**2.1 Globulins**

Globulins (7S and 11S) comprise of the majority of the total protein in many seeds that are consumed by humans. Vicilins (7S globulins) and legumins (11S globulins) share similar folds and belong to the cupin superfamily of proteins.

Ara h 1, a 7S vicilin, exists as trimer formed by three identical monomers and is also a glycoprotein. It compromises approximately 12–16% of peanut proteins [22]. When analyzed in SDS PAGE, the Ara h 1 vicilin shows two isoforms at 69 and 66 kDa [23]. 11S globulin seed protein is a hexamer (360–380 kDa) formed by two trimers [24], with each monomer having four linear epitopes [25]. Ara h 3 is a legumin-like seed storage protein that has high sequence similarity to glycinin, the major 11S globulin seed storage protein family in soybean. Ara h 3 and related proteins belong to the 11S globulin storage protein family that is characterized by three common features. The first one is that they contain an acidic and basic chain separated

#### **Figure 1.**

*SDS PAGE analysis of Total Seed Storage Proteins in Peanut (Arachis hypogaea) cultivars along side a marker (adapted from [19]).*

by a conserved Asn-Gly (N–G) peptide bond. Second, the formation of intra and inter-disulfide bonds is observed due to four conserved cysteine residue. Third, an Asn-Gln (N–Q ) peptide bond is present that serves as a potential proteolytic cleavage site. It also functions as a trypsin inhibitor [24, 26, 27]. Ara h 3 and soybean glycinin result in a sequence identity of 47.2%. Mature Ara h 3 is a hexamer (360–380 kDa) formed by a head-to-head association of two trimers [25, 28]. Ara h 3 was originally identified as 14 kDa [28]. Later, it was found to be of 60 kDa [24]. This Ara h 3 is post translationally modified and cleaved into 43 kDa acidic and 28 kDa basic subunits. In SDS PAGE, several fragments can be identified as 14, 25, 42 and 45 kDa.

Ara h 4 is also arachin, an isoform of Ara h 3. Ara h 4 is no more used but it is renamed as Ara h 3.02 [29]. Five different genes were found to encode for isoforms of Ara h 3 [30].

#### **2.2 Albumins**

Ara h 2, a 2S albumin is a glycoprotein and accounts for approximately 6 to 9% of total peanut protein [31] with a molecular weight of approximately 17 kDa [32]. Ara h 2 also known as conglutin and functions as a trypsin inhibitor. Structurally, Ara h 2 has five α-helices arranged in right-handed super helix connected by several extended loops with four conserved disulfide bridges and 10 highly exposed epitope binding sites [33].

Ara h 5 (15 kDa) belongs to the profilin family and regulates the polymerization of actin [34]. It is presented at low levels in peanut extracts. Ara h 6 is a 15 kDa protein and belongs to the conglutin family [35]. It is 59% homologous to Ara h 2 and has similar allergenicity [36, 37]. Ara h 6 is a heat and digestion stable protein and showed resistance to proteolytic treatment [38, 39]. Ara h 7 is also a 15 kDa protein and belongs to the conglutin family [35]. The sequence identity between Ara h 2 and Ara h 6 is 35%.

#### **2.3 Other proteins**

Ara h 8 (17 kDa) is a Pathogenesis related protein. It is homologous to Betv1 proteins. Ara h 9 and Ara h 17 (9.8 kDa, 2 isoforms) are nonspecific lipid-transfer (nsLTPs) proteins of type 1 category. Ara h 16 is an nsLTP of type 2 category (approx. 7 kDa) [40].

Ara h 10 (16 kDa, 2 isoforms) and Ara h 11 (14 kDa) belong to oleosin. Ara h 14, Ara h 15 are peanut oleosins with amphiphilic structural proteins. Ara h 12 and Ara h 13 are defensin, with molecular weight ranging from 5 to 12 kDa [35]. Oleosins are also abundant in peanut seeds.

#### **3. Importance as a functional food**

Peanut is increasingly recognized as a functional food. The protein quality is based on amino acid pattern and percent digestibility. According to Protein Digestibility Corrected Amino Acid Score (PDCAAS), the plant protein peanut is nutritionally equivalent to animal proteins such as meat and eggs. The PDCAAS for peanuts has been estimated to be about 0.70 out of 1, whereas, for whole wheat PDCASS is 0.46. After the oil is extracted, the protein content in peanut cake can reach upto 50% [41]. All the protein components are highly digestible.

