Glucans in cereals

Basic Protocol Analysis of P-Glucan in Cereal Flours and P-Glucan Concentrates E3.5.1... 

Alternate Protocol 3 Determination of P-Glucan in Cereal Bars E3.5.7... 

ANALYSIS OF P-GLUCAN IN CEREAL FLOURS AND p-GLUCAN CONCENTRATES... 

The scientific interest in cereal /1-glucans arose partly from the problems they cause in brewing and animal-feed industries in the case of barley [318] and partly from the health benefits, such as cholesterol reduction [319-321], regulation of postgrandial seriun glucose levels in humans and animals [319,322], and immunostimulatory activity [323,324]. Some of these activities have been observed with both oat and barley )6-glucans [325]. 

Starch is a homopolymer of glucose forming an a-glucosidic chain, called a glucosan or glucan. It is the most abundant dietary carbohydrate in cereals, pota-... 

Lehtonen, M., and R. Aikasalo. Beta-glucan in two-and six-rowed barley. Cereal Chem 1987 64(3) 191-193. Argandona, V. H., G. E. Zuniga, and L. ]. Corcuera. Distribution of gramine and hydroxamic acids and wheat leaves. Phytochemistry 1987 26(7) 1917-1918. 

Glucan in dry pasta products can be determined using the Basic Protocol. Since pasta particles tend to be firmer than other cereal products, cooking time may be extended if necessary (up to 15 min see Basic Protocol, step 6). Fresh pasta products require additional sample preparation steps. It can be analyzed in either pureed or dried form. In ready-to-eat meals, P-glucan may be incorporated into a side dish such as pasta or pot barley. Because it will most likely be mixed with a sauce, which will interfere with P-glucan determination, the pasta must be washed prior to analysis. 

AACC (American Association of Cereal Chemists) 1995. Approved Methods of the American Association of Cereal Chemists. Method 32-23 Measurement of (3-Glucan in Barley and Oats— Rapid Enzymatic Procedure. AACC, St. Paul, Minn. 

Figure 3. Section of cooked rolled oat sample fixed in 3% glutaraldehyde, dehydrated and embedded in glycolmethacrylate. The stain is Calcofluor which is specific for P-Glucans in cell walls of cereals. Epifluorescence optics, (x 200).[From 26]...

The seeds of oats [Avena sativa) have been studied by Dr. Percival and shown to have 85% of their IAA esterified to a glucoprotein (28). The glucan is of the lichenan type having both 61-9-3 and 6l- -4 linkages. Recently, Ms. P. Hall in our laboratory (personal communication) has isolated IAA-myo-inositol from rice [Oryza sativa) thus showing the compound originated early in cereal evolution. 

Amyloses of five commercially important starches (wheat, corn, rice, tapioca and potato) were purified by fractional crystallization of their amylose-alcohol complexes and shown to be free of amylopectin.111,205 All five amyloses showed comparable iodine affinity, blue value and max of their polyiodide complexes (Table 10.5), which is consistent with their being (1 —4)-linked a-glucans with an average DPn of —500 or above.206 The average size of amylose molecules in cereal starches is smaller than... 

The noncellulose (1-n-glucans in hemicellulose are generally 1,3- and 1,4-bonded arabinans, xylans, arabinoxylans, arabinogalactans, etc. Their aqueous dispersions are quite viscous to the detriment of filters used to clarify cereal-based fermented beverages. Oat (3-glucans are Theologically... 

It is not always clear whether cell-wall polysaccharides have a structural or reserve function because some, for example, the /3-glucans of cereal grains, may have dual roles. However, it is likely that the /3-glucans and other hemicelluloses in cell walls of tissues other than those in... 

The various soluble starch synthetases extend ot-(l->4)-glucans, starting from chain lengths of various sizes. SSI, for example, appears to have an extended starch-binding-domain at the C-terminus and transfer glucose residues up to a chain length of about 10. The three other soluble starch synthetases found in cereals (SSIIa, SSIIb and SSIII) appear to make longer chains between clusters there is a possibility that branches may have to be introduced before some of them operate. 

Amylose is a linear a-D-(l—s-4)-glucan (4-136), and, therefore, is actually a polymer of the disaccharide maltose. To a limited extent, branching occurs at about ten sites of the molecule. Amylose is partially esterified with phosphoric acid (wheat starch contains 0.055% and potato starch 0.07-0.09% of phosphorus) and in cereal starches forms complexes with lipids. An amylose molecule has one reducing monosaccharide residue. 

The basic raw materials for the production of beer are sweet worts formed by en2ymatic hydrolysis of cereal starches. The principal cereal is barley which, after malting, is also the source of en2ymes that hydroly2e starches, glucans, and proteins. In some countries, eg, Germany, the mash biH consists... 

The technological troubles of barley j0-glucan and the health benefits of cereal j0-glucans result, in general, from their ability to form highly viscous solutions and gels. The gel formation is controlled by the molecular weight as well as the solubility of the polysaccharides in aqueous media, which... 

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