Particle size determines the anti-inflammatory effect of wheat bran in a model of fructose over-consumption : implication of the gut microbiota

We investigated the impact of the particle size of wheat bran on gut dysbiosis and inflammation induced by a fructose overload. Mice received drinking water with or without fructose (30%) and a standard diet supplemented with or without 5% of wheat bran fractions characterized by different average particle sizes (1690 pm versus 150 um) for 8 weeks. Fructose increased Enterobacteriaceae associated with higher expression of key inflammatory genes in the liver. The two wheat bran fractions differently affected specific gut bacteria known to be involved in the regulation of the gut barrier function and/or inflammatory processes. Moreover, wheat bran with small particle size was the sole fibre that reduced hepatic and systemic inflammatory markers upon high fructose intake. The anti-inflammatory effects of wheat bran may be dependent on their particle size and could be related to the changes in caecal Enterobacteriaceae

Wheat grain fructans: quantification, structural characterization and impact of bread making

Fructans are fructose based carbohydrates that have been studied intensively during the last two decades because of their claimed health promoting properties. In particular inulin-type fructans received much scientific attention. They consist almost exclusively of ß(2,1)-linked fructose units and are commercially available as food ingredient derived mostly from chicory root. They are not only considered as dietary fibers but are also under investigation as prebiotic. The latter implies that the consumption of inulin-type fructans is thought to selectively stimulate the growth and/or activity of health promoting bacteria in the colon and as such induce a beneficial health effect. Despite their claimed beneficial effects, fructans may cause unwanted gastro-intestinal side effects as well. Yet, negative effects are mainly reported for patients suffering irritable bowel syndrome or related diseases and the majority of the healthy population easily tolerates the generally consumed fructan levels. Hence, most subjects are assumed to benefit from their consumption due to their dietary fiber nature and claimed prebiotic effects. However, these effects were demonstrated for inulin-type fructans only and the majority of the fructans present in a regular western diet are not those inulins or derived fructo-oligosaccharides. The major dietary fructan source by far is wheat. Despite their abundance in our diet, little is known about wheat grain fructan structure, their degradation during food processing and their physiological effects. However, as wheat grain fructans are thought to belong to the branched, graminan-type fructans, their behavior and possible health effects might differ from inulin-type fructans. In view of the lack of knowledge in this area, this dissertation focused on wheat grain fructans.The general aim of this dissertation was to investigate wheat grain fructan structure, fructan formation and degradation starting from their formation in developing wheat grains up to wheat based bread making. This required the development of analytical methods for the quantification and structural characterization of fructans in wheat and wheat based products. Firstly, an improved fructan quantification method based on high performance anion exchange chromatography (HPAEC) analysis of sample extracts before and after mild acid hydrolysis was established and tested. This method allows, in contrast to the existing methods, the calculation of the average fructan degree of polymerization (DP). Indeed, not only the amount of fructose set free from fructans but also that of released glucose is accurately determined with this new method. To obtain more detailed information on wheat grain fructan structure, an improved liquid chromatography-mass spectrometry (LC-MS) method was developed. Columns with a trifunctional C18 alkyl (T3) stationary phase were used for LC. They proved to possess superior analytical features in comparison with the conventional columns and result in lower and more stable retention times. The higher separating power of the T3 phase allowed the resolution of all fructan molecules in complex fructan mixtures, and enabled their structural characterization. The new method was subsequently used for the elucidation of the MS2 fragmentation patterns of branched, graminan-type fructans. To this end, such fructans were synthesized in vitro with a recombinant sucrose:fructan 6-fructosyltransferase (6-SFT) from Pachysandra terminalis and with either unlabeled or 13C labeled substrates. Comparison of the MS2 spectra of native and 13C labeled reaction products allowed their structural identification and demonstrated for the first time that LC-MS is also applicable to structural characterization of branched fructans. To gain insight in fructan metabolism in developing wheat grains and to assess their function(s) in this development, fructan content and fructan metabolism related enzyme activities were studied in a set of immature grains. In contrast to previous studies, not only fructans were evaluated but all major carbohydrates present in wheat grains were studied simultaneously and this by both microscopy and quantitative analysis. This integrated approach allowed to detect correlations between the different maturation processes and enabled obtaining a comprehensive overview on wheat grain development. Fructan synthesis appeared to be restricted to the first phase of grain development. During this phase of cell division and expansion high sucrose:sucrose 1-fructosyltransferase (1-SST) and 6-SFT activities were observed together with smaller fructan:fructan 1-fructosyltransferase (1-FFT) activities. Accordingly, low DP fructan oligosaccharides were mainly of the graminan- and inulin-type during the first week after anthesis. Yet, starting from 14 days after anthesis, the occurrence of neofructans, fructans with an internal glucose, was clearly observed. The analytical improvements achieved in the first part of this doctoral work allowed to demonstrate the presence of several neo-type fructan structures for the first time. Neofructan formation coincided with the start of the second development phase or grain filling phase when large amounts of starch, proteins and arabinoxylans accumulated. The share of neofructan-type fructans gradually increased during grain filling at least for the DP 4 fructans. At the same time fructan exohydrolase (FEH) activities were high. During the final phase of grain development, only moisture loss occurred. Finally, fructan degradation during wheat based bread making was assessed. For the first time, the extent of this degradation was accurately determined owing to the accuracy of the quantification method optimized in the first part of this dissertation. Up to 80% of all wheat grain fructans were degraded during bread making due to the action of yeast invertase. The extent of this degradation depended on the yeast strain used and its growth conditions. Fructan degradation could be prevented completely by use of a yeast strain lacking invertase. In conclusion, this doctoral work revealed the structure of wheat grain fructans and gave more insight in their synthesis during wheat grain development. Against expectations, wheat grains contain not only graminan-type fructans but also neo-type fructans. Consequently, wheat grain fructan structure clearly differs from that of linear inulin-type fructans. The nutritional implications of this structural difference open up an interesting avenue for future research. The analytical tools provided in this work will aid future research on the physiological effects of wheat grain fructans. Results on fructan degradation during bread making and the tunable role of yeast in this open up perspectives for steering fructan concentrations in bread, and as such, modulating fructan consumption.status: publishe

