*3.2. Aflatoxin Content of Maize Samples*

Levels of aflatoxin in maize samples stored in polypropylene and hermetic bags ranged between 0.9 and 20 ppb, as shown in Figure 2. Results from the aflatoxin analysis revealed that maize sampled from polypropylene bags had relatively higher aflatoxin levels (13.9–20 ppb) than those from hermetic bags (0.90–2.60 ppb). These values were significantly different (*p* < 0.05). Similar observations were made for aflatoxin levels in grains sampled at Ejura, PP bag (18 ppb), hermetic bag (2.6 ppb), and Asante Akyem Agogo, PP bag (13.9 ppb), hermetic bag (1.6 ppb), respectively.

All maize samples stored in the traditional (polypropylene) bags had aflatoxin concentrations above the recommended limit (15 ppb) for human consumption as reported by Omari et al. [12] whereas those of hermetic storage bags were below the limit.

**Figure 2.** Aflatoxin concentration of maize stored in hermetic and polypropylene storage bags. Means within the graph followed by a different letter are significantly different at *p* < 0.05 (ANOVA: *t*-test).

#### *3.3. Pesticide Residue Concentration in Maize Samples*

Detected concentrations of the various pesticide residues in each maize sample from the three research areas (Abofour, Ejura and Asante-Akyem Agogo) are presented in Figures 3 and 4. Thirty-five pesticide residues were analyzed for two storage bags from each of the study areas. A total of 33 residues representing about 94.29% of the residues that were screened were found absent. These included bifenthrin, chlorpyrifos, dimethoate, permethrin, fenvalerate, profenofos, delta-HCH, fenpropathrin, p,p'-DDT, cyfluthrin, fonofos, ethoprophos, malathion, methoxychlor, chlorfenvinphos, heptachlor, lindane, p,p'-DDD, fenitrothion, dieldrin, endosulfan sulfate, alpha-endosulfan, p,p'-DDE, endrin, aldrin, betaendosulfan, beta-HCH, diazinon, methamidophos, pirimiphos-methyl, gamma chlordane and parathion. The absence of organochlorine pesticide residues in the maize samples could be attributed to farmers' adherence to the ban on the application of organochlorine pesticides [13].

Lambda-cyhalothrin was detected in all maize samples stored in polypropylene and all were above the EU maximum residue limit of 0.02 mg/kg. Deltamethrin residues were detected in hermetic bags and were below the EU maximum residue limit of 2.0 mg/kg as reported by Milne [14].

**Figure 3.** Deltamethrin residue in hermetic and polypropylene bags among study locations.

**Figure 4.** Lambda-cyhalothrin residue in hermetic and polypropylene bags among study locations.

#### **4. Discussion**

#### *4.1. Grain Quality of Maize Samples*

Generally, the recorded moisture content of the samples suggests adequate drying of the grains before storage by the warehouse operators; however, the relatively higher moisture content of maize samples stored in the polypropylene bags could be due to the gaseous exchange between the maize samples and the immediate environment in the storage area. Polypropylene bags have been reported to be porous in nature and therefore allows for moisture absorption or loss unlike hermetic bags that have a restrictive gaseous interchange barrier [9]. Moisture content beyond 13% encourages microbial growth and favors mycotoxin development, implying that maize grains stored in polypropylene bags will be susceptible to microbial and aflatoxin contamination compared to those stored in hermetic bags [8]. Gasparin et al. [10] and Bewley et al. [11] reported that control of maize grain moisture is the surest way of sustaining its viability, quality and safety throughout storage.

The variability in the organic and inorganic matter and stained and other grain qualities assessed could be attributed to decreased metabolic respiration/activity of mold in the hermetic bags compared to the polypropylene bags. Inorganic matter constitutes the presence of inanimate objects like stones, metals, plastics, cloth, etc. whereas organic matter takes into account wood, cobs, leaves, sticks, etc. in maize grains [15]. Both organic and inorganic matter are given keen attention by stakeholders in the maize value chain as they pose food safety threats to humans and animals aside from increasing the cleaning costs of processing industries. The decomposition of organic matter in maize adds to filth, stain and discolor of maize grains. The presence of diseased grains was significantly higher in the polypropylene bags than the hermetic bags. According to [16] this could be attributed to bacterial or fungal infections due to the presence of insect activities in the bag.

