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Vol. 14(2), pp.14-23, July-December 2023
DOI: 10.5897/JSPPR2023.0335
Article Number: DE3996471237
ISSN 2141-6567
Copyright ©2023
Author(s) retain the copyright of this article
http://www.academicjournals.org/JSPPR
Journal of Stored Products and Postharvest
Research
Full Length Research Paper
Assessing the efficacy of hermetic storage bags
against woven polypropylene bags by farmers in Ghana
for maize grain storage
Bernard Darfour1 and Kurt A. Rosentrater2*
1Biotechnology and Nuclear Agriculture Research Institute Ghana Atomic Energy Commission, Ghana.
2Agricultural and Biosystems Engineering Department, Elings Hall, Iowa State University of Science and Technology,
Ames, Iowa 50011, USA.
Received 21 March, 2023; Accepted 4 September, 2023
The main insects that deteriorate stored maize grain in the tropics are maize weevils (Sitophilus
zeamais). S. zeamais can cause significant post-harvest losses (PHL) in maize during storage. The
objective of this study was to help farmers in Ghana appreciate and understand the benefits of using
GrainPro bags compared to woven polypropylene bags (WPB) for storing maize grain. Eight farmers
participated in the study, where 25 kg bags were loaded with 20 kg of naturally S. zeamais-infested
white maize grain. The sealed bags were stored for 6 months at 28±6°C. A representative sample of 1 kg
was taken from each bag for further analysis after homogenization. Percentages and ANOVA were
calculated for all the quality parameters measured. The results showed that all the WPB bags were
damaged, while the GrainPro bags remained intact. The damaged grain in WPB bags ranged from 91.9
to 94.4%, whereas in GrainPro bags, it ranged from 0.2 to 0.7%. Approximately 0 g of maize powder
(fines) were produced within the GrainPro bags, compared to up to 73.7 g in WPB bags. S. zeamais
mortality was 90% higher in GrainPro bags than in WPB bags. Therefore, GrainPro bags are suitable
alternatives to WPB for maize storage.
Key words: Maize grain, GrainPro bags, Polypropylene bags, Hermetic storage, Sitophilus zeamais.
INTRODUCTION
Some controllable factors limit the production of maize in
Sub-Saharan Africa (SSA) and many other developing
nations. In developing countries, insects and rodents
cause huge losses in quality and quantity of stored grain
(Kamanula et al., 2010). The main insects that damage
stored maize grain in the tropics are maize weevils
(Sitophilus zeamais) (Rugumamu, 2012). S. zeamais
(Figure 1) can inflict serious damage to maize grain that
may lead to 20-50% or more losses when grain is stored
for about 6 months (Mulungu et al., 2007; World Bank,
2011). Grain weight loss contributes largely to post-
harvest losses (PHL) (Kumar and Kalita, 2017).
Therefore, having effective grain storage systems can
drastically reduce food losses and improve the livelihood
of smallholder farmers.
Preventing infestation is essential during storage
to maintain food quality, make food accessible, and to
stabilize food security and income security of farmers
*Corresponding author. E-mail: karosent@iastate.edu.
Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution
License 4.0 International License
Darfour and Rosentrater 15
Figure 1. A diagram of a maize weevil (S. zeamais).
(Rosegrant et al., 2015). One of the available options to
control pests infestation in SSA is to use synthetic
pesticides. However, synthetic pesticides are expensive,
may be adulterated or not readily available in markets
(Njoroge et al., 2014). Also, synthetic chemicals may be
ineffective and have detrimental health and
environmental effects (Addo et al., 2002). The worse of it
all is that the increased use has resulted in resistance
among certain species that has reduced the effectiveness
of the chemicals (Benhalima et al., 2004; Collins, 2006).
Hermetic containers and bags are appropriate and
effective alternatives to synthetic pesticides (Suleiman et
al., 2018).
