Dietary fibre fractions in cereal foods measured by a new integrated AOAC method.

The reliable determination of soluble, insoluble and total dietary fibre in baked goods and cereal flours is an important issue for research, nutritional labelling and marketing. We compared total dietary fibre (TDF) contents of selected cereal based foods determined by AOAC Method 991.43 and the new AOAC Method 2009.01. Fifteen bread and bakery products were included in the study. Our results showed that TDF values of cereal products determined by AOAC Method 2009.01 were always significantly higher than those determined by AOAC Method 991.43. This was explained by the inclusion of low molecular weight soluble fibre fractions and resistant starch fractions in the TDF measurement by AOAC 2009.01. This documents that nutritional labelling of cereal products poses the challenge how to update TDF data in nutrient databases in a reasonable time with an acceptable expenditure.

Chemopreventive effects of in vitro digested and fermented bread in human colon cells.

PURPOSE: Bread as a staple food product represents an important source for dietary fibre consumption. Effects of wheat bread, wholemeal wheat bread and wholemeal rye bread on mechanisms which could have impact on chemoprevention were analysed in colon cells after in vitro fermentation. METHODS: Effects of fermented bread samples on gene expression, glutathione S-transferase activity and glutathione content, differentiation, growth and apoptosis were investigated using the human colon adenoma cell line LT97. Additionally, apoptosis was studied in normal and tumour colon tissue by determination of caspase activities. RESULTS: The expression of 76 genes (biotransformation, differentiation, apoptosis) was significantly upregulated (1.5-fold) in LT97 cells. The fermented bread samples were able to significantly increase glutathione S-transferase activity (1.8-fold) and glutathione content (1.4-fold) of the cells. Alkaline phosphatase activity as a marker of differentiation was also significantly enhanced (1.7-fold). The fermented bread samples significantly inhibited LT97 cell growth and increased the level of apoptotic cells (1.8-fold). Only marginal effects on apoptosis in tumour compared to normal tissue were observed. CONCLUSIONS: This is the first study which presents chemopreventive effects of different breads after in vitro fermentation. In spite of differences in composition, the results were comparable between the bread types. Nevertheless, they indicate a potential involvement of this staple food product regarding the prevention of colon cancer.

Modification of an in vitro model simulating the whole digestive process to investigate cellular endpoints of chemoprevention.

In vitro gut fermentation systems are relevant tools to study health benefits of foodstuffs. Most of them are commonly used to investigate the degradation of nutrients or the development of gut flora. Using these models, strong cytotoxic effects of the resulting samples on cultured cells were observed. Hence, the aim of the present study was to develop a modified in vitro fermentation model that simulates the whole digestive tract and generates fermented samples that are suitable for testing in cell culture experiments. Wholemeal wheat flour (wwf) was digested and fermented in vitro with a fermentation model using different ox gall concentrations (41·6 and 0·6 g/l). The resulting fermentation supernatants (fs) were characterised for metabolites and biological effects in HT29 cells. The fermentation of wwf increased chemopreventive SCFA and decreased carcinogenic deoxycholic acid (DCA). The strong cytotoxic effects of the fs, which were partly due to cholic acid and DCA, were diminished by lowering the ox gall concentration, allowing the use of the samples in cell culture experiments. In conclusion, an in vitro digestion model, which can be used to study the effects of foodstuffs on chemoprevention and gut health in colon cells, is introduced and its physiological relevance is demonstrated.

Distribution of ergot alkaloids and ricinoleic acid in different milling fractions.

The sclerotia of the fungus Claviceps sp. are still a challenge for the milling industry. Ergot sclerotia are a constant contamination of the rye crop and have to be removed by modern milling technologies. Changing sizes and coloration of the sclerotia make it difficult to separate them from the grain. Ergot sclerotia are a problem when cleaning is insufficient and non-separated specimens or sclerotia fragments get into the milling stream and thus ergot alkaloids are distributed into the different cereal fractions. In model milling experiments, the residues of ergot in rye flour and the distribution of ergot into different milling fractions were investigated. Rye grains were mixed with whole ergot sclerotia and in another experiment with ergot powder and cleaned afterwards before milling. The ergot alkaloids ergometrine, ergosine, ergotamine, ergocornine, ergocryptine, ergocristineand their related isomeric forms (-inine-forms), and additionally ricinoleic acid as a characteristic component of ergot, were quantified in the different milling fractions. From the first experiment, it can be shown that after harvesting even simple contact of sclerotia with bulk grains during ordinary handling or movement of bulk grain in the granary is sufficient to contaminate all the healthy or sound rye grains with ergot alkaloids. Thereby, the amount of ergot residue correlates with the amount of peripheral layers of rye grains in the flour. In an additional experiment without sclerotia specimens, bulk rye grains were loaded with powder of sclerotia. After subsequent cleaning, aconcentration of ergot alkaloids was detected, which was tenfold higher than the ergot alkaloidconcentration of the experiment with intact ergot sclerotia.

Fermented wheat aleurone inhibits growth and induces apoptosis in human HT29 colon adenocarcinoma cells.

