Selectivity for water-unextractable arabinoxylan and inhibition sensitivity govern the strong bread improving potential of an acidophilic GH11 Aureobasidium pullulans xylanase

An acidophilic xylanase of Aureobasidium pullulans (XAPI) was recombinantly produced, characterised and its functionality in bread making compared with that of Bacillus subtilis Xyn A xylanase (XBS), an enzyme frequently used in bread making. Prominent characteristics of XAPI were its high specific activity towards arabinoxylan (AX), its relative preference for hydrolysis of water-unextractable AX (WU-AX), its optimal activity under acidic conditions and its sensitivity towards TAXI (Triticum aestivum xylanase inhibitor) and XIP (xylanase inhibiting protein). Optimally developed dough containing XAPI had a considerably drier feel after mixing and was less sticky after fermentation than dough treated with XBS. Both xylanases improved bread loaf volume by 24% under the conditions of the process. In spite of the higher dosage of XAPI necessary to obtain this result, the similar loaf volume increase coincided with less solubilisation of WU-AX and even lesser degradation of solubilised AX (S-AX) and water-extractable AX (WE-AX) by XAPI than by XBS during the bread making process. This is probably due to different dynamics and extent of xylanase inhibition in the dough matrix for both xylanases. AX solubilisation by the acidophilic XAPI was not boosted by the drop in pH in the dough during fermentation. Results show that significant bread loaf volume increase goes hand in hand with excellent dough properties when a limited solubilisation of WU-AX during mixing is coupled to retention of a high molecular mass of S-AX and WE-AX during the rest of the process.     

Evolution of aroma volatiles during storage of sourdough breads made by mixed cultures of Kluyveromyces marxianus and Lactobacillus delbrueckii ssp. bulgaricus or Lactobacillus helveticus

Two mixed starter cultures were used for sourdough bread making to evaluate their ability to improve quality and increase bread shelf-life: Lactobacillus delbrueckii ssp. bulgaricus or Lactobacillus helveticus mixed with the lactose fermenting yeast Kluyveromyces marxianus as alternative baker’s yeast. Control sourdough breads (K. marxianus) without the addition of bacteria, were also prepared. The changes on the headspace aroma volatiles during storage were assessed using solid-phase microextraction (SPME) GC–MS analysis. The effect of these changes on bread flavour was evaluated by consumer preference evaluations and the results were co-evaluated with those from the GC–MS analysis. The obtained results showed differences in the volatile composition of the different types of breads examined, as well as dramatic decreases of the number and the amount of volatiles after five days of storage. The sourdough breads made with K. marxianus and L. bulgaricus, had a more complex aroma profile, longer shelf-life and achieved the highest scores in the sensory tests.     

Evaluation of antioxidant property and quality of breads containing Auricularia auricula polysaccharide flour

The polysaccharide in the fruit bodies of Auricularia auricula (commonly called black woody ear or tree ear) was extracted, lyophilized and ground. Auricularia auricula polysaccharide (AAP) flour blended bread was developed. Physical qualities and antioxidant activities of breads with different levels of substitution of AAP flour for wheat flour were analyzed.The results showed that up to 9% of AAP flour could be included in bread formulation without altering the sensory acceptance of the blended bread. The incorporation of AAP in bread markedly increased the antioxidant property of the bread as tested by DPPH free radical-scavenging method. Breads containing AAP flour can broaden the utilization of the fruit bodies of Auricularia auricula and may be regarded as possible health-promoting functional foods.     

