Effect of β-glucans on viscoelastic properties of barley kernels and their relationship to structure and soluble dietary fibre

The stress relaxation behaviour of barley kernels with differences in β-glucan was studied using the generalized Maxwell model for explaining the differences in quality. The relaxation moduli show that cultivar significantly affected the relaxation times (τ₂ and τ₃) and compressional viscosity (η_E2 and η_E3) of the 3 Maxwell elements and the pure elastic component (E₀). These data were twice as high in cultivars with high β-glucans compared to low β-glucans. Protein and malt extract, as well as β-glucan, showed similar patterns to the corresponding cultivars from the same locations. Malt extract was correlated with both insoluble fibre (−0.71; P < 0.0007) and total fibre (−0.66; P < 0.006). High β-glucan cultivars presented relatively high soluble fibre, wort viscosity and presented higher relaxation times. Soluble fibre and the wort viscosity were correlated with relaxation times τ₁, τ₂, τ₃. Also, β-glucans were correlated with τ₃ and viscosity η_E3. The overall importance of the effect of β-glucans on viscoelasticity, malting and food quality as shown in this investigation is in agreement with earlier investigations.     

Effect of β-glucans on viscoelastic properties of barley kernels and their relationship to structure and soluble dietary fibre

The stress relaxation behaviour of barley kernels with differences in β-glucan was studied using the generalized Maxwell model for explaining the differences in quality. The relaxation moduli show that cultivar significantly affected the relaxation times (τ₂ and τ₃) and compressional viscosity (η_E2 and η_E3) of the 3 Maxwell elements and the pure elastic component (E₀). These data were twice as high in cultivars with high β-glucans compared to low β-glucans. Protein and malt extract, as well as β-glucan, showed similar patterns to the corresponding cultivars from the same locations. Malt extract was correlated with both insoluble fibre (−0.71; P < 0.0007) and total fibre (−0.66; P < 0.006). High β-glucan cultivars presented relatively high soluble fibre, wort viscosity and presented higher relaxation times. Soluble fibre and the wort viscosity were correlated with relaxation times τ₁, τ₂, τ₃. Also, β-glucans were correlated with τ₃ and viscosity η_E3. The overall importance of the effect of β-glucans on viscoelasticity, malting and food quality as shown in this investigation is in agreement with earlier investigations.     

Evaluation of malting barley quality using exploratory data analysis. I. Extraction of information from micro-malting data of spring and winter barley

This paper presents an exploratory multivariate approach for analysis of malting barley quality data. By using principal component analysis (PCA) and partial least squares regression (PLSR) complex malting quality data are combined into functional factors which are used for malting barley quality characterisation. Fifty barley samples were used in this investigation, representing 15 spring barley and 10 winter barley varieties grown at two locations in Denmark. The samples were micro-malted and mashed and analysed for 13 quality parameters according to official methods of the European Brewery Convention. These data were combined and reduced into a few latent (functional) factors using PCA by which it is demonstrated that the modification of β-glucan plays a major role in both spring and winter barleys. Additionally, the spring barley and winter barley samples display different covariate latent structures, mainly in the nitrogen and diastatic power patterns. It is furthermore shown that graphic display as facilitated by exploratory data analysis, can be utilized in order to evaluate genotype-environmental interactions by considering the position and movements of the individual objects (genotypes in this instance) in the score plots. Thus, in contrast to the classical analysis of variance, the samples can be individually evaluated and the corresponding loadings can be used to validate the genetic and environmental effect of a given sample in a quality perspective.Several of the investigated malting quality parameters are highly intercorrelated. This fact is utilized by applying PLSR to barley and malt data for the prediction of wort quality in order to exclude the mashing step. This approach was successful for the modification-dependent wort parameters, extract, wort β-glucan and viscosity.     

