In vitro potential antioxidant activity of (1-->3),(1-->6)-beta-D-glucan and protein fractions from Saccharomyces cerevisiae cell walls

(1-->3),(1-->6)-Beta-D-Glucan, a cell wall polysaccharide in many microorganisms, fungi and algae, is a well-known biological response modifier. Recently, it was found that (1-->3)-beta-D-glucan from Saccharomyces cerevisiae also exhibits antioxidative capabilities. In this study the antioxidative activity of the cell wall fractions of brewer's yeast was investigated. Particular emphasis was put on the question to which extent glucan is responsible for the antioxidative activity of the cell walls and how the other cell wall components might contribute. For the experiments yeast cell walls from brewery fermentations were used. Glucan was isolated by a three-step extraction procedure including a combination of hot water and enzymatic treatment. The level of (1-->3),(1-->6)-beta-D-glucan in the cell walls was analyzed enzymatically. The antioxidant activity was determined by electron paramagnetic resonance spectrometry and Trolox equivalent antioxidant capacity assay. The results show that the antioxidative activity of yeast cell wall proteins exceeds that of beta-glucan greatly. Especially aromatic side chains and free thiols from denatured proteins seem to work as antioxidants.     

Improvement of malt modification by use of Rhizopus VII as starter culture

The development of a selected starter culture on malting barley and its effects on malt quality aspects were studied. Application of Rhizopus sporangiospores in a malting process resulted in increased beta-glucanase and xylanase contents of the malting barley and improved starchy endosperm cell-wall degradation. Activation of the sporangiospores and optimization of the inoculation procedure led to a further increase in enzyme levels and to larger and more consistent impacts on cell-wall modification. Whereas the main effect of the starter culture on beta-glucan degradation was observed during malting, a further decrease in beta-glucan during mashing suggests that the microbial enzymes that survived the kilning step were active during mashing. Other quality aspects that were influenced by the starter culture activity were protein modification, wort color, and wort pH. The level of microbial enzymes produced was related to the amount of barley kernels infected with the starter culture.     

Esterases in Barley and Malt

Several esterases from barley and malt have been separated on polyacrylamide gels. The slowest moving bands appear to represent a single enzyme displaying a spread of migration owing to differences in surface charge. During malting, this enzyme, which is located in the starchy endosperm, shifts to a more migratory form. Two other main esterase groups are identified through gel electrophoresis, notably a highly anionic, highly labile enzyme, MW 62,000, located in the aleurone. The slowest and fastest moving bands have been partially purified using salt fractionation and ion‐exchange chromatography. The former, MW 47,000, has strong capability for hydrolyzing acetylxylan and it is speculated that its role in the starchy endosperm is as part of the enzyme system that hydrolyzes the cell walls.     

Deposition of cell wall polysaccharides in wheat endosperm during grain development: Fourier transform-infrared microspectroscopy study

The time course and pattern deposition of the cell wall polysaccharides in the starchy endosperm of wheat (Triticum aestivum cv. Recital) during grain development was studied using Fourier transform infrared microspectroscopy (micro-FTIR). Three stages of grain development identified as key stages for cell wall construction were retained as follows: the end cellularization, the beginning of cell differentiation, and the beginning of maturation. Micro-FTIR revealed that beta-(1-->3),(1-->4) glucans and arabinoglactan proteins are the main cell wall components of endosperm at the end of the cellularization stage, whereas arabinoxylans (AX) appeared only at the cell differentiation stage. Past the differentiation stage, FTIR spectra were dominated by AX features. Cell walls at the beginning of cell differentiation and at endosperm maturation could be distinguished by spectral features that were ascribed to AX substitution. AX appeared more substituted at the beginning of cell differentiation. Moreover, a difference in the degree of AX substitution was found between peripheral and central parts of the grain at the cell differentiation stage; AX in central cells was less substituted. Thus, dramatic changes in endosperm cell wall composition were detected during wheat grain development with respect to both the relative occurrence of individual constituents and the fine structure of the AX.     

