The combined use of hull-less barley flour and xylanase as a strategy for wheat/hull-less barley flour breads with increased arabinoxylan and (1 -> 3,1 -> 4)-beta-D-glucan levels

Bread-making with a composite flour (CF) consisting of 60% wheat flour (WF) and 40% hull-less barley flour, increased the total and soluble (1-->3,1-->4)-beta-D-glucan and total arabinoxylan (AX) contents of dough and bread samples, but decreased the specific bread loaf volume. A xylanase insensitive to inhibition by Triticum aestivum L. xylanase inhibitor (TAXI) and xylanase inhibiting protein (XIP), increased loaf volume by 8.8 and 20.1 % for WF and CF breads, respectively. Xylanase addition not only markedly improved loaf volume of CF bread, but also increased the soluble AX content of the WF and CF dough and bread samples because of conversion of water-unextractable AX into soluble AX. The xylanase had no impact on the extractability and molecular weight of (1-->3,1-->4)- beta-D-glucan, but (1-->3,1-->4)-beta-D-glucan was degraded during bread-making probably because of endogenous beta-glucanase activity. Taken together, the results clearly show that the combined use of hull-less barley flour and a xylanase active during bread making, lead to palatable breads with high total and soluble AX and (1-->3,1-->4)-beta-D-glucan contents. The sum of total AX and (1-->3,1-->4)-beta-D-glucan was 1.70% for WF bread and 3.06% for CF bread, while the sum of soluble AX and (1-->3,1-->4)-beta-D-glucan was 0.49 and 1.41% for control WF and CF xylanase supplemented breads, respectively. (C) 2004 Elsevier Ltd. All rights reserved.status: publishe

Milling performance of north European hull-less barleys and characterization of resultant millstreams

Four hull-less barley samples were milled on a Buhler MLU 202 laboratory mill and individual and combined milling fractions were characterized. The best milling performance was obtained when the samples were conditioned to 14.3% moisture. Yields were 37-48% for straight-run flour, 47-56% for shorts, and 5-8% for bran. The beta-glucan contents of the straight-run white flours were 1.6-2.1%, of which approximate to49% was water-extractable. The arabinoxylan contents were 1.2-1.5%, of which approximate to17% was water-extractable. Shorts and bran fractions contained more beta-glucan (4.2-5.8% and 3.0-4.7%, respectively) and arabinoxylan (6.1-7.7% and 8.1-11.8%, respectively) than the white flours. For those fractions, beta-glucan extractability was high (58.5 and 52.3%, respectively), whereas arabinoxylan extractability was very low (approximate to6.5 and 2.0%, respectively). The straight-run white flours had low alpha-amylase, beta-glucanase, and endoxylanase activities. The highest alpha-amylase activity was found in the shorts fractions and the highest beta-glucanase and endoxylanase activities were generally found in the bran fractions. Endoxylanase inhibitor activities were low in the white flours and highest in the shorts fractions. High flavanoid, tocopherol, and tocotrienol contents were found in bran and shorts fractions.status: publishe

Wheat Cell Wall Polysaccharides (Dietary Fibre)

Wheat is a major source of dietary fibre in the human diet, with whole grain containing about 11–15% fibre/g dry wt. However, in most countries wheat is most widely consumed after milling to give white flour, reducing the fibre content to less than 5%. The major dietary fibre components in white flour are the cell wall polysaccharides arabinoxylan and β-glucan. This chapter therefore focuses on these components, reviewing their structures and properties, biosynthesis, variation in amount and composition and genetic control. This provides a basis for increasing the content of wheat fibre and manipulating its properties to optimise the health benefits of wheat-based foods

The impact of processing on potentially beneficial wheat grain components for human health

Wheat based foods, mainly in the form of bread and pasta, are staples of the human diet in many countries around the world. The dry weight of mature wheat grain is composed of 70–75% starch and around 10–14% protein, which has led to the widespread perception of wheat foods as sources of energy and protein. However, whole grains are also important sources of dietary fiber, vitamins and minerals, and contain notable levels of bioactive compounds with potential health benefits like lignans, phenolic acids, alkylresorcinols, phytosterols, folates and tocols. The prominence of wheat grain in the human diet is largely due to its versatility in being processed into diverse products like flour, semolina, and other bakery products. Processing is a pre-requisite for using cereal grains as food and obtaining end products with various unique properties that are safe and appealing to consume. Processing may also help reduce the amount of hazardous molecules potentially present in harvested wheat, such as pesticides, mycotoxins and heavy metals. Each regulated step in a processing series influences the composition and/or the physicochemical properties of the different grain components, which in turn define the technological quality and the nutritional and health promoting properties of the end product. The unique textural properties of wheat foods are largely determined by the starch and gluten proteins present in the starchy endosperm, the main constituents of white flour and semolina. The health-promoting effects of wheat-based products are mainly associated with the dietary fiber and bioactive compounds that are enriched in the grain peripheral layers, and mainly the aleurone layer, which is generally a component of the bran fraction after milling. Fractionation by milling and the way the different milling streams are subsequently recombined therefore has a considerable impact on the relative abundance of each grain component in the wheat flour/semolina and, consequently, in end products. Further processing steps, such as dough making, microbial fermentation, extrusion, and baking can also affect the relative amounts and bioavailability of grain components. Some examples of the effects of grain processing procedures on the bioavailability of important grain components in wheat foods consumed by humans will be presented in this chapter. Suggestions of how to improve these processes in light of the implications for human health will also be discussed