Rheology Study of Starch Extracted from Germinated Ragi and its Application in Textile Printing

Rheology Study of Starch Extracted from Germinated Ragi and its Application in Textile Printing

Finger millet (Ragi) is a non-conventional carbohydrate rich source, which can be used as source of starch. Germinated ragi is generally discarded as a waste material and is used for non productive purposes. In the present investigation, starch extracted from germinated ragi has been compared with the starch from non-germinated ragi, as a thickener in textile printing. Extraction of starch was done by alkali steeping method. Analysis of both the starches was done by measuring swelling power, paste clarity, crystallinity and iodine binding. Printing of vat dyes on 100% cotton fabric was carried out using both the starches as thickener. The effect of solid contents of thickener and the shearing time on the viscosity of paste over a wide range of shear rates was studied for both germinated and non germinated ragi. The solid contents of the starch obtained from both germinated and sound grains were adjusted to have printable viscosity of the pastes. The prints were analyzed by measuring colour value (K/S and L*, a*, b* value), bending length, light fastness and fastness to washing and crocking. Results suggest that germinated ragi can be used partially in blends if not fully, as a thickener in printing.