#### **3.1 Amino acids content**

Peanuts contain all the twenty amino acids, including 9 essential amino acids, necessary for normal body growth and metabolism [12]. They also show high levels of arginine and histidine. The remaining amino acids were present in substantial quantities except methionine, tryptophan and cystine that were considered low [42].

**125**

*Functional Uses of Peanut (*Arachis hypogaea *L.) Seed Storage Proteins*

Comparisons across common tree nuts and peanuts show that all are naturally high in both acidic and basic amino acids, in addition to also being naturally high in hydrophobic amino acids, including leucine, glycine and valine, among others [43]. Peanut has a high percentage of arginine (12.5%), which gives added benefit with its overall high protein content, making peanut an important dietary source of this amino acid whose consumption has been directly linked to various cardiovascular health promoting activities [14]. The arginine is highest in peanuts among foods [44]. The amino acid profile of the peanut meals shows that it can be an ingredient for protein fortification [45]. Being a leguminous plant protein, it also has additional components that have positive health benefits like fiber and unique bioactive components besides amino acids (**Tables 1** and **2**). They also contain many important functional components including

coenzyme Q10 [46], and polysterols, which make it a functional food [47, 48].

Amino acid data for blanched seed (without peanut skin or testa) is ultimately most relevant to peanut nutrition as the skin only accounts for approximately 3% of the total seed weight after shelling and skins are relatively low in total protein compared with the blanched seed, i.e., approximately 15% versus 25%. For blanched seed, asparagine/aspartic acid and glutamine/glutamic acid residues predominate, accounting for approximately 35% of the amino acids, which is in good agreement

In the fats, peanut contains 50% monounsaturated fatty acids (MUFAs), 33% polyunsaturated fatty acids (PUFAs) and 4% saturated fatty acids [50]. PUFA needs to be given through diet and cannot be synthesized. This way presence of high MUFAs and PUFAs reduce heart stress. So, the oils of peanuts are very important and healthy. Carbohydrates that contain fiber or starch, these two types of carbohydrates have a slower, less pronounced effect on blood sugar. The American Diabetes Association ranks peanuts and other nuts as diabetes superfoods. Peanut have a low glycemic index (GI) and glycemic load (GL) [51]. On a 100 –point scale, the GI of peanuts is 14, and the GL of peanuts is one. Mature groundnut kernels were reported to contain 9.5–19% carbohydrates in which starch and sucrose are the major constituents.

The peanut is also a good source of minerals like Magnesium, Calcium, Phosphorus,

potassium, iron, zinc, iron, copper, selenium and vitamins as well as dietary fibers (**Table 1**). Minerals like calcium and phosphorus are important for normal growth and development of bones and muscles. While minerals required in trace amounts like zinc,

Peanuts are a vital source for introducing most of the water soluble vitamins into the human body along with vitamin E which is fat soluble [1, 12]. A 100 g peanuts consumption is capable of providing up to 75% recommended dietary allowances (RDA) of Niacin, 60% RDA of folate, 53% RDA of thiamin, 10% RDA of Riboflavin, 35% RDA of pantothenic acid, 27% RDA of pyridoxine, 55.5% RDA of vitamin E [12, 52]. In 42 g of peanuts, more than 10% provide recommended dietary allowances (RDA) for niacin, pantothenic acid, and total folate is present. Another important vitamin which is supplemented in the body by the intake of peanuts is vitamin B3 [53] (known as Niacin or Niacinamide or Nicotinamide), to an extent of 13.525 mg. The vitamin B5 pantothenic acid is also provided by peanuts [52]. This vitamin plays an important role in the normal functioning of the respiratory chain and participates in hydrogen transfer, and electron transfer reactions through its coenzymes, Nicotinamide adenine dinucleotide (NAD) and Nicotinamide adenine dinucleotide phosphate (NADP). Roasted peanuts will provide B6 to the human body to the extent of 0.256 mg. Vitamin B9, more commonly known as folate or folic acid, is a water-soluble vitamin that is part of the B vitamin family and required for normal

selenium whose daily requirement can be met by 100 g of peanuts [12, 52].

*DOI: http://dx.doi.org/10.5772/intechopen.96871*

with data from other sources [43, 49].