Changes in crude arabinoxylan during cloudy wheat beer brewing on a production scale

As one of the major non‐starch polysaccharides in the cloudy wheat beer, arabinoxylan has a crucial influence on the wort viscosity, foam profile and stability of the beer. In this study, the cloudy wheat beer was fermented on a production scale with a ratio of barley to wheat malt of 1:1, during which the changes in arabinoxylan were monitored in order to determine the key steps which influence the content, substitution degree of arabinoxylan (A/X) and average degree of polymerization (avDP) value of crude arabinoxylan during cloudy wheat beer brewing. The results show that the total contents of crude arabinoxylan, arabinose, xylose and galactose increased until the end of mashing and then dropped with the addition of spent grain sparging water. The crude arabinoxylan decreased during the saccharification, and then stabilized at ~10.00 mg/g. During fermentation and storage, the content of crude arabinoxylan did not change remarkably. The A/X remained at ~0.50 in the process of wort preparation and brewing and the avDP value of crude arabinoxylan decreased during saccharification and then stayed at ~3.00 in the fermentation and storage phases, which was lower because the contents of free arabinose, xylose and galactose were not subtracted from the total contents of the sugars. Therefore, wort preparation is shown the key step influencing the changes in crude arabinoxylan during cloudy wheat beer brewing. Copyright © 2017 The Institute of Brewing & Distilling     

Application of Kluyveromyces marxianus, Lactobacillus delbrueckii ssp. bulgaricus and L. helveticus for sourdough bread making

The application of Kluyveromyces marxianus (IFO 288), Lactobacillus delbrueckii ssp. bulgaricus (ATCC 11842) and Lactobacillus helveticus (ATCC 15009) as starter cultures for sourdough bread making was examined. Production of lactic and acetic acids, bread rising, volatile composition, shelf-life and organoleptic quality of the sourdough breads were evaluated. The amount of starter culture added to the flour, the dough fermentation temperature and the amount of sourdough used were examined in order to optimise the bread making process. The use of mixed cultures led to higher total titratable acidities and lactic acid concentrations compared to traditionally made breads. Highest acidity (3.41 g lactic acid/kg of bread) and highest resistance to mould spoilage were observed when bread was made using 50% sourdough containing 1% K. marxianus and 4% L. delbrueckii ssp. bulgaricus. The use of these cultures also improved the aroma of sourdough breads, as shown by sensory evaluations and as revealed by GC–MS analysis.     

Aleurone cells are the primary contributor to arabinoxylan oligosaccharide production from wheat bran after treatment with cell wall-degrading enzymes

Arabinoxylans and in particular arabinoxylan oligosaccharides (AXOS) from wheat are recognised for their prebiotic potential. A high-yield, non-chemical production of AXOS is therefore of interest when producing functional foods. This study investigated the enzymatic production of AXOS from wheat bran with the aim of establishing the main fraction contributing to production of AXOS. Fractions of wheat bran, outer pericarp and aleurone with two different purities were treated with the cell wall-degrading enzymes: xylanase, cellulase and β-glucanase. The yield of solubilised arabinoxylans upon treatment was greatest in the most pure aleurone fraction (164 g kg⁻¹) and lowest in the outer pericarp fraction (15 g kg⁻¹). The yield was mainly recovered as AXOS rather than soluble arabinoxylans and was negatively related to the arabinose/xylose ratio found in the raw material. In conclusion, wheat aleurone cell walls are the main contributor to the production of AXOS from wheat bran and this seems to depend on the A/X ratio of the raw material.     

Physicochemical and nutritional properties of reduced-caloric density high-fibre breads

The influence of some physicochemical properties (chemical and nutritional composition, particle size, colour, dynamic viscosity, viscoelastic moduli) of associated binary mixtures of structuring hydrocolloids (cellulose derivatives, galactomannans) and prebiotic oligosaccharides (fructo- and gluco-oligosaccharides) in diluted hydrated wheat flour matrixes is discussed in terms of nutritional (higher resistant starch, lower digestible starch and lower in vitro Glycaemic Index) and technological functional profiles (higher sensory scores and longer keepability) of reduced-caloric density (−20%) high-fibre (>6 g/100 g) breads. Few technological functional (sensory firmness and overall acceptability) and most nutritional bread properties (protein digestibility, rapidly digestible starch, slowly digestible starch, in vitro expected Glycaemic Index, total digestible starch and resistant starch) were found to depend on dietary fibre molecular characteristics (mean particle diameter (D[4, 3]), storage modulus (G′), loss modulus (G″), complex viscosity (η*), and lactic acid solvent retention capacity. Dietary fibres with larger particle size resulted in highly sensory acceptable breads with higher amounts of resistant starch and slightly lower protein digestibility. Fibres exhibiting high viscoelasticity -G′, G″- and complex viscosity -η*- in concentrated solutions yielded breads with better sensory perception, lower digestible starch and higher resistant starch contents bringing to lower in vitro expected Glycaemic Index.     

