Isolation,structural features and rheological properties of water‐extractable β‐glucans from different Greek barley cultivars

β‐Glucans were isolated from six Greek barley cultivars (Persefoni, Kos, Thessaloniki, Athinaida, Dimitra and Triptolemos) by water extraction at 47 °C, enzymatic removal of starch and protein and subsequent precipitation of the water‐soluble β‐glucans with 37% (w/v) ammonium sulfate saturation. The purity of barley β‐glucans was high (>93% dry basis) with some small contamination by protein (<3.84%). The molecular size of the β‐glucan isolates was determined by high‐performance size‐exclusion chromatography (HPSEC); the weight‐average molecular weights and the intrinsic viscosities ranged between 0.45 × 10⁶ and 1.32 × 10⁶ and 2.77 and 4.11 dl g^?1, respectively. Structural features of barley β‐glucans were revealed by ¹³C NMR spectroscopy and high‐performance anion‐exchange chromatography (HPAEC) of the oligomers released by the hydrolytic action of lichenase. Lichenase degradation showed that β‐glucans from all barley cultivars consisted of blocks of cellotriosyl and cellotetraosyl units, accounting for 90.6–92.3% of the total oligomers released, with a molar proportion of these units between 2.31 and 2.77. Rheological measurements of aqueous solutions/dispersions of β‐glucans showed the behaviour of non‐interacting polysaccharides and a transition from the typical viscoelastic response to gel‐like properties after a time period that depended on the molecular size of the polysaccharide. The lowest molecular size β‐glucans from the Triptolemos cultivar showed shorter gelation times than their higher molecular weight counterparts. The effect of sugar incorporation (glucose, fructose, sucrose, xylose and ribose), at a concentration of 30% (w/v), to the β‐glucans gels (6% w/v) on compression parameters seemed to be related to the type of sugar used; the pentose sugars substantially reduced gel firming. Copyright © 2004 Society of Chemical Industry     

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.     

Acid gelation of native and heat‐denatured soy proteins and locust bean gum

The effects of protein concentration and locust bean gum (LBG) addition on the mechanical properties, microstructure and water holding capacity of acidified soy protein (SPI) gels were studied. The protein was employed in two different states: (i) native and (ii) heat denatured. A slow acidification rate was induced in both systems by applying glucono‐δ‐lactone (GDL). The results indicated that the gels of native SPI were weaker, less deformable and showed lower water holding capacity than the gels of heat‐denatured SPI. The LBG addition led to an increase in the strength and water holding capacity of SPI gels, independent of the protein state (native or denatured). These results indicated that the properties of texture and water holding capacity of the SPI acid gels can be modulated by the process conditions or by the addition of other ingredients, such as polysaccharides.     

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.     

Calcium sulphate‐induced soya bean protein tofu‐type gels: influence of denaturation and particle size

Soya bean protein isolate (SPI) dispersions (7.25%, w/v) were heated at 65, 75, 85 or 90 °C for different time periods to produce SPI aggregates with diverse degrees of denaturation and particle size to investigate the effects on calcium sulphate (CaSO₄)‐induced tofu‐type gel. The results revealed that gel hardness and water‐holding capacity correlated positively with the degree of denaturation of glycinin (11S) and the particle size of the SPI aggregates. The formed gels showed more uniform and denser network structures with increasing degrees of denaturation and particle size of SPI. Hydrophobic interaction was speculated to be the crucial factor for the retention of gels prepared by SPI whose degree of denaturation by 11S was lower than 4.35%. However, disulphide bonds probably played a more important role in the retention of gels generated by SPI with the 11S denaturation degree of >84.47%. Moreover, the bulk density of the protein aggregates might determine the gel structures to a certain extent.     

大豆蛋白对鲢鱼肌原纤维蛋白凝胶特性的影响

将大豆分离蛋白经不同的变性温度及变性时间处理后,与鲢鱼肌原纤维蛋白以不同的比例混合制备热诱导凝胶。通过测定混合蛋白体系的凝胶强度及保水性,分析热变性大豆分离蛋白对混合凝胶特性的影响。结果表明,热变性后的大豆分离蛋白可以改善混合蛋白凝胶体系的凝胶强度及保水性,其中,大豆分离蛋白经过100℃变性180 min后,二者以1∶4的比例混合,得到的混合凝胶强度及保水性最佳。     