**3.2 Fats, vitamins and minerals**

*Functional Uses of Peanut (*Arachis hypogaea *L.) Seed Storage Proteins DOI: http://dx.doi.org/10.5772/intechopen.96871*

Comparisons across common tree nuts and peanuts show that all are naturally high in both acidic and basic amino acids, in addition to also being naturally high in hydrophobic amino acids, including leucine, glycine and valine, among others [43]. Peanut has a high percentage of arginine (12.5%), which gives added benefit with its overall high protein content, making peanut an important dietary source of this amino acid whose consumption has been directly linked to various cardiovascular health promoting activities [14]. The arginine is highest in peanuts among foods [44]. The amino acid profile of the peanut meals shows that it can be an ingredient for protein fortification [45]. Being a leguminous plant protein, it also has additional components that have positive health benefits like fiber and unique bioactive components besides amino acids (**Tables 1** and **2**). They also contain many important functional components including coenzyme Q10 [46], and polysterols, which make it a functional food [47, 48].

Amino acid data for blanched seed (without peanut skin or testa) is ultimately most relevant to peanut nutrition as the skin only accounts for approximately 3% of the total seed weight after shelling and skins are relatively low in total protein compared with the blanched seed, i.e., approximately 15% versus 25%. For blanched seed, asparagine/aspartic acid and glutamine/glutamic acid residues predominate, accounting for approximately 35% of the amino acids, which is in good agreement with data from other sources [43, 49].

#### **3.2 Fats, vitamins and minerals**

*Grain and Seed Proteins Functionality*

**2.2 Albumins**

**2.3 Other proteins**

also abundant in peanut seeds.

**3.1 Amino acids content**

**3. Importance as a functional food**

by a conserved Asn-Gly (N–G) peptide bond. Second, the formation of intra and inter-disulfide bonds is observed due to four conserved cysteine residue. Third, an Asn-Gln (N–Q ) peptide bond is present that serves as a potential proteolytic cleavage site. It also functions as a trypsin inhibitor [24, 26, 27]. Ara h 3 and soybean glycinin result in a sequence identity of 47.2%. Mature Ara h 3 is a hexamer (360–380 kDa) formed by a head-to-head association of two trimers [25, 28]. Ara h 3 was originally identified as 14 kDa [28]. Later, it was found to be of 60 kDa [24]. This Ara h 3 is post translationally modified and cleaved into 43 kDa acidic and 28 kDa basic subunits. In

Ara h 4 is also arachin, an isoform of Ara h 3. Ara h 4 is no more used but it is renamed as Ara h 3.02 [29]. Five different genes were found to encode for isoforms of Ara h 3 [30].

Ara h 2, a 2S albumin is a glycoprotein and accounts for approximately 6 to 9% of total peanut protein [31] with a molecular weight of approximately 17 kDa [32]. Ara h 2 also known as conglutin and functions as a trypsin inhibitor. Structurally, Ara h 2 has five α-helices arranged in right-handed super helix connected by several extended loops with four conserved disulfide bridges and 10 highly exposed epitope binding sites [33]. Ara h 5 (15 kDa) belongs to the profilin family and regulates the polymerization of actin [34]. It is presented at low levels in peanut extracts. Ara h 6 is a 15 kDa protein and belongs to the conglutin family [35]. It is 59% homologous to Ara h 2 and has similar allergenicity [36, 37]. Ara h 6 is a heat and digestion stable protein and showed resistance to proteolytic treatment [38, 39]. Ara h 7 is also a 15 kDa protein and belongs to the conglutin family [35]. The sequence identity between Ara h 2 and Ara h 6 is 35%.

Ara h 8 (17 kDa) is a Pathogenesis related protein. It is homologous to Betv1 proteins.

Ara h 9 and Ara h 17 (9.8 kDa, 2 isoforms) are nonspecific lipid-transfer (nsLTPs) proteins of type 1 category. Ara h 16 is an nsLTP of type 2 category (approx. 7 kDa) [40]. Ara h 10 (16 kDa, 2 isoforms) and Ara h 11 (14 kDa) belong to oleosin. Ara h 14, Ara h 15 are peanut oleosins with amphiphilic structural proteins. Ara h 12 and Ara h 13 are defensin, with molecular weight ranging from 5 to 12 kDa [35]. Oleosins are

Peanut is increasingly recognized as a functional food. The protein quality is based on amino acid pattern and percent digestibility. According to Protein Digestibility Corrected Amino Acid Score (PDCAAS), the plant protein peanut is nutritionally equivalent to animal proteins such as meat and eggs. The PDCAAS for peanuts has been estimated to be about 0.70 out of 1, whereas, for whole wheat PDCASS is 0.46. After the oil is extracted, the protein content in peanut cake can

Peanuts contain all the twenty amino acids, including 9 essential amino acids, necessary for normal body growth and metabolism [12]. They also show high levels of arginine and histidine. The remaining amino acids were present in substantial quantities except methionine, tryptophan and cystine that were considered low [42].

reach upto 50% [41]. All the protein components are highly digestible.

