**2. Protein content**

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


**107**

*Pea Seed Proteins: A Nutritional and Nutraceutical Update*

the collection of nitrogen depends on assimilation before flower development [15]. It has been reported that low rainfall and high temperature is positively correlated with high protein content in pea genotypes [13, 16]. A total of 7% high protein content was observed in pea crop raised in dry location than another location having 209 mm higher rainfall indicating role of low rainfall has a significant influence on protein content [13]. However, in another study, there was 1.5% rise in pea protein content between the crop raised in the periodic wilting moisture content of 10 percent versus 26 per cent moisture content at field capacity [17]. In addition, seed yield is known to be negatively correlated with protein content, and these conclusions were made by various independent studies in different years and locations [14, 16, 17]. The dry matter in seed constitutes approximately 50% starch [18, 19]. The dietary fibre and total protein content account for 20 and 24% of the dry matter, respectively. Whereas, 2.5% of dry matter is contributed by lipids [20]. Protein content and starch are highly variable, but other components show little variation [18]. It was found in a study that protein content was negatively correlated with lipid, starch, ash, fibre content and soluble sugar and among these variations in starch content had a significant effect on protein content levels [21]. This study was conducted at four locations in Canada using dehulled pea cultivar, and it was observed that protein content of the cultivar was variable across locations showing levels 14.5%, 18.3%, 24.3%, and 28.5%. The starch synthesis was reported to be a critical factor in determining pea protein content as smooth seeded pea having a higher content of amylopectin and starch showing lower protein levels (23–31%) than wrinkled pea seeds (26–33%) [22]. Recessive gene account for higher protein

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.

*DOI: http://dx.doi.org/10.5772/intechopen.95323*

levels in wrinkled pea seeds.

**3. Amino acids**

#### **Table 1.**

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

*Pea Seed Proteins: A Nutritional and Nutraceutical Update DOI: http://dx.doi.org/10.5772/intechopen.95323*

the collection of nitrogen depends on assimilation before flower development [15]. It has been reported that low rainfall and high temperature is positively correlated with high protein content in pea genotypes [13, 16]. A total of 7% high protein content was observed in pea crop raised in dry location than another location having 209 mm higher rainfall indicating role of low rainfall has a significant influence on protein content [13]. However, in another study, there was 1.5% rise in pea protein content between the crop raised in the periodic wilting moisture content of 10 percent versus 26 per cent moisture content at field capacity [17]. In addition, seed yield is known to be negatively correlated with protein content, and these conclusions were made by various independent studies in different years and locations [14, 16, 17]. The dry matter in seed constitutes approximately 50% starch [18, 19]. The dietary fibre and total protein content account for 20 and 24% of the dry matter, respectively. Whereas, 2.5% of dry matter is contributed by lipids [20]. Protein content and starch are highly variable, but other components show little variation [18]. It was found in a study that protein content was negatively correlated with lipid, starch, ash, fibre content and soluble sugar and among these variations in starch content had a significant effect on protein content levels [21]. This study was conducted at four locations in Canada using dehulled pea cultivar, and it was observed that protein content of the cultivar was variable across locations showing levels 14.5%, 18.3%, 24.3%, and 28.5%. The starch synthesis was reported to be a critical factor in determining pea protein content as smooth seeded pea having a higher content of amylopectin and starch showing lower protein levels (23–31%) than wrinkled pea seeds (26–33%) [22]. Recessive gene account for higher protein levels in wrinkled pea seeds.
