Soluble Β-glucan Content Research Articles

Relationships Between Barley Hordeins and Malting Quality in a Mutant of cv. Triumph. II. Genetic and Environmental Effects on Water Uptake

The spring malting barley mutant TL43 and its parent cultivar, Triumph, were grown in field trials at Dundee, Scotland and Lleida, Spain in 1997 and 1999, to study water uptake and distribution after steeping and the grain properties that influence them. In 1997, TL43 absorbed more water than Triumph at both sites despite having higher protein and hordein contents. However, it had a lower proportion of B hordein. In 1999 a different steeping regime was employed, incorporating longer air rests, and water uptake of both TL43 and Triumph from Spain was extremely high. At Dundee, Triumph showed greater water uptake than TL43, but poorer distribution of water through the endosperm. This was attributed to the high B-hordein content in the sub-aleurone region of Triumph, which created an effective barrier to initial hydration of the endosperm. Subsequent hydration was, as demonstrated by the Spanish-grown samples, more effective in Triumph compared to TL43, due to the less compacted structure of the inner endosperm. NMR imaging suggested that hydration in TL43 spread throughout the sub-aleurone layer before moving to the inner endosperm, but, in Triumph, proceeded on a broader front from the scutellum towards the distal parts of the grain. A general conclusion was that water uptake in malting, although influenced both by genotype and environment, was more dependent, here, on the latter. B-hordein quantity and distribution were significant factors, but soluble β-glucan content, previously implicated in water uptake differences between Spain and Scotland, appeared to have little effect on the germplasm in this study.

Improvement of malting quality of barley by complementing the malt enzyme spectrum

The processing quality of cereals can be modified by altering the structural grain constituents or the enzyme activities that mobilize storage reserves of the seeds. In order to complement the malt enzyme spectrum, a gene encoding for a thermotolerant fungal endo-(1,4)-β-glucanase was introduced into two barley cultivars, Kymppi and Golden Promise. The gene was expressed in the seeds during germination, thus providing a thermotolerant enzyme that is active under mashing conditions. The amount of thermotolerant β-glucanase produced by the seeds (ca. 0.025% soluble seed protein) has been shown to be sufficient to reduce wort viscosity by decreasing the soluble β-glucan content. For the safe commercial cultivation of transgenic plants risk assessment of their cultivation is needed. In our study experimental estimates of the transgene flow from transgenic barley by pollen dispersal were produced. Field trials were conducted during the summers of 1996 and 1997. A transgenic barley line homozygous for the gene encoding for neomycin phosphotransferase was used as a source of pollen and male-sterile barley lines as recipients. In order to be able to transform the cross-fertilization frequencies to corresponding values of normal male-fertile barley, plots of normal barley were also included in the experimental plan. On the basis of our study, cross-fertilization in male-sterile recipient barley is possible with very low frequency up to 50 meters from the donor area. However, the frequency dramatically decreases with distance and due to self-pollination the possibility of cross-fertilization remains very low in normal cultivated barley.

Variation in total and soluble beta-glucan content in hulless barley: effects of thermal, physical, and enzymic treatments.

Total and soluble beta-glucan content and effects of various treatments of barley grain on extractability and molecular characteristics of soluble beta-glucan were studied. Four types of hulless barley (normal, high amylose, waxy, and zero amylose waxy) from 29 registered and experimental genotypes were analyzed. For each, moisture, protein, amylose, 100 kernel weight, starch, beta-glucan (total and soluble), beta-glucanase activity, and slurry viscosity were determined. Significant differences in total beta-glucan were observed among the groups, with average values of 7. 49%, 6.86%, 6.30%, and 4.38% for high amylose, waxy, zero amylose waxy, and normal barley, respectively. The extractability of beta-glucan in high amylose barley was relatively low (20.6-29.7%) compared to that in normal (29.8-44.3%), zero amylose waxy (34.0-52. 5%), and waxy (36.7-52.7%) barley genotypes. Viscosity of barley flour slurries was affected by the content of soluble beta-glucans, beta-glucanase activity, and molecular weight of beta-glucans. Hydrothermal treatments (autoclaving and steaming) of barley had no effect on extractability of beta-glucans, but prevented enzymic hydrolysis of beta-glucans, and thereby substantially improved their molecular weight. The addition of enzymes (protease and esterase) during extraction and/or physical treatments (sonication) increased extractability of beta-glucans from barley.