Another alternative to chemical use during grain
storage is the hermetic metal bin. It is a galvanized metal
sheet made into an airtight storage silo. A hermetic metal
silo is effective against rodents, birds, molds, and insects
to reduce grain losses (Tefera et al., 2011; SDC, 2017).
Although metal silo is effective in controlling insects or
infestations to improve food security and incomes
of farmers, it is expensive to buy or manufacture (Gitonga
et al., 2013; De Groote et al., 2013). Hermetic bags
including the Purdue Improved Crop Storage (PICS)
bags, Super Grain Bags, and GrainPro bags are all
effective at controlling insects and are less costly.
Comparatively, hermatic bags reduce grain losses better
than woven polypropylene bags (WPB) when storage
conditions are similar (Baoua et al., 2013a, b).
Hermatic bags are extensively utilized in some SSA
countries (Tanzania, and Kenya) because they are
effective, simple, low cost, durable, easy to produce, and
require small storage space (Baoua et al., 2012).
However, hermetic bags have some disadvantages
including high susceptibility to physical damages. These
damages could be punctures from sharp end objects,
abrasions, and perforations by insects and rodents (De
Groote et al., 2013; García-Lara et al., 2013). These bags
can also burst during transportation. The bags then lose
their usefulness when they get damaged and further add
extra cost to farmers.
Hermetic conditions work on a simple principle involving
oxygen and carbon dioxide concentrations. Low oxygen
concentration is created in these bags or containers that
reduce insect development (Murdock et al., 2012;
Suleiman et al., 2018). Within 1 month of storage, about
98% mortality of all insect pests can be achieved which
reduces damage to grain by insects (Baoua et al., 2012).
(2012) found that hermetic bags give protection to grain
against insect infestations without any loss in quality.
Similarly, PICS bags maintained grain quality more
effectively compared to WPB (Williams et al., 2017).
The use of WPB in developing countries to store grain
cannot wholly be condemned or eliminated. This is
because they are readily available in the markets and
less expensive compared to hermetic bags or silos.
However, they are used with caution. To effectively
control insects/pests, insecticides/pesticides such as
Malathion, Deltamethrin, and Actellic super, and
Phosphine (fumigant) are used. To prevent
16 J. Stored Prod. Postharvest Res.
damage to WPB and hermetic bags, poison baits (Naik
and Kaushik, 2017) and traps (Yee and Leung, 2009) can
be used to control the rodents.
With the intention to reduce or avoid the overreliance
on synthetic chemicals based on their toxicity and
expensiveness, farmers have been advised to accept and
use hermetic technology although relatively new in
Ghana. Hence, farmers were allowed to participate in the
use of GrainPro bags (hermetic bags) to appreciate the
significance of hermetic technology. The objective of this
study was to help farmers in Ghana appreciate and
ascertain the benefits of using GrainPro bags compared
to WPB in the storage of maize grain.
MATERIALS AND METHODS
Experimental set-up
Eight farmers were selected for this experiment. Farmers were
selected from a town called Tontro in the Eastern region of Ghana
where the study happened. Each farmer was provided with six
bags, three each of GrainPro bags (hermetic) and WPB (non-
hermetic) for the 6 months storage period. Hence, a completely
randomized factorial design was used. Both types of bags had 25
kg storage capacity, and the GrainPro bag had a single layer
(78±10% thickness) of high strength polyethylene (PE) with a
barrier layer and 2 track PE zipper (GP, 2018). Similarly, the
polypropylene bag was single-layered. The white maize grain used
in the study was obtained from the farmers, and the grain had a
natural S. zeamais infestation (Baoua et al., 2014). Damaged grain
(grain with holes, and broken grain), foreign materials, and dead S.
zeamais were sorted and discarded prior to loading the bags.
