PUFFING AND JET COOKING AFFECT SOLUBILITY AND MOLECULAR WEIGHT OF BARLEY β‐GLUCANS

Foods containing barley or oats are often marketed as healthy because of the dietary fiber (1→3) (1→4)‐β‐D‐glucan. Processing conditions can affect the molecular structure of these dietary fibers, which in turn affect quality and properties of the products. In this study, the effect of puffing and jet cooking conditions on changes in the solubility and molecular weight of barley β‐glucans was investigated. Barley flour was processed in a pasta extruder to produce particles similar in size and shape to rice. These particles were puffed at 230, 250 and 270C for 6, 8 and 10 s in a rice cake machine. Solubility and molecular weight of barley β‐glucans were determined by using water extracts (25 or 65C). The amount of β‐glucan extracted in water at 25C increased from 41.1% in cakes puffed at 230C/6 s to 69.7% in cakes puffed at 270C/10 s. The amount of β‐glucan extracted in water at 65C increased from 63.6% in samples puffed at 230C/6 s to 99.1% in samples puffed at 270C/10 s. The molecular weight of β‐glucans in barley was reduced by puffing and jet cooking treatments.     

Effects of β‐Glucans and Environmental Factors on the Viscosities of Wort and Beer

This paper reports on the influence of molecular weight and concentration of barley β‐glucans on the rheological properties of wort and beer. Environmental conditions such as pH, maltose level in wort, ethanol content of beer, shearing and shearing temperature were also examined for their effects on wort and beer viscosities. In the range of 50–1000 mg/L, β‐glucans increased solution viscosity linearly with both molecular weights (MW) of 31, 137, 250, 327, and 443 kDa and concentration. The influence of MW on the intrinsic viscosity of β‐glucans followed the Mark‐Houwink relationship. Shearing wort and beer at approximately 13,000 s^?1for 35 s was found to increase the wort viscosity but reduce beer viscosity. Shearing wort at 20°C influenced β‐glucan viscosity more than shearing at 48°C and 76°C whereas the shearing temperature (0, 5 and 10°C) did not effect the viscosity of beer. At lower pHs, shearing was found to reduce the viscosity caused by β‐glucans in wort but had no effect in beer. Higher concentrations of maltose in wort and ethanol in beer also increased the viscosity of β‐glucan polymers. It was found that β‐glucans had higher intrinsic viscosities in beer than in wort (5°C), and lower critical overlap concentrations (C^*) in beer than in wort.     

Effects of β‐glucans on properties of soya bean protein isolate thermal gels

The effects of concentration and molecular weight of oat β‐glucans on properties of soya bean protein isolate (SPI) thermal gels prepared by heating at 90℃for 30 min were investigated. Compared with control (free of β‐glucan) formulations, the presence of β‐glucans (0.5–1.5%, w/v) largely enhanced storage modulus (G′) and texture properties of SPI (12%, w/v) thermal gels measured by dynamic oscillatory rheometry and texture profile analysis, which were developed as increasing β‐glucan concentration and molecular weight. It is possible that β‐glucans could cause the formation of protein aggregates to produce gels through hydrophobic interactions. Mixed gel systems at low ionic strength showed higher G′ resulting from the lower denaturation temperature of SPI, which was beneficial to the formation of gel structure. In addition, although adding a certain amount of β‐glucan into SPI reduced water‐holding capacity of mixed gels, high molecular weight of β‐glucan improved their water‐holding capacity compared to control formulations attributed to the improvement of the structural integrity of the mixed gel network.     

Amylose and β‐Glucan Content of New Waxy Barleys

Starch was isolated from four new waxy barleys and compared with normal and high‐amylose barley starch. The waxy barley samples were selected lines from crosses of Swedish hulled and naked barley cultivars with the cultivar Azhul as donor of the waxy gene. The starches from the waxy barley samples were found to contain 0.7–2.6% amylose when determined iodimetrically by amperometric titration and 0.0–0.9% when determined by size exclusion chromatography after debranching. However, Sepharose CL‐2B elution profiles of the starches detected by iodine staining showed that all four waxy samples were free from detectable amounts of amylose. The amylopectin starches were found to contain a small polysaccharide fraction with molecular size smaller than amylopectin, with an iodine staining λ_max range of 550–600 nm. The water extractable and acid extractable β‐glucan contents in the waxy barley cultivars were generally found to be higher than those in normal barley.     

