2.6. Determination of Available Carbohydrates

Available carbohydrate contents of chapattis (dry weight basis) were measured by following phenol-sulphuric acid method [24]. One hundred milligrams of a homogeneous sample of dried chapattis powder was hydrolyzed in boiling water with 5 ml 2.5N HCl for 3 hr and neutralization was performed with sodium carbonate crystals. Boiling tubes carrying samples were cooled to 25°C. Samples were centrifuged, and 5 ml of H₂SO₄ was rapidly added in supernatant (2 ml); subsequently, 1 ml of 5% aqueous phenol was added to tube contents. The samples were vortexed (30 s) and kept at room temperature for 20 min. The intensity of color resulting so was measured against blank at 490 nm using a spectrophotometer (UV–Vis 3000, ORI, Germany). All chapatti samples were tested in three replicates and carbohydrate concentrations were determined using glucose standard solutions of known concentration.