**Abstract**

Peanut (*Arachis hypogaea* L.) is an important grain legume crop of tropics and subtropics. It is increasingly being accepted as a functional food and protein extender in developing countries. The seed contains 36% to 54% oil, 16% to 36% protein, and 10% to 20% carbohydrates with high amounts of P, Mg, Ca, riboflavin, niacin, folic acid, vitamin E, resveratrol and amino acids. Seed contains 32 different proteins comprised of albumins and globulins. The two-globulin fractions, arachin and non-arachin, comprise approximately 87% of the peanut seed proteins. Peanut worldwide is mainly used for oil production, consumption as raw, roasted, baked products, peanut butter, peanut flour, extender in meat product formulations, confectionary and soups. Peanut proteins have many properties such as good solubility, foaming, water/oil binding, emulsification that make them useful in various food products. Very limited studies have been carried out in peanut functional properties, which has been reviewed in the present article. Adequate modifications can be done in protein functionality that are influenced by pH, temperature, pressure etc. However, some individuals develop severe IgE-mediated allergies to peanut seed proteins. Thus, methods to improve nutrition and reduce allergenicity have also been discussed. Within the last decade, manipulations have been done to alter peanut chemistry and improve nutritional quality of peanuts and peanut products. Hence, improved comprehensive understanding of functional properties and nutritional chemistry of peanut proteins can generate better source of food grain to meet nutritional requirement of growing population. In the present review, composition of peanut seed proteins, functional properties, nutritional components and nutraceutical value have been discussed with respect to beneficial aspects to health, reducing hunger and usage in food end products.

**Keywords:** seed proteins, albumin, globulin, nutritional value, functional properties

## **1. Introduction**

Peanut, or groundnut, of genus *Arachis* is a member of the legume family (Fabaceae). Cultivated peanut (*Arachis hypogaea*), an allopolyploid with AABB genome composition, is the second-most important grain legume crop worldwide after soybean [1]. The genus *Arachis* is endemic to South America [2] and the probable center of origin of *Arachis hypogaea* has been recognized in Gran Panatanal (Mato Grosso, Brazil) and also on the eastern slopes of the Bovilian Andes [3].

Peanut has now become one of the major global oil-seed crops covering approximately 26 million ha land area in about 120 countries [4–6]. According to FAO, world production of groundnut is above 45 million tons, averaging about 1.8 t/ha. Significant level of annual peanut production has been recorded in India amounting to approximately seven million tons [7]. China leads in production of peanuts, with a share of about 41% of overall world production, whereas India has 14% share and the United States has (7%) [8]. *Arachis hypogaea* has been divided into two subspecies *A. hypogaea* ssp. *hypogaea* and *A. hypogaea* ssp. *fastigiata* [9]. Morphological variations in branching and flowering patterns, pod and seed traits are used to characterize different botanical varieties [10]. The varieties are further distinguishable into a number of market types or cultivars like Virginia (large seeded), Runner (small seeded), Peruvian runner, Valencia and Spanish type. Some market types or cultivars are more preferred for some particular uses due to differences in flavor, oil content, size, shape, and disease resistance [11].

Peanut is accepted as a potential source of food grade protein and an energy dense food. The seed typically contains 36% to 54% oil, 16% to 36% protein, and 10% to 20% carbohydrates as well as high amounts of macro minerals, trace elements, vitamins riboflavin, niacin, folic acid, fiber and vitamin E, resveratrol, phytosterols. It is also known as poor man's nut and being seen as potential functional food. A 100 g of peanut kernels provide 567 kcal of energy and 8.5 g of dietary fiber [12]. Consumption of peanuts can reduce risk of inflammation and diseases like diabetes, cancer, gallstone and alzheimer's [12, 13].

Peanuts are consumed all over the world in a wide variety of forms such as raw, boiled or roasted, and are widely used to prepare a variety of packaged foods (peanut butter, candies, confections, and snack products) in the United States. Peanuts and peanut butter contain monounsaturated fatty acids besides plant proteins, minerals like magnesium, potassium, fiber, arginine and various bioactive components. The by-product of the oil extraction is a meal that is also high in proteins, dietary fiber, antioxidants, vitamins, and minerals, and can be utilized as animal feed or processed further for human consumption. The defatted protein flour after oil extraction in peanuts, has immense uses and has been exploited in meat-like products that can be used to formulate cholesterolfree vegetarian alternatives [14]. Peanut flour is used in composite flours with non-wheat cereals to improve the nutritional value of bread [12]. Peanut bars, peanut milk and fermented peanut are also different forms of consumption. Protein energy malnutrition in third world developing countries is a problem due to dependence on animal proteins which are expensive and thus, affordable plant proteins with its additional benefits are being exploited such as peanut proteins, which can be used to combat protein-energy malnutrition. Partially defatted peanut flour, is a protein-rich, inexpensive and underutilized product that offers the same health and dietary benefits of peanut with less fat and can be utilized for making value added products to eradicate malnutrition among children [15]. Peanut proteins play an important role in many food products because of their properties such as nutritional value, contribution to food texture, solubility etc., among others. Huge tons of by-products obtained from peanut industries can be utilized to generate a reasonably high quantity of protein, that could be further used in a variety of food formulations due to its properties such as water and oil absorption, gel formation, foaming, emulsification etc. Functional properties depend upon extraction procedure and use of adequate modification methods [16].

Thus, the present chapter focuses on the peanut seed storage proteins composition, nutritional value, bioactive components, functional properties, its usage and methods to reduce allergenicity.

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**Figure 1.**

*(adapted from [19]).*

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

are very similar in the A and B genomes of *Arachis* [20].

been designated from Ara h 1 to Ara h 17.

Seed storage proteins are present as one or more groups of proteins in high amounts in seeds to provide a store of amino acids for use during germination and seed growth. The peanut seed contains 32 different proteins comprised of albumins and globulins. The seed storage proteins are mainly composed of arachin (legumin), conarachin (vicilin) - I, II fractions [17]. Many papers have highlighted the composition of seed storage proteins (SSPs) using one dimensional and two dimensional PAGE [18–21]. The different fractions of seed proteins by SDS PAGE in groundnut cultivars is shown in **Figure 1**. SSPs in peanut are composed of families of 2S, 7S, and 11S proteins that can be subdivided in homology groups. 11S proteins are more diverse than 2S and 7S proteins in peanut seeds, but 2S and 11S subgroups

However, peanut proteins is also a source of severe IgE-mediated allergies in some individuals. Due to peanut being recognized as one of the potent allergens, the immunological protein names with prefix *Ara* with different numbers have also

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

*SDS PAGE analysis of Total Seed Storage Proteins in Peanut (Arachis hypogaea) cultivars along side a marker* 

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

**2. Peanut proteins**

**2.1 Globulins**