Evaluation of Leuconostoc citreum HO12 and Weissella koreensis HO20 isolated from kimchi as a starter culture for whole wheat sourdough

Leuconostoc citreum HO12 and Weissella koreensis HO20 isolated from kimchi were evaluated as starter cultures in the making of whole wheat sourdough bread. After 24 h of fermentation at 25 °C, both lactobacilli grew to the final cell numbers of ca. 10⁹ cfu/g dough, and both doughs had similar pHs and total titratable acidities. In addition, the fermentation quotient of the dough with Lc. citreum HO12 was slightly lower than that of the dough with W. koreensis HO20 (1.6 versus 2.8). Sourdoughs and bread with 50% sourdough produced with the starter cultures exhibited consistent ability to retard the growth of bread spoilage fungi (Penicillium roqueforti and Aspergillus niger) and rope-forming bacterium (Bacillus subtilis). Sourdough breads underwent a significant reduction in bread firming during storage. It seems that both lactobacilli have the potential to improve the shelf-life of wheat bread. The results indicate that the selected lactobacilli have unique fermentation characteristics and produce sourdough breads with overall satisfactory quality.     

Effects of dietary inclusion of xylooligo‐ saccharides,arabinoxylooligosaccha‐ rides and soluble arabinoxylan on the microbial composition of caecal contents of chickens

BACKGROUND: Arabinoxylan (AX)‐derived preparations have raised particular interest by the suggestion that they exert prebiotic properties. Therefore an in vivo experiment was conducted to study the effects of xylooligosaccharides (XOS), arabinoxylooligosaccharides (AXOS) and soluble AX (S‐AX) on several groups of gut bacteria of chickens. Chickens were fed a control diet or the same diet supplemented with 2.5 g kg^?1 of XOS (average degree of polymerisation (avDP) of 3, average degree of arabinose substitution (avDS) of 0.09), wheat bran‐derived AXOS (avDP 9, avDS 0.34) or wheat endosperm alkali‐solubilised AX (S‐AX, avDP > 6000, avDS 0.5). RESULTS: All treatment groups showed an increase in the number of caecal bifidobacteria after 2 weeks of feeding (P < 0.05), while the treatments did not impact numbers of Enterobacteriaceae and aerobic lactobacilli in the caeca relative to the control. XOS led to a tremendous increase in caecal bifidobacteria counts (10⁸ g^?1 for the XOS treatment versus 10³ g^?1 for the control treatment) after only 1 week of supplementation, while AXOS and S‐AX led to similar strong increases in bifidobacteria counts after 2 weeks of supplementation. Addition of S‐AX to the diet, but not of AXOS or XOS, led to a significantly decreased (P < 0.05) body weight gain after 2 weeks of feeding relative to animals on the control diet, consistent with its known viscosity‐related antinutritive effects in chickens. CONCLUSION: Similar to XOS, AXOS selectively stimulate the presence of bifidobacteria in the caeca of chickens, establishing their bifidogenic effect as a first indicator for prebiotic potential. Copyright © 2008 Society of Chemical Industry     

Extractability and chemical and enzymic degradation of psyllium (Plantago ovata Forsk) seed husk arabinoxylans

