Water-extractable Arabinoxylan Content Research Articles

Formation of Phenolic Microbial Metabolites and Short-Chain Fatty Acids from Rye, Wheat, and Oat Bran and Their Fractions in the Metabolical in Vitro Colon Model

Rye bran and aleurone, wheat bran and aleurone, and oat bran and cell wall concentrate were compared in their in vitro gut fermentation patterns of individual phenolic acids and short-chain fatty acids, preceded by enzymatic in vitro digestion mimicking small intestinal events. The formation of phenolic metabolites was the most pronounced from the wheat aleurone fraction. Phenylpropionic acids, presumably derived from ferulic acid (FA), were the major phenyl metabolites formed from all bran preparations. The processed rye, wheat, and oat bran fractions contained more water-extractable dietary fiber (DF) and had smaller particle sizes and were thus more easily fermentable than the corresponding brans. Rye aleurone and bran had the highest fermentation rate and extent probably due to high fructan and water-extractable arabinoxylan content. Oat samples also had a high content of water-extractable DF, β-glucan, but their fermentation rate was lower. Enzymatic digestion prior to in vitro colon fermentation changed the structure of oat cell walls as visualized by microscopy and increased the particle size, which is suggested to have retarded the fermentability of oat samples. Wheat bran was the most slowly fermentable among the studied samples, presumably due to the high proportion of water-unextractable DF. The in vitro digestion reduced the fructan content of wheat samples, thus also decreasing their fermentability. Among the studied short-chain fatty acids, acetate dominated the profiles. The highest and lowest production of propionate was from the oat and wheat samples, respectively. Interestingly, wheat aleurone generated similar amounts of butyrate as the rye fractions even without rapid gas production.

Flour Mill Stream Blending Affects Sugar Snap Cookie and Japanese Sponge Cake Quality and Oxidative Cross‐Linking Potential of Soft White Wheat

The purpose of this research was to study the functional differences between straight grade (75% extraction rate) and patent (60% extraction rate) flour blends from 28 genetically pure soft white and club wheat grain lots, as evidenced by variation in sugar snap cookie and Japanese sponge cake quality. Functional differences were examined relative to arabinoxylan content, protein content, and oxidative cross-linking potential of flour slurries. Oxidative cross-linking measurements were obtained on flour slurries with a low shear Bostwick consistometer and considered endogenous oxidative cross-linking potential (water alone) or enhanced oxidative cross-linking potential (with added hydrogen peroxide-peroxidase). A 2-way ANOVA indicated that flour blend was the greater source of variation compared to grain lot for all response variables except water-extractable arabinoxylan content. Patent flours produced larger sugar snap cookies and Japanese sponge cakes, and contained significantly less total and water-unextractable arabinoxylans, protein, and ash than did straight grade flours. Patent flours produced more viscous slurries for endogenous and enhanced cross-linking measurements compared to the straight grade flours. The functional differences between patent and straight grade flours appear to be related to the particular mill streams that were utilized in the formulation of the 2 flour blends and compositional differences among those streams.

Water-extractable arabinoxylan content in milling fractions of spring wheats Contenido de arabinoxilano extraíble en agua en fracciones pulverizadas de trigos de primavera

The core objective of the present investigation was to extract and determine water-extractable arabinoxylan (WEAX) content in spring wheat varieties and their milling fractions. WEAX was extracted by ethanol method and both monosaccharides (arabinose and xylose) were determined by gas chromatograph–mass spectrometer (GC/MS). The WEAX content in whole wheat flour and milling fractions of wheat varieties ranged from 6.9 to 12.1 g/kg and 3.6 to 7.9 g/kg, respectively. WEAX has negative impact on gluten quality as reduced gluten strength was observed. Moreover, adding WEAX in bread formulation resulted in significant increase in volume and improvement in texture of the final product. WEAX holds potential to be extracted and utilized in cereal-based products for best quality and value addition. El principal objetivo de la presente investigación fue extraer y determinar el contenido de arabinoxilanos extraíbles en agua en variedades de trigo de primavera y sus fracciones pulverizadas. Arabinoxilanos extraíbles en agua (WEAX) fueron extraídos con en método etanol y ambos monosacáridos (arabinosa y xilosa) fueron determinados con cromatógrafo de gases – espectrómetro de masa (GC/MS). El contenido de WEAX en harina de trigo integral y fracciones pulverizadas de variedades de trigo se situó entre 6,9 y 12,1 g/kg y entre 3,6 y 7,9 g/kg, respectivamente. WEAX tuvo un impacto negativo en la calidad de gluten, al observarse una reducción en la fortaleza del gluten. Además, la adición de arabinoxilano extraíble en agua a la preparación de pan mostró un aumento significativo en volumen y mejora de textura del producto final. El arabinoxilano extraíble en agua tiene potencial para ser extraído y utilizado en productos basados en cereales para una mejor calidad y adición de valor.

