**2. Nutrition deficiency and related challenges**

With the increasing world population, enhancing the production of food and nutritional quality of staple crops is the strategy to address the emerging food crises [7]. A food crisis causes multidimensional effects on human nutrition, and it causes malnutrition. It also has effects on the supply of food quantity and quality of food. In the last two decades, these problems have been tried to be solved to reduce the proportion of the world's malnourished population [8]. Protein deficiency malnutrition has emerged as a major nutritional problem, particularly in the developing countries [9]. In the developing countries, cereals play an important source of dietary protein for humans, which comprise 70% of the protein intake [10]. Maize is the world's third primary cereal crop, which is an important protein source used as food and feed for humans and animals and also used in corn starch industry, corn oil production, etc. [11]. QPM has more quantity of carbohydrates, fats, proteins, vitamins and minerals. It is also called as a 'poor man's cereal crop'. In developing countries like Africa and Latin America, as the animal protein is very limited and expensive, which results in being unavailable to a vast sector of the population, maize grains provide about 15–56% of total daily calories in people's diets [12]. Nearly 9.09 million hectares were allocated to cultivate maize, which produces nearly 24.26 million tons in India and can be cultivated throughout the year [13]. Maize proteins consists just 1.81 and 0.35% of lysine and tryptophan content, respectively, which is very low compared with the Food and Agriculture Organization (FAO) recommendation. From the human nutrition perspective, lysine and tryptophan are the most considerable limiting amino acid in the maize endosperm protein. Thus humans and other monogastric animals should include other alternative sources of lysine and tryptophan in their healthy diets [14]. Babies fed on normal maize without any protein supplements suffer from malnutrition and develop Kwashiorkor disease [15]. In this context, the International Maize and Wheat Improvement Center (CIMMYT) and the International Institute of Tropical Agriculture (IITA) are developing varieties to improve the protein quality of maize by incorporating the opaque-2, along with modifier genes, thus increasing the amount of lysine (>4.0%) and tryptophan (>0.8%) contents in the whole grain compared with normal maize [16]. Maize cultivars containing high yield with increasing levels of lysine and tryptophan and having the kernel structure of conventional maize have the potential to reduce the malnutrition [14].

## **3. Storage proteins in QPM**

The mature maize kernel consists of a germ, pericarp and endosperm. An endosperm consists of 90% starch which is a source of concentrated energy and 10% protein which include albumins, globulins, zein and glutelin out of which zein consists 50–70% of total proportion [10]. Zeins are the important storage proteins; these forms as deposit on rough endoplasmic reticulum-delimited protein bodies (PBs) [17]. During the maturation of kernel, these protein bodies become densely packed between starch grains in the vitreous regions of the endosperm [18]. Zeins

**35**

*DOI: http://dx.doi.org/10.5772/intechopen.89038*

**3.1 Zein gene**

22,000 gene promoters [23].

in the endosperm development.

**4. Nutrition analysis of QPMs**

*Quality Protein Maize: An Alternative Food to Mitigate Protein Deficiency in Developing…*

are a group of four structurally distinct alcohol-soluble proteins (α-zein, β-zein, γ-zein and δ-zein) [17] present only in seeds' endosperm and playing a key role in storing and supplying N, C and S to the germinating seedling [12]. Among those zein proteins, α-zeins and δ-zeins are deposited in the central region, and γ-zeins and β-zeins were deposited in the outer region of protein bodies [19]. The zein fractions are rich in cysteine and methionine amino acids, and it also consists of glutamine, leucine and proline and is completely devoid of two important essential amino acids lysine and tryptophan, whereas other proteins consist of these amino acids in large quantities [20]. The zein synthesis serves as a model system to study coordinated genetic regulation of several genes expressed at very high levels at a specific developmental stage. Suppression of zein fraction without drastically altering the contribution of other fractions could be, thus, seen as a feasible approach to

bring about improvements in the amino acid balance in maize grain [12].

Zein is a class of prolamin proteins that are mainly present in maize. All the zein polypeptides are products of different structural genes [21]. Most of the prolamin genes have a promoter element called the endosperm or prolamin box. The promoter element is present about the 300 base pairs upstream of the translation start codon and has a conserved 15-bp element that contains the 7-bp endosperm motif (TGTAAAG) [22]. This endosperm motif acts as a tissue-specific enhancer in Mr.