To assess the potential of arabinoxylan (AX)-rich psyllium (Plantago ovata Forsk) seed husk (PSH) as a source for production of arabinoxylo-oligosaccharides (AXOS), the parameters determining PSH AX extraction yield and the chemical and enzymic hydrolysis of PSH AX were investigated. The seed husk material had a high content of AX (62.5%) with an arabinose to xylose ratio of 0.41. The water extractability of PSH AX was affected by suspension concentration rather than by temperature. Maximally, 27% of all AX could be extracted, even when using very dilute suspensions (0.1% w/v). When subjected to alkaline conditions, a pH of at least 12 was needed to significantly increase extractability (up to 77% of all AX). The extractability-increasing effect of alkali was, however, reversible, as extractability decreased again when lowering the pH. Acid hydrolysis at high temperature drastically increased AX extraction yields (up to 97% of all AX), released monomeric arabinose (up to 38%), and lowered the average degree of polymerisation (DP_avg) of the AX (down to 31). The presence of substituents (arabinose, xylose, rhamnose and galacturonic acid) on the xylan backbone was an important factor limiting degradation by xylanases. Enzyme preparations containing substituent-removing enzymes were far better for enhancing the extractability of a large portion of the AX population (up to 82%) and for degrading the extracted fragments (down to DP_avg 14) than preparations lacking such activities. The above results show that PSH is a good source for the production of AXOS, since both chemical and enzymic treatments significantly increase the extractability of PSH AX and convert PSH AX molecules into small fragments.     

Effect of endo‐xylanase‐containing enzyme preparations and laccase on the solubility of rye bran arabinoxylan

Three commercial enzyme preparations with endo‐xylanase activity, namely Bio‐Feed Wheat, Bio‐Feed Plus and Grindamyl H 640, and laccase have been tested for their effects on the solubilisation of arabinoxylan (AX) in rye bran or autoclaved rye bran. Autoclaving efficiently increased the availability of AX for enzymatic degradation. Both Bio‐Feed Wheat (a monocomponent enzyme) and Bio‐Feed Plus (a multicomponent preparation with different enzymatic activities) efficiently degraded the autoclaved rye bran AX into lower‐molecular‐weight fragments. As much as 70% of the xylose residues and 58% of the arabinose residues in the autoclaved bran were soluble after treatment with Bio‐Feed Plus; the weight—average molecular weight of the detectable portion of these soluble polymers was 104 000 Da. Grindamyl H 640 solubilised only a small fraction of the AX in autoclaved rye bran; the molecular weight of these soluble fragments was higher than that of those released by the Bio‐Feed xylanases. Addition of laccase during treatment with Bio‐Feed Wheat or Grindamyl H 640 decreased the yield of water‐soluble AX. © 2003 Society of Chemical Industry     

Physical,chemical and sensorial properties of healthy and mixture breads in Portugal

This study was conducted to characterize different samples of regional bread made from mixed rye and wheat flours and healthy bread produced from a special formulation. The bread samples were evaluated in terms of their physical, chemical and sensory properties following the standard methods. The regional breads showed some differences in the chemical composition: Flor de Carregal had the highest protein content (14.59 %) and the lowest salt content (0.40 %), Pedregal had the highest fibre content (0.89 %), and Pazurara was the richest in minerals (4.90 %). Although the sensory properties of bread samples were not statistically different, Flor de Cabanas obtained the highest overall acceptability among the samples (6.95 points). With respect to the healthy bread samples, slight differences were observed on their physical and sensory properties, which may attributed to their similarity in ingredient compositions. Furthermore, significant differences were observed from the fiber, carbohydrate, protein and chloride contents of healthy bread samples. In comparison with the two types of breads, it was found that they have different chemical, physical and sensory properties. Sensory analysis also showed that regional breads were more preferred by the panellists, with an average punctuation for global appreciation of 5.83 against 4.71.     

