Measurement of Wheat Starch Granule Size Distribution Using Image Analysis and Laser Diffraction Technology

Abstract

Cereal Chem. 83(3):259-268Starch 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 μm), B-type granules (5-15 μm), and C-type granules (<5 μm). 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 ≈40% underestimation of the A-type granule diameter and a ≈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 R 2 = 0.02 ns to 0.55 *** . After adjustment, these correlations improved to R 2 = 0.

Physicochemical characterization of starch from hexaploid triticale (X TriticosecaleWittmack) genotypes

“…All triticales showed a bimodal starch granule distribution as reported previously (Ao & Jane, 2007;Stoddard, 1999;Wilson et al, 2006). However, starches from complete and substituted triticales showed significant difference in size distribution as well as in the volume per cent of the granules ( Table 2).…”

“…The A-type starch granules of complete and substituted triticales displayed disk shapes whereas the B-type starch granules displayed a more spherical-type shape such as those reported by Wilson et al (2006) and Ao and Jane (2007). SEM also showed that the starch of substituted triticales contained spherical or elongated B-type starch granules in higher number than those observed in the complete triticales.…”

“…SEM also showed that the starch of substituted triticales contained spherical or elongated B-type starch granules in higher number than those observed in the complete triticales. Bechtel, Zayas, Kaleikau, and Pomeranz (1990) and Wilson et al (2006) also observed the presence of smaller starch granules in hard red winter wheat starch. Therefore, the presence of a high amount of small starch granules in substituted triticales might be due to their genomic composition, which includes the D genome from hexaploid wheats.…”

“…According to previous reports, substituted triticales contain lower amounts of amylose than complete triticales (Navarro-Contreras et al, 2014), which have been related to the size of starch granules (Ao & Jane, 2007). Starch granules of triticales show a bimodal size distribution (Ao & Jane, 2007;Stoddard, 1999;Wilson, Bechtel, Todd, & Seib, 2006) and are identified as A-and B-type starch granules. A-type granules are large and disk-like or lenticular in shape (Ao & Jane, 2007;Li et al, 2011) with a diameter around 10-35 µm, whereas the B-type granules are small and spherical shaped with a diameter of about 2 µm (Ao & Jane, 2007).…”

Isolation of differentially expressed genes in wheat caryopses with contrasting starch granule size

“…The starch granules, designated A-and B-type [5], can be distinguished based on size, shape, relative proportion, and the timing of their initiation in the endosperm, a process which, presumably, is under a defined genetic program. C-type starch granules have also been reported in wheat [6,7].…”