Growth of Trichoderma viride on crude cell wall preparations from barley

Trichoderma viride can utilize crude cell wall preparations from barley starchy endosperm as sole source of carbon and energy. In the process beta-(1-->3)(1-->4)-glucan and arabinoxylan are released. The onset of release of the latter preceded that of glucan, consistent with arabinoxylan being encountered and utilized first. The release of several enzymes was observed during growth of Trichoderma on this substrate: endo-beta-(1-->3)(1-->4)-glucanase, endo-beta-(1-->4)-glucanase, endo-xylanase, arabinofuranosidase, esterase, carboxypeptidase, and "beta-glucan solubilase". It is inferred that each of these activities is necessary for the digestion of this substrate.     

Release of β‐Glucan from Cell Walls of Starchy Endosperm of Barley

β‐Glucan can be solubilized from barley by warm water, with increasing solubilization as the temperature is increased. Substantially less glucan is extracted if the barley is dehusked using sulfuric acid, particularly if the dehusked barley is denatured. This indicates that enzymes capable of solubilizing glucan are present in barley. Various purified enzymes promote the solubilization of glucan from denatured and dehusked barley. Apart from endo‐β‐(1→3)(1→4)‐glucanase, these enzymes include endo‐xylanases, arabinofuranosidase, xyloacetylesterase, and feruloyl esterase. Ferulic acid and, probably, acetyl groups are esterlinked to arabinoxylan, not β‐glucan, in the cell walls of barley starchy endosperm, so the ability of the esterases, xylanases, and arabinofuranosidase to solubilize glucan indicates the pentosan component of the cell wall can restrict the extraction of glucan.     

The effect of fungicidal treatment on selected quality parameters of barley and malt

Protection of barley grain against contamination by fungi such as Fusarium spp., particularly by those producing mycotoxins, secondary metabolites with adverse health effects, is of principal importance. Fungicides applied immediately after full heading of spring barley is one method of direct protection. In this work, extensive two-year field experiments combined with a detailed chemical laboratory analysis (barley and malt) were performed with the aim to study the effect of previous crops, different fungicides, and other conditions on the selected barley and malt quality parameters (content of beta-glucans, pentosans, oxalic acid, deoxynivalenol, and gushing), while the main task was to follow the effect of the fungicide (used as a treatment to protect against pathogens, mostly Fusarium) on changes of the chemical composition in barley and malt, and gushing. It was found that the relationship between the studied factors and the parameters usually applied to the evaluation of barley and malt quality is quite complex and not straightforward. The responses show typical features of a multifactorial influence with both positive and negative correlations resulting in a decrease or increase in grain quality (concentrations of beta-glucans, pentosans, deoxynivalenol, and other studied parameters). The role of previous crops was also found to be important. The fungicides should be applied at the time of heading but not at the very beginning of this period.     

Visualization of the Anticaging Effect of Ronozyme WX Xylanase on Wheat Substrates

A fluorescence microscope was used for visualization of the anticaging effect of a commercial xylanase on milled wheat, microtome cuts of wheat grains, and digesta samples obtained from piglets 1 or 4 h after feeding a wheat‐based diet (wheat 490 g/kg of diet, barley 100 g/kg of diet, and oats 100 g/kg of diet). Both starchy endosperm and aleurone cell walls were shown to be broken down by Ronozyme WX commercial xylanase. Data obtained by fluorescence microscopy was supplemented with measurements of starch and xylose released as a result of degradation of nonstarch polysaccharides by the xylanase. The results visualize and provide evidence that Ronozyme WX commercial xylanase can overcome the so‐called cage effect. This release of nutrients from their encapsulation in cereal cell wall structures has positive impact on nutrient digestibility and partially explains the positive effect of xylanase supplementation on livestock performance.     

Ferulic acid release and 4-vinylguaiacol formation during brewing and fermentation: indications for feruloyl esterase activity in Saccharomyces cerevisiae

The release of ferulic acid and the subsequent thermal or enzymatic decarboxylation to 4-vinylguaiacol are inherent to the beer production process. Phenolic, medicinal, or clove-like flavors originating from 4-vinylguaiacol frequently occur in beer made with wheat or wheat malt. To evaluate the release of ferulic acid and the transformation to 4-vinylguaiacol, beer was brewed with different proportions of barley malt, wheat, and wheat malt. Ferulic acid as well as 4-vinylguaiacol levels were determined by HPLC at several stages of the beer production process. During brewing, ferulic acid was released at the initial mashing phase, whereas moderate levels of 4-vinylguaiacol were formed by wort boiling. Higher levels of the phenolic flavor compound were produced during fermentations with brewery yeast strains of the Pof(+) phenotype. In beer made with barley malt, ferulic acid was mainly released during the brewing process. Conversely, 60-90% of ferulic acid in wheat or wheat malt beer was hydrolyzed during fermentation, causing higher 4-vinylguaiacol levels in these beers. As cereal enzymes are most likely inactivated during wort boiling, the additional release of ferulic acid during fermentation suggests the activity of feruloyl esterases produced by brewer's yeast.     