Arabinoxylan and fructan in the malting and brewing process

Introduction Soluble dietary fibre is of interest in the malting and brewing process for at least two reasons. In the past, brewers feared them because of possible lautering and filtration problems, and thus a prolonged production time of wort and beer. On the other hand, they have beneficial attributes for colonic and consumer's overall health and are a fermentable part of dietary fibre in the human diet. As diseases caused by poor diet or malnutrition are becoming a severe problem in Western countries, interest in health-beneficial compounds like dietary fibre are of growing interest in the diet. Objectives In this work, the influence of the malting and brewing process on the content of soluble dietary fibre in malt, wort and beer derived from it was investigated. Methods Arabinoxylan was measured by HPAEC/PAD after acidic hydrolisis. Fructan was determined subsequent to enzymatic digestion β-glucan was analysed using calcoflour. Malt and beer analysis were carried out following the methods outlined in MEBAK and EBC. The amount of water-extractable arabinoxylan (WEAX) rapidly increased during malting whereas the brewing and fermentation process showed no influence on the WEAX content in the finished beer. The amount of fructan in most of the investigated cereals was not affected by malting and wort production but decreased to <10% of the initial amount during fermentation. An analysis of 40 German wheat beer samples from different breweries showed arabinoxylan contents ranging from 0.87 up to 2.88 g l−1. The arabinoxylan content correlated very well with the original gravity. Conclusion The amount of malt used in beer production and the grist load seems to be the key factors for the arabinoxylan content of the bottled beer. Only negligible amounts of fructans were found in beer, although fructans were present in wort. Higher arabinoxylan contents did not result in increased viscosity of wort and beer.

Effects of Laccase and Xylanase on the Chemical and Rheological Properties of Oat and Wheat Doughs

The effects of Trametes hirsuta laccase and Pentopan Mono BG xylanase and their combination on oat, wheat, and mixed oat-wheat doughs and the corresponding breads were investigated. Laccase treatment decreased the content of water-extractable arabinoxylan (WEAX) in oat dough due to oxidative cross-linking of feruloylated arabinoxylans. Laccase treatment also increased the proportion of water-soluble polysaccharides (WSNSP) apparently due to the beta-glucanase side activity present in the laccase preparation. As a result of the laccase treatment, the firmness of fresh oat bread was increased. Xylanase treatment doubled the content of WEAX in oat dough and slightly increased the amount of WSNSP. Increased stiffness of the dough and firmness of the fresh bread were detected, probably because of the increased WEAX content, which decreased the amount of water available for beta-glucan. The combination of laccase and xylanase produced slight hydrolysis of beta-glucan by the beta-glucanase side activity of laccase and enhanced the availability of AX for xylanase with concomitant reduction of the amount and molar mass of WSNSP. Subsequently, the volume of oat bread was increased. Laccase treatment tightened wheat dough, probably due to cross-linking of WEAX to higher molecular weight. In oat-wheat dough, laccase slightly increased the proportion of WSNSP between medium to low molecular weight and increased the specific volume of the bread. Xylanase increased the contents of WEAX and WSNSP between medium to low molecular weight in oat-wheat dough, which increased the softness of the dough, as well as the specific volume and softness of the bread. The results thus indicate that a combination of laccase and xylanase was beneficial for the textures of both oat and oat-wheat breads.

