Wheat pentosan

Didehydroferulic Acid 23 Formation. It should be noted that no direct evidence has ever been obtained in vivo to prove that didehydroferulic acid 23 is formed via free radical coupling reactions. This mechanism is assumed, since in vitro incubation of ferulic acid 1 and wheat pentosan, with... 

In certain examples where the Smith-degradation fragments have been separated more conveniently by paper chromatography, the structure of these fragments has been demonstrated by examining their methylation products by gas-liquid chromatography. This approach has been used in studying the fine structure of lichenan,644 isolichenan,645 and wheat pentosan.848... 

Wheat pentosans were dehydrated to furfural with concentrated HC1, and the furfural was dissolved in dibutyl ether in preparation for GC (Folkes, 1980). This method is claimed to be specific, accurate, and precise for pentoses and pentosans (Folkes, 1980), because 5-hydroxymethylfurfural is not produced, as is the case in hexose decomposition. Previously, furfural was distilled and analyzed colorimetrically. Alkalization increases the yield of 1-, 2-, and 3-carbon, vapor-phase compounds at the expense of anhydro sugars and furans (Ponder and Richards, 1993). Hydrolysis-GC is adaptable to the estimation of DP (Morrison, 1975) applicability to carbohydrates is limited to oligomers with DP = 6 (Traitler et al., 1984). 

Certain cereal grains, especiaUy wheat and rye, contain hemicelluloselike arabinoxylans [9040-27-1], commonly caUed pentosans. Wheat flour pentosans are divided into two types water-soluble and water-insoluble arabinoxylans, which respectively constitute - 1.1 1.6% and 0.4—0.7% of the total flour. These polysaccharides have functional roles in dough development and baking performance. The water-soluble wheat-flour arabinoxylans consist of a (1 — 4)-linked chain of P-D-xylopyranosyl units substituted at 0-2 and/or 0-3 with single-unit a-L-arabinofuranosyl units. Preparations from each source consist of a family of molecules of various molecular weights and xyl ara ratios. 

The minor content of impurities found ia the starch slurry are connected to the starch granules themselves. To faciUtate the purification of the starch duriag filtration, ceUulases, pentosanases, glucanases, proteases, and pectinases are sometimes used. Wheat starch is known to form precipitates or hazes that are difficult to filter. Arabiaoxylan, pentosanes, andlysophosphoHpids are claimed to be responsible for this problem (73). 

Dried Gluten. This material is sold as vital wheat gluten, it is produced by a scaled up version of the process for producing wet gluten for flour testing. A flour and water dough is made and then washed to remove the starch, the soluble proteins and the pentosan-based gum fraction. This latter fraction is an example of a non-starch carbohydrate. 

Rye Proteins. While rye is the only European cereal able to completely replace wheat in bread, rye protein is not as effective as wheat protein. One reason for this is that as much as 80% of the protein in a rye sour dough is soluble compared with 10% of soluble protein in a wheat dough. One factor that inhibits the formation of a gluten-like complex is the 4-7% of pentosans present, which bind water and raise the viscosity of the dough. The crumb structure is then formed from the pentosans in combination with the starch. 

Pentosans. These compounds are polysaccharides which may he considered as anhydrides of pentose sugars, after the manner of the hexosans. sucrose, starch, from glucose, fructose. When pentosans or pentoses are heated with hydrochloric ot sulfuric acid, furfural C fljO CHO is formed, and addition of aniline produces a red color. Pentosans are present in gummy carbohydrates, in bran of wheat seed, and in woods. 

Labat, E., Morel, M.H., Rouau, X. 2001. Effect of laccase and manganese peroxidase on wheat gluten and pentosans during mixing. Food Hydrocoil 15(1)47-52. 

All wheat starches give the same A-type crystal pattern, but their degree of crystallinity is inversely proportional to amylose content. In addition, the intensity of one reflection of an amylose-lipid complex at 2 20-23° (d 4.4A) increases proportionally to the amylose level.265,271,281,284,289 The lipid content of waxy wheat starch is much lower (0.02-0.17%) than that in non-waxy wheat starch (0.6-0.7%).286,291 However, the crude fat content of waxy wheat flour is elevated by 20-40% (3-glucan and pentosan are increased by 30%.291,292 The degree of crystallinity of waxy wheat starch is reported to be 18-21% versus 13-16% for the wild type.284,289 Increases of 35% for waxy wheat starch, 23-28% for double nulls, 20-23% for single nulls and 22% for the wild type have also been reported.271... 

The industrial use of rye starch is limited. Industrial production of rye starch was carried out during World War II, but as soon as the supply of wheat, maize and potato starches returned to normal production ceased.2 Rye flour is a difficult raw material from which to isolate starch, because of its high pentosan content and the poor gluten-forming ability of the proteins. It has, therefore, been suggested that the whole rye kernel, and not the isolated starch, should be used in industrial applications (e.g. production of insulating and plastic material).3 Rye is also a problematic raw material because of the variation in the climatic conditions in northeastern Europe,... 

Beet pectin and wheat-flour pentosans undergo an oxidative gelation (Neukom, 1976 Neukom and Markwalder, 1978) instigated by ferulic acid peroxidase through diferulic acid crosslinking. Crowe (1989) and Thibault et al. (1991) effected the same crosslinking with persulfate and chlorine, respectively. 

Crowe, N. L. (1989). Effect of chlorine compounds and other oxidants on the oxidative gelation and cake baking properties of wheat flour pentosans. Diss. Abstr. Int. B. 50 13. 

Neukom, H., and Markwalder, H. U. (1978). Oxidative gelation of wheat flour pentosans a new way of cross-linking polymers. Cereal Foods World 23 374-376. 

Another component of flour, the pentosans, have a very high capacity to bind water. Pentosans are present in wheat to about 4-5% and in patent wheat flour to about 2.5-3%. Pentosans contribute to about one quarter of the adsorption of dough water which is disproportionately more than the starch or protein fractions. Pentosans can absorb about 6.5 times their weight of water. A significant anti-staling effect has been claimed by the addition of pentosanase to bread (17-18). 

B. H. Howard, Hydrolysis of the soluble pentosans of wheat flour and Rhodymenia palmata by ruminal micro-organisms, Biochem. J., 67 (1957) 643—651. 

The main factors to bind liquids and/or to influence the consistency of the dough are wheat glutens, pentosanes and mechanically damaged starch (through the grinding process of the com) or hydrocolloids (for example thickeners). 

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