Handpicking was the mode of sorting and was done by spreading
small portions of the grain on a white cloth. The initial numbers of S.
zeamais found in 1 kg of infested grains before the start of the
research study was estimated to be 67±14. The GrainPro bags
containing the grains were hermetically sealed with the 2 track PE
zipper according to WPB
containing the grains were firmly tied to prevent the escape of the
S. zeamais. The grain used had an average moisture content (MC)
of 14.0±0.5%, which was measured (triplicate) with DICKEY-JOHN
(Auburn, IL) mini GAC® plus hand-held Moisture Tester
(Minigac1P). The individual farmers stored the stacked bags in their
storage rooms on raised platforms at a temperature of 28±6oC.
The storage bags were opened after 6 months, and the content
of each bag was homogenized. Homogenization was done by
spreading and gently mixing the content of an opened bag on a
clean rubber sheet. A representative sample sum of 1 kg (USDA,
2013) was taken from different sites of the homogenized bag for
further analysis. A sieve of size 0.99 mm (99*10-5 m) was used to
separate the powder by retaining the S. zeamais and grain. The
mass of powder produced was measured (g/1 kg of the sample).
The retained S. zeamais and grain were used to determine the
percentage of damaged grain (i.e. by weight, grain with holes or
devoured endosperm and/or germ caused by S. zeamais), grain
weight loss (%), and percent mortality of S. zeamais (%
).
The percentage of grain weight loss was determined by using the
count and weigh method developed by Adams and Schulten
(1978). The percentage of storage bags damaged (visible holes
created in bags due to the frequent movements outside and into the
bags by S. zeamais) was also calculated.
The determination of damaged bags was done based on the
physical observation of holes in the bags.
Data analysis
Percentages were calculated, and the data set was presented in
graphs and tables. For the ANOVA, Tukey-Kramer HSD was used
to separate the means that were significantly different (P < 0.05).
RESULTS
Although eight farmers were used in the study, data from
seven farmers were analyzed because there was
unexpected damage to the experimental units of one
farmer. As shown in Figure 6a, two of the GrainPro bags
were damaged by mice during storage. Figure 2 shows
the percent number of storage bags that were damaged
by S. zeamais. The S. zeamais damaged (holes created
due to frequent in and out movements) all the WPB used.
All the GrainPro bags used were resilient to S. zeamais
attack, and hence no damaged bag was recorded. In
Figure 3, the percentage of grain damaged by S. zeamais
was recorded. The damages consisted of holes created
in the kernels, and consumption of the entire endosperm
and germ (embryo) of the kernel. In most cases, only the
grain bran and hull remained. The percentage of
damaged grain in the WPB ranged between 91.9 and
94.4%. Compared to damaged grain in the GrainPro
bags, the percentage was between 0.2 and 0.7%. Figure
4 shows the powder (flour/fines) produced in both types
of storage bags. The powder or fines was produced due
to S. zeamais feeding on the grain. The GrainPro bags
recorded zero (0) gram of powder weight. In the WPB,
due to the extensive grain damage, the weight of powder
recorded ranged from 48 to 73.7 g.
In Figure 5, the percent of S. zeamais mortality was
determined. 100% S. zeamais mortality was recorded in
GrainPro bags (using stored grains). The number of live
S. zeamais found in the WPB was extremely high, hence,
S. zeamais mortality in WPB was between 5.0 and 8.4%.
Table 1 shows the number of dead and live S. zeamais
in both types of bags and the percent mortality. Table 2
shows the means of the measured parameters recorded
in the GrainPro and WPB. The mortality in GrainPro bags
(100.0%) was significantly high (P < 0.05) compared to
that of the WPB (7.2%). The mass of powder produced
(g), the percentage of damaged bags, the percentage of
damaged grain, and percentage of grain weight loss in
the GrainPro bags were all significantly low in contrast to
that of WPB.
DISCUSSION
Number of damaged bags (%)
Grains, animal feed, flour, and many other products are
packaged in WPB (indBAG, 2016). GrainPro bags are
liners specially designed from high-density polyethylene
with a barrier layer (Baoua et al., 2013a; GrainPro, 2017)
Darfour and Rosentrater 17
Figure 2. Percent of WPB and GrainPro bags damaged by S. zeamais during the 6
months of grain storage in Ghana.