Genetic analysis of o2 modifiers revealed several quantitative trait loci (QTLs) dispersed on the chromosomes. These identified QTLs were correlated with the 27-kDa γ-zein gene expression and protein quantity in QPM [24]. The 27-kDa γ-zein gene expression is not under the control of the o2 protein [25]. The o2 modifier genes involved in the 27-kDa γ-zein gene expressions are observed in two different QTLs. The first of these is associated with increased expression [26]. Single copy of γ-zein genes encodes the 50, 27 and 16-kDa proteins, which were observed in the B73 genome [27]. Based on the allotetraploidization and protein-sequence similarity, both 27 and 16 kDa γ-zein genes originated from a common progenitor [28]. It is about 20–25% of total zeins; the low abundance 50-kDa γ-zein gene has low similarity with other two γ-zein genes [27]. The γRNAi and βRNAi were involved in maize kernel opacity to increase the intensification. It reveals that opacity was not involved in reducing the thickness of the opaque-2-mutated endosperm; it is due to partial arrangement of starch granules in the endosperm [29]. Although discrete protein bodies were observed in endosperm cells, honeycomb-like masses of protein bodies were observed. It indicates that different zeins have played an important role

Generally, quality of protein nutrition was estimated by composition of amino

acids, digestibility and amino acid requirement to consume the protein. The QPMs are reported to have increased levels of lysine and tryptophan in the endosperm protein, which enhances the biological value of protein similar to the milk protein. It has brought about great hope in the effort to improve human nutrition [30]. Firstly there is a significant difference in the QPM kernel when compared to normal maize kernel. Kernel hardness was determined by calculating floatation index where it is 57% for QPM, whereas for normal maize, it is 19.7%. The whole kernel protein was 13.15% in QPMs with contribution of 8.6 and 13.88% from

*DOI: http://dx.doi.org/10.5772/intechopen.89038 Quality Protein Maize: An Alternative Food to Mitigate Protein Deficiency in Developing…*

are a group of four structurally distinct alcohol-soluble proteins (α-zein, β-zein, γ-zein and δ-zein) [17] present only in seeds' endosperm and playing a key role in storing and supplying N, C and S to the germinating seedling [12]. Among those zein proteins, α-zeins and δ-zeins are deposited in the central region, and γ-zeins and β-zeins were deposited in the outer region of protein bodies [19]. The zein fractions are rich in cysteine and methionine amino acids, and it also consists of glutamine, leucine and proline and is completely devoid of two important essential amino acids lysine and tryptophan, whereas other proteins consist of these amino acids in large quantities [20]. The zein synthesis serves as a model system to study coordinated genetic regulation of several genes expressed at very high levels at a specific developmental stage. Suppression of zein fraction without drastically altering the contribution of other fractions could be, thus, seen as a feasible approach to bring about improvements in the amino acid balance in maize grain [12].

#### **3.1 Zein gene**

*Maize - Production and Use*

maize' [3].

modifier genes, which present hard endosperm in the o2 background, were developed at the International Maize and Wheat Improvement Center (CIMMYT), Mexico [5], and University of Natal, South Africa [6]. This leads to the development of nutritionally enriched hard endosperm maize, widely known as 'quality protein

With the increasing world population, enhancing the production of food and nutritional quality of staple crops is the strategy to address the emerging food crises [7]. A food crisis causes multidimensional effects on human nutrition, and it causes malnutrition. It also has effects on the supply of food quantity and quality of food. In the last two decades, these problems have been tried to be solved to reduce the proportion of the world's malnourished population [8]. Protein deficiency malnutrition has emerged as a major nutritional problem, particularly in the developing countries [9]. In the developing countries, cereals play an important source of dietary protein for humans, which comprise 70% of the protein intake [10]. Maize is the world's third primary cereal crop, which is an important protein source used as food and feed for humans and animals and also used in corn starch industry, corn oil production, etc. [11]. QPM has more quantity of carbohydrates, fats, proteins, vitamins and minerals. It is also called as a 'poor man's cereal crop'. In developing countries like Africa and Latin America, as the animal protein is very limited and expensive, which results in being unavailable to a vast sector of the population, maize grains provide about 15–56% of total daily calories in people's diets [12]. Nearly 9.09 million hectares were allocated to cultivate maize, which produces nearly 24.26 million tons in India and can be cultivated throughout the year [13]. Maize proteins consists just 1.81 and 0.35% of lysine and tryptophan content, respectively, which is very low compared with the Food and Agriculture Organization (FAO) recommendation. From the human nutrition perspective, lysine and tryptophan are the most considerable limiting amino acid in the maize endosperm protein. Thus humans and other monogastric animals should include other alternative sources of lysine and tryptophan in their healthy diets [14]. Babies fed on normal maize without any protein supplements suffer from malnutrition and develop Kwashiorkor disease [15]. In this context, the International Maize and Wheat Improvement Center (CIMMYT) and the International Institute of Tropical Agriculture (IITA) are developing varieties to improve the protein quality of maize by incorporating the opaque-2, along with modifier genes, thus increasing the amount of lysine (>4.0%) and tryptophan (>0.8%) contents in the whole grain compared with normal maize [16]. Maize cultivars containing high yield with increasing levels of lysine and tryptophan and having the kernel structure of