SDS PAGE, several fragments can be identified as 14, 25, 42 and 45 kDa.

**124**

In the fats, peanut contains 50% monounsaturated fatty acids (MUFAs), 33% polyunsaturated fatty acids (PUFAs) and 4% saturated fatty acids [50]. PUFA needs to be given through diet and cannot be synthesized. This way presence of high MUFAs and PUFAs reduce heart stress. So, the oils of peanuts are very important and healthy.

Carbohydrates that contain fiber or starch, these two types of carbohydrates have a slower, less pronounced effect on blood sugar. The American Diabetes Association ranks peanuts and other nuts as diabetes superfoods. Peanut have a low glycemic index (GI) and glycemic load (GL) [51]. On a 100 –point scale, the GI of peanuts is 14, and the GL of peanuts is one. Mature groundnut kernels were reported to contain 9.5–19% carbohydrates in which starch and sucrose are the major constituents.

The peanut is also a good source of minerals like Magnesium, Calcium, Phosphorus, potassium, iron, zinc, iron, copper, selenium and vitamins as well as dietary fibers (**Table 1**). Minerals like calcium and phosphorus are important for normal growth and development of bones and muscles. While minerals required in trace amounts like zinc, selenium whose daily requirement can be met by 100 g of peanuts [12, 52].

Peanuts are a vital source for introducing most of the water soluble vitamins into the human body along with vitamin E which is fat soluble [1, 12]. A 100 g peanuts consumption is capable of providing up to 75% recommended dietary allowances (RDA) of Niacin, 60% RDA of folate, 53% RDA of thiamin, 10% RDA of Riboflavin, 35% RDA of pantothenic acid, 27% RDA of pyridoxine, 55.5% RDA of vitamin E [12, 52]. In 42 g of peanuts, more than 10% provide recommended dietary allowances (RDA) for niacin, pantothenic acid, and total folate is present.

Another important vitamin which is supplemented in the body by the intake of peanuts is vitamin B3 [53] (known as Niacin or Niacinamide or Nicotinamide), to an extent of 13.525 mg. The vitamin B5 pantothenic acid is also provided by peanuts [52]. This vitamin plays an important role in the normal functioning of the respiratory chain and participates in hydrogen transfer, and electron transfer reactions through its coenzymes, Nicotinamide adenine dinucleotide (NAD) and Nicotinamide adenine dinucleotide phosphate (NADP). Roasted peanuts will provide B6 to the human body to the extent of 0.256 mg. Vitamin B9, more commonly known as folate or folic acid, is a water-soluble vitamin that is part of the B vitamin family and required for normal

functioning. Folate (vitamin B9) present in peanuts to an extent of 145 μg may also help protect against cancers of the lung, colon, and cervix [12].

Peanut flour which is most commonly used for fortification contains protein ranging in between 47% - 55% i.e. a good amount of protein. Peanut flour has been


**127**

for 10 min.

**Table 2.**

*Functional Uses of Peanut (*Arachis hypogaea *L.) Seed Storage Proteins*

used to replace animal proteins in a variety of products. Peanut flour blends well with cereal flour to yield products with excellent flavor texture and color [12].

**BIOACTIVE COMPOUNDS TYPE AMOUNT (per 100 gm of dry roasted peanuts)**

49.7 mg 82.6 mg

Genistein

Phenolic acids p-coumaric acid 6.9 mg Phytosterols b-sitosterol 61 mg to 114 mg Stilbenes Resveratrol 0.48 mg to 3.96 mg

Peanut is a reservoir of secondary metabolites like flavonoids, polyphenols, phytosterols, stilbenes ( **Table 2**). The evaluation of peanuts role in a heart-healthy diet has increased in the last decade [54]. Extraction procedures would play a big role in getting these bioactive components since extracting solvent, isolation procedures, purity of active compounds, as well as the test system and substrate to be protected

