Bran Size Distribution at Milling and Mechanical and Biochemical Characterization of Common Wheat Grain Outer Layers: A Relationship Assessment

International audienceMechanical properties of wheat grain outer layers from common wheat (Triticum aestivum L.) cultivars known to display distinct milling behavior were analyzed using uniaxial tension tests. Tensile modulus and strain to rupture of the tissues distinguished between the wheat cultivars. Values of strain to rupture were related to coarse bran size generated by grain milling, a characteristic that distinguishes the two hardness classes. As content of an aleurone marker in total or first break flour was also related to coarse bran size, extensibility of wheat grain outer layers' could be a key parameter to explain the observed tissue mechanical behavior and thus distribution of the aleurone layer content in flours. As tissue mechanical properties are generally linked to the cell wall biochemical composition and structure, analysis of the main wheat outer layers' cell wall compounds was undertaken to establish relationships with the differences observed in mechanical properties. No clear correlation could be found with one of the wheat outer layers' component but involvement of the outer layers' cell wall structure in the tissues behavior at milling was confirmed

Mechanical behavior of wheat endosperm. Local measurements by AFM and numerical modeling

Mechanical behavior of wheat endosperm. Local measurements by AFM and numerical modelin

Losses of nutrients and anti-nutritional factors during abrasive decortication of two pearl millet cultivars (Pennisetum glaucum)

Losses of nutrients such as starch, lipids, proteins, iron and zinc as well as phytase activity and of recognised anti-nutritional compounds (some insoluble fibres, iron-binding phenolic compounds and phytates) were determined following abrasive decortication of grains from two pearl millet cultivars (Gampela and IKMP-5) with different composition cultivated in Burkina Faso. In both cultivars, abrasion of the starchy endosperm started when about 12% of the dry matter had been removed from grains but lipid and protein losses followed the loss of dry matter. Zinc loss (%) was lower than that of iron; however, both were higher than dry matter losses. By contrast, phytate loss was lower than dry matter loss. Interestingly, decortication led to significant losses in fibres and iron-binding phenolic compounds with different level depending on the cultivar. Changes in phytase activity also differed in the two cultivars (42% and 11% losses of phytase activity in grains from Gampela and IKMP-5 cultivars, respectively, at 12% of abrasion). Hence, decortication of pearl millet grains does not decrease lipid and protein contents but does considerably decrease some anti-nutritional factors (part of the fibres and iron-binding phenolic compounds). However, as mineral contents and particularly iron content decreased while phytate content remains high, decortication may be insufficient to increase Fe and Zn bioavailability. (c) 2005 Elsevier Ltd. All rights reserved

Changes in common wheat grain milling behavior and tissue mechanical properties following ozone treatment

Correspondance: fax: +334 9961 3076. E-mail address: [email protected] audienceOzone treatment (10 g/kg) of common wheat grains with a new patented process, Oxygreen®, used before milling was found to significantly reduce (by 10-20%) the required energy at breaking stage whatever the grain hardness and without changes in the flour yield. Detailed study of each of the milling steps undertaken on a hard type cultivar showed that both the breaking and the reduction energy were decreased. Reduction of the coarse bran yield was also observed concomitantly with an increase in the yield of white shorts. Biochemical characterization of the milling fractions pointed out changes in technological flour properties as starch damage reduction, aleurone content enrichment and increase of insoluble glutenin polymers. Measurement of wheat grain tissue mechanical properties showed that ozone treatment leads to reduction of the aleurone layer extensibility and affects the local endosperm resistance to rupture. These data as well as the direct effect of ozone oxidation on biochemical compounds could explain the observed changes in milling energy, bran and shorts yield and flour composition. (Résumé d'auteur

On the effect of local sample slope during modulus measurements by contact-resonance atomic force microscopy

International audienceContact-resonance atomic force microscopy (CR-AFM) is of great interest and very valuable for a deeper understanding of the mechanics of biological materials with moduli of at least a few GPa. However, sample surfaces can present a high topography range with significant slopes, where the local angle can be as large as ± 50°. The non-trivial correlation between surface slope and CR-frequency hinders a straightforward interpretation of CR-AFM indentation modulus measurements on such samples. We aim to demonstrate the significant influence of the surface slope on the CR-frequency that is caused by the local angle between sample surface and the AFM cantilever and present a practical method to correct the measurements. Based on existing analytical models of the effect of the AFM set-up's intrinsic cantilever tilt on CR-frequencies, we compute the non-linear variation of the first two (eigen)modes CR-frequency for a large range of surface angles. The computations are confirmed by CR-AFM experiments performed on a curved surface. Finally, the model is applied to directly correct contact modulus measurements on a durum wheat starch granule as an exemplary sample

Production in Escherichia coli and site-directed mutagenesis of a 9-kDa nonspecific lipid transfer protein from wheat

3 illus. 2 tables 2 graph.International audienc

Exploring plant biodiversity to extract oil bodies for sustainable food applications

International audienceOleoproteaginous and cereal seeds enclose a wide range of nutriments such as lipids, proteins, polysaccharides and various mineral and organic micronutrients. These nutrients are found under the form of natural assemblies such as oil or protein bodies or starch granules, that have interesting functionalities (micronic sizes, surface activity, high physicochemical stability, etc.). These assemblies are extracted by various processes using energy, organic solvents, steam, alone or in combination. Thus, their natural structures are often strongly damaged, and some of their functionalities disappear. Storming through natural assemblies’ biodiversity to address the societal demand for more natural and minimally-processed food, seems promising. Indeed, the soft extraction of such assemblies could be an alternative to traditional intensive fractionation methods of plant raw materials to isolate target ingredients (sucrose, starch, refined oils, etc.). This would allow energy savings and avoid solvent use, but must be balanced with potential challenges of this new green refinery scheme.The purpose of the present work is to highlight the physicochemical properties of various oil bodies from diverse plant origins. A green refinery protocol is proposed for their extraction from various matrices. Then their size distribution, surface activity, resistance to oxidation and fatty acids and liposoluble vitamins bioaccessibility is also presented. Omega-3 rich sources (linseed, chia, hemp…) are of special interest to correct the low dietary intake of US and European population as well as the ω6/ω3 balance. Oil bodies from these plant species can thus constitute new dietary carriers of ω3 and other bioactive molecules. Moreover, the combination of oil bodies with specific features (fatty acid profiles, stabilities, vitamin contents) can help meeting the requirements of specific nutritional targets (infants, children, elderly, athletes, etc.). Altogether, we are convinced that the valorization of these diverse oil bodies can be a strategic route in the development of sustainable food systems