conventional maize have the potential to reduce the malnutrition [14].

The mature maize kernel consists of a germ, pericarp and endosperm. An endosperm consists of 90% starch which is a source of concentrated energy and 10% protein which include albumins, globulins, zein and glutelin out of which zein consists 50–70% of total proportion [10]. Zeins are the important storage proteins; these forms as deposit on rough endoplasmic reticulum-delimited protein bodies (PBs) [17]. During the maturation of kernel, these protein bodies become densely packed between starch grains in the vitreous regions of the endosperm [18]. Zeins

**2. Nutrition deficiency and related challenges**

**34**

**3. Storage proteins in QPM**

Zein is a class of prolamin proteins that are mainly present in maize. All the zein polypeptides are products of different structural genes [21]. Most of the prolamin genes have a promoter element called the endosperm or prolamin box. The promoter element is present about the 300 base pairs upstream of the translation start codon and has a conserved 15-bp element that contains the 7-bp endosperm motif (TGTAAAG) [22]. This endosperm motif acts as a tissue-specific enhancer in Mr. 22,000 gene promoters [23].

Genetic analysis of o2 modifiers revealed several quantitative trait loci (QTLs) dispersed on the chromosomes. These identified QTLs were correlated with the 27-kDa γ-zein gene expression and protein quantity in QPM [24]. The 27-kDa γ-zein gene expression is not under the control of the o2 protein [25]. The o2 modifier genes involved in the 27-kDa γ-zein gene expressions are observed in two different QTLs. The first of these is associated with increased expression [26]. Single copy of γ-zein genes encodes the 50, 27 and 16-kDa proteins, which were observed in the B73 genome [27]. Based on the allotetraploidization and protein-sequence similarity, both 27 and 16 kDa γ-zein genes originated from a common progenitor [28]. It is about 20–25% of total zeins; the low abundance 50-kDa γ-zein gene has low similarity with other two γ-zein genes [27]. The γRNAi and βRNAi were involved in maize kernel opacity to increase the intensification. It reveals that opacity was not involved in reducing the thickness of the opaque-2-mutated endosperm; it is due to partial arrangement of starch granules in the endosperm [29]. Although discrete protein bodies were observed in endosperm cells, honeycomb-like masses of protein bodies were observed. It indicates that different zeins have played an important role in the endosperm development.

## **4. Nutrition analysis of QPMs**

Generally, quality of protein nutrition was estimated by composition of amino acids, digestibility and amino acid requirement to consume the protein. The QPMs are reported to have increased levels of lysine and tryptophan in the endosperm protein, which enhances the biological value of protein similar to the milk protein. It has brought about great hope in the effort to improve human nutrition [30]. Firstly there is a significant difference in the QPM kernel when compared to normal maize kernel. Kernel hardness was determined by calculating floatation index where it is 57% for QPM, whereas for normal maize, it is 19.7%. The whole kernel protein was 13.15% in QPMs with contribution of 8.6 and 13.88% from

endosperm and germ, whereas it is 9.25% in normal maize with contribution of 7.9 and 1.28% from endosperm and germ, respectively [18]. An improvement of protein quality has been correlated with the presence of the opaque-2 mutant gene [31]. Crude protein of QPM was higher than the normal maize, and the proportional contribution of the germ is lower in QPMs than with normal varieties. These structural and biochemical changes that happen in the kernel lead to the modifications of the protein profile, both in content and structure, and therefore on the functionality of the protein extracted from QPM [30]. Based on the chemical component analysis, QPM whole kernels showed highest protein content compared with normal maize [32].