Milling of barley to obtain β‐glucan enriched products

The methods for laboratory and commercial milling of dehulled barley grain are described. In the laboratory‐scale barley at 10%, 12% and 14% moisture, was milled to produce three fine‐products (flours) and two coarse‐products (grits). The yield of flours and grits was about 40% and 60%, respectively. Increased products yield and the β‐glucan content in products with increasing moisture of ground grain were observed. Barley at 14% moisture was milled under commercial conditions to produce the following end‐products: fine‐ and coarse‐grained flours, middlings and fine grits. These products differed in their average contents of β‐glucans, total dietary fiber, ash and protein. The fine‐grained grit from impact milling coarse grit had the highest contents of β‐glucans, total dietary fiber, ash and protein. This product, with a weight yield of 18.6%, contained 6.72% β‐glucans, 25.12% total dietary fiber, 2.19% ash, and 15.83% protein. All these values were at about 50%, 72%, 55% and 24%, respectively higher than in dehulled barley. Lowest contents of chemical components in fine‐grained flours were found. Developed method of commercial milling of barley will allow to obtain new, nutritionally valuable barley products, which have potential for use in human foods.     

Structural characterisation of β‐cyclodextrin crosslinked by adipic acid

This study was conducted to investigate the structural characterisation of β‐cyclodextrin (β‐CD) crosslinked by adipic acid. β‐CD was treated with different concentrations (0%, 5%, 10% and 15%, w/v) of adipic acid. Different instruments, such as scanning electron microsope (SEM), Fourier‐transform infrared (FT‐IR) spectroscopy and ¹H and ¹³C nuclear magnetic resonance (NMR) spectra were used to find out chemical structure in the crosslinked β‐CD. SEM analysis suggested that crosslinking β‐CD with 15% adipic acid changed the original morphology and considerably increased the particle size of the raw material. FT‐IR spectroscopy data showed that an intensive absorption band at 1706 cm^?1 was present in the β‐CD samples treated with 10% and 15% adipic acid, indicating a crosslinking between hydroxyl groups of β‐CD and carboxyl groups of adipic acid. NMR spectra revealed that the ester linkages between hydroxyl groups of β‐CD and carboxyl groups of adipic acid were formed after crosslinking of β‐CD with adipic acid.     

Artificial simulated gastrointestinal digestion of four carbohydrates containing beta‐d‐1 → 4 linkages and new GC‐TQ/MS‐MS method for characterising released monosaccharides

Four types of carbohydrates, including Dendrobium officinale polysaccharide, Dendrobium aphyllum polysaccharide and β‐glucans from yeast and barley, were examined, and their structures were found to mainly contain 1,4‐linked‐β‐d ‐Glcp. Artificially simulated gastrointestinal digestion was conducted to characterise the changes of molecular weight, reducing sugars and released free monosaccharides by high‐performance liquid chromatography, kits and the newly developed gas chromatography (GC)‐mass spectrometry (MS)/MS analysis, which indicated that high molecular weight and complex spatial structures contributed to delayed monosaccharide release following exposure to digestive solution. The spatial structures of carbohydrates were changed during gastric digestion, but their primary structures were destroyed during intestinal digestion. Additionally, for the developed 7890A/7000 GC‐TQ/MS‐MS, the new analytical method was successfully used to analyse very low concentrations of monosaccharides in the simulated gastrointestinal digestive system.     

