Measurement of wheat starch granule size distribution using image analysis and laser diffraction technology

• Published in: Cereal chemistry Vol. 83; no. 3; pp. 259 - 268
• Main Authors: Wilson, J.D, Bechtel, D.B, Todd, T.C, Seib, P.A
• Format: Journal Article
• Language: English
• Published: St. Paul, MN The American Association of Cereal Chemists, Inc 01.05.2006; American Association of Cereal Chemists
• Subjects: Biological and medical sciences; Cereal and baking product industries; digital images; durum wheat; flour; Food industries; Fundamental and applied biological sciences. Psychology; hard red spring wheat; hard red winter wheat; image analysis; measurement; measuring devices; new methods; particle size distribution; spelt wheat; Starch and starchy product industries; starch granules; wheat; Starch granule; Measurement; Image analysis; Technology; Size; Distribution; Laser; Polysaccharide; Wheat starch
• ISSN: 0009-0352; 1943-3638
• DOI: 10.1094/CC-83-0259

Starch was isolated from flour of four wheats representing hard red winter (Karl), hard red spring (Gunner), durum (Belfield 3), and spelt (WK 86035-8) wheat classes. Digital image analysis (IA) coupled with light microscopy was used to determine starch size distributions where the volume of granules was calculated as spherical particles or oblate spheroids. Starch granules were classified into three size ranges: A-type granules (>15 micrometer), B-type granules (5-15 micrometer), and C-type granules (<5 micrometer). An error was noted in using digital image analysis because the perimeter of some granules touch the edge (PTE) of the field being analyzed. To correct for this error, the PTE granules were manually replaced into the field by measuring their diameters and entering them into the database. The results showed differences in the starch size distributions between the classes of wheat evaluated, as well as the method of analysis. Four laser diffraction sizing (LDS) instruments were used to measure granule distributions of the four classes of wheat. LDS compared with IA resulted in a approximately equal to 40% underestimation of the A-type granule diameter and a approximately equal to 50% underestimation of the B-type granule diameter. A correction factor (adjustment) was developed from IA data to correct LDS analysis. LDS data correlations before adjustments to IA data were R2 = 0.02ns to 0.55***. After adjustment, these correlations improved to R2 = 0.81*** to 0.93*** depending on the class of wheat starch evaluated.