Wheat pentosan content

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,... 

The pentosan content of cereals varies. Rye flour is exceptionally rich (6-8%) in comparison to wheat flour (1.5-2.5%). A portion of pentosans, 25-33% in wheat and 15-25% in rye, is water-soluble. 

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). 

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... 

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