Figure 3. Percent of maize grain damaged by S. zeamais in both bags during the 6
months of grain storage in Ghana.
18 J. Stored Prod. Postharvest Res.
Figure 4. Weight (g/1 kg) of powder produced as a result of grain damaged by S.
zeamais during the 6 months of grain storage in Ghana.
Figure 5. Percent mortality of S. zeamais in both storage bags during the 6
months of grain storage in Ghana.
Darfour and Rosentrater 19
Figure 6. Maize grain in (a) mice-damaged GrainPro bags, (b) intact WPB bags, and (c) in
undamaged GrainPro bags during the six months of grain storage in Ghana.
Table 1. The average number of live and dead S. zeamais in 1 kg of grain, and percent mortality during the 6
months of grain storage in Ghana.
Farmers
S. zeamais in WPB
S. zeamais in GrainPro bags
Dead
Alive
% Mortality
Dead
Alive
% Mortality
1
13.3
192.7
6.5
66.7
0.0
100.0
2
14.0
208.3
6.3
67.7
0.0
100.0
3
14.3
174.3
7.6
74.0
0.0
100.0
4
-
-
-
-
-
-
5
15.0
287.0
5.0
64.7
0.0
100.0
6
16.7
180.0
8.5
68.0
0.0
100.0
7
15.7
264.0
5.6
69.0
0.0
100.0
8
19.3
212.0
8.4
72.0
0.0
100.0
Table 2. ANOVA showing significant differences between the use of GrainPro and WPB among the seven
farmers during the 6 months of grain storage in Ghana.
Packaging bags
Mass of powder
(g/1 kg grain)
Damaged
bags (%)
Damaged
grain (%)
Grain weight
loss (%)
Mortality of S.
zeamais (%)
GrainPro
0.0±0.0b
0.0 ± 0.0b
0.5±0.2b
0.2±0.1b
100.0±0.0a
WPB
61.5±9.4a
100.0±0.0a
93.0±1.0a
100.0±0.0a
7.2±2.4b
P-values
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
Means ± standard deviation in the same column with different letters are significantly different at P < 0.05.
used to store mostly dried grains. The resilience of both
storage bags to S. zeamais is not similar. This was
exhibited in the results obtained in this study. All the WPB
(100.0%) used to store the grain were susceptible to
damage by S. zeamais. The damage was caused by S.
zeamais in the infested grain. The S. zeamais perforated
the bags and were seen moving back and forth the inside
of the bags. This resulted in many larger holes been
created in the bags.
In comparison, the resilience of GrainPro bags was
b
a
c
b
a
c
20 J. Stored Prod. Postharvest Res.
Figure 7. The quality of maize kernels stored in WPB (a) and GrainPro bags (b) during the 6 months of grain
storage in Ghana.
shown in this study. None of the GrainPro bags was
damaged by S. zeamais. This indicates that the
mouthparts of S. zeamais are not robust enough to gnaw
and perforate the GrainPro bags compared to WPB. In
spite of this, the few GrainPro bags that were exposed
accidentally to rodents were severely damaged (Figure
6b). Hermetic bags are comparable to many other
improved storage methods. However, there are some
disadvantages including high susceptibility to physical
mishandling like punctures or perforations, and scratches
which may be caused by insects or rodents or sharp
objects (De Groote et al., 2013; Baoua et al., 2013 b;
García-Lara et al., 2013).