Effects of Cultivar and Environment on β-(1,3)-(1,4)-D-glucan Content and Acid Extract Viscosity of Spanish Barleys

The acid extract viscosities and β-glucan contents of ten two- and six-rowed barley cultivars grown at seven locations in three consecutive years in Spain were studied in the present work. The viscosities varied from 2·4 to 24·8 centistokes (cSt) and the mean value was 6·4 cSt. The average β-glucan content of barleys determined by HPLC was 3·5% with a range of 1·9–5·5%. Significant differences were found in both β-glucan content and acid extract viscosity between different cultivars, locations and years. The β-glucan contents and viscosities of winter cultivars were higher than those of spring. Cvs. Barbarrosa and Hatif de Grignon were the genotypes with the highest values for both parameters, while cv. Beka had the lowest viscosity and β-glucan content. Environmental factors influenced both parameters. The acid extract viscosities of barleys were correlated negatively with the amount of precipitation (r=−0·754;P<0·05). Barleys grown in wet and rainy areas (Girona and La Coruña) had lower viscosity values.     

Water extractable (1→3,1→4)-β-d-glucans from barley and oats: An intervarietal study on their structural features and rheological behaviour

The fine structures and rheological behaviours of aqueous flour dispersions and of β-glucan, (1→3,1→4)-β-d-glucan isolates obtained from 18 registered varieties of normal covered barley seeds and four registered oat varieties, grown in the same location in Greece, were investigated. The β-glucan content of the barleys and oats varied between 2.5–5.4 and 2.1–3.9%, respectively (dry matter basis). Heat treatment of the barley and oat flour dispersions with 80% (v/v) ethanol, to inactivate endogenous β-glucanases, had a stabilizing effect on the viscosity profile of the flour slurries. The relationship between total β-glucan content and aqueous slurry viscosity (at 247 s⁻¹) of the heat-treated barley flours was weak (r²=0.45, p<0.05, n=18). β-Glucans were isolated by water extraction at temperatures slightly below the gelatinization temperature of starch, enzymatic removal of starch and partial removal of contaminating proteins by adjustment to pH 4.0–4.5, and subsequent precipitation of the water-soluble β-glucans with 80% (v/v) ethanol. The cellulosic oligomers released by the action of a (1→3,1→4)-β-d-glucan hydrolase showed cellotriosyl and cellotetraosyl units, accounted for 91.1–92.1% for barley and between 92.4 and 94.1% for the oat preparations; the respective molar ratios of tri- to tetra-saccharides (DP3/DP4) ranged between 2.73–3.05 (barley) and 2.16–2.42 (oat). Steady shear measurements confirmed the random coil type behaviour of freshly prepared β-glucan solutions (5 and 7%, w/v). The rate at which shear thinning began was dependent on both concentration and molecular size of the polysaccharide. Most of the β-glucan dispersions followed the Cox–Merz rule, except Mucio, a variety with high M_w β-glucan (2.39×10⁵). Viscoelastic characterization, at 8% (w/v), of three barley β-glucan aqueous dispersions differing in molecular size, indicated that the low molecular weight sample exhibited shorter gelation time and higher gelation rate (I_E=[dlog G′/dt]_max) than its higher molecular weight counterparts. Small deformation oscillatory measurements on gels of all barley β-glucan isolates (10% (w/v), 7 d storage, 25 °C) revealed a strong negative relationship (r²=0.88, p<0.01) between G′ (1 Hz, strain 0.1%) and apparent M_w of the polysaccharide.     

The effects of a xylanase and α β-glucanase from Trichoderma reesei on the non-starch polysaccharides of whole meal rye slurry

The effects of extraction conditions (pH, temperature, enzymic treatment) on the extractability of rye meal non-starch polysaccharides were studied. The yield of pentosans and extractable matter increased with increases in both temperature and pH during extraction. The extract viscosity was correlated closely with the pentosan content of the extract. The molecular size of the extracted non-starch polysaccharides decreased as the extract pH decreased. Enzymic treatment during extraction increased the amount of pentosan solubilised. Xylanases almost doubled the amount of extractable pentosans, but these were degraded to oligosaccharides. With β-glucanase and protease, the pentosan content of the extract increased by 65% and 40%, respectively. In addition, the β-glucan extractability was increased with protease by 10% and with β-glucanase by 90%. Using size-exclusion HPLC it was observed that the molecular size of extractable rye β-glucans was lower than that of the extractable rye pentosans. β-Glucanase caused considerable hydrolysis of β-glucan and no more β-glucan could be detected by size-exclusion HPLC. Protease treatment decreased the molecular size of extractable β-glucan. All enzymatic treatments caused a disruption of the endosperm cell walls in the extract residue.     

