**3. Amino acids**

*Grain and Seed Proteins Functionality*

**2. Protein content**

digestion and may have various prospective deleterious effects pea is still viewed as a too wholesome meal as well as is linked with total health benefits beyond elementary nutrition. The health benefits of pea seed proteins derive primarily from the qualities of starch, vitamins, fibre, protein, phytochemicals and minerals in peas. In this direction, mineral contents and the vitamin of peas may play crucial roles in the protection against deficiency-related diseases, particularly those regarding deficiencies of Folate or Selenium. Peas include a range of phytochemicals previously considered just as antinutritive factors. These contain polyphenolics, in coloured seed layer sorts particularly, that contains anticarcinogenic and antioxidant activity, saponins which might exhibit anticarcinogenic and hypocholesterolemic activity, as well galactose oligosaccharides which might exert beneficial prebiotic consequences within the large intestine [5, 6]. Many strategies for the extraction of protein from pea flours have been reported. Each extraction method might select for different protein sorts which consequently influences the final composition and functionality of the isolated product. In this chapter, we have compiled the information related to pea proteins targeting isolation methods, extraction, and of the seed proteins in pea.

Protein content in pea lies in a range of 21 to 30 per cent with an average of 23 per cent depending on genotype, growing environment and related factors [6]. The overall phenotypic expression of protein content is a result of environmental as well as genotypic components. The cultivars originating from various geographical areas show a range of protein content levels (**Table 1**). The heritability estimates show that pea protein content and quality is a heritable trait [10, 11], thus target for improvement through selection in breeding programs. Changes in environmental factors such as temperature, rainfall, soil type result in a differential response in performance of pea cultivars; thus multi-location and multi-year data is required for final estimation of protein content [12–14]. Most of the nitrogen supplies during fruit development relies on assimilation after the flowering and only a portion of

**Pea seeds Protein content Country Reference** *Pisum sativum* L. cv. *Ucero* 25.48 Spain [7] *Pisum sativum* L. cv. *Ramrod* 21.17 Spain [7] *Pisum sativum* L. cv. *Agra* 22.90 Spain [7] *Pisum sativum* L. cv. *Maja* 24.21 Serbia [8] *Pisum sativum* L. cv. *Calvedon* 27.70 Serbia [8] *Pisum sativum* L. cv. *Miracle of America* 22.31 Serbia [8] *Pisum sativum* L. cv. *Sprinter* 23.98 Turkey [6] *Pisum sativum* L. cv. *Manuell* 23.26 Turkey [6] *Pisum sativum* L. cv. *Century* 23.9 Canada [9] *Pisum sativum* L. cv. *Trapper* 24.5 Canada [9] *Pisum sativum* L. cv. *Delviche Scotch Green* 24.0 Canada [9] *Pisum sativum* L. cv. *Ceser* 24.9 Canada [9] *Pisum sativum* L. cv. *CD647 4* 24.9 Hungry [9]

*Protein content of famous pea cultivars grown in various parts of the world.*

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**Table 1.**

Peas are an excellent source of human nutrition owing to 25% protein in seeds [1], and it has a comparable amino acid (AA) profile to other legumes. Pea protein contains a lesser amount of sulphur amino acids, i.e., methionine and cystine and lower levels of tryptophan AA, whereas high levels of lysine AA [23]. The bioactive peptides of pulses are popularized due to affordable prices when compared with animal protein [24]. During the processing of food, microbial agents or digestive enzymes cause the hydrolysis of large proteins and release bioactive peptides which are usually 3–20 AA long [25]. Nutritional and functional properties food protein are studied using bioactive peptides obtained by hydrolysis through enzymatic action [26]. AA composition of a peptide is the key to its biological activity [24]. Oxidative stress damage in human beings can be prevented by developing nutraceuticals and foods using such peptides. High levels of antioxidants in natural foods can be even more appealing than synthetic counterparts [24, 27]. In a study by Amarakoon [28] the amino acid profile of pea showed that pea grown in central Europe was rich in leucine, lysine and arginine which were sufficient for a normal diet. The amino acid profiles of pea were compared with soybean and reference FAO/WHO requirements. The essential AA content was higher in pea in comparison to soybean. The lysine content was 6.39–6.93/16gN in pea, which was also higher than soybean. Another comparison of AA profile of flour and isolates and concentrates of protein of pea, soybean and lupin was made by Tomoskozi et al. [29]. They concluded that composition of AA was the same in all compounds with the highest amount of glutamine and comparatively lower amounts of aspartic acid, lysine and arginine and smallest contributions of methionine, cysteine and tryptophan.

In comparison to soybean and lupin, pea compounds had high levels of arginine, methionine and valine and comparatively low levels of cysteine and glumatic acid.


#### **Table 2.**

*Amino acid profile of different pea cultivars [7, 25].*

The muscle development and growth in human body is dependent on postprandial essential amino acid availability particularly leucine [30]. AA composition, essential AA content and anti-nutritional factors regulate the availability of essential AA [31]. Thus, variation in AA composition particularly in essential AA are desirable for improving AA profile of pea proteins. Natural variation among varieties for AA profile is present as depicted in **Table 2**. Wide crosses and mutants can be searched for more desirable AA profile of pea proteins. Furthermore, introgression approach can be deployed for improvement of existing germplasm using a natural variation.
