Particle Size Distribution in Wheat Starch and Its Importance in Processing

The sedimentation balance is useful for the determination of specific surface area but requires relatively large amounts of sample. There is imprecision for large granule starches suspended in water and small granule starches require long settling times. Both these problems could be alleviated by the use of dispersing liquids with different viscosity and density to water. The laser beam scattering apparatus used (Mastersizer X, Model MSX025A, Malvern Instruments Ltd., Malvern, U.K.) used only small amounts (10‐20 mg) of starch and as the mixture is stirred continuously, it can give rapid results on products having a wide range of particle size. The instrument generates particle size distribution data enabling it to compare different botanical varieties of starch and to assess starch processing, especially the efficiency of centrifugal operations. Extraction of further quantities of protein and other nitrogenous substances from large granule wheat starch can be achieved by incubation of the starch with dilute sodium hydroxide at pH 12. After 48 h, the protein content of the starch was reduced by 60%. Impurities remaining in the starch may consist almost solely of lipids such as lysolecithins, enabling the starch to be classified as ‘Gluten‐free’ in most countries.