Hardness Changes and Endosperm Modification During Sorghum Malting in Grains of Varying Hardness and Malt Quality

This study examined the interaction between sorghum grain hardness and sorghum malt quality in terms of diastatic power and free amino nitrogen with endosperm modification during malting. The changes in kernel hardness during malting of four commercial sorghum cultivars of differing quality in terms of endosperm texture and potential malt quality were measured using tests for hardness and density, and endosperm modification was followed by scanning electron microscopy. The general pattern of modification during sorghum malting was confirmed to start at the endosperm–scutellum interface and then continue into the floury endosperm toward the kernel distal end. Significantly, a cultivar of intermediate hardness and low malting quality remained harder and modified more slowly than a harder cultivar of high malting quality. It appeared that intrinsic grain hardness and malt amylase and protease activity both affected malt hardness and endosperm modification, but amylase and protease activity had a greater effect because of their degradation of endosperm starch and protein. Of the hardness and density tests studied, the tangential abrasive dehulling device (TADD) gave the best measure of hardness throughout malting; maximum range was 24–100% kernel removed over five days of malting. Also, the data agreed with the observed malt modification rates. Thus, the TADD may have application as a simple and rapid test for estimating sorghum malt quality.     

Surface Abrasion of Hulled and Hulless Barley: Physical Characterization of the Milled Fractions

Abrasion techniques were used to remove the hull and pericarp layers of barley kernels to obtain a smaller kernel enriched in endosperm. The objective of this study was to evaluate the fractions produced by two alternative abrading systems on four barley cultivars for potential use in fuel ethanol processes that feature an upstream (of the fermentation) dry fractionation system. Four barley cultivars, two hulled (Thoroughbred and Nomini) and two hulless (Doyce and Merlin), were scarified and whitened at 22 scarification times and three milling degrees (settings 2, 4, and 6), respectively. Three different abrasive surfaces (36, 40, and 50 grit) were used in the scarifier to determine the material removal ratio for each barley cultivar. Material balances and color analyses were conducted for all of the fractions produced. Three fractions were produced with the whitener at each milling degree: broken kernels, fine fractions >323 μm, and fine fractions <323 μm. Setting #2 seems to be the milling level that releases most of the hull in the hulled barley with the whitener. After 50 sec of scarification, rougher surfaces produced more fine material (<1,410 μm diameter) and consequently less coarse material (>1,410 μm diameter). A lower grit (36 grit) abrasive surface induced faster hull removal in hulled barley. Color parameters L* and b* were good indicators of the fine and coarse fractions produced by abrasive methods because they indicate the kernel layer removed and were modeled as a function of the fraction of the material produced. The information obtained in this study has application in designing processes capable of removing and recovering hull and pericarp layers of barley kernels and thereby producing smaller kernels or kernel pieces containing mainly endosperm tissue.     

Endosperm structure affects the malting quality of barley (Hordeum vulgare L.)

Twenty-seven barley (Hordeum vulgare L.) samples collected from growing sites in Scandinavia in 2001 and 2002 were examined to study the effect of endosperm structure on malting behavior. Samples were micromalted, and several malt characteristics were measured. Samples were classified as having a mealier or steelier endosperm on the basis of light transflectance (LTm). Because endosperm structure is greatly dependent on protein content, three barley sample pairs with similar protein contents were chosen for further analysis. During malting, the steelier barley samples produced less root mass, but showed higher respiration losses and higher activities of starch-hydrolyzing enzymes. Malts made from steelier barley had a less friable structure, with more urea-soluble D hordein and more free amino nitrogen and soluble protein. The reason for these differences may lie in the structure or localization of the hordeins as well as the possible effects of endosperm packing on water uptake and movement of enzymes.     

