Starch-free fiber

Combined Steam Pretreatment and Enzymatic Hydrolysis of Starch-Free Wheat Fibers... 

Steam treatment of an industrial process stream, denoted starch-free wheat fiber, was investigated to improve the formation of monomeric sugars in subsequent enzymatic hydrolysis for further bioconversion into ethanol. The solid fraction in the process stream, derived from a combined starch and ethanol factory, was rich in arabinose (21.1%), xylose (30.1%), and glucose (18.6%), in the form of polysaccharides. Various conditions of steam pretreatment (170-220°C for 5-30 min) were evaluated, and their effect was assessed by enzymatic hydrolysis with 2 g of Celluclast + Ultraflo mixture/ 100 g of starch-free fiber (SFF) slurry at 5% dry matter (DM). The highest overall sugar yield for the combined steam pretreatment and enzymatic hydrolysis, 52 g/100 g of DM of SFF, corresponding to 74% of the theoretical, was achieved with pretreatment at 190°C for 10 min followed by enzymatic hydrolysis. 

Index Entries Wheat fibers steam pretreatment enzymatic hydrolysis starch-free fiber microwave oven. 

Nitrogen-free extract consists of material which is not protein, fat, fiber (including cellulose) or ash (mineral nutrients). Thus starch, free sugars and dextrins are the usual components. Based on Crocker and Barton, 1957 [2] and Winton and Winton, 1932 [74]... 

Rosin sizing usually involves the addition of dilute aqueous solutions or dispersions of rosin soap size and alum to a pulp slurry (44—46). Although beater addition of either coreactant is permissable, addition of both before final pulp refining is unwise because subsequently exposed ceUulose surfaces may not be properly sized. The size and alum should be added sufficiendy eady to provide uniform distribution in the slurry, and adequate time for the formation and retention of aluminum resinates, commonly referred to as size precipitate. Free rosin emulsion sizes, however, do not react to a significant degree with alum in the pulp slurry, and addition of a cationic starch or resin is recommended to maximize retention of size to fiber. Subsequent reaction with aluminum occurs principally in the machine drier sections (47). 

The pressure fed screens are connected in a manner that gives a countercurrent passage of water with respect to fiber in order to achieve high water use efficiency. Several different operating configurations for using these devices in a starch factory have been described.199-201 The number of successive units may vary with the manufacturer s goal of complete starch recovery. Typically, finished fiber contains 15-20% starch, about half free and half bound. 

Wheat starch is low in protein, ash and fiber, and contains no residual sulfites. Sulfur dioxide is detrimental to the viscoelastic character of wheat gluten and is not used in the commercial production of wheat starch.28,323 The protein content of ten samples of unmodified and modified wheat starches ranged from 0.06-0.22%.28 A 0.23% protein (0.0404% nitrogen) level in wheat starch essentially indicates a gluten-free starch, as confirmed by an enzyme immunoassay.324 That purity of wheat starch is important in diets for celiac individuals. Wheat starch-based, gluten-free flour products were not harmful in the treatment of celiac sprue and dermatitis herpetiformis,325 although traces of an immunoreactive gliadin can be found in wheat starch.326... 

After fiber extraction, a slurry containing starch, small fiber particles that were not removed during extraction and some remaining protein is obtained. The goal of the classification step is to free the starch slurry of fiber. This classification is done in a separator centrifuge. Figure 11.16 shows a schematic diagram of this type of separator. 

The introduction of polyester fibers has brought about major changes in the way we care for our clothing. Nearly all modern permanent-press fabrics owe their wrinkle-free behavior to polyester, often blended with other fibers. These polyester blends have reduced or eliminated the need for starching and ironing clothes to achieve a wrinkle-free surface that holds its shape. 

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