Evaluation of Microbial Load, Formation of Odorous Metabolites and Lipid Stability during Wet Preservation of Nannochloropsis gaditana Concentrates

Wet preservation of algae allows us to bridge the time period between algae harvest and processing while avoiding the costs and nutritional losses associated with algae drying. This study aimed to identify suitable storage conditions for the wet preservation of Nannochloropsis gaditana concentrates. The impact of storage temperature, time and the way of closing the storage recipient was evaluated using a full factorial design. The effect of acetic acid addition was tested for one storage condition. Storage temperature was the main factor determining the microbial count and had a vast impact on the formation of odorous metabolites. Storage at 20 °C in closed recipients led to rapid O2 consumption, accumulation of malodorous short-chain fatty acids above their odor thresholds, and the production of H2S and methanethiol. These odorous metabolites were not formed or to a much lower extent during 4 °C and 8 °C storage in closed recipients. Acetic acid supplementation (50 mM) suppressed the formation of short-chain fatty acids during 8 °C storage in unsealed recipients and reduced the aerobic microbial count and the number of yeasts and molds by approximately one log unit after 14 days. Yet, acetic acid addition also induced lipid hydrolysis and decreased chlorophyll levels when algae were stored for more than one week. This study demonstrated that temperature control is needed and that acetic acid addition is a promising approach when N. gaditana concentrates are stored for less than one week

The effect of amylolytic activity and substrate availability on sugar release in non-yeasted dough

During bread making, the sugar content in dough changes continuously due to enzymatic starch degradation. Despite its importance, the relation between amylase activity and sugar release in dough is ill documented. In this work, the relative importance of a- and b-amylase activity and substrate availability on the dynamics of sugar release in dough was studied. Analysis of non-yeasted dough samples from Bilux flour (Falling number [FN] 477 s) and Bison flour (332 s) revealed that maltose was released quickly during mixing (1.0% dm) and reached 2.0% dm after resting (180 min). Inhibition of aamylase in Bilux flour indicated that >85% of the maltose release during resting could be attributed to endogenous b-amylase activity. a-Amylase supplementation markedly increased maltose release from 2.0 to 4.7% dm after resting. Barley b-amylase addition, on the contrary, left maltose levels virtually unchanged. Maltose concentrations were also increased, up to 3.6% dm, by increasing the damaged starch content from 6.4 to 10.6% dm. In conclusion, this work shows that b-amylase can provide a relatively high amount of maltose in the absence of a-amylase. Higher maltose levels require either higher levels of endogenous or added a-amylases or increased damaged starch levels.publisher: Elsevier articletitle: The effect of amylolytic activity and substrate availability on sugar release in non-yeasted dough journaltitle: Journal of Cereal Science articlelink: http://dx.doi.org/10.1016/j.jcs.2016.02.016 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved.status: publishe