Discolored maize is grain that has an alteration in its regular (white or yellow) coloration to red, brown or a dark smear, which is usually influenced by excessive heat and/or excessive respiration [17]. The percentage of discolored grains in the polypropylene bags (3.70%) was significantly (*p* < 0.05) higher than that of the hermetic bags (0.79%). The observed discoloration could be attributed to respiration from insect and fungi activity within polypropylene bags and is an indication of a higher population of insects and fungi present in maize stored in the polypropylene bags compared to the grains in the hermetic bags. Fungi that occur in maize storage include members of the genera Aspergillus and Penicillium; their adaptation leads to the colonization of the embryo, which causes discoloration and rotting due to increased fatty acid content, oil rancidity and heating of the seed mass [18]. The grain quality analysis conducted on the stored maize samples revealed a significant (*p* < 0.05) concentration of broken/chipped maize in polypropylene bags (7.85%)

as compared to grains in hermetic bags (6.04%) in all the three study communities. The difference could be ascribed to the high moisture content of grains and poor post-harvest handling practices such as shelling, cleaning and winnowing. High moisture content has been found to significantly contribute to breakage of grains during shelling [19]. A similar study by Adu et al. [3] established that traditional shelling where maize cobs are packed in sacks and beaten with sticks usually results in an uncontrolled breakage of maize grains.

Mutungi et al. [7] reported that hefty sums of broken grain facilitate insects and microbial development and hence are undesirable in grain lots projected for longstanding storage. Maize grain processors lay emphasis on the amount of broken/chipped maize in their decision to accept or reject raw materials (maize) since it has the tendency to increase percentage grain losses in cleaning processes.

Maize samples stored in polypropylene bags recorded a higher amount of insect damaged grains (9.75%) in comparison to 1.96% recorded of sampled grains from the hermetic bags. Invasion of insects such as the maize weevil and the larger grain borer is responsible for such observation and was very profound in polypropylene bags due to its porous nature, permitting influx of oxygen for insect activity. These insects feed on maize endosperm leading to reduction in grain weight and end-product yield [8]. The lower insect damaged grains recorded in hermetic bags shows that it is better to store maize grains in hermetic bags than in polypropylene bags. The results further inform stakeholders along the maize value chain of the benefits of hermetic storage in the quest to reduce post-harvest losses in maize due to insect activity, which contributes to about 90% of post-harvest losses of maize globally according to [19].

Shriveled maize grains are underdeveloped, thin and papery in appearance, potentially resulting from a couple of factors such as soil and nutrient condition, moisture deficiency, drought and incidence of diseases [20,21]. Limiting growth factors that affect biomass and photosynthetic potential hinder the development of the reproductive organs of maize and consequently affect grain sizes. Results from the comparative analysis revealed that the percentages of shriveled grains in the polypropylene bags (3.52%) were not significantly different (*p* > 0.05) from those of the hermetic bags (1.45%), informing that the parameter is independent of the method of storage.

Maize grain quality assessment between the two methods of storage revealed a significant difference between the overall or total defective grains found in the polypropylene (30.49%) and hermetic bags (9.58%). The lower percentage of total defective grains in hermetic bags makes it a better option over polypropylene bags for maize storage.

#### *4.2. Aflatoxin Content of Maize Samples*

Aflatoxin contamination in maize usually occurs in two different phases: pre-harvest and post-harvest contamination. High humidity, insufficient grain drying, high temperatures and poor storage surroundings are typical causes of aflatoxin development [9]. Efficient post-harvest management of maize is an important factor in mitigating postharvest storage-related losses. Aflatoxin in maize significantly affects the market value of maize and threatens consumer health and food security. A study by Bakoye et al. [22] revealed that aflatoxin contamination is not directly correlated to moisture content but emphasized moldy grains, foreign materials, and the prevalence of insects as a function of aflatoxin contamination in grains.

