Increased accuracy of starch granule type quantification using mixture distributions

BACKGROUND

The proportion of granule types in wheat starch is an important characteristic that can affect its functionality. It is widely accepted that granule types are either large, disc-shaped A-type granules or small, spherical B-type granules. Additionally, there are some reports of the tiny C-type granules. The differences between these granule types are due to its carbohydrate composition and crystallinity which is highly, but not perfectly, correlated with the granule size. A majority of the studies that have considered granule types analyse them based on a size threshold rather than chemical composition. This is understandable due to the expense of separating starch into different types. While the use of a size threshold to classify granule type is a low-cost measure, this results in misclassification. We present an alternative, statistical method to quantify the proportion of granule types by a fit of the mixture distribution, along with an R package, a web based app and a video tutorial for how to use the web app to enable its straightforward application.

RESULTS

Our results show that the reliability of the genotypic effects increase approximately 60% using the proportions of the A-type and B-type granule estimated by the mixture distribution over the standard size-threshold measure. Although there was a marginal drop in reliability for C-type granules. The latter is likely due to the low observed genetic variance for C-type granules.

CONCLUSIONS

The determination of the proportion of granule types from size-distribution is better achieved by using the mixing probabilities from the fit of the mixture distribution rather than using a size-threshold.

Physicochemical Properties of A- and B-type Granules of Wheat Starch and Effects on the Quality of Wheat-Based Noodle

This work fractionated native wheat starches into A- and B-type granules fractions to accurately assess granules physicochemical properties and effects on water distribution, storage modulus (E′) and loss modulus (E″) of two type noodles with A- and B-type granules. Pasting viscosity and starch crystallization of A- and B-type granules were determined by Rapid Visco Analyzer (RVA) and X-ray diffraction (XRD) respectively. The noodles were prepared from wheat flour, which 20 % was replaced with the A or B starch fractions, respectively. The water distribution and dynamic mechanical properties of noodles were characterized through Low-field Nuclear Magnetic Resonance (LF-NMR) and Dynamic Mechanical Analysis (DMA). The results demonstrated that A- and B-type granules almost had a round shape with smooth surface. The crystal models of A- and B-type granules were the same but the relative crystallinity were different. A-type granules contained higher starch content, higher ratio between amylose and amylopectin and less damaged starch than B-type granules. B-type granules easily aggregated into clump in deionized water. A- and B-type granules were different in swelling properties and pasting viscosity under the same conditions. A-type granules possessed lower swelling power and water-binding capacity, higher solubility and pasting viscosity than B-type granules. A-noodles (relative to B-noodles) had higher ratio of immobilized water, E′ and E″.

C-type starches and their derivatives: structure and function

The C-type starches are widely distributed in seeds or rhizomes of various legumes, medicinal plants, and crops. These carbohydrate polymers directly affect the application of starchy plant resources. The structural and crystal properties of starches are crucial parameters of starch granules, which significantly influence their physicochemical and mechanical properties. The unique crystal structure consisting of both A- and B-type polymorphs endows C-type starches with specific crystal adjustability. Furthermore, large proportions of resistant starches and slowly digestible starches are C-type starches, which contribute to benign glycemic response and proliferation of gut microflora. Here, we review the distribution of C-type starches in various plant sources, the structural models and crystal properties of C-type starches, and the behavior and functionality relevant to modified C-type starches. We outline recent advances, potential applications, and limitations of C-type starches in industry, aiming to provide a theoretical basis for further research and to broaden the prospects of its applications.

Physicochemical properties of A- and B-starch granules isolated from hard red and soft red winter wheat

Large A- and small B-starch granules separated from hard red and soft red winter wheat grains were investigated for their morphological, structural, and physicochemical properties. A-granules displayed a disk or lenticular shape, and B-granules showed a spherical or polygonal shape according to SEM. XRD analysis showed that both A- and B-granules had A-type crystallinity. A-granules contained a higher amount of amylose and a lower protein content and amylopectin/amylose ratio than B-granules. A-type granules exhibited a higher hydrolysis extent and swelling power and a lower iodine affinity than did B-granules. A-granules showed a higher peak, trough, breakdown and final viscosity, and gelatinization enthalpy than did B-granules, while B-granules exhibited a higher gelatinization temperature. The study demonstrated that the A- and B-granules separated from both hard red and soft red winter wheat grains exhibited a similar structure and very different physicochemical properties.