ISOLATION, PURIFICATION AND CHARACTERIZATION OF β-GLUCANS FROM INDIAN BARLEY

Abstract

ABSTRACT Efforts have been made to isolate and purify β-glucans from barley (variety Rekha). The seeds were roller-milled in a Brabender experimental mill to bran, flour and meal. All fractions exhibited similar milling performance on the basis of fraction yield and composition. Bran was found rich in ash, protein, fat, β-glucans and soluble and insoluble fiber, but was poor in starch content. The amount for all components is small in the flour fraction compared to whole meal fraction, but it was not significant. By using three solvents ([1] distilled water adjusted to pH 10.0 with 20% Na2CO3; [2] distilled water adjusted to pH 7.0; and [3] 4% NaOH solution) The β-glucans yield was observed to be 61, 72 and 83% in solvent 1, 2 and 3, respectively. The barley bran was darker in color than flour and meal. The ratio of β- (1–4) and β- (1–3) linkage was 71:29. On hydrolysis of β-glucans, glucose monomers accounted for more than 97% of the recovered sugars. The data on permethylated analysis of oligosaccharides of β-glucans confirmed that major structural features were (1–4) β-linked cellotrisoly and cellotetraosyl units. PRACTICAL APPLICATIONS In barley, 70% of the endosperm walls consist of β-glucans, and the reminder are mainly arabinoxylans, glucomannans, cellulose, protein and phenolic constituents. Great variability among barley cultivars exists in cell wall thickness, total amount and degree of solubility of β-glucans. Hulled barley grown in India ranged from 3.0 to 6.9% β-glucans with about half the total amount being soluble. It was of commercial interest to isolate, purify and characterize β-glucans from Indian hulled barley cultivar Rekha, which could be a good source of soluble dietary fiber. Consumers today are concerned with health-promoting foods and this trend is growing. The food industry is searching for alternative economical sources of soluble fiber. Barley offers a viable choice.