Fermentation of dietary fibre by the gut microflora may enhance levels of SCFA, which are potentially chemoprotective against colon cancer. Functional food containing wheat aleurone may prevent cancer by influencing cell cycle and cell death. We investigated effects of fermented wheat aleurone on growth and apoptosis of HT29 cells. Wheat aleurone, flour and bran were digested and fermented in vitro. The resulting fermentation supernatants (fs) were analysed for their major metabolites (SCFA, bile acids and ammonia). HT29 cells were treated for 24-72 h with the fs or synthetic mixtures mimicking the fs in SCFA, butyrate or deoxycholic acid (DCA) contents, and the influence on cell growth was determined. Fs aleurone was used to investigate the modulation of apoptosis and cell cycle. The fermented wheat samples contained two- to threefold higher amounts of SCFA than the faeces control (blank), but reduced levels of bile acids and increased concentrations of ammonia. Fs aleurone and flour equally reduced cell growth of HT29 more effectively than the corresponding blank and the SCFA mixtures. The EC(50) (48 h) ranged from 10 % (flour) to 19 % (blank). Markedly after 48 h, fs aleurone (10 %) significantly induced apoptosis and inhibited cell proliferation by arresting the cell cycle in the G0/G1 phase. In conclusion, fermentation of wheat aleurone results in a reduced level of tumour-promoting DCA, but higher levels of potentially chemopreventive SCFA. Fermented wheat aleurone is able to induce apoptosis and to block cell cycle - two essential markers of secondary chemoprevention.

Quantitative protein composition and baking quality of winter wheat as affected by late sulfur fertilization.

Increasing prices for wheat products and fertilizers, as well as reduced sulfur (S) contributions from the atmosphere, call for an improvement of product quality and agricultural management. To detect the impact of a time-dependent S fertilization, the quantitative protein composition and the baking quality of two different wheat cultivars, Batis and Turkis, were evaluated. The glutathione concentration in grains serves as a reliable marker of the need for added S fertilizer. The quantitation of gliadins and glutenin subunits by reversed-phase high-performance liquid chromatography confirmed that S-rich proteins significantly increased with S fertilization, whereas the S-poor proteins significantly decreased. Proteome analysis by means of high-resolution protein profiles detected 55 and 37 proteins from Batis and Turkis changed by late S fertilization. A microscale baking test using wholemeal flour was implemented for the evaluation of baking quality, and late S fertilization was found to improve the composition of gluten proteins and baking quality.

Both wheat (Triticum aestivum) bran arabinoxylans and gut flora-mediated fermentation products protect human colon cells from genotoxic activities of 4-hydroxynonenal and hydrogen peroxide.

Dietary fibers are fermented by the gut flora to yield short chain fatty acids (SCFAs), which inhibit the growth of tumor cells, induce glutathione S-transferases (GSTs), and protect cells from the genotoxic activity of 4-hydroxynonenal (HNE). Here, we investigated effects of wheat bran-derived arabinoxylans and fermentation products on these parameters of chemoprevention. Newly isolated water extractable (WeAx) and alkali extractable arabinoxylans (AeAx) were fermented under anaerobic conditions with human feces. Resulting fermentation supernatants (FSs) were analyzed for SCFAs and used to treat HT29 colon cancer cells. Cell growth, cytotoxicity, antigenotoxicity against hydrogen peroxide (H2O2) or HNE, and GST activity were determined. Nonfermented WeAx decreased H2O2-induced DNA damage by 64%, thus demonstrating chemoprotective properties by this nonfermented wheat bran fiber. The fermentation of WeAx and AeAx resulted in 3-fold increases of SCFA, but all FSs (including the control without arabinoxylans) inhibited the growth of the HT29 cells, reduced the genotoxicity of HNE, and enhanced the activity of GSTs (FS WeAx, 2-fold; FS AeAx, 1.7-fold; and control FS, 1.4-fold), which detoxify HNE. Thus, increases in SCFAs were not reflected by enhanced functional effects. The conclusion is that fermentation mixtures contain modulatory compounds that arise from the feces and might add to the effectiveness of SCFAs.

Spectrophotometric determination of yellow pigment content and evaluation of carotenoids by high-performance liquid chromatography in durum wheat grain.

The so-called "yellow pigment" content of durum wheat has been used for a long time as an indicator of the color quality of durum wheat and pasta products. For decades the chemical nature of these pigments has been assigned to carotenoids, mainly to the xanthophyll lutein and its fatty acid esters. The chemical composition of the yellow pigments of eight German durum wheat cultivars was studied. Grains were milled on a laboratory mill. Pigment extraction of millstream fractions was performed according to the optimized ICC standard method 152 procedure, and the chemical composition of the extract was analyzed by isocratic reversed phase high-performance liquid chromatography. all-trans-Lutein ranged from 1.5 to 4 mg kg(-1), and zeaxanthin was found in traces. No lutein esters and carotenes were detected. Surprisingly, the fraction of carotenoids of the complete yellow pigment content amounted to only 30-50% of the yellow pigment quantities, so there are still compounds in durum wheat not yet identified that contribute considerably to the yellow color of the grain extracts. The isolation and chemical identification of those pigments are under investigation.