Evaluation of Blue Value in different plant materials as a tool for rapid starch determination

Abstract

In order to determine the concentration of starch in plant materials from the intensity of the blue iodine complex, it is necessary to know the Blue Value (B.V.), which is defined in this paper as the absorbancy of 100 mg of a starch-iodine complex in 100 ml of aqueous solution. An adequate amount of plant material is treated with a hot CaCl₂ solution for 1/2 hour and the solute is diluted to 25 ml with CaCl₂. This basic solution serves to measure absorbancy, as well as for starch determination. The first measurement is done by the dilution of a proper amount of basic solution with water and after adding a diluted iodine-iodide solution the reading of B.V. is taken off. The second measurement is done by the precipitation of a starch iodine complex from a proper amount of the basic solution, which is then purified, destroyed by Na₂SO₃ solution, and starch is determined by the anthrone method. These two readings serve for the establishing of B.V. for the starch. Once established, B.V. can be used for starch determination in the proper plant material. A high degree of variation of the B.V. was found. The highest B.V. was obtained for wrinkled pea seeds (17.4); walnut, potato, smooth pea and pear gave values from 12.6 to 11.0, common bean and broad bean - 10.3 and 9.7, Triticale, carrot, rye, wheat and garden parsley from 8.7 to 8.0 and maize, oat, normal rice from 7.6 to 6.2. The B.V. for amylose was 25.3, for potato starch 12.4, soluble starch 11.9, wheat starch 8.8 and for Triticale and rye starches, 8.7.