The effects of refined barley β‐glucan on the physico‐structural properties of low‐fat dairy products: curd yield,microstructure, texture and rheology

The beneficial role of dietary fibre in human nutrition has lead to a growing demand for incorporation of novel fibres, particularly barley β‐glucans, into foods. Barley β‐glucans are regarded as dietary fibre ingredients that are partially soluble in water. The aim of the present work was to investigate the possibility of using barley β‐glucan in milk systems in relation to the coagulation properties of milk containing β‐glucan, and to the rheology, texture and microstructure of fresh curds. The rate of coagulation and optimum coagulum cutting time were evaluated using rheological measurements. Results show that coagulation/gelation time of the milk can be reduced significantly with the incorporation of β‐glucan; curd yield increased and the viscoelastic properties of the curd were altered with β‐glucan additions. The relationships between curd rheological behaviour and its microstructure are discussed in relation to use of novel hydrocolloids in dairy processing. The results suggest that barley β‐glucan has the potential to be used as a fat replacer in low‐fat dairy systems. Copyright © 2004 Society of Chemical Industry     

Characterization of Solubilized Forms of Bound ß‐Amylase Released by Various Agents

In a previous study the patterns of release of bound β‐amylase caused by various agents were investigated. In the present study the released β‐amylase isoforms were purified and characterized. The agents used to release bound β‐amylase at different temperatures were papain, thiols, starchy endosperm extract and several substances with amphipathic characteristics. The isoforms released were compared to those present in soluble β‐amylase from 8‐day malt. They were characterized by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE), isoelectric focusing (IEF), native polyacrylamide gel electrophoresis (PAGE), western blotting and attempts were made to use matrix assisted lazer desorption ionization (MALDI) mass spectrometry. β‐Amylase released by papain was similar in molecular weight (57 kDa by SDS‐PAGE) to soluble β‐amylase from 8‐day malt (56 kDa). The isoforms released by thiol reagents were larger (57–58 and 60–62 kDa) and were similar to the soluble β‐amylase extracted from barley (56–57 and 60–61 kDa). Agents with amphipathic characteristics (bovine serum albumin and the detergents CHAPS and Triton X‐100) released higher molecular weight material (62 kDa). Extracts from starchy endosperm containing proteolytic activity released a β‐amylase isoform, intermediate in size (58 kDa) between that released by papain and those released by thiol‐containing and amphipathic agents. Heat‐treated starchy endosperm extract (lacking protease activity) caused limited (15%) release of β‐amylase isoforms (58 and 61 kDa). These resembled the isoforms released by thiol and hydrophobic agents. The β‐amylase isoforms exhibited heterogeneity when analyzed by IEF, native PAGE and MALDI. The results confirm that a complex combination of mechanisms is involved in the release of bound β‐amylase during the germination of barley.     

Preparation and characteristics of squid pen β‐chitin prepared under optimal deproteinisation and demineralisation condition

Squid (Todarodes pacifica) pen was an excellent source of β‐chitin with 25.5% yield. The optimal condition to prepare squid pen β‐chitin was established: deproteinisation with 3% NaOH for 30 min at 15 psi/121 °C and a solid/solvent ratio of 1:10 (w/v) and a subsequent demineralisation with 1 N HCl for 30 min at room temperature and a solid/solvent ratio of 1:10 (w/v). Squid pen β‐chitin contained 6.29% nitrogen, 0.25% ash, and negligible fat with degree of acetylation of 94.02%, residual amino acid of 0.499 g/100 g and bulk density of 0.28 g mL^?1. Depending on its particle size, squid pen β‐chitin visually looked white (L* = 82.82, a* = ?0.67, b* = 6.31; particle size of 0.15–0.18 mm) or light grey (L* = 62.88, a* = 0.33, b* = 10.66; particle size of 0.425–0.841 mm). Water, fat and dye‐binding capacity of squid pen β‐chitin was 694.67%, 194.03% and 79.81%, respectively.     

Quantification of uncertainty using Bayesian and bootstrap models to simulate the impact of nitrogen fertilisation on β‐glucan levels in barley

