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 g ranule starches require long settling times. Both these problems could be alleviated by the use of dispersing liquids with different viscosi ty and density to water. The laser beam scattering apparatus used (Mas tersizer X, Model MSX025A, Malvern Instruments Ltd., Malvern, U.K.) us ed only small amounts (10-20 mg) of starch and as the mixture is stirr ed continuously, it can give rapid results on products having a wide r ange of particle size. The instrument generates particle size distribu tion data enabling it to compare different botanical varieties of star ch and to assess starch processing, especially the efficiency of centr ifugal operations. Extraction of further quantities of protein and oth er nitrogenous substances from large granule wheat starch can be achie ved 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%. Imp urities remaining in the starch may consist almost solely of lipids su ch as lysolecithins, enabling the starch to be classified as 'Gluten-f ree' in most countries.