Frédéric Mabille

Mechanical Properties of Wheat Seed Coats

ABSTRACT The crumbliness of starchy endosperm and the resistance of bran are key characteristics that enhance milling behavior of wheat and are dependent on the genetic origin and moisture content of the grain. A method was developed to measure the mechanical properties of bran samples based on the measurement of tensile stress and strain. Tests conducted with this highly reproducible and sensitive method documented cultivar and moisture-content effects (6.3, 13.8, and 18%, wb) on rheological behavior of wheat seed coats. A moisture-dependent reduction in stress to fracture (-15 to -30%) and in Youngs modulus (-45 to -55%) was quantified. An increase in deformation to fracture of seed coats was also correlated with bran size differences after milling. The energy required to fracture a sample (from 0.4 to 1.3 J/mm3) was considered the most valid of all presented parameters for assessing the milling behavior of wheat seed coats and the size of bran fractions.

Mechanical and Physicochemical Characterization of Vitreous and Mealy Durum Wheat Endosperm

ABSTRACT The mechanical, physical, and biochemical characteristics of mealy and vitreous endosperm were investigated. Endosperm were obtained from four durum wheat cultivars grown under different nitrogen fertilization designs. The textural properties and the density of the endosperm were measured on hand-shaped parallelepiped endosperm samples. Endosperm protein content and composition and also gliadin composition were investigated by HPLC. Mechanical tests showed that mealy and vitreous endosperm differed in hardness and vitreousness. Vitreousness increased with nitrogen fertilization supply whereas there was no variation among the different cultivars. Hardness seemed to be linked to genotype and insensitive to nitrogen supply. From this result, we concluded that hardness and vitreousness are not related. Endosperm protein content and gliadin-to-glutenin ratio were related to nitrogen supply and increased especially when nitrogen supply was applied at flowering. At the same time, endosperm vitreousness ...

Contribution of Specific Flour Components to Water Vapor Adsorption Properties of Wheat Flours

ABSTRACT The dynamic water vapor adsorption properties were determined for two wheat flours (hard wheat flour and soft wheat flour) and compared with those of flour components (starch, damaged starch, gluten, water-soluble pentosans, and water-insoluble pentosans). Water vapor adsorption rates were determined from the changes in sample mass as a function of time during hydration after a step increase in relative humidity (rh). It was not possible to significantly discriminate the selected products by initial rates of adsorption (5.1 × 10-2 to 6.4 × 10-2 g/100 g of dry matter/min), except the water-insoluble pentosans that were characterized by high values of adsorption rates (14 × 10-2 g/100 g of dry matter/min). Changes in initial relative humidity conditions and %rh step sizes induced significant changes in adsorption rates. Calculations of apparent water diffusion coefficients were done using a derived form of Ficks law for polydisperse spherical particles. Apparent water diffusion coefficients (at 25...

A Study of Puroindoline b Gene Involvement in the Milling Behavior of Hard-Type Common Wheats

ABSTRACT Differences in milling behavior among hard-type common wheat (Triticum aestivum) cultivars are well known to millers. Among them, the French cultivar Soissons, which contains the Pinb-D1d allelic form of the puroindoline b gene, is particularly distinguished for its high milling value. Near-isogenic lines (NILs) differing by the allelic forms of the puroindoline b gene, Pinb-D1d or Pinb-D1b (one of the most frequent alleles found in the European wheat population), were constructed. Grain characteristics obtained after wheat cultivation in distinct environmental conditions were compared between NILs and the cultivar Soissons, as was their fractionation behavior. Results showed that NILs containing the Pinb-D1d allele displayed lower values of grain hardness and vitreousness than did the corresponding lines containing the Pinb-D1b allelic form under the same cultivation conditions. Both genetic background and environmental conditions appeared to affect grain texture. Measured single-kernel characte...

Collaborative Analysis of Wheat Endosperm Compressive Material Properties

ABSTRACT The objective measurement of cereal endosperm texture, for wheat (Triticum spp. L.) in particular, is relevant to the milling, processing, and utilization of grain. The objective of this study was to evaluate the interlaboratory results of compression failure testing of wheat endosperm specimens of defined geometry. Parallelepipeds (bricks) and cylinders were prepared from individual soft and hard near-isogenic wheat kernels and compressed in two orientations (parallel and perpendicular to the long brush-to-germ axis). Compression curves were used to derive failure stress, failure strain, work density (area under the curve), and Youngs modulus. In all five laboratories, the ability to delineate hard from soft wheat endosperm material properties was quite high. Four laboratories compressed endosperm bricks in the same orientation, on edge; texture class (soft vs. hard) was consistently the greatest source of variation in analysis of variance models (F-values from 417 to 1401, Youngs modulus and ...