BACKGROUND: β‐Glucans have enjoyed renewed interest as a functional food ingredient, with current attention focused on optimising β‐glucan levels in finished products without compromising final product quality. In order to measure the uncertainty about the level of β‐glucans in barley, two different statistical methods (Bayesian inference and Bootstrap technique) were applied to measured levels of β‐glucan in three different varieties of barley grain (n = 83). RESULTS: The resulting probability density distributions were similar for the full data set and also when applied to smaller sample sizes, highlighting the potential for either method in quantifying the total uncertainty in β‐glucan levels. Bayesian inference was used to model the effect of nitrogen treatment on β‐glucan and protein contents in barley. The model found that a low level of fertilisation (50 kg N ha^?1) did not have a significant effect on β‐glucan or protein content. However, fertilisation above this level did result in an increase in β‐glucan and protein levels, the effect seeming to plateau at 100 kg N ha^?1. In addition, the uncertainty distributions were significantly different for two consecutive years of data, highlighting the potential environmental influence on β‐glucan content. CONCLUSION: The model developed in this study could be a useful tool for processors to quantify the uncertainty about the initial level of β‐glucan in barley and to evaluate the influence of environmental factors, thus enabling them to formulate their ingredient base to optimise levels of β‐glucan without compromising final product quality. Copyright © 2009 Society of Chemical Industry     

Effect of High Hydrostatic Pressure‐Temperature Combinations on the Activity of β‐Glucanase from Barley Malt

β‐Glucanase from barley malt is known to be thermolabile but important in the mashing process. Therefore, the potential of increasing the thermostability of β‐glucanase in ACES buffer (0.1 M, pH 5.6) by high hydrostatic pressure has been investtigated. Inactivation of the enzyme as well as changes of the conversion rate in response to combined pressure‐temperature treatments in the range of 0.1–900 MPa and 30–75°C were assessed by analyzing the kinetic rate constants. A significant stabilization of β‐glucanase against temperature‐induced inactivation was detected at 400 MPa. With increasing pressure up to 600 MPa the catalytic activity of β‐glucanase was progressively decelerated. However, for the overall depolymerization reaction of β‐glucans in ACES buffer (0.1 M, pH 5.6) a maximum was identified at 215 MPa and 55°C yielding approximately 2/3 higher degradation of β‐glucan after 20 min as compared to the maximum at ambient pressure (45°C).     

THE MODE OF BINDING OF β-GLUCANS AND PENTOSANS IN BARLEY ENDOSPERM CELL WALLS

β-Glucans in barley endosperm cell walls exist as polymers of very high molecular weight (about 4 × 10⁷ daltons) containing firmly linked peptide sequences. This peptidic material is an essential part of the structure of the β-glucan complex as it exists in the cell wall. Rupture of peptide bonds by hydrazinolysis or with the proteolytic enzyme thermolysin gives β-glucans similar in size to those from short-grown green malts (about 10⁶ daltons). This suggests that proteolysis is the first step in β-glucan degradation. Large β-glucans are not all precipitated in 30% (w/v) ammonium sulphate; only 34% of the β-glucan in a hot aqueous extract of cell walls is precipitated. The amount is increased to 63% if the cell walls have been previously dehydrated. Prolonged incubation of cell wall β-glucan at 40°C, mechanical stress, chromatography lasting 8–10 h at or above 65°C, or chromatography in M sodium chloride causes some disassociation of high molecular weight β-glucan to a size of about 10⁷ daltons. Heating a solution for 1 h at 100°C does not disassociate the β-glucan. Pentosans isolated from cell walls are not covalently linked to the β-glucans and can be separated from them by molecular sieve chromatography. They have a higher xylose/arabinose ratio than previously reported for barley pentosans. The pentosan molecules extracted by water are smaller (10⁶ daltons) than those extracted by alkali (5 × 10⁶ daltons). Little difference was observed in the chemical or physical properties of cell wall materials of barley cultivars of different malting qualities.     

A predictive model of the effects of genotypic,pre‐ and postharvest stages on barley β‐glucan levels

