Wheat germ supplementation of a low vitamin E diet in rats affords effective antioxidant protection in tissues.

Background: Oxidative stress is implicated in the etiology of many diseases, but most of clinical trials failed to demonstrate beneficial effects of antioxidant supplementation.

Methods: In the present experiment, we assessed the mean-term effect of wheat germ supplementation, as a dietary source of vitamin E, on antioxidant protection in rat.

Results: Feeding rats a 20% wheat germ diet significantly increased plasma and liver vitamin E levels, compared to the low vitamin E basal diet.

Restoration of thiamine status with white or whole wheat bread in a thiamine-depleted rat model.

Long-term thiamine deficiency has been largely documented, whilst little is known about effects of short-term depletion/repletion periods on thiamine vitamers status. Rats were submitted to short-term depletion (8 days) followed by different durations of repletion (3 or 14 days) with thiamine from bread (whole wheat bread or white bread, whole B and white B respectively) or corresponding controls. Short-term depletion drastically decreased plasma thiamine (-97%) and its urinary excretion (-77%).

Genetic analysis of bread-making quality scores in bread wheat using a recombinant inbred line population.

Bread-making quality has been evaluated in a progeny of 194 recombinant inbred lines (RILs) from the cross between the two French cultivars Récital and Renan, cultivated in three environments. These cultivars have been previously identified as having contrasting grain protein content and dough rheology properties, although they achieve similar scores for the official bread-making test used for cultivar registration in France. However the progeny displayed a wide range of variations, suggesting that favourable alleles at several loci are present in the two parental lines.

Wheat lipoxygenase activity induces greater loss of carotenoids than vitamin E during breadmaking.

The current study was undertaken to provide solutions to optimize the unsaponifiable antioxidants content of bread. We report a complete description of changes in wheat carotenoids and vitamin E content from grain to bread and highlight the most important processing steps affecting their level in wheat bread. Major carotenoids losses occurred during kneading.

Moderate decrease of pH by sourdough fermentation is sufficient to reduce phytate content of whole wheat flour through endogenous phytase activity.

Whole wheat bread is an important source of minerals but also contains considerable amounts of phytic acid, which is known to impair their absorption. An in vitro trial was performed to assess the effect of a moderate drop of the dough pH (around 5.5) by way of sourdough fermentation or by exogenous organic acid addition on phytate hydrolysis.

Mechanical effects of plant cell wall enzymes on cellulose/xyloglucan composites.

Xyloglucan-acting enzymes are believed to have effects on type I primary plant cell wall mechanical properties. In order to get a better understanding of these effects, a range of enzymes with different in vitro modes of action were tested against cell wall analogues (bio-composite materials based on Acetobacter xylinus cellulose and xyloglucan). Tomato pericarp xyloglucan endo transglycosylase (tXET) and nasturtium seed xyloglucanase (nXGase) were produced heterologously in Pichia pastoris.

Tensile deformation of bacterial cellulose composites.

The polymeric basis for the mechanical properties of primary plant cell walls has been investigated by forming analogous composites based on fermentation of the bacterium Acetobacter xylinus, either alone or in the presence of xyloglucan or pectin. Simultaneous small-angle X-ray scattering and uniaxial deformation experiments has shown how the cellulose microfibrils reorient during deformation. Despite very different stress/strain curves, the reorientation behaviour is similar, regardless of the presence or absence of xyloglucan or pectin.

Mechanical properties of primary plant cell wall analogues.

Mechanical effects of turgor pressure on cell walls were simulated by deforming cell wall analogues based on Acetobacter xylinus cellulose under equi-biaxial tension. This experimental set-up, with associated modelling, allowed quantitative information to be obtained on cellulose alone and in composites with pectin and/or xyloglucan. Cellulose was the main load-bearing component, pectin and xyloglucan leading to a decrease in modulus when incorporated.

Structure of Acetobacter cellulose composites in the hydrated state.

The structure of composites produced by the bacterium Acetobacter xylinus have been studied in their natural, hydrated, state. Small-angle X-ray diffraction and environmental scanning electron microscopy has shown that the ribbons have a width of 500 A and contain smaller semi-crystalline cellulose microfibrils with an essentially rectangular cross-section of approximately 10 x 160 A(2). Incubation of Acetobacter in xyloglucan or pectin results in no changes in the size of either the microfibrils or the ribbons.

In vitro synthesis and properties of pectin/Acetobacter xylinus cellulose composites.

Pectin and cellulose are major components of most primary cell walls, yet little is known about the way in which they interact either during assembly or in subsequent functional performance of the wall. As a mimic of cell wall assembly, we studied the formation of molecular composites formed by deposition of cellulose from Acetobacter xylinus into pectin/calcium systems, and the molecular, architectural and mechanical properties of the composites obtained. The formation of interpenetrating cellulose/pectin composite networks (as envisaged in current models for primary cell walls) required a pre-existing, but not too strong, pectin network.