The flavonoid content in peanuts was determined, which is second only to walnuts [56]. Studies [57, 58] reported that peanut seeds had an isoflavonoid content of daidzein and genistein in the greatest amounts with a content of 49.7 mg/100 g and 82.6 mg/100 g, respectively. A-type proanthocyanidins was determined in peanuts [59]. Luteolin was the principal antioxidative component from the methanolic extracts of peanut hulls [60]. Mature, red peanut skins contain about 17% by weight of procyanidins, nearly 50% of which are low molecular weight oligomers [61]. Catechins, A-type and B-type procyanidins dimers, trimers, and tetramers were also detected in chemically purified peanut skin aqueous and ethanol extracts [45]. Furthermore, higher concentrations of compounds mentioned were observed in

The polyphenolic content of raw and dry roasted peanut samples containing varying levels of oleic acid (normal, mid, and high) were determined [62, 63]. Normal oleic acid peanuts had higher concentrations of individual polyphenolics than mid- and high-oleic peanuts. Free p-coumaric acid, three esterified derivatives of p-coumaric, and two esterified derivatives of hydrobenzoic acid were identified as the predominant polyphenolics. Whole raw peanuts had a mean of 25 mg/ kg of p-coumaric acid (from a range of 8 to 66 mg/kg among cultivars) and the value increased to an average of 69 mg/kg when peanuts were roasted at 175 °C

Peanuts as a source of phytosterol has been getting a lot of attention with new research findings identifying phytosterols like beta-sitosterol, sitosterol in peanuts and peanut products as cancer growth inhibitors, as well as protectors against heart diseases [64]. The phytosterol contents of peanuts and peanut products were analyzed. Results show that among the four cultivars studied, the Valencia peanuts in raw, dry roasted, and oil roasted, contained the highest phytosterol concentration [65]. Studies with sitosterol or mixtures of plant sterols have shown that they reduce serum cholesterol levels in humans by approximately 10%. This discovery has resulted in subsequent research to evaluate the effects of sitosterol derivatives

on cholesterol absorption and serum cholesterol levels [48].

*DOI: http://dx.doi.org/10.5772/intechopen.96871*

Isoflavonoid Daidzein

**4. Presence of secondary metabolites**

*Composition of bioactive compounds.*

by the antioxidant affects its function [55].

raw peanut skins than roasted peanut skins.

**Table 1.** *Nutrient components in Peanut.*


**Table 2.**

*Grain and Seed Proteins Functionality*

functioning. Folate (vitamin B9) present in peanuts to an extent of 145 μg may also

Peanut flour which is most commonly used for fortification contains protein ranging in between 47% - 55% i.e. a good amount of protein. Peanut flour has been

**COMPONENTS CLASS TYPES AMOUNT (per 100gm of dry** 

Vitamins Fat soluble E (tocopherol) 8.2 mg (raw), 4.1 mg/ 100 g

Water soluble B2 (Riboflavin)

Micro \*Selenium

Non- essential Glycine

Others Total carbohydrates 21.51 gm

Monosaturated Polysaturated

B1 (Thiamine) B5 (Panthothenic acid) B3 (Niacin) B6 (Pyridoxine) B9 (Folate) Choline

> Sodium Calcium Magnesium Phosphorus

\*Copper \*Manganese Iron Zinc (\* antioxidant minerals)

Leucine Isoleucine Methioione Phenyalanine Valine Lysine Threonine

Alanine Cysteine Tyrosine Arginine Histidine Aspartic acid Glutamic acid Proline Serine

Dietary fibers 8.0 gm

Total Sugars 4.18 gm

Coenzyme Q10

**roasted peanuts)**

6.893 gm 24.640 gm 15.694 gm

roasted

0.098 mg 1.0 mg 1.395 mg 13.525 mg/ 0.256 mg 145 mg 55.3 mg

658 mg Approx.5.56 mg 54 mg 175 mg 358 mg

7.5 mg 0.671 mg Approx.2.06 mg 2.26 mg 3.31 mg

> 0.230 gm 1.535 gm 0.833 gm 0.291 gm 0.304 gm 0.993 gm 0.850 gm 0.811 gm

> 1.427 gm 0.941 gm 0.304 gm 0.963 gm 2.832 gm 0.599 gm 2.888 gm 4.949 gm 1.045 gm 1.167 gm

help protect against cancers of the lung, colon, and cervix [12].

Lipids Fatty acids Saturated

Minerals Macro Potassium

Amino acids Essential Tryptophan

Functional components

**126**

**Table 1.**

*(Adapted from Source USDA 2011)*

*Nutrient components in Peanut.*

*Composition of bioactive compounds.*

used to replace animal proteins in a variety of products. Peanut flour blends well with cereal flour to yield products with excellent flavor texture and color [12].