Effect of hydrogen peroxide and ozone treatment on improving the malting quality

The effect of hydrogen peroxide (HP) and ozone (O₃) treatment during barley steeping on the quality of malt produced from two barley varieties (GrangeR and AC Metcalfe) by micro-malting was investigated. The two steeping oxidation treatments that was observed to promote barley acrospire growth. Ozone treatment improved the malt enzyme activity of endo-protease, α-amylase, free beta-amylase and total limit dextrinase to differing extents, with GrangeR improving to a greater degree. HP treatment contributed to the increase of α-amylase, β-glucanase and endo-protease. Surprisingly, HP or ozone oxidation during malting resulted in different and novel outcomes for total beta-amylase in GrangeR and AC Metcalfe. In GrangeR, total beta-amylase activity reduced with respect to the control in both treatments. In comparison with AC Metcalfe there was a substantial increase of 78% with HP and 90% O₃ in total beta-amylase activity. Malt quality including wort free amino nitrogen, β-glucan, turbidity and diastatic power was differentially increased by the oxidation induction treatment during steeping in malting. Gene expression analysis indicated that the effects of the steep oxidation treatments on enzyme and malt quality were putatively linked with the up-regulation of certain genes involved in GA synthesis (GA20ox1) and ABA catabolism (ABA8′OH). Barley grain germination assay results also showed that moderate HP induction could improve barley germination tolerance to the ABA effect. Malting including steep oxidation induction was shown to be beneficial to malt quality by improving the resultant wort quality and the efficiency of the beer brewing process. These observations point the way towards improving malt quality and the efficiency of the malting process.     

Barley genotypic β-glucan variation combined with enzymatic modifications direct its potential as a natural ingredient in a high fiber extract

β-Glucan dietary fiber rich food systems hold a great potential for improving human health. Here, we evaluate the extractability and quality of β-glucan liquid formulations from eight different barley genotypes varying in β-glucan content and molecular structure using Termamyl^® SC (T), Attenuzyme^® (A) and Attenuzyme^® Flex (AF) amylolytic enzymes in combinations. Extracts from barley lines Lys5f, KVL408, KVL1104 and CDC Fibar exceeded 4 g β-glucan/l, providing European Food Safety Authority (EFSA) and U.S. Food and Drug Administration (FDA) recommended amounts (3 g β-glucan/day) from three portions. TAF extracts of Lys5f and KVL408 grains reached extraordinary high concentrations of 8–9 g β-glucan/l. The β-glucan molecular mass decreased with enzyme treatment T < TA < TAF due to minor lichenase side activity. Extractability was generally higher and molecular mass lower for barley lines low in triosyl/tetraosyl (DP3/DP4) ratios than for those high in DP3/DP4 ratios (Lys5f, KVL408 and KVL1104). Overall, the higher β-glucan content and structural robustness in Lys5f and KVL408 raw materials favor these in a β-glucan rich extract with potential for EFSA and FDA health and nutrition claims.     

Effect of processing on the beta-glucan physicochemical properties in barley and semolina pasta

A health claim linking the consumption of barley β-glucan and the lowering of blood cholesterol has been allowed in North America and Europe which resulted in increased interest in barley products. Waxy barley flour rich in β-glucan (10% d.b.) was used to produce barley functional spaghetti and compared to semolina spaghetti. The impact of processing (extrusion, drying and cooking) on the physicochemical properties of barley blends and pasta as the molecular characterization of β-glucan were investigated. Pasta processing did not significantly affect the amount of β-glucan, but it impacted the β-glucan physicochemical properties in the end products. In all pasta, extrusion and drying were detrimental to the β-glucan properties, while cooking significantly increased the extractability and molecular weight of β-glucan, and in turn its viscosity, which determines its physiological effectiveness. In general, replacing wheat semolina with barley flour rich in β-glucan resulted in improved barley pasta containing the recommended amount of β-glucan per serving and enhanced β-glucan properties.     