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     

β‐1,3/1,6‐Glucans and Immunity: State of the Art and Future Directions

The innate immune system responds in a rapid and non‐specific manner against immunologic threats; inflammation is part of this response. This is followed by a slower but targeted and specific response termed the adaptive or acquired immune response. There is emerging evidence that dietary components, including yeast‐derived β‐glucans, can aid host defense against pathogens by modulating inflammatory and antimicrobial activity of neutrophils and macrophages. Innate immune training refers to a newly recognized phenomenon wherein compounds may “train” innate immune cells, such that monocyte and macrophage precursor biology is altered to mount a more effective immunological response. Although various human studies have been carried out, much uncertainty still exists and further studies are required to fully elucidate the relationship between β‐glucan supplementation and human immune function. This review offers an up‐to‐date report on yeast‐derived β‐glucans as immunomodulators, including a brief overview of the current paradigm regarding the interaction of β‐glucans with the immune system. The recent pre‐clinical work that has partly decrypted mode of action and the newest evidence from human trials are also reviewed. According to pre‐clinical studies, β‐1,3/1,6‐glucan derived from baker's yeast may offer increased immuno‐surveillance, although the human evidence is weaker than that gained from pre‐clinical studies.     

青稞β-葡聚糖凝胶形成及其特性研究

研究了相对分子质量分布范围为9×103～12×103的青稞β-葡萄糖凝胶形成条件以及质量分数、pH等因素对凝胶的质构特性和持水性的影响.结果表明,在5和21℃时,质量分数较高的小分子的青稞β-葡聚糖容易形成凝胶,且随着质量分数的增加凝胶强度增大;水合时间对凝胶强度影响不显著;质量分数为5.3%的β-葡萄糖在中性条件下形成的凝胶特性较好,添加蔗糖和Ca2+对凝胶质构特性也有明显影响;较高质量分数的青稞β-葡聚糖凝胶具有良好的持水性.     

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.     

Improvement of microbial transglutaminase‐induced gelation of β‐conglycinin by conjugation with dextran

This work focused on the effect of glycosylation on the gelation ability of β‐conglycinin induced by microbial transglutaminase (MTGase). Rheological results indicated that the gels of β‐conglycinin‐dextran conjugate products exhibited higher G′ value (172.2 ± 8.6 Pa) compared with those of dry‐heated β‐conglycinin (75.2 ± 5.1 Pa), β‐conglycinin (53.3 ± 4.0 Pa) and β‐conglycinin‐dextran mixture (38.6 ± 2.6 Pa) after 4 h incubation with MTGase. The gels prepared from β‐conglycinin‐dextran conjugate products had higher hardness, fracturability, springiness and cohesiveness values determined by textural profile analysis. The turbidity of β‐conglycinin‐dextran conjugate products solution incubated with MTGase increased faster than those of the other three protein samples. The conjugated dextran in β‐conglycinin‐dextran conjugate products could inhibit extensive protein–protein interactions which might result in the formation of more ordered and stronger gel network structures during MTGase cross‐linking process. A compact and homogeneous gel networks in β‐conglycinin‐dextran conjugate products gels were also observed by scanning electron microscopy.     

β‐Glucans and Pentosans and their Degradation Products in Commercial Beers

Several commercial beers have been analyzed for their content of β‐glucans, pentosans and their degradation products using high performance liquid chromatography, thin layer chromatography and chemical and enzymic analysis procedures. The beers tested contained high levels of residual high molecular weight pentosan, but much less high molecular weight β‐glucan. The beers also contained sizeable levels of oligosaccharides, especially trisaccharides, reflecting the incomplete degradation of polymeric materials in malting and mashing and the inability of yeast to ferment them. There is substantially more β‐linked glucosyl material in beer than pentosyl substances, although the higher molecular weight of the latter probably makes it more likely to represent soluble fibre. In respect of fibre claims for the beers examined, even for the beer containing the least pentosan, it seems that less than a litre of the product would afford sufficient material.     

In vivo effect of oat cereal β‐glucan on metabolic indexes and satiety‐related hormones in diet‐induced obesity C57‐Bl mice

This study explored the dose‐dependent effect of oat cereal β‐glucan on improving metabolic indexes of obesity mice. C57‐Bl mice were randomized to chow diet (N) group and high fat diet group and other three doses of oat β‐glucan groups (low β‐glucan, medium β‐glucan, and high β‐glucan). Energy intake, glucose, lipids, and appetite related hormones were tested. Dose‐dependent relation was observed on oat β‐glucan doses and body weight change, average energy intake, total cholesterol, HDL cholesterol, plasma neural peptide Y, arcuate neural peptide Y mRNA, and arcuate neural peptide Y receptor 2 mRNA level. Oat β‐glucan helped to increase plasma peptide Y‐Y and intestine peptide Y‐Y expression in obesity mice.     