Effect of Dietary Barley β-Glucan on Cholesterol and Lipoprotein Fractions in Rat

The flours of three barley cultivars, namely Dolma (hull-less), DL-88 (hull-less) and BH-331 (hulled), containing 6·23, 4·60, 2·18% total β-glucan and 5·39, 2·06, 1·08% soluble β-glucan contents, respectively, were used in the diets of rats to compare their hypocholesterolaemic effects. Comparison was also made with a standard casein diet. After 40 days of feeding trial, feed intake and weight gain were found to be the highest for the casein diet and differed significantly from those of the barley diets. Dolma (hull-less) based diet, fed to rats caused significant (p<0·05) reductions in the levels of total cholesterol (39%), LDL-cholesterol (61%) and triglyceride (21%), and significant elevation in the level of HDL-cholesterol (34%) in serum compared with the casein diet. Similar changes were observed in liver also. There was a significant increase in the HDLc/TC ratio and decrease in the LDLc/HDLc ratio in the serum and livers of Dolma diet-fed rats. The casein group had the highest total serum protein and liver protein compared with other test groups. Among the test diets, DL-88 had an intermediate and BH-331 the lowest cholesterol-lowering effect. Total and soluble β-glucan appeared to be strong predictors of the cholesterol-lowering in serum and liver of rats. The viscous property of soluble β-glucan may result in reduced absorption, or reabsorption of lipids.

Effects of the Fungicide Propiconazole on Agronomic and Quality Traits of Hulled and Hulless Barley

The hypocholesterolemic effect of hulless waxy barley (Hordeum vulgare L.) has increased its use in food products. Hulless cultivars currently grown in the Upper Midwest U.S. barley growing region are susceptible to a foliar disease, spot blotch, that can severely reduce yield. Spot blotch and kernel blight generally occur in the eastern area of the region; thus, hulless barley production is limited to the western area. Research on chemical control of spot blotch and kernel disease in hulless barley genotypes grown in the Upper Midwest has not been conducted. The objectives of this study were to determine whether natural field infections of the pathogen responsible for causing spot blotch and partly responsible for causing kernel blight similarly affect kernel and flour brightness of hulled and hulless barley genotypes, and to determine whether disease control with the fungicide propiconazole {1[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole} similarly affect agronomic and quality traits of hulled and hulless barley genotypes. Propiconazole reduced spot blotch severity. This resulted in increased yield and yield-related traits in hulled and hulless genotypes. Responses to propiconazole by the hulled and hulless genotypes were generally similar for spot blotch control, and similar for grain yield and 1000-kernel weight. The reduction in spot blotch severity did not result in brighter kernels or flour, nor did it affect mean total or soluble β-glucan content of hulled and hulless genotypes. Thus, hulless barley cultivars susceptible to spot blotch can be produced in the eastern area of the Upper Midwest barley growing region if they are protected with propiconazole.

Changes in extract viscosity, amino acid content, and soluble and insoluble β-glucan and dietary fibre content of barley during different high moisture storage conditions