Changes of β-glucan physicochemical characteristics in frozen and freeze dried oat bran bread and porridge

The ability of oat foods to lower serum cholesterol and post-prandial blood glucose concentrations has been linked to the physicochemical properties of the bioactive component, mixed linkage β-glucan. Oat foods frequently need to be shipped or stored prior to analysis and β-glucan characteristics may change over time. Reductions in β-glucan solubility or molecular weight lead to lower viscosity development which decreases bioactivity. Impact of freezing and freeze drying conditions on the β-glucan physicochemical characteristics in oat bran bread and porridge were studied. Two in vitro digestibility methods were used to produce physiological extracts and the results were compared. The β-glucan molecular weight, solubility and viscosity for oat bread stored at room temperature were unchanged for 3 days, followed by a gradual decline in these parameters. The extract viscosity for bread decreased significantly after freezing at −80 °C and freeze drying after freezing at −18 and −80 °C, whereas freezing in liquid nitrogen did not significantly influence viscosity. Freezing of oat bran porridge did not affect extract viscosity, but freeze drying resulted in reduction of extract viscosity compared to the fresh porridge. Freezing and freeze drying did not dramatically affect the molecular weight or solubility of β-glucan in either product. The rapid visco analyzer was more effective and reliable for sample digestion than when physiological extraction was conducted in the shaking water bath. Generally, freezing at −18 °C or by submersion in liquid nitrogen maintained the physicochemical characteristics of β-glucan in food products either for commercial products or subsequent analysis.     

Influence of growth temperature on content,viscosity and relative molecular weight of water-soluble β-glucans in barley (Hordeum vulgare L.)

β-Glucan content and viscosity of water-soluble β-glucans have a considerable impact on the digestion of barley. Eight different 2-row barley (Hordeum vulgare L.) cultivars were grown in controlled environment chambers at five different temperatures until maturity. The samples were pearled, milled and analysed for their content of total, insoluble and soluble β-glucan. The water-soluble fraction was extracted at 37 °C, subjected to amylase treatment and freeze-dried. Water-soluble crude β-glucans were solubilised in distilled water, analysed for viscosity and their purity was checked by nuclear magnetic resonance. Molecular weights were profiled by size exclusion chromatography with RI detection. The content of total β-glucan varied from 4.0% to 7.4%, and was significantly affected by the growth temperature. An interaction between cultivar and growth temperature was observed for the total β-glucan content. The extractability was significantly affected by growth temperature, as there was recorded an increasing amount of water-soluble β-glucan with increasing growth temperature. Both the viscosity and the molecular weight of the water-soluble β-glucans increased with the growth temperature.     

海拔对啤酒大麦产量和品质的影响

为丰富大麦立体栽培理论,更好地推动高海拔地区大麦的生产,通过不同海拔种植大麦试验,分析了海拔对大麦农艺性状、品质及产量的影响。结果显示,随海拔升高大麦生育期显著延长,株高显著增高,千粒重增大,籽粒发芽率和蛋白质含量显著降低,麦芽浸出物和库尔巴哈值先升高后降低,可溶性氮先降低再升高;海拔对产量也有明显影响,在试验区内产量随海拔升高呈现先升高后降低的趋势。海拔对两个大麦品种的产量和品质的效应相同。因此,生产上应因地制宜,发挥区域优势,重视海拔对大麦品质的调控作用,以改善大麦的品质。     

Barley grain β-glucan content as affected by nitrogen and irrigation

Barley (Hordeum vulgare L.) with high grain β-glucan content in the soluble dietary fiber fraction may be useful as a specialty crop for human food. In contrast, low β-glucan content is desirable for brewing or animal feed. The objective of this study was to evaluate the effect of nitrogen and irrigation on barley grain β-glucan content. Relationships between barley grain β-glucan content and some agronomic traits were examined. Generally, high nitrogen levels increased barley grain β-glucan content in both years. The N₂ treatment gave the best grain β-glucan contents. A negative effect of irrigation was observed for barley grain β-glucan content. Increased levels of irrigation tended to decrease grain β-glucan content in barley. Non-irrigated treatments commonly had the greatest values for grain β-glucan content in all treatments. Higher positive correlations between β-glucan and protein content were observed in both years. A negative correlation between β-glucan content and 1000 grain weight was significant in 1999 while a negative correlation between β-glucan content and sieve analysis was significant in 2000. It may be concluded that increased nitrogen is desirable for high grain β-glucan content in barley but not irrigation.     