Study of the chemical composition, hydration characteristics and structure of bran of wheat, rye, oat and maize

Due to the growing interest in healthy and qualitative food, there is an increasing interest in dietary fiber. In Europe, the average daily intake of fiber lies beneath the recommended intake. In this context, bran may be part of the solution because it is one of the most concentrated sources of dietary fiber. The objective of this study is to examine the differences in chemical composition, physical characteristics and structure of wheat-, rye-, oat- and maize bran. This information is important in the context of understanding the physiological effects of bran consumption. Commercial bran contains residual endosperm that interferes with the characterization of the botanical bran. Therefore, methods were developed to reduce the endosperm contamination with a minimal loss of non-endosperm material. The starch content of wheat bran was drastically reduced (from 24% to 2%) and a clear reduction in starch content was also obtained for rye bran (from 45% to 7%), oat bran (from 57% to 13%) and maize bran (from 62% to 2%). Chemical characterization was performed, showing large differences in composition between bran of different cereals. Oat bran had the highest beta-glucan content (17%). Maize bran was characterized by a high arabinoxylan content (43%) and a low mineral content (1%). Rye bran contained more water-soluble compounds, mainly fructan (7.5%) and water extractable arabinoxylan (1.3%), than wheat bran (3.4% and 0.6%, respectively). The bran samples furthermore differed in physical characteristics. Oat bran had the highest capacity to strongly bind water (1.7 g/g dry bran) compared to wheat bran (0.8 g), rye bran (0.8 g) and maize bran (0.9 g). Moreover, when an extract was made of the different bran samples, the oat bran extract was the most viscous. Furthermore, the water extractable content of rye (35%) and oat bran (31%) was higher compared to wheat (24%) and maize bran (13%). Also bran morphology, which was examined using cryo-SEM microscopy, was highly cereal dependent. It can be concluded that the chemical composition, the physical characteristics and the structure of wheat, rye, oat and maize bran differ markedly. Hence, their physiological effects in humans can be expected to differ accordingly.status: publishe

FODMAP Reduction in Yeast-Leavened Whole Wheat Bread

© 2018 AACC International, Inc. Patients suffering from IBS should follow a very strict diet that is low in FODMAPs. To accomplish this they must avoid consumption of most cereal products. Removal of cereal products from the diet has negative health effects, however, because cereal grains are a major source of energy, dietary fiber, vitamins, and minerals in the diet. To enable IBS patients to consume nutritious whole wheat breads without negative health effects, the FODMAP levels in these breads must be reduced. Different strategies can be applied for this purpose, including the use of an alternative yeast species for fermentation (K. marxianus) or the addition of enzymes such as inulinase. When addition of alternative ingredients is not desirable, adaptations to the breadmaking process, such as a prolonged proofing time, may be utilized to reduce FODMAP levels.status: publishe

A closer look at FODMAPs in cereal bread products

status: publishe

Quantification and visualization of dietary fibre components in spelt and wheat kernels

This study was undertaken to determine contents and structural characteristics of arabinoxylan (AX), fructan and β-glucan in 28 spelt accessions, and to compare them with those of dietary fibre components in 11 wheat accessions. In addition, microscopic visualization of AX and β-glucan distribution in a selection of these accessions was performed. On average, wheat contained more total AX (TOT-AX; 6.90 versus 5.74%) and water-extractable AX (WE-AX; 0.71 versus 0.59%) than spelt. The overall arabinose to xylose ratio (A/X; 0.72 for wheat and 0.71 for spelt) was similar for both subspecies, but that of water extractable material was higher for spelt than for wheat (1.25 versus 0.97). Fructan content and degree of polymerization (DP) were lower in spelt than in wheat (fructan content; 1.29% versus 1.53% and DP; 3.3 versus 4.5). β-glucan content was similar for both subspecies (0.54% for spelt and 0.51% for wheat). In the spelt accessions, the contents of the different fibre components significantly differed (up to 74% difference) between accessions and countries of origin, but were not affected by accession status and bread making quality. Microscopic visualizations showed that the two subspecies are very similar in terms of dietary fibre distribution over the kernel cell walls.publisher: Elsevier articletitle: Quantification and visualization of dietary fibre components in spelt and wheat kernels journaltitle: Journal of Cereal Science articlelink: http://dx.doi.org/10.1016/j.jcs.2015.01.003 content_type: article copyright: Copyright © 2015 Elsevier Ltd. All rights reserved.status: publishe