In Vitro Bile Acid Binding Capacity of Milled Wheat Bran and Milled Extruded Wheat Bran at Five Specific Mechanical Energy Levels

The in vitro binding of bile acids of milled wheat bran (MWB) and milled extruded wheat bran (MEB) at five specific mechanical energy (SME) levels of 120 (MEB‐120), 177 (MEB‐177), 234 (MEB‐234), 291 (MEB‐291), and 358 (MEB‐358) Whr/kg on a fat‐free dry weight basis was determined using a mixture of bile acids secreted in human bile at duodenal physiological pH 6.3. Relative to cholestyramine (bile acid binding, cholesterol lowering drug) in vitro bile acid binding capacity on dry matter, total dietary fiber (TDF), and insoluble dietary fiber (IDF) basis was for MWB: 21, 43, 45%; the range for MEB was 18–21%, 34–41%, and 36–43%, respectively. MWB resulted in significantly higher bile acid binding than that of MEB at 120, 234, and 291 Whr/kg on a dry matter, TDF, and IDF basis. These results demonstrate the relative health‐promoting potential of MWB = MEB‐177 = MEB‐358 > MEB‐120 = MEB‐234 = MEB‐291 as indicated by the bile acid binding on a dry matter basis. Data suggest that significant improvement in health‐promoting (cholesterol‐lowering and cancer‐preventing) potential could be obtained in WB by milling (low‐cost processing) the bran to finer particle sizes and extruding (high‐cost technology). Milling WB to small particle size (weighted mean 0.508 mm) increased surface area, in addition it may have induced changes in the physical and chemical characteristics of WB or created new linkages, binding sites of the proteins, starches, and nonstarch polysaccharides, which significantly increased the bile acid binding ability of the MWB.     

Effect of water migration between arabinoxylans and gluten on baking quality of whole wheat bread detected by magnetic resonance imaging (MRI)

A new method, a magnetic resonance imaging (MRI) technique characterized by T(2) relaxation time, was developed to study the water migration mechanism between arabinoxylan (AX) gels and gluten matrix in a whole wheat dough (WWD) system prepared from whole wheat flour (WWF) of different particle sizes. The water sequestration of AX gels in wheat bran was verified by the bran fortification test. The evaluations of baking quality of whole wheat bread (WWB) made from WWF with different particle sizes were performed by using SEM, FT-IR, and RP-HPLC techniques. Results showed that the WWB made from WWF of average particle size of 96.99 μm had better baking quality than those of the breads made from WWF of two other particle sizes, 50.21 and 235.40 μm. T(2) relaxation time testing indicated that the decreased particle size of WWF increased the water absorption of AX gels, which led to water migration from the gluten network to the AX gels and resulted in inferior baking quality of WWB.     

In Vitro Bile‐Acid‐Binding of Whole vs. Pearled Wheat Grain

Health benefits of consuming whole grains are reduced risk of heart disease, stroke, and cancer. The U.S. Health and Human Services and USDA dietary guidelines recommend consumption of 6–10 oz of grain products daily and one‐half of that amount should contain whole grains. Whole grains contain vitamins, minerals, fiber, and phytonutrients. Bile‐acid‐binding capacity has been related to cholesterol lowering potential of food fractions. Lowered recirculating bile acids results in utilization of cholesterol to synthesize bile acid and reduced fat absorption. Secondary bile acids have been associated with increased risk of cancer. Bile‐acid‐binding potential has been related to lowering the risk of heart disease and that of cancer. It has been reported that bile‐acid‐binding of wheat bran is not related to its total dietary fiber (TDF) content. Whole (W) grain as well as pearled (P) hard red winter wheat (Hrw), hard white winter wheat (Hww), and durum wheat (DU) cooked grains were evaluated for in vitro, bile‐acid‐binding relative to cholestryramine (a cholesterol lowering bile‐acid‐binding drug). On dry matter basis (db) relative bile‐acid‐binding values were 7.7% WHrw; 7.5% WHww; 6.3% PHww; 6.0% PHrw; 5.5% WDU; and 5.4% PDU. On a TDF basis, binding values were 42–57% of that for cholestyramine for the whole and pearled wheat grains tested. Bile‐acid‐binding values (db) for WHrw and WHww were similar and significantly higher than those of PHww, PHrw, WDU and PDU. Similar bile‐acid‐binding of WHww to that of WHrw suggest that the red color commonly associated with whole grain may not necessarily indicate more healthful potential. Data suggest that cooked WHrw and WHww wheat have significantly higher health‐promoting potential than pearled grains. WDU or PDU wheat health‐promoting potential was similar to that of PHww or PHrw. Consumption of products containing WHrw and WHww are recommended.     