Composition and molecular structure of polysaccharides released from barley endosperm cell walls by sequential extraction with water,malt enzymes,and alkali

Isolated and purified endosperm cell walls (CW), used in this study, were derived from a Canadian malting barley variety, AC Metcalfe, grown in three different environments in Canada in 2003, and varying in grain protein and β-glucan contents, as well as in grain hardness. The CW were initially extracted with water at 45 °C and subsequently digested with barley malt crude enzyme extract resulting in two fractions designated CW-WE45 and CW-MD, respectively. The remaining non-digested cell wall material (CW_ND) was further fractionated by sequential extraction with water at 95 °C (CW_ND-WE95), saturated barium hydroxide (CW_ND-BaE), and 1 N sodium hydroxide (CW_ND-NaE) at 25 °C. Composition and molecular structure analyses were carried out for all fractions including the remaining cell wall residue (CW_RES). Extraction of CW with water followed by digestion with malt crude enzyme extract solubilized the majority of β-glucans (∼55–70%) and glucomannans (∼60–80%) but only a small portion of arabinoxylans (∼20–30%) present in the intact CW. The CW-WE45 and CW_ND-WE95 fractions consisted mostly of β-glucans exhibiting high average molecular weights (M_w) (2–3 × 10⁶), whereas the CW_ND-BaE consisted mainly of arabinoxylans with M_w about 1–1.5 × 10⁶. The CW_ND-NaE contained almost equal amounts of β-glucans and arabinoxylans and a small amount of glucomannans, whereas the CW_RES contained approximately equal proportions of β-glucans, arabinoxylans and glucomannans. β-Glucans in CW_ND-WE95, CW_ND-NaE, and CW_RES exhibited a higher ratio of 3-O-β-d-cellobiosyl-d-glucose to 3-O-β-d-cellotriosyl-d-glucose (DP3/DP4) compared to β-glucans in CW-WE45 and CW-MD. β-Glucans in CW_ND-NaE showed the highest level of long cellulosic oligosaccharides with DP ≥ 5, whereas those in the CW_RES had the highest DP3/DP4 ratio. The CW-MD was fractionated by ultrafiltration into high (CW-MD_HMW) and low-molecular weight (CW-MD_LMW) sub-fractions, with weight-average M_w of ∼150–350 × 10³ and <10 × 10³, respectively, as confirmed by size-exclusion chromatography. The monosaccharide composition of the sub-fractions indicated a more extended enzymic degradation of β-glucans and glucomannans than arabinoxylans. Some differences in composition and molecular structure of the cell wall constituents among the three barley samples were related to their solubility and enzymic digestibility.     

Relationship between specific weight of spring barley and malt quality

The assessment of malting barley to determine if it meets grain quality requirements is an integral step in ensuring an efficient malting process and a good quality malt output. Specific weight (SW) is an industry standard criterion, however links between SW and malting are not well understood. In this study the effect of a changing SW on malting was investigated. Samples were manipulated according to both grain size and weight, creating grain fractions with a range in SW. Prior to malting, grain quality traits were measured, and after malting, malt quality traits were examined. Increased SW resulted in a reduced number of whole, unmodified corns in malt, implying increased levels of modification. Specific weight correlated with both hot water malt extract (r = 0.82, P < 0.01) and predicted spirit yield (r = 0.84, P < 0.01), this highlights an increased malt output. Furthermore peak gelatinisation temperature of extracted starch from the malt correlated with both SW (r = 0.69, P < 0.05) and grain density (r = 0.65, P < 0.05). This could benefit malt efficiency by increased conversion of starch to fermentable sugars, but with the same energy input. The changes in SW and consequently malt output in this study are a result of changing grain density rather than packing efficiency.     

Digestion of barley malt porridges in a gastrointestinal model: Iron dialysability,iron uptake by Caco-2 cells and degradation of β-glucan

Iron availability and degradation of (1→3,1→4)-β-d-glucan (β-glucan) in three whole grain porridges made from two optimised barley malts and unprocessed barley were studied in a dynamic gastrointestinal model. The malting processes, with steeping at 15 or 48 °C with lactic acid (LA), enabled a complete reduction of phytate by subsequent soaking of ground malt, still with well preserved β-glucan. Iron dialysability and iron uptake by Caco-2 cells were higher in phytate reduced porridges, compared to the reference porridge. During simulated digestion, the extractability of β-glucan increased and the Calcofluor average molecular weight decreased for all porridges, indicating a gradual degradation during passage through the model. The degradation rate, however, appeared lower in porridge prepared from malted barley steeped at 48 °C with LA. The gastrointestinal model ranked iron availability according to human absorption data and showed high repeatability when evaluating changes in β-glucan. The results indicate the potential for using high temperature steeping with LA to yield improved iron availability combined with reduced degradation of β-glucan in the small intestine, maintaining the beneficial properties of barley.     