Immobilization of kefir and Lactobacillus casei on brewery spent grains for use in sourdough wheat bread making

New types of bread were produced employing baker’s yeast, kefir or Lactobacillus casei immobilized on brewer’s spent grains. Bread was produced either by the straight-dough or the sourdough method. All the studied biocatalysts and their corresponding sourdoughs were found efficient for breadmaking. Good rising was achieved and the produced breads had good overall quality and remained fresher for longer, compared to commercial type baker’s yeast bread. The best results were obtained for sourdough breads, with higher moisture retention during baking, lower rates of water evaporation and staling, and maintenance of freshness for longer (4–5 days). Consumer evaluation showed bigger preference for the sourdough breads as far as aroma, taste and overall quality were concerned, justified by the GC-MS analysis of volatiles that revealed a different aroma profile, with more compounds identified than in breads produced by the straight-dough method, obviously due to variations in microbial populations.     

Application of FT-IR and Raman spectroscopy for the study of biopolymers in breads fortified with fibre and polyphenols

Adding dietary fibres (DFs) and polyphenols (PPs) to bread is a convenient way to deliver the health benefits of DFs and PPs to consumers. In this study, we investigate the interactions among added pectin polysaccharides, PPs and bread components such as wheat proteins in different bread formulations. Two sets of breads with a 20% difference in the water content were prepared in the absence (Control), or presence of pectin and/or fruit PP extracts (Treated). Results show that adding pectin and PPs caused changes in the molecular conformations and polymer structure of wheat gluten and starch in the finished breads, especially in the secondary protein conformation (Amides I and II, as revealed by FTIR Spectroscopy). An increase of water content during dough formulation also affected secondary protein conformation. The Treated breads gained β-sheets in the protein's secondary conformation at the expense of β-turns, and contained more un-ordered conformations especially in the presence of berry PPs. These results were confirmed by complementary Raman spectroscopic measurements. Both hydrophobic and H bonding interactions occurred among bread components and the added PPs and pectin, which affected PP stability during breadmaking and the total extractable PP content of finished breads. Schematic Loop and Train models for breads enhanced with PPs and pectin are proposed that illustrate the possible conformational changes in wheat protein structure due to the presence of added PPs and pectin.     

Quality and antioxidant property of buckwheat enhanced wheat bread

Common buckwheat (Fagopyrium esculentum Moench) was used to substitute 15% of wheat flour to make buckwheat enhanced wheat breads. Proximate composition, physical quality, functional components and antioxidant properties of buckwheat enhanced wheat breads were analysed and compared with those of white bread. Specific volumes of three breads were 6.10–6.75 cm³/g. Buckwheat enhanced wheat bread showed lower lightness and whiteness index values and higher redness and yellowness values. On a seven-point hedonic scale, all sensory results were 5.33–5.91, indicating that three breads were moderately acceptable. No differences were found in appearance, colour and overall sensory attributes for three breads, whereas both buckwheat enhanced wheat breads were rated higher in flavour and mouth feel. Buckwheat enhanced wheat bread contained more rutin and quercetin as expected. Buckwheat enhanced wheat bread was good in antioxidant activity, reducing power and 1,1-diphenyl-2-picrylhydrazyl radical scavenging ability with unhusked buckwheat enhanced wheat bread being the most effective. Overall, buckwheat enhanced wheat bread could be developed as a food with more effective antioxidant properties.     

Effect of kilning on the composition of protein and arabinoxylan in wheat malt

To explore the effect of kilning on the quality of wheat malt, wheat variety LM21 was malted with three different kilning programmes. Protein composition and arabinoxylan, xylanase (EC 3.2.1.8) activity, diastatic power and free amino nitrogen (FAN) were evaluated. Arabinoxylan content and xylanase activity were monitored during the kilning process. The results showed that the malt obtained from the kilning programme A showed the highest diastatic power, Kolbach index, FAN and lowest wort viscosity. Total arabinoxylan content showed no significant change during the kilning process, while the water extractable arabinoxylan and the xylanase activity reached the maximum values at the kilning temperature of 55°C, after which the xylanase activity decreased with the increase in kilning temperature. Extending kilning time at 40–50°C increased the diastatic power, FAN and Kolbach index and reduced the wort viscosity. © 2019 The Institute of Brewing & Distilling     