In Vitro Binding of Bile Acids by Rice Bran,Oat Bran,Wheat Bran,and Corn Bran

The in vitro bile acid binding by rice, oat, wheat, and corn brans was determined using a mixture of bile acids normally secreted in human bile at a physiological pH of 6.3. The objective of the study was to relate bile acid binding of cereal brans to health promoting properties. Three experiments were conducted testing substrates on an equal weight (dry matter) basis, an equal total dietary fiber (TDF) basis, and an equal TDF and equal fat basis. Each experiment was repeated to validate the results (for a total of six experiments). The relative in vitro bile acid binding of the cereal brans on an equal TDF basis considering cholestyramine as 100% bound was rice bran 51%, wheat bran 31%, oat bran 26%, and corn bran 5%. The data suggest that cholesterol lowering by rice bran appears to be related to bile acid binding. The primary mechanism of cholesterol lowering by oat bran may not be due to bile acid binding by soluble fiber. Bile acid binding did not appear to be proportional to the soluble fiber content of the cereal brans tested. Bile acid binding by wheat bran may contribute to cancer prevention and other healthful properties.     

In Vitro Binding of Bile Acids by Rice Bran,Oat Bran,Barley and β‐Glucan Enriched Barley

The in vitro bile acid binding by rice bran, oat bran, dehulled barley, and β‐glucan enriched barley was determined using a mixture of bile acids at a duodenal physiological pH of 6.3. Six treatments and two blank incubations were conducted testing substrates on an equal protein basis. The relative in vitro bile acid binding of the cereal brans on an equal total dietary fiber (TDF) and insoluble dietary fiber (IDF) basis considering cholestyramine as 100% bound was rice bran 45 and 49%; oat bran 23 and 30%; dehulled barley 33 and 57%; and β‐glucan enriched barley 20 and 40%, respectively. Bile acid bindings on equal protein basis for the respective cereals were 68, 26, 41, and 49%. Bile acid binding by rice bran may account to a great extent for its cholesterol‐lowering properties, while bile acid binding by oat bran suggests that the primary mechanism of cholesterol lowering by oat bran is not due to the bile acid binding by its soluble fiber. Bile acid binding was not proportional to the soluble fiber content of the cereal brans tested. Except for dehulled barley, bile acid binding for rice bran, oat bran, and β‐glucan enriched barley appear to be related to their IDF content. Highest relative bile acid binding values for rice bran and β‐glucan enriched barley were observed on an equal protein basis, whereas highest values for dehulled barley were based on IDF. Data suggest that of all four cereals tested, bile acid binding may be related to IDF or protein anionic, cationic, physical and chemical structure, composition, metabolites, or their interaction with active binding sites.     

Effect of Wheat Bran Fiber and Bran Particle Size on Fat and Fiber Digestibility and Gastrointestinal Tract Measurements in the Rat

The effect of wheat bran (AACC hard red) and bran particle size on fat and fiber digestibility and gastrointestinal tract measurements were investigated with diets containing 5.7–10.7% dietary fiber. Fifty‐six male weanling Sprague‐Dawley rats were randomly assigned to four diets containing 5% cellulose (C5); 10.5% cellulose (C10); 21.5% coarse (2 mm) wheat bran (CB); or 22.2% fine (0.5 mm) wheat bran (FB) in a sixweek study. Dietary fiber digestibilities were significantly different (P < 0.05) among treatment diets (CB > FB > C5 > C10) but there was no effect in fat digestibility among treatments. High‐fiber diets fed to rats resulted in significantly greater wet and dry fecal weights than low‐fiber diets. Bran diets resulted in significantly higher fecal moisture than cellulose diets. Cecum lengths increased significantly with bran diets compared with cellulose diets. The CB diet resulted in significantly higher stomach weights than with cellulose diets. Stomachs were heavier and cecal lengths were greater with bran diets than with cellulose diets; however, a high‐cellulose diet resulted in increased colon weight. Except for higher fiber digestibility of coarse bran, bran particle size had no significant effects. Healthful effects of wheat bran may be associated with gastrointestinal morphology and function. Fecal bulking and decreased intestinal transit time can prevent constipation and may dilute or reduce absorption of toxic or carcinogenic metabolites, thus improving gastrointestinal health and lowering the risk of tumor development and cancer.     