Effects of environment and variety on content and molecular weight of β-glucan in oats

Oat β-glucan has been shown to have cholesterol, insulin and glucose lowering effects, which are related to increased viscosity of the intestinal contents. Some important factors influencing the viscosity are molecular weight, structure and concentration. To study the effect of variety and environment on β-glucan content and molecular weight of β-glucan, four oat varieties were grown in 11 different environments (location × year combinations) in a field experiment. The β-glucan content varied between 2.3 and 3.2% and the average molecular weight of β-glucan between 1.73 and 2.02 × 10⁶ g mol⁻¹. There was a significant difference between varieties and environments for both β-glucan content and molecular weight of β-glucan. The effect of environment was much greater on molecular weight (71%) than on β-glucan content (42%), while the effect of variety was greater on β-glucan content (23%) than on molecular weight (4%). There was also a positive significant correlation between β-glucan content and molecular weight of β-glucan (p < 0.001, r = 0.46). These results show that β-glucan content is a better target for plant breeding than molecular weight. However, both factors are important for the physiological effects of β-glucan, and selection for high β-glucan content will probably also give higher molecular weight.     

Effects of roasting on barley β-glucan,thermal, textural and pasting properties

Different hulled barley cultivars were subjected to roasting in hot sand (280 °C) and the effects on β-glucan extractability, physico-chemical, thermal and pasting properties were studied. The grain puffed upon roasting and grain hardness and colour difference ΔE were significantly lowered. The roasted barley flour had significantly higher water absorption and water solubility index. The cultivars DWR-28, RD-2503 and PL-172 had the highest total β-glucan content (up to 5.47%). Roasting brought about a decrease in the soluble β-glucan content in all the cultivars and this decrease ranged from 4.9 to 25.3%. The β-glucan extractability was not affected by the roasting process but roasting lowered the ratio of soluble to insoluble β-glucan content by 8.1–41.9%. Roasting significantly affected the pasting and thermal properties of the flours, together with an increase in the cooked starch content that ranged from 28.8 to 43.1%.     

Influence of germination time and temperature on the properties of rye malt and rye malt based worts

The effects of germination time and temperature on the quality of rye malt and worts derived thereof were investigated using Response Surface Methodology. Amylolytic and proteolytic enzyme activities were increased by long germination periods, while β-glucanase activity was not influenced. Total and Soluble Nitrogen content were also not significantly affected by the variations in germination conditions. Free Amino Nitrogen (FAN) was found in higher amounts in worts prepared from rye malts with long germination times. Extract contents were higher in rye malt than in the control barley malt and could be increased by a favourable germination regime, while no such impact on wort fermentability was found. High wort viscosities could be significantly reduced by a long germination period at low temperatures, but were still unacceptably high. The same conditions favoured the development of endoxylanase activity. Arabinoxylan (AX) accumulated during the germination process and their extractability increased. The results suggest that longer germination periods resulted in an increased number of AX molecules with lower molecular mass. Optimal rye malt qualities within the limits of this study were found for a germination time of 144 h at 10 °C, which resulted in an acceptable FAN content and the lowest measured viscosity.     

Effect of technological process on the nutritional quality of naked barley enriched rye bread

Naked barley products used in bread making gain popularity as a source of both soluble and insoluble fractions of dietary fibre, especially β-glucans. The aim of the study was to investigate the effects of different naked barley flour share in rye bread formulations and dough preparation methods (Single-phase and Detmold sourdough) on non-starch polysaccharides content and solubility and antioxidant properties of products at different processing stage. Naked barley incorporation to rye contributed to the increase in dietary fibre content with higher soluble fraction share, highly enriched products in β-glucan and increased antioxidant activity of products. It also contains high amounts of arabinoxylans, but less soluble than those from rye. A Single Phase method of rye bread production resulted in higher β-glucan concentration in products and their antioxidant activity, compared to Detmold method products. The nutritional quality of bread is highly influenced by the process parameters.