The r.h. in the interstitial air remained below 50% along the entire storage period. The temperature of the grain inside the bag followed the monthly average ambient temperature. The CO 2 concentration ranged from 1 to 8 %, indicating low to moderate biological activity in the grain mass. The m.c., foreign matters and fat values remained unchanged throughout the storage period. The fat acidity increased during storage in 0.7 % points, reaching a final value of 1.4 %, but did not represent a commercial quality loss. It was concluded that under the conditions of temperature and m.c. evaluated in this study it is possible to store canola in hermetic plastic bags without commercial quality deterioration. Keywords : Silobags, CO 2 concentration, Interstitial air, Moisture content, Fat acidity.
Technical Report
Full-text available
Grain harvest bags provide a useful and safe storage option for short to medium term storage of dry grain on-farm. This was the major outcome of a recent two-year study by CSIRO Entomology to evaluate the limits of existing harvest bag technology under Australian conditions.
Conference Paper
Full-text available
In Argentina about 35 million tonnes of grains were stored in hermetic systems (silo-bags) during 2007, and it is expected that in the future a bigger proportion of the grain will be stored in these silo-bags in Argentina and other countries. The silo-bags are made of a 235-micrometer plastic film of 2.74 m diameter and 60 m long (holding approximately 200 tonnes of wheat each). Grain quality monitoring is carried out with a standard torpedo probe. This operation has several disadvantages, including perforating the plastic film (disturbing the air tightness of the system), difficulties to target the grain spoilage area (especially when it is located in the bottom of the silo-bag), and the relatively intense labor demand. Monitoring stored grain conditions through temperature measurement is not an option, since the grain stored in the silo-bags does not increase temperature during spoilage. A study was made with several silo-bags filled with wheat and soybean located at different farms and grain elevators in the South-West of Buenos Aires province. The silo-bags were sampled with a torpedo probe, and the corresponding value of CO2 concentration of the silo-bag was measured. The collected grain samples were analyzed in the laboratory for moisture content (MC). Additionally, the silo-bag overall condition was evaluated (bad sealing, openings, occurrence of occasional flooding in the area of the silo-bag, etc), and evidence of spoiled grain at bag unloading was collected. Periodic CO2 monitoring of silo-bags allowed for the early detection of biological activity and spoiled grain. A distinctive value of CO2 for different MC grains was established, which represents the typical atmospheric composition for a silo-bag with and without conservation problems. The silo-bags holding grains with different levels of conservation problems were identified by the unusually high CO2 concentrations of the modified atmosphere.
A lumped capacitance model was applied to simulate the change in gas concentration in a wheat silobag. The sensitivity of the solution to a given model respiration rate and permeability (degree of gastightness of the silo-bag) was examined. Results showed that gas concentration is more sensitive to changes in respiration rate than to permeability of the plastic film. Considerable changes occur in gas concentration in a damaged silo-bag. The definition of an effective permeability to account for gas transfer through holes and plastic film allowed the examination of the effect of different holes configurations (number and size of perforations) on the evolution of gas concentration. The influence of grain storage conditions on the evolution of gas concentration was investigated. The model was run for initial grain temperatures of 20, 25, 30 and 40C and MC in the range (12e16% w.b) and climatic conditions of the South East of Buenos Aires province, Argentina. When dry grain (12e13% w.b) is stored, O2 level remained above 12% and CO2 level below 7%. For wet grain (15e16% w.b), CO2 level was in the range 14e16% after six month storage. The simulations showed that for wet grain anaerobic conditions may be achieved within two weeks to three months of storage, depending on the grain initial temperature. Estimated mean DML for all the storage conditions remained always below 0.04%, the critical limit for safe storage of wheat that will be used for seeds.
Fumigation with phosphine has the potential to disinfest grain stored in silo bags but only limited research has been conducted on whether phosphine fumigation can be undertaken effectively and safely in this form of storage. Fumigation with phosphine was tested on two (70 m) replicate silo bags each containing 240 t of wheat (9.9 and 9.2% m.c.). The target application rate of phosphine was 1.5 g m−3 with a fumigation period of 17 days. Aluminium phosphide tablets were inserted into each bag at ten release points spaced at 7 m intervals starting 3.5 m from either end of the bag. A total of 14 bioassay cages containing mixed age populations of strongly phosphine resistant Rhyzopertha dominica (F.) were inserted into each fumigated silo bag. Complete control of all life stages of R. dominica was achieved at all locations in the fumigated silo bags. Phosphine concentrations at release points increased rapidly and remained high for the duration of the fumigation. Concentrations at midway points were always lower than at the release points but exceeded 215 ppm for ten days. The diffusion coefficient of available phosphine averaged over the first three full days of the fumigation for both fumigated silo bags was 2.8 × 10−7. Venting the silo bag with an aeration fan reduced the phosphine concentration by 99% after 12 h. Relatively small amounts of phosphine continued to desorb after the venting period. Although grain temperature at the core of the silo bags remained stable at 29 °C for 17 days, grain at the surface of the silo bags fluctuated daily with a mean of 29 °C. The results demonstrate that silo bags can be fumigated with phosphine for complete control of infestations of strongly phosphine resistant R. dominica and potentially other species.