Microstructure and Composition of Digitaria exilis Stapf (acha): A Potential Crop

Microstructure of the mature caryopsis of Digitaria exilis Stapf was studied by light and scanning electron microscopy and compared to chemical composition. The general structure of the caryopsis was similar to that of other grains, notably the millets. Thin bracts (the palea and lemma) and two glumes encased the caryopsis which consists of the thin, compressed layers of pericarp, testa, and cuticle surrounding the endosperm and embryonic tissues. The endosperm consisted of a single layer of aleurone cells and the starchy endosperm. The aleurone layer was thin over most of the starchy endosperm and thicker at the junction of the embryo and starchy endosperm. Aleurone cells contained lipid droplets and protein bodies. The cell contents of the starchy endosperm consisted of simple, polyhedral starch granules, lipid droplets, and protein bodies. Protein bodies were more abundant toward the periphery, and diminished toward the central portion of the starchy endosperm. Cells in certain regions of the embryo contained few, small, spherical starch granules and an abundance of protein bodies. Protein bodies containing phytic acid inclusions were located in the scutellum of the embryo. Compositional analyses revealed that the grain contained 8.2% protein, 2.1% fat, 0.48% fiber, and 1.4% ash.     

Fusarium Species on Barley Malt: Is Visual Assessment an Appropriate Tool for Detection?

Fusarium infections in malting barley cause mycotoxin contamination, quality impairment, and processing difficulties. The visual assessment of barley malt is a commonly applied practice in the malting and brewing industry to screen cereal batches for fungal infection, because it assumes a direct connection between occurring symptomatology and actual fungal contamination. The exceedance of a defined limit of red kernels (usually five to seven) in a 200 g subsample of malt is associated with an unjustifiable risk for further processing and can lead to reductions in price or the rejection of the entire batch. The present study evaluated the suitability of this method to ensure product quality and safety. It was further intended to resolve the presumed linkage between kernel discoloration and Fusarium infection. In general, symptomatology showed low predictability for Fusarium contamination. However, significant correlations became apparent between the number of discolored kernels and fungal DNA contents under conditions of higher levels of infection, although this was not the case for mycotoxin levels. Although symptomatology is likely overinterpreted in regard to its reliability as an indicator for Fusarium contaminations, it might still assist in assessing the risk of certain fungal contaminants.     

Influence of Barley and Malt Storage on Lipoxygenase Reaction

The dioxygenation of linoleic acid (LA) by aqueous flour suspensions of barley and malting samples was studied. The rate of this lipoxygenase (LOX) reaction varied as the malting process proceeded, giving a characteristic LOX reaction profile for a malting. The differences in the profiles from one malting to another were dramatic. It also appeared that during storage of dry, intact kernel samples from a single malting, a reduction in the rate of LOX reaction always occurred, and the rates of reduction with time were dependent on the stage of malting at the time of sampling. The kinetics of this aging could roughly be divided into four categories representing different stages of malting. Consequently, greatly varying LOX reaction profiles can be obtained from a single malting depending on the time of storage of kernels before assays. The results indicate that steeping, germination and the subsequent drying render the state of kernels unstable with respect to the LOX reaction for at least two to three weeks. Homogeneity of malt quality is important in the further applications of malt, especially in the brewing industry. Therefore, the rate of LOX reaction should be considered as a quality factor of malt.     

Inactive fluorescently labeled xylanase as a novel probe for microscopic analysis of arabinoxylan containing cereal cell walls

A new technique to visualize cereal cell walls by fluorescence microscopy was developed. The novel staining technique is based on an inactive fluorescently labeled xylanase binding to arabinoxylan (AX), an important polysaccharide in grain cell walls in terms of the technological and physiological functionalities of grain. The xylanase probe could stain AX in the seed coat, nucellar epidermis, aleurone layer, and starchy endosperm, but not the highly substituted AX of the pericarp layer. The advantage of this new staining technique over the existing immunolabeling techniques is that the staining procedure is clearly faster and less laborious, and uses a smaller probe that can easily be produced by marking a well characterized enzyme with a fluorescent label. In the future, the here proposed technology can be used to develop probes having specificity also for cell wall components other than AX and thus to study plant cell walls further through fluorescence microscopy.     

