Starch is a polysaccharides, alpha-glucan and can be divided into straight-chain amylase and branched chain amylopectin.
The starch granules in the barley endosperm are laid down within amyloplasts and fall into two size groups: 1,7-2.5 um and 22.5 – 47.5 um.
These starch granules contain traces of lipids, minerals, protein and nucleotide.
The “diastatic” enzymes responsible for degrading the starch in germination are phosphorylase, alpha glucosidase, alpha-amylase, beta-amylase, debranching enzymes, and transglucosylase.
These starch in the endosperm is 95% deposited in 11-28 days after ear emergence and the ratio of amylopectin increases to the final ratio.
In normal barleys the ration of amylase to amylopectin is about 1:3, in high amylase Glacier about 1:1 and waxy barley is 97-100% amylopectin.
Soluble sugar
At least nine monosaccharides and seven closed related compounds occur in barley. Glucose and fructose are found free and in combination, whereas, other monosaccharides are polymerized as oligosaccharides, polysaccharides, glycosides, glycolipids and glycoproteins.
Soluble sugar content of normal barley is about 2-3%, hulless barleys 2-4%, high lysine barleys 2-6%, and high sugar barleys 7-13%.
The total sugars and reducing sugars decline from anthesis to maturity, whereas non-reducing sugars are constant in amount during plant growth.
The major sugar found inviting tissues of barley is sucrose.
Nonstarch Polysaccharides
Polysaccharides can be defined as “pectin fraction” hemicellulosic materials, which are then divided into gums of soluble in hot water and hemicellulose.
The material remaining after delignification and removal of gums and hemicellulose is termed “holo-cellulose.” Endosperm gums consists of beta-glucan and an arabinoxylan.
Endosperm cell walls in barley are unique in cereals, since they completely enclose the cell forming barriers to proteolytic and amylolytic enzymes.
Some of the polysaccharides are linked to phenolic acid and some to lignin. The dietary fiber of barley is comprised of the nonstarch polysaccharides, resistant starch, and lignin.
Carbohydrates in Barley