Percentage of damaged grain
Due to late harvest of maize, grain gets infested in the
field before harvesting commences (Kaaya et al., 2005;
Lane and Woloshuk, 2017). Delaying harvesting can
result in many pre-harvest losses including S. zeamais
infestation (ICVolunteers, 2014). Maize weevils found in
grain before harvest multiply rapidly due to favorable
temperature and RH. S. zeamais if not killed through
chemical treatment, then an appropriate storage bags
should be used. The percentage of grain damaged in the
WPB was from 91.9 to 94.4%. This shows that S.
zeamais rapidly reproduced, and caused extensive kernel
damage. Although storing grain in WPB is not expensive
there is the need to apply an insecticide (De Groote et al.,
2013; Maina et al., 2016). Since WPB is permeable to air,
gases are exchanged between the environment and
bags, and therefore S.
zeamais survive, grow, and multiply.
In the GrainPro bags, the percentage of damaged grain
ranged from 0.2 to 0.7%. GrainPro bags can deny
weevils of oxygen (Murdock et al., 2012). S. zeamais die
when denied of oxygen, and hence kernel damage due to
S. zeamais is reduced or prevented. The values of
damaged grain in GrainPro bags although low could be
attributed to the feeding activities of the S. zeamais
before their demise. Secondly, S. zeamais could survive
under hermetic conditions in the first few days (Bern et
al., 2010; Yakubu et al., 2011; Bbosa et al., 2017;
Suleiman et al., 2018), and during this period their
feeding activities might have resulted in kernel damage.
Kernels found in the GrainPro bags were very clean and
undamaged. Similar findings were reported by Lane and
Woloshuk (2017), and Williams et al. (2017). These
investigators reported low numbers of infested kernels in
PICS bags while in WPB the number was significantly
huge. Hermetic bags (GrainPro bags) are not entirely the
panacea for reducing PHL because rodents can
compromise the integrity of such bags. Rodents can
cause bag damage, spillage, and grain damage which
result in PHL (Figure 8b). Therefore, hermetic bags must
be properly kept away from storage pests like rodents.
Mass of powder (fines) and grain weight loss
In the GrainPro bags, no powder was produced which
might be attributed to the early demise of all the S.
zeamais. Because of the early demise of the S. zeamais,
the kernels remained undamaged (whole grains without
holes) and safe for consumption and possible germination
a
b
Darfour and Rosentrater 21
Figure 8. Powder (flour) produced in WPB due to S. zeamais (a), and kernel spillage due to mice attack on
GrainPro bags (b) during the 6 months of grain storage in Ghana.
(Figure 7b). The mass of powder in WPB was between
48.0 and 73.7 g, which could be ascribed to the extensive
grain damage (Figure 7a) caused by S. zeamais. The
extensive feeding activity of S. zeamais on the grain
might have resulted in the huge mass of powder
produced (Figure 8a). The massive mass of powder
exposes the ineffectiveness of WPB as a suitable storage
package; especially when the grain is already infested
before storage. It was not surprising that the kernels
found in WPB had only the hull and bran remnants
without the endosperm and embryo. The S. zeamais
completely devoured the entire endosperm and germ
(embryo) in all kernels. The powder produced means the
grain had been rendered useless both as food and seed.
Grain infestations cause quality and quantity losses
limiting food accessibility to humans and animals
(Rajendran, 2005; Suleiman et al., 2018).
The higher the grain weight loss or mass of powder, the
massive the grain uselessness. Recently, Walker et al.
(2018) found that grain when hermetically stored reduces
grain weight loss. Grain storage was completely
ineffective and unsafe when WPB were used. However,
the hermetic bags were effective at protecting the stored
grain against S. zeamais, as similarly reported earlier
(Murdock et al., 2012; Baoua et al., 2014; Suleiman et al.,
2018).
