**1. Introduction**

According to [1], microbial contamination of grains has resulted in a decrease in its nutritional quality, therefore, negatively affecting the productivity of humans (the workforce of a nation). Grains (cereals and legumes) are staple foods and widely consumed around the world due to their nutritional value and calories. Eating food prepared from contaminated grains could lead to malnutrition due to insufficient nutrients in the grains or food poisoning from mycotoxins.

The presence of these mycotoxins affects the safety, quality, and functional properties of grains. Moreover, the organoleptic properties of products made from these grains could also be altered because some fungi strains produce potent odors, which serve as an antibiotic against other microorganisms [2]. There have been several reports regarding microbial contamination of grains [3–5] and the mycotoxins produced by some of these organisms potentially pose a health risk to consumers.

The ability of fungi to penetrate grains, reside within the endosperm, and utilize nutrients makes conventional methods insufficient to deal with the menace [6]. Therefore, the fundamental problem remains unsolved. A convenient and practical approach where the nutritional quality, sensorial properties, color, and shelf life of the grains remain unchanged is warranted in curbing this menace. Therefore, we propose nanoparticles as the ultimate solution to the predicament mentioned above since they are known to exert potent biocidal activities against the vast myriad of microorganisms [7–17] involves in contaminating grains, hence could be utilized as antifungal agents during grain storage.

This chapter summarizes the microbial contamination of grains and the existing conventional methods employed to curb and or minimize this menace. Also, the potential application of silver nanoparticles as an alternative to the traditional techniques is discussed.

#### **1.1 The economic importance of grains**

Foodgrains could be cereals or legumes (pulses). The world leading cereal grains are wheat, barley, rice, maize, oats, rye, millet, and sorghum. Reports show that cereals are the dominant crops cultivated globally, with 2500 million tons harvested in 2011. The proportion of maize, rice, and wheat harvested is 883; 723; 704 million tons, respectively [18, 19]. Cereals are whole, hulled, cracked, rolled, or ground forms of products produced from various grains constituting staple foods for many localities globally. They contain a substantial amount of starch, a carbohydrate that provides dietary energy [20]. Also, cereals are utilized in feeding livestock. Huntington [21] reported a starch content of 72% for corn and sorghum, while 57, 58 and 77% for barley, oat and wheat. Thus could be utilized to feed ruminants due to their high energy values. The role of cereal grains in the world food supply cannot be undermined as it provides 75% of the calories and protein in the human diet [22]. In Russia, folks use cereals in brewing (beer, kvass), production of distillates, and food (i.e., sweets, cookies, porridge, among others).

The second most important family of crops are the legumes, used for their grains, and as forage [23]. Previous works [24–26] have reported that legume seeds contain protein, soluble and insoluble fiber, slowly digested starch, micro- and macronutrients, and vitamins, in addition to various bioactive phytochemicals such as flavonoids and other antioxidants which are beneficial to human health. Legumes complement proteins in cereals and contain 20–45% protein compared to 7–17% in cereals [27]. Grain legumes are also utilized in feeding livestock, either as a concentrated compound feed (in poultry production) or as whole-crop forage (in cattle, sheep, and pig production) [23]. The presence of antinutritional factors (ANFs) such as Kunitz trypsin inhibitor (KTI), Bowman-Birk inhibitor, and lectins in legumes limits their utilization by humans and in animal husbandry with exception to ruminants (i.e., cattle, sheep and goat), which can degrade ANFs due to the microbial fermentation in their stomach [28]. ANFs can decrease the nutritive value of legumes and cause health problems that may be fatal for both humans (if a substantial amount is consumed) and animals [29]. Nevertheless, various methods have been proposed to decrease the concentration of these ANFs [30–32]. Legumes are also utilized in feeding fish, thus limit the need for expensive fishmeal in the

**105**

*The Potential Application of Nanoparticles on Grains during Storage: Part 1 – An Overview…*

pisciculture industry [33–35]. Therefore, the safety and quality of grain legumes ought to be screened before utilization to avoid any further complications due to

Microorganisms plays vital role in balancing the ecosystem; they aid in the digestion of food in humans; are utilized in the production of food (i.e., starter culture in brewing, cheese production, among others), and serve as a good source of vital enzymes (exogenous enzymes). Nevertheless, these microorganisms could cause problems such as food poisoning (due to some mycotoxins they secrete), food

The entire production process (sowing, harvesting, postharvest drying, and storage) of grains are possible sources of fungi contamination [36]. Dust, water, diseased plants, insects, soil, fertilizers, animal excreta, and environmental pollutants are possible origins of fungi cross contamination. The farmer, the processor, and the distributor could be a source of microbial contamination as well as contaminated farm machinery and unclean storage facilities (silos, etc.). According to [37], microbial contamination from the skin, mouth, and nose of food handlers could be directly introduce into the food chain. During drying, most farmers step on the grains with their Wellington boots, which is a possible route of introducing