Isolation, modification and characterization of soluble arabinoxylan fractions from rye grain

Because of the positive role of arabinoxylans and especially their water-soluble fractions in establishing bread properties, it seems reasonable to use them as natural bread improvers. In this work, an adequate isolation procedure of water-soluble arabinoxylans from rye grain with efficient purification steps is presented, delivering 2.9?% yield from wholemeal with a content of arabinoxylan of approximately 70?% and an arabinose/xylose ratio of 0.7. Furthermore, soluble arabinoxylans were modified by enzymatic hydrolyses, cross-linking with peroxidase/H₂O₂ treatment and combination of both for developing preparations applicable for bread making with different quality profiles. Additionally, a detailed analysis of chemical composition and molecular dimension was carried out by HPLC, SEC, HPSEC and viscosity measuring. The preparation after cross-linking showed considerably higher molar mass values, lower solubility and higher viscosity with high Huggin??s constant compared to the not modified sample. Otherwise, the combination of enzymatic hydrolysis and cross-linking resulted in the formation of arabinoxylan preparations with only slight degree of cross-linking and properties comparable with the only hydrolyzed sample.     

Selenium levels in breads from Sakarya,Turkey

Selenium (Se) is an important trace element for human and animal health. It accumulates in wheat and corn, which is consumed mostly as bread. The Turkish population consumes mainly white wheat, whole wheat (brown bread) and corn breads. In this study, samples of these breads were collected from six different bakeries in the city of Sakarya, and their selenium levels were determined by ICP–OES after a chemical digestion. It was found that average selenium levels in white wheat, whole wheat and corn breads were 1149, 1204 and 2023?µg/kg, respectively. The results are compared with daily recommended intake and upper tolerable levels for selenium.     

Quality and storage life of par-baked frozen breads

During storage of frozen par-baked breads for a prolonged period of time, bread quality may undergo changes such as increased firmness, moisture and flavour losses resulting in product deterioration. Four categories of par-baked breads namely—variety, white, multi-grain and rye were stored at −18°C for 9 months to evaluate the effects of storage period on product quality, and to develop prediction models that describe kinetics of deterioration of selected quality parameters. The quality was evaluated based on sensory, chemical and physical attributes and properties. Storage life was determined based on the changes in bread quality below certain level. The principal component analysis indicated that approximately 90% of the total variability of 19 quality parameters can be explained with only two principal components. The zero-order kinetic reaction showed good agreement (R²>80%) with quality changes observed by the sensory panel over the storage period. A prediction model, based on the bread quality at zero time and the quality at the time when the bread was rejected by the sensory panel, was developed. The proposed prediction model would provide a useful means of estimating storage life of par-baked breads made with similar formulations.     

Assessing the xylanolytic bacterial diversity during the malting process

The presence of microorganisms producing cell wall hydrolyzing enzymes such as xylanases during malting can improve mash filtration behavior and consequently have potential for more efficient wort production. In this study, the xylanolytic bacterial community during malting was assessed by isolation and cultivation on growth media containing arabinoxylan, and identification by 16S rRNA gene sequencing. A total of 33 species-level operational taxonomic units (OTUs) were found, taking into account a 3% sequence dissimilarity cut-off, belonging to four phyla (Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria) and 25 genera. Predominant OTUs represented xylanolytic bacteria identified as Sphingobacterium multivorum, Stenotrophomonas maltophilia, Aeromonas hydrophila and Pseudomonas fulva. DNA fingerprinting of all xylanolytic isolates belonging to S. multivorum obtained in this study revealed shifts in S. multivorum populations during the process. Xylanase activity was determined for a selection of isolates, with Cellulomonas flavigena showing the highest activity. The xylanase of this species was isolated and purified 23.2-fold by ultrafiltration, 40% ammonium sulfate precipitation and DEAE-FF ion-exchange chromatography and appeared relatively thermostable. This study will enhance our understanding of the role of microorganisms in the barley germination process. In addition, this study may provide a basis for microflora management during malting.