Effect of CMC Molecular Weight on Acid‐Induced Gelation of Heated WPI‐CMC Soluble Complex

Acid‐induced gelation properties of heated whey protein isolate (WPI) and carboxymethylcellulose (CMC) soluble complex were investigated as a function of CMC molecular weight (270, 680, and 750 kDa) and concentrations (0% to 0.125%). Heated WPI‐CMC soluble complex with 6% protein was made by heating biopolymers together at pH 7.0 and 85 °C for 30 min and diluted to 5% protein before acid‐induced gelation. Acid‐induced gel formed from heated WPI‐CMC complexes exhibited increased hardness and decreased water holding capacity with increasing CMC concentrations but gel strength decreased at higher CMC content. The highest gel strength was observed with CMC 750 k at 0.05%. Gels with low CMC concentration showed homogenous microstructure which was independent of CMC molecular weight, while increasing CMC concentration led to microphase separation with higher CMC molecular weight showing more extensive phase separation. When heated WPI‐CMC complexes were prepared at 9% protein the acid gels showed improved gel hardness and water holding capacity, which was supported by the more interconnected protein network with less porosity when compared to complexes heated at 6% protein. It is concluded that protein concentration and biopolymer ratio during complex formation are the major factors affecting gel properties while the effect of CMC molecular weight was less significant.     

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.     

Extraction and Isolation of β‐Glucan from Grain Sources—A Review

A collective report on the extraction and isolation of β‐glucan from grain sources, namely, oat, barley, and wheat is presented. An analysis on the effect of medium, pH, and temperature on the purity and yield of the β‐glucan derived under acidic/alkaline/aqueous/enzymatic conditions is also made. Water extraction and alkali extraction processes are preferred as the yield and recovery of extracted β‐glucan were good. Cost‐effective development of the process for deriving high molecular weight β‐glucan is the current requirement for its wide applications in food and pharmaceutical industries.     

大豆分离蛋白对肌原纤维蛋白加热过程中结构及流变特性的影响

大豆分离蛋白（soybean protein isolate,SPI）作为优质的植物蛋白常被用于肉制品加工中,以提高产品产量和质地。研究添加SPI对肌原纤维蛋白（myofibrillar protein,MP）凝胶特性及MP加热过程中结构和流变特性的影响。结果表明：添加10%、20% SPI能提升混合凝胶的凝胶强度及保水性（P＜0.05）;加热过程中混合蛋白凝胶二级结构发生改变,但其变化规律尚不明确;添加SPI使混合凝胶储能模量及损耗模量下降;混合凝胶上清液十二烷基硫酸钠-聚丙烯酰胺凝胶电泳图谱显示,肌球蛋白重链、肌动蛋白、SPI部分亚基均是参与凝胶形成的蛋白质。     

Preparation of spent brewer's yeast β-glucans for potential applications in the food industry

A preparation of β‐glucan, obtained from spent brewer's yeast, was evaluated for potential food applications. This material was autolysed and the cell walls that were obtained were homogenized, extracted firstly with alkali, then with acid, and then spray dried. Effects of the homogenization on the chemical composition, rheological properties and functional properties of β‐glucan were investigated. Homogenized cell walls exhibited higher β‐glucan content and apparent viscosity than those which had not been homogenized because of fragmentation of the cell walls. When compared with commercial β‐glucan from baker's yeast, it was found that the β‐glucan obtained from this study had higher apparent viscosity, water‐holding capacity and emulsion stabilizing capacity, but very similar oil‐binding capacity. These findings suggest that β‐glucan obtained from brewer's yeast can be used in food products as a thickening, water‐holding, or oil‐binding agent and emulsifying stabilizer.     

Formulation of an oat‐based fermented product and its comparison with yoghurt

In an attempt to develop a fermented, non‐dairy product based on oats, a new kind of oat base, Adavena® M40, was fermented with two different yoghurt cultures. Adavena® M40 is a concentrated liquid (with a dry matter content of 16 or 18%) derived entirely from oats, with maltose as the main carbohydrate source and an intact β‐glucan content. The oat base was heat treated for 5 min at 85 °C prior to inoculation. Additives in the form of stabiliser, fat and flavours were used. Texture, syneresis, colour and sensory parameters were evaluated. Yoghurt was used as a control. The final product had an acidity and viscosity similar to those of yoghurt. Addition of xanthan gum (0.03% w/v) improved the texture and overall appearance of the product. The product had the same texture as yoghurt but showed less syneresis. The mixture was less white than the control. The oat‐based, yoghurt‐like product showed high acceptability in terms of acidity, texture and overall appearance. The addition of flavours resulted in a higher acceptance of the final products by the panellists. The β‐glucan content was still high after the fermentation process. The results indicated the potential for a new, fermentable, oat‐based product with high acceptance and a high final β‐glucan content. © 2001 Society of Chemical Industry