The microflora of grains mainly belong to the *Alternaria, Fusarium, Helminthosporium*, and *Cladosporium* families. Yeasts were isolated from grains; however, its load was less compared to mold [4]. Mechanical damage during harvesting or processing could serve as a route via which fungi could penetrate the endosperm of seeds, reproduce, and secrete mycotoxins (aflatoxins, etc.), rendering the food unsafe for human consumption. According to the International Commission on Microbiological Specifications for Foods [39], isolated fungi were mainly on the surface of the kernel; only a few species occupy the inner parts of the seeds due to damage. Birds could introduce fungi on grains by (1) feeding on crops in the field. This can introduce gut microbiota to these plants, which could subsequently be spread by rainwater. (2) Their feet could also aid to spread microbes by landing and picking up fungi spores from a diseased plant/crop to healthy ones. Bats, and insects (bees) could also aid the contamination of crops on the field,

According to [40], the primary cause of spoilage in stored grains in developed countries is attributed to fungi, because insects and rodents are controlled successfully. Factors such as high temperature, humidity, and poor storage conditions create a conducive environment for fungi to flourish and synthesize mycotoxins. These secondary metabolites can cause diseases in humans and animals. For instance, aflatoxins, ochratoxin A, deoxynivalenol, zearalenone, fumonisins, HT-2, and T-2 are classes of mycotoxins produced by various fungus species [41, 42]. Grapes were found to be contaminated with ochratoxin A, thus contaminating any product

processed from them (juice, wine, vinegar, and dried grapes) [3].

**2. Factors promoting microbial growth and mycotoxin production**

When deciding whether moisture, temperature, etc., affects the safety of grains, other factors should be considered to settle on a scientifically proven conclusion. Extrinsic factors (temperature, relative humidity, mechanical injury on seeds during harvest or processing, insects, and rodents infestation) are environmental and

*DOI: http://dx.doi.org/10.5772/intechopen.91005*

**1.2 Sources of fungi contamination of grains**

spoilage, and grain contamination.

which can spread during harvesting.

ANFs and mycotoxins.

microorganism [38].

#### *The Potential Application of Nanoparticles on Grains during Storage: Part 1 – An Overview… DOI: http://dx.doi.org/10.5772/intechopen.91005*

pisciculture industry [33–35]. Therefore, the safety and quality of grain legumes ought to be screened before utilization to avoid any further complications due to ANFs and mycotoxins.

### **1.2 Sources of fungi contamination of grains**

*Mycotoxins and Food Safety*

antifungal agents during grain storage.

**1.1 The economic importance of grains**

food (i.e., sweets, cookies, porridge, among others).

techniques is discussed.

The presence of these mycotoxins affects the safety, quality, and functional properties of grains. Moreover, the organoleptic properties of products made from these grains could also be altered because some fungi strains produce potent odors, which serve as an antibiotic against other microorganisms [2]. There have been several reports regarding microbial contamination of grains [3–5] and the mycotoxins produced by some of these organisms potentially pose a health risk to consumers. The ability of fungi to penetrate grains, reside within the endosperm, and utilize

nutrients makes conventional methods insufficient to deal with the menace [6]. Therefore, the fundamental problem remains unsolved. A convenient and practical approach where the nutritional quality, sensorial properties, color, and shelf life of the grains remain unchanged is warranted in curbing this menace. Therefore, we propose nanoparticles as the ultimate solution to the predicament mentioned above since they are known to exert potent biocidal activities against the vast myriad of microorganisms [7–17] involves in contaminating grains, hence could be utilized as

This chapter summarizes the microbial contamination of grains and the existing conventional methods employed to curb and or minimize this menace. Also, the potential application of silver nanoparticles as an alternative to the traditional

Foodgrains could be cereals or legumes (pulses). The world leading cereal grains are wheat, barley, rice, maize, oats, rye, millet, and sorghum. Reports show that cereals are the dominant crops cultivated globally, with 2500 million tons harvested in 2011. The proportion of maize, rice, and wheat harvested is 883; 723; 704 million tons, respectively [18, 19]. Cereals are whole, hulled, cracked, rolled, or ground forms of products produced from various grains constituting staple foods for many localities globally. They contain a substantial amount of starch, a carbohydrate that provides dietary energy [20]. Also, cereals are utilized in feeding livestock. Huntington [21] reported a starch content of 72% for corn and sorghum, while 57, 58 and 77% for barley, oat and wheat. Thus could be utilized to feed ruminants due to their high energy values. The role of cereal grains in the world food supply cannot be undermined as it provides 75% of the calories and protein in the human diet [22]. In Russia, folks use cereals in brewing (beer, kvass), production of distillates, and

