Joel Abecassis

Particle size distribution of break, sizing and middling wheat flours by laser diffraction

The particle size distributions of wheat flours collected along a milling diagram were assessed. Nine wheat varieties from the genetic trait Triticum aesticum vulgare and differing in hardness were studied for two consecutive years. Break, sizing and middling flours were collected for each wheat at different stages in an experimental mill, with all the milling conditions being kept constant. The particle size distributions were measured from 1·5 to 600 μm by using a laser light diffraction apparatus. The distributions were compared by principal component analysis. The method provided a global and synthetic comparison of all the flour fractions. In the case of the soft varieties, the distributions exhibited a first mode around 25 μm, corresponding mainly to isolated starch granules. The distribution of this mode was very low or non-existent for the hard varieties. As the milling conditions were the same for all the wheats, the different proportions measured for this mode were interpreted as being directly representative of the wheat hardness. The proportion of the 25 μm mode was considered as a measure of the ability of the wheat to release starch granules and could be used to follow a grinding or milling process.

Influence of Arabinoxylans and Endoxylanases on Pasta Processing and Quality. Production of High-Quality Pasta with Increased Levels of Soluble Fiber

ABSTRACT As part of a general study aiming to clarify the role of arabinoxylans (AX) in pasta processing and quality, AX were modified by the addition of endoxylanases during pasta processing. The influence on processing parameters and quality were determined. Pasta (800 g) was produced from two commercial semolinas (semA and semB) using dosages of Bacillus subtilis (XBS) and Aspergillus niger (XAN) endoxylanases of 0–0.225 Somogyi units/g of semolina. Increased dosages resulted in a drop of extrusion pressure. The endoxylanase treatments had no great effect on the resulting pasta quality (color of dry products and surface condition, viscoelastic index, and resistance to longitudinal deformations of cooked products). High dosages of XAN and XBS resulted in high levels of solubilized AX (as an extra source of soluble dietary fiber) of low molecular weight which were expected to easily leach out during the cooking process of pasta. Surprisingly, only low levels of AX were found in the cooking water, even wi...

Relationships between wheat grain physical characteristics studied through near-isogenic lines with distinct puroindoline-b allele

Key messageGenetic (different forms of puroindoline-b) and environment (through variations in vitreousness), have important effects on wheat grain mechanical properties. The two methods of hardness measurements (NIRS, SKCS) do not give the same information.AbstractBread wheat near-isogenic lines differing in hardness, due to distinct puroindoline-b alleles (the wild type, Pinb-D1a, or the mutated forms, Pinb-D1b or Pinb-D1d), were grown for three years in seven sites and under two nitrogen fertilization levels, to study genetic and environmental effects on grain mechanical properties. Two methods, Near-Infrared Reflectance Spectroscopy (NIRS) and Single Kernel Characterization System (SKCS), currently used for grain hardness characterization, were carried out. Grain vitreousness, which is known to affect the grain mechanical behavior but is generally not studied, was also measured, as well as three other characters (Thousand Grain Weight, Test Weight and protein content). The relationships between the different characters were studied. Results revealed a clear effect of the different Pinb-D1 alleles on NIRS hardness, and a marked impact of the environmental conditions on vitreousness. SKCS hardness was influenced by both Pinb-D1 alleles and environmental conditions. The relationship between SKCS and NIRS hardness was strong when considering together soft and hard genotypes, but moderate within a class of genetical hardness. Vitreousness had only a weak effect on NIRS hardness, whereas vitreousness and SKCS values were strongly correlated, with two distinct regressions for soft and hard genotypes. Vitreousness was positively related to protein content, especially in the case of hard genotypes, which were able to reach high vitreousness values never observed for soft genotypes.

Influence of Instrument Rigidity and Specimen Geometry on Calculations of Compressive Strength Properties of Wheat Endosperm

ABSTRACT Endosperm texture is one of the most important quality features in wheat; it defines milling energy requirements and end-use suitability. From an engineering perspective, texture can be quantified by measuring the physical property of the resistance force to crushing of precisely machined specimens of endosperm. In such procedures, cylindrical or parallelepiped blocks are crushed under a constant rate of strain, in which values are reported of maximum stress, strain at maximum stress, Youngs modulus, and the energy of compression to the point of maximum stress. Generally overlooked, however, is the instrument itself, which can significantly affect the apparent values of the latter three properties. Because no instrument is infinitely rigid, departures between apparent and actual strength properties occur. In this study, the physical principles for compressive strength measurement with respect to corrections for instrument rigidity are developed. Results show that the departures are exacerbated i...

Assessment of the quality of durum wheat products by spectrofluorometry and fluorescence video image analysis

Because assessment of Durum wheat semolina purity by standard ash-test has been widely criticized, we attempted to characterize products of a semolina mill by spectrofluorometry and fluorescence imaging. A collection of milled wheat products ranging from very pure semolina to brans were chosen for this study. Multidimensional statistical analyses (Principal component analyses) were applied to the spectral and image data. Maps showing a classification of the products according to purity were obtained without biochemical calibration. Principal component regression was applied to the data in order to test the relationship of aleurone fluorescence to ash content. Both spectrofluorometry and fluorescence imaging gave similar results with good determination coefficients (r2 equals 0.97 and 0.92) for the study of a single wheat variety. Products obtained from different wheat varieties were more difficult to compare.