Two experiments were conducted to investigate changes in barley during anaerobic high moisture storage of whole barley. To study the effect of micro-organisms and enzymes present in the grain, samples were irradiated or steamed prior to storage. The effects of enzyme addition and gibberellic acid addition were also investigated. When micro-organisms were not inhibited, considerable lactic acid, acetic acid, and ethanol production occurred, and the numbers of lactic acid bacteria were high. Soluble β-glucan content was lower ( P < 0.05) and dietary fibre content was reduced in the high moisture barley stored for 35 or 90 days compared with the dry control barley, regardless of pretreatments or additives. Correspondingly acid extract viscosity was also greatly ( P < 0.05) reduced. Insoluble β-glucan content was higher ( P < 0.05) in high moisture barley than in dry barley, other than when enzymes with β-glucanase activity were added to the samples. Enzyme addition enhanced fibre breakdown and reduction in acid extract viscosity, while gibberellic acid addition had no effect. Regardless of additives or pretreatments, the reduction in β-glucan content and acid extract viscosity was largest in the first days of storage, and generally only small changes occurred after the sixth day. A correlation of 0.55 to 0.81 ( P < 0.05) was found between soluble β-glucan content and acid extract viscosity, while a significant ( P < 0.05) negative correlation (−0.74 to −0.90) was found between soluble and insoluble β-glucan content. The correlation between total β-glucan content and acid extract viscosity was of the order of 0.51 to 0.63 ( P < 0.05), while the correlation between dietary fibre content and acid extract viscosity was low (0.23 to 0.33) and not significant ( P > 0.05). Amino acid content was only slightly affected by high moisture storage. These results demonstrate that high moisture storage of barley results in a rapid change in the fibre content, and that viscosity is reduced due to a reduction in soluble β-glucan content. It appears that this process is not related to activity of enzymes in the grain, or activity of lactic acid bacteria during storage.

Soluble and Insoluble Dietary Fiber and β-Glucan Contents in Domestic and Imported Breakfast Cereals Consumed in Finland

Insoluble and soluble dietary fiber contents and β-glucan concentration in breakfast cereal products consumed in Finland were evaluated. The mean contents of total dietary fiber of all porridge flakes made of barley, wheat, oat, or rye as well as ready-to-eat breakfast cereal samples of the same raw materials (except those made of wheat) were over 8%. Very low total dietary fiber contents were found in rice and maize products. A significant part of the total dietary fiber in oat, rye, barley, and wheat products and müslies was soluble dietary fiber. On the other hand, the soluble dietary fiber contents of rice and maize products were very low. The highest β-glucan contents were found in barley flakes. The β-glucan contents of oat products were also high. The β-glucan level was slightly lower in the rye products, four cereal flake mixtures, and müslies. The contents were clearly lower in wheat products; very little β-glucan was detected in maize products and none was detected in rice products.

Evaluation of hull-less barley genotypes varying in extract viscosity in broiler chick diets

Both hull-less and hulled barley cultivars, representing high and low extremes in extract viscosity (reflective of soluble β-glucan content), were compared in broiler chick diets both with and without dietary β-glucanase supplementation. In both experiments both body weight gain ( P < 0.01) and feed conversion ( P < 0.01) of chicks fed barley were improved with β-glucanase. Body weight gain of chicks indicated a greater response to dietary β-glucanase in the high viscosity barleys (16.5%, Experiment 1; 23.5%, Experiment 2), although some response was also evident in chicks given low viscosity barley (5.6%, Experiment 1; 8.2%, Experiment 2). Feed conversions of chicks also indicated a larger response to β-glucanase supplementation for the high viscosity (−9.6%, Experiment 1; −15.0%, Experiment 2) as compared with low viscosity (−2.6%, Experiment 1; −7.4%, Experiment 2) barleys. Both high and low viscosity hull-less barley gave equivalent performance with β-glucanase supplementation. Comparisons with hulled barley indicated that hull-less barley diets gave higher body weight gain (8.2%, P < 0.01) and lower feed conversion (−3.83%, P < 0.10) in chick diets when supplemented with β-glucanase.

Amylodextrins containing β-glucan from oat flours and bran

Amylodextrins with soluble β-glucan contents as high as 10% were prepared from milled oat flours and bran. The level of enzymatic conversion was measured by high performance liquid chromatography and gel permeation chromatography. The large molecular weight amylodextrin fragments containing the β-glucan from low level amylolytic conversions were measured by gel permeation chromatography. The different elution times of the two separate enzyme conversion mixture components suggest different modes of enzyme actions. Lower molecular weight fractions are produced by the action of Bacillus licheniformis α-amylase in contrast to the action of B. stearothermophilus α-amylase, due possibly to dissimilar enzyme dosages. Comparisons of the amylodextrin compositions produced by B. stearothermophilus α-amylase and B. licheniformis α-amylase systems at intermediate conversion levels revealed that the B. stearothermophilus α-amylase gave much larger quantities of the maltohexaose component than the B. licheniformis α-amylase.