The second most important family of crops are the legumes, used for their grains, and as forage [23]. Previous works [24–26] have reported that legume seeds contain protein, soluble and insoluble fiber, slowly digested starch, micro- and macronutrients, and vitamins, in addition to various bioactive phytochemicals such as flavonoids and other antioxidants which are beneficial to human health. Legumes complement proteins in cereals and contain 20–45% protein compared to 7–17% in cereals [27]. Grain legumes are also utilized in feeding livestock, either as a concentrated compound feed (in poultry production) or as whole-crop forage (in cattle, sheep, and pig production) [23]. The presence of antinutritional factors (ANFs) such as Kunitz trypsin inhibitor (KTI), Bowman-Birk inhibitor, and lectins in legumes limits their utilization by humans and in animal husbandry with exception to ruminants (i.e., cattle, sheep and goat), which can degrade ANFs due to the microbial fermentation in their stomach [28]. ANFs can decrease the nutritive value of legumes and cause health problems that may be fatal for both humans (if a substantial amount is consumed) and animals [29]. Nevertheless, various methods have been proposed to decrease the concentration of these ANFs [30–32]. Legumes are also utilized in feeding fish, thus limit the need for expensive fishmeal in the

**104**

Microorganisms plays vital role in balancing the ecosystem; they aid in the digestion of food in humans; are utilized in the production of food (i.e., starter culture in brewing, cheese production, among others), and serve as a good source of vital enzymes (exogenous enzymes). Nevertheless, these microorganisms could cause problems such as food poisoning (due to some mycotoxins they secrete), food spoilage, and grain contamination.

The entire production process (sowing, harvesting, postharvest drying, and storage) of grains are possible sources of fungi contamination [36]. Dust, water, diseased plants, insects, soil, fertilizers, animal excreta, and environmental pollutants are possible origins of fungi cross contamination. The farmer, the processor, and the distributor could be a source of microbial contamination as well as contaminated farm machinery and unclean storage facilities (silos, etc.). According to [37], microbial contamination from the skin, mouth, and nose of food handlers could be directly introduce into the food chain. During drying, most farmers step on the grains with their Wellington boots, which is a possible route of introducing microorganism [38].

The microflora of grains mainly belong to the *Alternaria, Fusarium, Helminthosporium*, and *Cladosporium* families. Yeasts were isolated from grains; however, its load was less compared to mold [4]. Mechanical damage during harvesting or processing could serve as a route via which fungi could penetrate the endosperm of seeds, reproduce, and secrete mycotoxins (aflatoxins, etc.), rendering the food unsafe for human consumption. According to the International Commission on Microbiological Specifications for Foods [39], isolated fungi were mainly on the surface of the kernel; only a few species occupy the inner parts of the seeds due to damage. Birds could introduce fungi on grains by (1) feeding on crops in the field. This can introduce gut microbiota to these plants, which could subsequently be spread by rainwater. (2) Their feet could also aid to spread microbes by landing and picking up fungi spores from a diseased plant/crop to healthy ones. Bats, and insects (bees) could also aid the contamination of crops on the field, which can spread during harvesting.

According to [40], the primary cause of spoilage in stored grains in developed countries is attributed to fungi, because insects and rodents are controlled successfully. Factors such as high temperature, humidity, and poor storage conditions create a conducive environment for fungi to flourish and synthesize mycotoxins. These secondary metabolites can cause diseases in humans and animals. For instance, aflatoxins, ochratoxin A, deoxynivalenol, zearalenone, fumonisins, HT-2, and T-2 are classes of mycotoxins produced by various fungus species [41, 42]. Grapes were found to be contaminated with ochratoxin A, thus contaminating any product processed from them (juice, wine, vinegar, and dried grapes) [3].

## **2. Factors promoting microbial growth and mycotoxin production**

When deciding whether moisture, temperature, etc., affects the safety of grains, other factors should be considered to settle on a scientifically proven conclusion. Extrinsic factors (temperature, relative humidity, mechanical injury on seeds during harvest or processing, insects, and rodents infestation) are environmental and

physical factors surrounding the grains whereas those attributed to the characteristics of the grains are intrinsic factors (pH, acidity, nutrient composition, biological structure, moisture content/water activity, redox potential, naturally occurring and added antimicrobial factors). Details on how these factors contribute to or promote microbial contamination of grains are examined below.