BACKGROUND: β‐Glucan is a bioactive component of cereal grains that has many potential uses and health‐promoting benefits. Recent research has focused on improving the nutritional value of food by increasing human exposure to β‐glucan. This study looks at the development of a farm‐level baseline model (including scenario analysis) to evaluate the impact of pre‐ and postharvest stages (including genotypic factors, environmental conditions, agronomic factors and storage) on β‐glucan levels in barley. Monte Carlo simulation techniques were employed to model various stages in pre‐ and postharvest processes and to simulate the factors influencing the level of β‐glucan content in both hulled barley (H_B) and hull‐less barley (H_LB) genotypes. RESULTS: The baseline model found that the mean simulated level of β‐glucan was 40.99 and 56.77 g kg^?1 for H_B and H_LB genotypes respectively. A sensitivity analysis highlighted that genotype was the most important parameter in determining the final β‐glucan content (correlation coefficients of 0.66 and 0.78 for H_B and H_LB respectively), more so than any of the agronomic factors analysed. The scenario analysis highlighted the importance of harvest date (scenario 2) and storage conditions (scenario 3), with a potential 32.6 and 32.7% decrease in β‐glucan (compared with the baseline model) if harvesting is carried out early during physiological maturity (i.e. at growth stage 92) and a potential 20.1 and 19.5% increase in β‐glucan for H_B and H_LB respectively if storage time is minimised. CONCLUSION: This study predicted the influence of genotypic, pre‐ and postharvest operations on β‐glucan content and thus allows strategies to be identified to influence β‐glucan content in barley products. Copyright © 2008 Society of Chemical Industry     

Porosity and Water Activity Effects on Stability of Crystalline β‐Carotene in Freeze‐Dried Solids

Abstract: Stability of entrapped crystalline β‐carotene as affected by water activity, solids microstructure, and composition of freeze‐dried systems was investigated. Aliquots (1000 mm³, 20% w/w solids) of solutions of maltodextrins of various dextrose equivalents (M040: DE6, M100: DE11, and M250: DE25.5), M100‐sugars (1:1 glucose, fructose and sucrose), and agar for gelation with dispersed β‐carotene were frozen at ?20, ?40, or ?80 °C and freeze‐dried. Glass transition and α‐relaxation temperatures were determined with differential scanning calorimetry and dynamic mechanical analysis, respectively. β‐Carotene contents were monitored spectrophotometrically. In the glassy solids, pore microstructure had a major effect on β‐carotene stability. Small pores with thin walls and large surface area allowed β‐carotene exposure to oxygen which led to a higher loss, whereas structural collapse enhanced stability of β‐carotene by decreasing exposure to oxygen. As water plasticized matrices, an increase in molecular mobility in the matrix enhanced β‐carotene degradation. Stability of dispersed β‐carotene was highest at around 0.2 a_w, but decreasing structural relaxation times above the glass transition correlated well with the rate of β‐carotene degradation at higher a_w. Microstructure, a_w, and component mobility are important factors in the control of stability of β‐carotene in freeze‐dried solids Practical Application: β‐Carotene expresses various nutritional benefits; however, it is sensitive to oxygen and the degradation contributes to loss of nutritional values as well as product color. To increase stability of β‐carotene in freeze‐dried foods, the amount of oxygen penetration need to be limited. The modification of freeze‐dried food structures, for example, porosity and structural collapse, components, and humidity effectively enhance the stability of dispersed β‐carotene in freeze‐dried solids.     

Enzymatic Properties of β‐1,3‐Glucanase from Streptomyces sp Mo.

Streptomyces sp Mo endo‐β‐1,3‐glucanase was found to have hydrolyzing activity toward curdlan and released laminarioligosaccharides selectively. The molecular weight was estimated to be 36000 Da and its N‐terminal amino acid sequence was VTPPDISVTN. The optimal pH was 6 and the enzyme was found to be stable from pH 5 to 8. The optimal temperature was 60 °C and the activity was stable below 50 °C. The enzyme hydrolyzed selectively curdlan containing only β‐1,3 linkages. The enzyme had 89% relative activity toward Laminaria digitata laminarin, which contains a small amount of β‐1,6 linkages compared with curdlan, while Eisenia bicyclis laminarin with a higher amount of β‐1,6‐linkages, was not hydrolyzed. Mo enzyme adsorbed completely on curdlan powder. The enzymatic hydrolysis of curdlan powder resulted in the accumulation of laminaribiose (yield 81.7%). Trisaccharide was inevitably released from the hydrolysis of laminarioligosaccharides with 5 to 7 degrees of polymerization (DP). Although the enzyme cleaved off disaccharide (DP 2) from tetrasaccharide (DP 4), the reaction rate was lower than those of DP 5 to 7. The results indicated that the active site of Mo endo‐β‐1,3‐glucanase can efficiently recognize glucosyl residue chain of greater than DP 5 and hydrolyzes the β‐1,3 linkage between the 3rd and 4th glucosyl residue.     