Content and solubility of mixed-linked (1→3), (1→4)-β- d-glucan in barley and oats during kernel development and storage

The concentration of mixed-linked (1 →3), (1 →4)-β- D -glucan (mixed-linked β-glucan) increased during kernel development of two-rowed and six-rowed barley, with a levelling off or decrease at later stages of maturity. Consequently, the stage of development as well as cultivar and growing conditions influenced total mixed-linked β-glucan content. In barley and oat kernels, dry matter was largely deposited before the majority of mixed-linked β-glucan in the endosperm cells walls was synthesized. High contents of soluble mixed-linked β-glucan as well as high mixed-linked β-glucan solubilities were observed before harvest. Close to harvest and early during subsequent storage significant decreases in total and soluble mixed-linked β-glucan contents were apparent. During the remainder of the 6-month storage time studied, however, the contents of soluble and insoluble mixed-linked β-glucan remained constant, indicating no activity of endogenous mixed-linked β-glucan degrading enzymes.

QUANTITATIVE CHANGES IN THE CONCENTRATIONS OF THE MAJOR COMPONENTS OF FOUR GENOTYPES OF BARLEY GRAINS DURING MALTING AND MASHING

Four genotypes of barley, including good and poor malting varieties, were sampled as grain, green malt, kilned malt and spent grains. Each of these samples were analysed for total protein, aggregated protein, total and soluble β-glucan, starch and husk contents. Protein sub-units were separated using sodium dodecyl sulphate polyacrylamide electrophoresis. Activities of β-glucanase, endopeptidase and α-amylase were measured and starch from each sample was purified and separated into large and small granules, and analysed for total protein and sub-unit protein content. Results calculated as % of dry weight and as a proportion of the weight of dry grain showed quantitatively the changes which occurred in the components of the grain during malting and mashing. Comparisons of the composition of the genotypes at the various stages showed that the best malting variety studied, Ark Royal, was better because of moderate superiority in several characters rather than a fundamental difference in a single attribute and supports the thesis that to further improve malting quality plant breeders should select for several characters which are independently inherited.

The effect of rain on β-glucan content in barley grains

The effect of rain on the viscosity of an acid flour extract and on the acid-soluble, acid-insoluble and total β-glucan contents of barley flour has been investigated. Four commercial varieties and two high lysine genotypes were studied. In the commercial varieties rain induces a decrease in the viscosity of the acid flour extract which is paralleled by decreases in soluble and total β-glucan contents. Furthermore, it is concluded that the rain did not alter the structural nature of the acid-soluble β-glucans. The genotype having the lys-3a allele is characterized by such a low extract viscosity and β-glucan content that the rain had no effect on these parameters. The rain had a very unexpected effect on the genotype having the lys allele, namely, a marked decrease in extract viscosity that was not accompanied by a decrease in β-glucan contents. Similar analyses on pure endosperm demonstrated that the rain effect is not a result of an altered 1000-grain weight. In addition, the extract viscosity and the soluble β-glucan content were found to decrease from yellow to full ripeness.

The relationship between the viscosity of an acid flour extract of barley and its β-glucan content

The relationship between the viscosity of an acid flour extract and the acid-soluble, acid-insoluble and total β-glucan content of barley flour has been investigated. The extract viscosity was found to be closely related (R2=0.99, S.E.E.=0.19) to the content of soluble β-glucan. It is concluded that the acid-soluble β-glucans from 14 of the 18 different genotypes studied have a similar structural nature. Genotypes containing the lys-3a allele were found to have very low extract viscosities and β-glucan contents. Quick and accurate methods are described for measuring viscosities of acid extracts made from flour derived from grains of a single plant and flour derived from a single grain. These methods can be used to screen plants for their soluble β-glucan content in a plant breeding program.