Variability in the release of free and bound hydroxycinnamic acids from diverse malted barley (Hordeum vulgare L.) cultivars during wort production

Volatile phenols have long been recognized as important flavor contributors to the aroma of various alcoholic beverages. The two main flavor-active volatile phenols in beer are 4-vinylguaiacol and 4-vinylphenol. They are the decarboxylation products of the precursors ferulic acid and p-coumaric acid, respectively, which are released during the brewing process, mainly from malt. In this study, the variability in the release of free and ester-bound hydroxycinnamic acids from nine malted barley ( Hordeum vulgare L.) varieties during wort production was investigated. A large variability between different barley malts and their corresponding worts was observed. Differences were also found between free ferulic acid levels from identical malt varieties originating from different malt houses. During mashing, free hydroxycinnamic acids in wort are both water-extracted and enzymatically released by cinnamoyl esterase activity. Esterase activities clearly differ between different barley malt varieties. Multiple linear regression analysis showed that the release of ferulic acid during mashing did not depend only on the barley malt esterase activity but also on the amount of ester-bound ferulic acid initially present in the wort and on its endoxylanase activity. The study demonstrates the importance of selecting a suitable malt variety as the first means of controlling the final volatile phenol levels in beer.     

Effect of selected herbicides on yielding and malting quality of spring barley cultivars

The aim of the study was to determine the effect of herbicides on yields, yield components and malting quality of the grains of barley cultivars. Literature worldwide lacks works on the impact of herbicides on the brewing quality of barley. This work presents the results of field experiments and laboratory studies concerning the evaluation of the impact of herbicides, differing in terms of an active substance, on the yields, weed control and malting quality of selected cultivars of barley. The research was conducted in Poland. The herbicides affected the increase in grain yields of barley, due to their high effectiveness of weed control, resulting in an increase in the number of ears per area unit. Certain herbicides increased grain protein content and grain filling. As for malt extractivity, Kolbach index, Q index, diastatic power and beta-glucans content in wort, there were interactions between herbicides and cultivars. The impact of herbicides on parameters varied depending on cultivars. The herbicides, especially Chwastox Turbo 340 SL (MCPA?+?dicamba) and Secator 125 OD (amidosulfuron?+?iodosulfuron-methyl-sodium), worsened several (not many) malt quality parameters, depending on cultivars, but it did not contribute to disqualifying malting quality of grains. Therefore, all tested herbicides can be recommended for use by farmers.     

Structure of (1→3)(1→4)‐β‐d‐Glucan in Waxy and Nonwaxy Barley

The endosperm cell walls of barley are composed largely of a (1→3)(1→4)‐β‐d ‐glucan commonly known simply as β‐d ‐glucan (Wood 2001). There has been much research into the characteristics of barley β‐glucan because of the influence of this polysaccharide on performance of barley in malting and subsequent brewing of beer, and in feed value, especially for young chicks (MacGregor and Fincher 1993). The potential for β‐glucan to develop high viscosity is a problem in these uses, but from the perspective of human nutrition, this characteristic may be an advantage. The glycemic response to oat β‐glucan is inversely related to (log)viscosity (Wood et al 1994a) and there is evidence to suggest that the lowering of serum cholesterol levels associated with oat and barley products (Lupton et al 1994; Wood and Beer 1998) is at least in part due to the β‐glucan (Braaten et al 1994) and probably also its capacity to develop viscosity in the gastrointestinal tract (Haskell et al 1992).     

Characterization using Raman microspectroscopy of arabinoxylans in the walls of different cell types during the development of wheat endosperm

The time course and pattern of arabinoxylan deposition in the wheat (Triticum aestivum) endosperm during grain development were studied using Raman spectroscopy. The presence of arabinoxylans (AX) is detected at the beginning of grain filling. At this stage, AX appear more substituted than at the later stages. Feruloylation of AX increases during the grain-filling stage, especially in the case of the aleurone layer. Whatever the stage of grain development, four populations of cells could be defined according to Raman arabinoxylan signatures. In the walls of the aleurone cells, AX appeared to be little substituted and highly esterified with phenolic acids. In the walls of prismatic cells, AX were found to be highly substituted and poorly esterified. Apart from aleurone and prismatic cells, the substitution degree of AX in endosperm was in the same range. Cells in the crease region were distinguished from cells in the starchy endosperm by their lower amount of esterified phenolic compounds.