Percent S. zeamais mortality
The 100.0% mortality in GrainPro bags shows that S.
zeamais were not able to survive in the bags. The high
mortality reveals that grain could be stored safely in
GrainPro bags without S. zeamais attacks. Thus, the life
cycle and multiplication of S. zeamais that were within the
GrainPro bags were curtailed. In a situation where
harvested grain becomes infested before storage, it
would be most convenient and appropriate to store the
grain in hermetic bags (GrainPro bags). Findings from
Murdock et al. (2012), and Murdock and Baoua (2014)
showed that the effectiveness of using hermetic
technology depends on oxygen (O2) depletion and the
rise in carbon dioxide (CO2) concentrations. This is due to
the respiratory ability of the insects and grain. In this
study, S. zeamais in the GrainPro bags might have been
denied O2. This is because O2 concentration in airtight
bags depletes with time, and CO2 concentration
increases with time (Yakubu et al., 2011; Murdock and
Bauoa, 2014; Bbosa et al., 2017; Suleiman et al., 2018).
In WPB, many live S. zeamais were found, and the
percent mortality was very low (5.0 to 8.4%). The S.
zeamais had access to oxygen, hence respired, multiplied
and caused serious kernel damage through their rigorous
feeding activities. According to Throne (1994), the
development of S. zeamais spans about 35 days.
Therefore, under optimum conditions, many generations
of S. zeamais might have occurred within the 6 months of
storage. The favorable temperature and humidity might
have enhanced the propensity of the female S. zeamais
to deposit many eggs (Throne, 1994). Hence a large
number of S. zeamais in WPB. The low mortality
recorded in WPB was not surprising. The reason might
be that the rate of S. zeamais multiplication far exceeded
the rate of mortality. A study in a warmer environment
a
b
22 J. Stored Prod. Postharvest Res.
(Arkansas) by Lane and Woloshuk (2017) asserted that
the insect population was distinctively high in WPB
compared to PICS bags. The results obtained in this
current study affirm that assertion.
Statistical comparison of woven polypropylene and
GrainPro bags
The mean S. zeamais mortality was significantly higher in
the GrainPro bags than woven polypropylene bags (100
and 7.2%, respectively). The mass of powder produced
(g), the percentage of damaged bags, the percentage of
damaged grain, and percentage of grain weight loss were
significantly low in the GrainPro bags compared to woven
polypropylene bags. Based on the measured parameters,
GrainPro bags proved a better method for storing grain
even if the grain was previously infested. S. zeamais
could not survive in the GrainPro bags, and therefore, the
grain quality and quantity were maintained. The woven
polypropylene bags, in this case, were similar to the three
indigenous methods discussed earlier. Thus, they were
not efficient in controlling S. zeamais, most especially
when grain was previously infested. This study supports
many findings that have reported on the efficacy of
hermetic bags (Murdock et al., 2012; Njoroge et al., 2014;
Amadou et al., 2016; Bbosa et al., 2017; Lane and
Woloshuk, 2017; Suleiman et al., 2018). Likewise, Walker
et al. (2018) recently reported that a hermetically stored
maize grain had reduced insect infestation and grain
weight loss. The hermetic bags also have a useful
lifespan of mostly two to four years (CIMMYT, 2011;
Ndegwa et al., 2016), and therefore farmers reduce
storage cost as bags are reused.
Conclusions
A good storage results in good quality grain and high
market value for the commodity. Income levels of farmers
could increase to reduce the poverty levels of farmers in
Sub-Saharan Africa through good storage methods. The
maize grains were safely stored in GrainPro bags
compared to WPB. The 100.0% S. zeamais mortality
could be the reason why grain damage was reduced in
the GrainPro bags. Farmers could make good earnings
by storing grain in hermetic bags, most importantly if
protected from rodents. Utilization of synthetic chemicals
and indigenous pseudo-effective methods should be
replaced with hermetic bags. Profit margins of farmers
could increase when grain quality and quantity are
maintained. Additionally, hermetic bags are reusable,
which further benefits farmers.
CONFLICT OF INTERESTS
The authors have not declared any conflict of interests.
ACKNOWLEDGEMENT
The authors express their gratitude for the funding
provided by the Ghana Agriculture Technology Transfer
Project under the International Fertilizer Development
Center, supported by the United States Agency for
International Development (USAID) in Ghana, in
partnership with Iowa State University.
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