Insight into the Distribution of Arabinoxylans, Endoxylanases, and Endoxylanase Inhibitors in Industrial Wheat Roller Mill Streams

To gain insight into the distribution of arabinoxylans (AX), endoxylanases, and endoxylanase inhibitors in industrial wheat roller milling, all streams, that is, 54 flour fractions, 4 bran fractions, and the germ, were analyzed for ash, starch, and protein contents, alpha-amylase activity levels, total (TOT-AX) and water-extractable arabinoxylan (WE-AX) contents, endoxylanase activity levels, and endoxylanase inhibitor (TAXI and XIP) contents. In general, bran fractions were significantly richer in TOT-AX and WE-AX contents, endoxylanase activity levels, and endoxylanase inhibitor contents than germ and, even more so, than flour fractions. In the 54 different flour fractions, minimal and maximal values for TOT-AX and WE-AX contents differed by ca. 2-fold, whereas they differed by ca. 15-fold for endoxylanase activity levels. The latter were positively correlated with ash and negatively correlated with starch content, suggesting that the endoxylanase activity in flour is strongly influenced by the level of bran contamination. TAXI contents in the flour fractions varied ca. 4-fold and were strongly correlated with bran-related parameters such as ash content and enzyme activity levels, whereas XIP contents varied ca. 3-fold and were not correlated with any of the parameters measured in this study. The results can be valuable in blending and optimizing wheat flour fractions to obtain flours with specific technological and nutritional benefits.

Variability in the Content of Water-Extractable and Water-Unextractable Non-Starch Polysaccharides in Rye Flour and Their Relationship to Baking Quality Parameters

The non-starch polysaccharide (NSP) content and composition of rye flours, differing in baking quality, were studied over three consecutive years at three locations. Rye flours were rich in water-extractable NSP and, consequently, rich in water-extractable arabinoxylans (WE-AX). A large variability of both components was observed in water-unextractable fraction, and especially, in the ratio of water-extractable to water-unextractable arabinoxylan content (WE/U-AX). The proportion of WE/U-AX in rye flour was found to be the primary factor contributing to both flour and bread quality parameters. However, the content of WE-AX correlated positively but not significantly, whereas water-unextractable (WU) counterpart was negatively correlated with quality attributes. The data showed that rye flour of high baking quality had a high ratio of WE/U-AX, which was also combined with high values of falling number and amylographic peak viscosity. Significant, positive correlations were also found between ratio of water extract viscosity to water-extractable arabinoxylan content (EV/WE-AX) and overall baking score and bread volume. Our results suggest that some AX populations, of specific structure and/or molecular weight, could be especially important for baking potential of rye flour.

Relationships Between Mixograph Parameters and Indices of Wheat Grain Quality

A 10-gram Mixograph was used to analyse 39 bread wheat cultivars having various agricultural characteristics and origins. Eleven parameters obtained during the first 8 minutes of the mixing procedure were selected using a repeatability analysis in order to investigate variations between genotypes. Several flour protein fractions characterised by their extractability properties and size distributions were quantified. In addition grain hardness, water-extractable arabinoxylan contents and relative arabinoxylan viscosity were also determined and correlated with dough formation during mixing. Dough consistency, as measured by the height of the Mixogram, was correlated with grain hardness, as expressed by the starch damage content and the proportion (%) of flour particles larger than 37·8 μm. No significant relation was found with the water-extractable arabinoxylan content or the relative arabinoxylan viscosity. The width and height of the Mixogram was related to the proportion of unaggregated proteins before the mixing peak and to polymeric proteins after the dough consistency reached a maximum. The Mixograph proved to be a powerful tool to investigate indices of bread making quality.

Arabinoxylan Solubilization and Inhibition of the Barley Malt Xylanolytic System by Wheat During Mashing with Wheat Wholemeal Adjunct: Evidence for a New Class of Enzyme Inhibitors in Wheat

Three EBC worts were made with 100% barley malt and eight with 60% barley malt and 40% wheat, of which two had additions of a Bacillus subtilis endoxylanase. The xylose (Xyl) levels of centrifuged wort (indicative of arabinoxylan levels) made from 100% barley malt were 0.46, 0.70, and 0.55% (% dry matter), while the corresponding malt water-extractable Xyl contents were 0.31, 0.44, and 0.41%. The Xyl levels in centrifuged worts from 60% barley malt and 40% wheat (0.37– 0.58%) depended mainly on the water-extractable arabinoxylan content of the starting material. The endoxylanolytic levels of the malts had only minor effect on the resulting Xyl contents of the worts. The increase of Xyl levels during mashing with 40% wheat (0.05–0.10%) were 12–58% lower than 60% of the increase in Xyl with a corresponding 100% malt wort. The addition of the endoxylanase from B. subtilis increased the centrifuged wort Xyl level. Experiments in which the endoxylanolytic activity of malt extracts was measured in the presence of wheat water-extractables provided evidence for the presence of one or more endoxylanase inhibitors in wheat that are inactivated by heat treatment. The wheat inhibitors however did not inactivate the B. subtilis endoxylanase.