Wheat bran

Fibers and Fiber Sources. Fibers are present ia varyiag amounts ia food iagredients and are also added separately (see Dietary fiber). Some fibers, including beet pulp, apple pomace, citms pulp, wheat bran, com bran, and celluloses are added to improve droppiags (feces) form by providing a matrix that absorbs water. Some calorie-controUed foods iaclude fibers, such as peanut hulls, to provide gastroiatestinal bulk and reduce food iatake. Peanut hulls normally have a high level of aflatoxias. They must be assayed for aflatoxia and levels restricted to prevent food rejection and undesirable effects of mycotoxias. 

Nicotinic acid is found in plants associated with both peptides and polysaccharides. For example in wheat bran, two forms are described a peptide with a molecular weight of approximately 12,000 and a carbohydrate complex that is called niacytin. Polysaccharides isolated from wheat bran have been found to contain 1.05% nicotinic acid in bound form. Hydrolysis yielded a fragment identified as P-3-O-nicotinoyl-D-glucose (25). 

The American Association of Cereal Chemists has made avaUable a certified food grade wheat bran as a reference standard for research purposes. This bran is a blend of soft white wheat (87.3%) and club white wheat (12.7%). 

Triticum vulgere Wheat bran phenol 5-nonadecylresorcinol N.W. Australia... 

K+ 150 g 2g Principal cation within cell fluid Fruits, nuts, fish, instant coffee, wheat bran... 

A recent study on wheat bran GAX [34] revealed the presence of lowly and highly substituted GAX fractions, which greatly differ in the amount and type of substitution by the Ara/ imits, but not in the content of the glucuronic acid, half of which occurs as the 4-0-methyl ether. Feruloylated GAX fractions were isolated from wheat bran by cold water, steam and dilute alkah [35]. The yields of water and steam-extracted material were 1.5 and 20-31%, respectively, however, they contained 1.5% and 19-28%, respectively, of GAX. The alkah extraction yielded 10-30% material containing more than 90% of the GAX with moderate FA content. 

Potential resources of xylans are by-products produced in forestry and the pulp and paper industries (forest chips, wood meal and shavings), where GX and AGX comprise 25-35% of the biomass as well as annual crops (straw, stalks, husk, hulls, bran, etc.), which consist of 25-50% AX, AGX, GAX, and CHX [4]. New results were reported for xylans isolated from flax fiber [16,68], abaca fiber [69], wheat straw [70,71], sugar beet pulp [21,72], sugarcane bagasse [73], rice straw [74], wheat bran [35,75], and jute bast fiber [18]. Recently, about 39% hemicelluloses were extracted from vetiver grasses [76]. 

From recent literature it is known that the disintegration of lignified cell walls can be achieved by steam explosion treatments resulting in solubilization of partially depolymerized hemicelluloses [91,92]. The application of this method on wheat bran yielded feruloylated GAX with different feruUc acid content [93]. Partly depolymerized water-soluble, acetylated AGX was obtained from spruce wood by employing microwave treatment [94]. 

Interactions with xanthan were investigated for some GAX fractions of wheat bran [109]. Whereas, for lowly substituted GaMs a synergy in viscosity was observed at low total polymer concentrations, yielding a maximum of the relative viscosity at nearly equal proportions of both polysaccharides [124], the xanthan/xylan mixtures at the same experimental conditions showed no synergy. The observed decrease in the relative viscosity values upon addition of the xylan indicates that a certain interaction with xanthan takes place, but that it leads to a contraction in the hydrodynamic volume. The authors suggested that structural and conformational differences between GaM and GAX might be the reason for this observation. 

Table 17.5 Comparison of phytonutrients and antioxidants of rice bran with com bran, oat bran and wheat bran...

Nutrients (values/100 g) Rice bran Com bran Oat bran Wheat bran... 

TOMLIN J, READ N w (1988) Comparison of the effects on colonic function caused by feeding rice bran and wheat bran. Eur J Clin Nutr, 42(10) 857-61. 

TOPPING D L, ILLMAN R J, ROACH P D, TRIMBLE R P, KAMBOURIS A, NESTED P J (1990) Modulation of hypolipidemic effect of fish oil by dietary fiber in rats studies with rice bran and wheat bran. JNutr, 120(4) 325-30. 

Extrusion-cooking of cell-wall rich products (e.g. wheat bran, apple pomace, citrus peels, sugar-beet pulp, pea hulls.) led to an important solubilisation of polysaccharides of various types without extensive degradation of the polymeric structure. The possibility of obtaining gelled systems directly with the extruded pectin-rich materials was demonstrated. 

Analysis of the products which become water-soluble after extrusioncooking showed that feroylated heteroxylans and glucans were solubilised from wheat bran (10), arabinans, heteroxyalans and pectins from pea hulls (11,12), and pectins from the other sources (13,14). 

Microorganism and cultivation conditions Rhizopus sp. 26R criltivated in 20 g solid substrates composed of wheat bran, rice bran and rice husk (6 12 2) in a plastic bags. Initial pH and moisture content were 5.7 and 58%, respectively. The fungus was incubated at 32°C for 6 days. 

Portions (50 mU MCA-hydrolsing activity) of purified CinnAE were incubated at 37°C with SBP (10 mg), both in the presence and absence of other carbohydrases, in 100 mM MOPS (pH 6.0) in a final volume of 1 mL. Incubations containing boiled enzyme were performed as controls. Reactions were terminated by boiling (3 min) and the amount of free ferulic acid determined using a method described previously for de-starched wheat bran [18]. The total amount of alkali-extractable ferulic acid present in the SBP was 0.87% [5]. 

When Rhizopus sp. 26R was cultivated in the solid substrates without addition of rice bran but composed of only wheat bran and rice husk at the ratio of 18 2. The pectinase activity from the culture was approx. 25-35 unit/ml within 2 days and the production remained constant for 4 days (Figure 3). One gram of raw starch from cassava tuber, 1 g of pectin or 0.5 g of yeast extract was added to the solid substrates in order to induce higher activity of the enzsrme. The results showed that either 1 g raw cassava starch or 1 g pectin that was added to the 20 g solid substrates increased the enzyme activity to 1.7 and 2.4 times, respectively (Figure 3). The production of pectinase in soHd substrates with wheat bran and rice husk could be enhanced with the addition of raw cassava starch and pectin. 

Figure 3 Pectinase activity in 20 g of solid substrates composting of wheat bran, rice bran and rice husk (18 0 2) with the addition of 1 g raw starch from cassava tuber, 1 g pectin or 0.5 g yeast extract.

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