Mutambuki et al. [23] explained that hermetically sealed containers operate on a phenomenon of restricting O2 availability to microbes and insects already in cereal grains upon storage. The elimination of oxygen is primarily achieved through the exchange of gases between cereals, insects and microbes inside airtight containers; respiration within the airtight container leads to a reduction in oxygen volumes with an increase in carbon dioxide volumes, causing suffocation and subsequent death of insects and microbes. Gaseous exchange within polypropylene sacks is unrestricted, as the porosity of the bags allows free movement of oxygen and carbon dioxide in and out of the bag, ensuring balance in respiration among maize grains, insects and microbes [24]. The accessibility of oxygen by microbes (fungi) supports their growth and consequently increases aflatoxin levels in the maize samples stored in the polypropylene sacks. The results obtained from the present study show that hermetic storage bags have competitive advantages over polypropylene bags in terms of aflatoxin prevention.

#### *4.3. Pesticide Residue Concentration in Maize Samples*

The detection of lambda-cyhalothrin and deltamethrin, all belonging to the synthetic pyrethroid class of pesticides, in sampled maize grains could be as a result of the substitution of organochlorines with a more biodegradable option of synthetic pyrethroids. Results from this study corroborate a study by Bempah et al. [25] that detected pyrethroid residues in fruits and vegetables, which emphasizes a signal of a paradigm shift in the usage of pesticides in Ghana from organochlorine to less toxic, biodegradable pyrethroid pesticides. Dziembowska et al. [26] reported that pyrethroids have a high efficacy of about 2250 counts and are particularly lethal to insects compared to advanced animals. The detection of lambda-cyhalothrin above its stipulated maximum residue limit of 0.02 mg/kg suggests the possibility of misapplication and abuse of the insecticide. The detection could also originate from environmental contamination as a result of previous agricultural activities (such as chemical spraying against weeds and insects) in the growing communities. Pyrethroids usually exhibit low toxicity with respect to humans, characterized by a speedy breakdown in adults, as they do not bio-accumulate in adult tissues and are expelled out of the body through urine [26]. Since pyrethroid insecticide residues have shown some form of toxicity to humans, bioaccumulation along the food chain may subject an exposed population to harmful long-term health hazards.

#### **5. Conclusions**

The study discovered that maize grains stored in hermetic bags recorded lower aflatoxin and pesticide residue concentrations and higher grain quality than those stored in polypropylene bags with respect to diseased, discolored, broken/chipped, insect-damaged, stained, germinated, shriveled, other grains, total defective, inorganic and organic matter. Only lambda-cyhalothrin and deltamethrin were detected in maize stored in polypropylene and hermetic bags, respectively. Lambda-cyhalothrin showed residue levels higher than its maximum residue limit (MRL) of 0.02 mg/kg and this poses safety issues for consumers, whilst maize samples stored in hermetic bags had deltamethrin residues below the MRL of 2.00 mg/kg. The findings point to the many benefits of the use of hermetic bags over polypropylene bags in maize grain storage and the urgent need to establish reliable monitoring programs for pesticides so that any exceedance in concentration over quality standards can be detected with appropriate actions taken.

Further research could focus on evaluating pesticide residue concentrations of maize from production through to the point of entry into the market to establish at what point(s) along the maize supply chain pesticides are being introduced.

**Author Contributions:** The following authors contributed to the work: Conceptualization, J.O.A. and F.D.W.-M.; data curation, S.K.N. and Y.G.A.; formal analysis, S.K.N. and Y.G.A.; funding acquisition, J.O.A.; investigation, S.K.N.; methodology, S.K.N.; project administration, F.D.W.-M.; resources, J.O.A. and F.D.W.-M.; Supervision, F.D.W.-M.; validation, Y.G.A.; visualization, Y.G.A.; writing—original draft, S.K.N.; writing—review & editing, Y.G.A., J.O.A. and F.D.W.-M. All authors have read and agreed to the published version of the manuscript.

**Funding:** Funding for this study was provided under grants from The Rockefeller Foundation (grant 2018 FOD 004) and the Foundation for Food and Agriculture Research (grant DFs-18-0000000008).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.