The Variation of β‐amylase Activity and Protein Fractions in Barley Grains as Affected by Genotypes and Post‐anthesis Temperatures

The variation of β‐amylase activity and protein fractions in barley grains was evaluated using 148 barley genotypes grown in the field and two cultivars under in vitro culture with two temperature treatments during grain development. The results showed that there was significant genotypic variation in β‐amylase activity and protein fraction content. Regression analysis indicated that β‐amylase activity was positively correlated with total protein and the level of each of the protein fractions, with the correlation coefficient between β‐amylase activity and hordein content being the highest. Furthermore, higher post‐anthesis temperatures (32/26°C, day/night) significantly enhanced β‐amylase activity and protein fraction content, presumably as a result of reduced starch content. Albumin and glutelin were the least and most affected, respectively, in comparison with the plants under lower temperature (22/16°C). Temperature post‐anthesis also influenced the morphology of the starch A granule and the number of B granules, suggesting the altered starch structure may also be a reason for deteriorated malting quality under high temperatures.     

A Reappraisal of the Differences Between Scandinavian and Spanish Barleys: Effect of β‐Glucan Content and Degradation on Malt Extract Yield in the cv. Scarlett

Forty one samples of the malting barley cultivar Scarlett were collected from both Scandinavia (15 from Finland and 10 from Denmark) and the Iberian Peninsula (15 from Spain and 1 from Portugal), during the harvest years of 1998 and 1999. These samples were subjected to grain analyses, comprising protein content, hordein fractions by high performance liquid chromatography (HPLC) and β‐glucan content. The samples were micro‐malted and the malts were analysed to determine different patterns in the influence of grain composition on malt extract development linked to the two contrasting environments. The most obvious difference found between the Scandinavian and Iberian barleys was the effect of the total and insoluble barley β‐glucans. They were an effective barrier of malt extract in the North, but appeared to increase extract in the South. A conclusion was that the positive effect of β‐glucans in the Iberian barleys was a consequence of their greater capacity to synthesise and release β‐glucan hydrolases during germination.     

Characterization of an extracellular β‐d‐fructofuranosidase produced by Aspergillus niveus during solid‐state fermentation (SSF) of cassava husk

β‐d ‐Fructofuranosidases are biotechnologically important enzymes produced by various organisms. Here, Aspergillus niveus produced an extracellular β‐d ‐fructofuranosidase during SSF of cassava husk. This enzyme was purified 8.5‐fold (recovery of 5.2%). A 37‐kDa protein band was observed after 8% SDS‐PAGE. Native molecular mass is 91.2 kDa. Optimal temperature and pH of activity were 55°C and 4.5, respectively. The enzyme was stable at 50°C for 1 hr, and 80% of its activity was retained after 1 hr at pH 8.0. The enzymatic activity was improved by Mn²⁺, was resistant to most solvents, and was inhibited by Triton X‐100 and Tween 20. K_m and V_max with sucrose were 22.98 mM and 120.48 U/mg of protein, respectively. With Mn²⁺, these values were 16.31 mM and 0.30 U/mg of protein. The enzyme did not hydrolyze inulin and for this reason can be considered a true invertase. Thus, A. niveus β‐d ‐fructofuranosidase holds promise for invert sugar production.

Practical applications

β‐d ‐Fructofuranosidase is an enzyme that can be applied to different industrial sectors, especially food and beverage industries. It is responsible for the hydrolysis of sucrose and yields an equimolar mixture of D‐glucose and D‐fructose, named as inverted sugar syrup, with broad applications in the confectionery industry. The Aspergillus niveus enzyme hydrolyzed only sucrose here and can be considered a true invertase, showing its potential for application to invert sugar production. Besides, the use of cassava husk for enzyme production means an interesting utilization route of this agroindustrial residue. Thus, characterization of this enzyme is an important step for identification of its potential for practical applications.