Pea starch contains a high percentage of amylose (35%) and as a result, it has superior thickening and gelling qualities than other regularly used starches. Furthermore, natural pea starch has features such as increased temperature, acidity, and shear stability. Smooth peas had a starch level ranging from 53.61 to 57.23 percent. The average amylose content was 27.8%. The percentage of resistant starch ranged from 2.07% to 6.31 percent. The starch content of wrinkled peas ranged from 26.57 percent to 32.55 percent.
Starch in the pea
The most abundant storage carbohydrate and a key component in pea seeds, starch accounts for nearly half of the dry seed weight. Pea starch is currently only used in low-value, commodity markets as a by-product of pea protein production. The pea fractionation industry faces a significant challenge in developing new markets for starch valorization due to the expanding global demand for pea protein. However, there are gaps in our knowledge of the genetic process underpinning starch metabolism and its link to physicochemical and functional qualities, which is required for focused tailoring functionality and new starch applications.
We discuss the perspectives and possible avenues for advancing our understanding of starch metabolism in peas to unprecedented levels, ultimately enabling the molecular design of multi-functional native pea starch and creating value-added utilisation, using currently available pea genetics and genomics knowledge and breakthroughs in omics technologies.
Starch, also known as amylum, is a polysaccharide produced by plants that is at the heart of the food and feed chains, as well as a renewable source of industrial raw materials.
The linear and mildly branched amylose, which contains glucose moieties linked together byα-1,4 glycosidic bonds, and the highly branched amylopectin, which contains shorter byα-1,4 linked glucan chains connected by byα-1,6 glycosidic bonds, make up starch.
Transient starch is created in chloroplasts in photosynthetic tissues and long-term store starch is formed in amyloplasts in non-photosynthetic tissues such as seeds, storage roots, and tubers in higher plants.
Starch Metabolic Pathway
Starch plays a crucial function in a plant’s life cycle as the primary storage carbohydrate. The unloading of sucrose to sink tissues from the phloem by sucrose transporters is the first step in starch metabolism. Sucrose is split into uridine diphosphate glucose (UDP-Glc) and fructose by sucrose synthase (SuSy) to supply a carbon skeleton for the production of adenosine 5′-diphosphate-glucose (ADP-Glc), the soluble precursor for starch biosynthesis . Characterization of naturally occurring or generated mutants with altered starch concentration, composition, and/or characteristics is an important technique for finding the genes that code for peas’ starch biosynthesis enzymes. These studies also revealed that the different isoforms of these enzymes are expected to play diverse roles in shaping the pea starch’s complex structure and characteristics.
Starch synthesis
The enzyme ADP-glucose pyrophosphorylase (AGPase), which catalyses the interaction of glucose-1-phosphate with ATP to create ADP-glucose, is the first step in the synthesis of starch in plant cells (liberating pyrophosphate). Starch synthase enzymes employ ADP-glucose as a substrate, adding glucose units to the end of a developing polymer chain to form a starch molecule (releasing the ADP in the process). Starch branching enzymes (SBEs) form branches in the chain by hydrolyzing 1,4-glycosidic linkages and replacing them with 1,6 links with other glucose units.
Although the starch production process appears to be straightforward, it is complicated by the fact that the enzymes involved come in a variety of forms, each of which differs in behaviour and the areas of the plant where they are active. The existence of de-branching enzymes (DBEs), which hydrolyze 1,6-glycosidic linkages and break apart branches in polymer chains, adds to the complexity. Although they are commonly thought of as starch breakdown catalysts, it appears that they also play a function in starch synthesis. The sugary mutants of maize, rice, and sorghum, which are defective in a certain de-branching enzyme, in which starch granules are destroyed as they develop and replaced with a different polymer, phytoglycogen, provide evidence for this.
One of the simplest and most obvious changes that could be made to starch synthesis would be to raise the rate at which it occurs, encouraging crop plants to devote as much energy as possible to starch production. Improving the nutritional yield of food crops is critical if a growing global population is to be fed adequately without increasing land use pressures, and starch, which makes up a large portion of the energy content of many staple foods (such as rice, potatoes, and cereals), is an obvious target for such changes. Enhancing agricultural starch content would also make the starch more cost-effective to produce for industrial usage, allowing it to compete more successfully with non-biological alternatives. Starch synthesis in pea is controlled by multiple alleles.
Conclusion
Pea starch contains a higher amount of amylose (35%) than other commonly used starches, giving it greater thickening and gelling properties. Starch is the most abundant storage carbohydrate in pea seeds, accounting for about half of the dry seed weight. As the principal storage carbohydrate in a plant’s life cycle, starch is critical. Starch, also known as amylum, is a polysaccharide generated by plants and found in the food and feed industries.
ADP-glucose is used as a substrate by starch synthase enzymes, which add glucose units to the end of a growing polymer chain to produce a starch molecule (releasing the ADP in the process).