Effect of High‐Pressure Processing on the Features of Wheat Milling By‐products

The ability of high hydrostatic pressure processing to promote changes in both the structural properties of fiber and the interaction of fiber with water were addressed. Both coarse and fine bran from milling of common wheat were considered. Treatment‐induced morphological changes were most pronounced in fine bran, whereas treatment of coarse bran resulted in the largest change in water‐holding capacity. The significance of the process‐induced changes is discussed in terms of their practical relevance in the production of fiber‐enriched foods.     

Influence of Bran Particle Size on Bread‐Baking Quality of Whole Grain Wheat Flour and Starch Retrogradation

The influence of bran particle size on bread‐baking quality of whole grain wheat flour (WWF) and starch retrogradation was studied. Higher water absorption of dough prepared from WWF with added gluten to attain 18% protein was observed for WWFs of fine bran than those of coarse bran, whereas no significant difference in dough mixing time was detected for WWFs of varying bran particle size. The effects of bran particle size on loaf volume of WWF bread and crumb firmness during storage were more evident in hard white wheat than in hard red wheat. A greater degree of starch retrogradation in bread crumb stored for seven days at 4°C was observed in WWFs of fine bran than those of coarse bran. The gels prepared from starch–fine bran blends were harder than those prepared from starch–unground bran blends when stored for one and seven days at 4°C. Furthermore, a greater degree of starch retrogradation was observed in gelatinized starch containing fine bran than that containing unground bran after storage for seven days at 4°C. It is probable that finely ground bran takes away more water from gelatinized starch than coarsely ground bran, increasing the extent of starch retrogradation in bread and gels during storage.     

Composition and Distribution of Pentosans in Millstreams of Different Hard Spring Wheats

Six commercially grown samples of hard spring wheat were milled using a tandem Buhler laboratory mill. Individual flour streams and branny by‐products, as well as whole‐grain wheat and straight‐grade flour, were characterized in terms of total (TP), water‐extractable (WEP), and water‐unextractable (WUP) pentosans. One representative cultivar sample was analyzed for its ratio of arabinose to xylose (A/X). TP and WEP of whole grain wheat of the six samples had ranges of 5.45–7.32% and 0.62–0.90% (dm), respectively. Neither TP nor WEP of whole grain was related to ash content variation. There was significant variation in the distribution and composition of pentosans in 16 millstreams of all the wheat samples, including bran and shorts fractions; TP and WEP contents had ranges of 1.69–32.4% and 0.42–1.76% (dm), respectively. When ash contents exceeded ≈0.6% (dm), strong positive correlations were obtained between ash and TP contents, and between ash and WUP contents for all the millstreams. Among bran and shorts fractions, TP and WUP content increased in the order of coarse bran > fine bran > shorts; while WEP, WEP/WUP and A/X showed the opposite pattern of variation of shorts > fine bran > coarse bran. Bran and shorts fractions had pentosan contents several times higher than would be predicted from the relationship between pentosan and ash contents of the flour streams. Pentosans therefore represented a much more sensitive marker of flour refinement compared with ash content. Pentosans of endosperm were substantially different in their extractability and composition from those of bran. On this basis, different functionalities of pentosans of bran and endosperm would be expected. Results demonstrated the importance of milling extraction and millstream blending in the functionality and quality of wheat flour for breadmaking.     

Bran Characteristics and Bread‐Baking Quality of Whole Grain Wheat Flour

Variations in physical and compositional bran characteristics among different sources and classes of wheat and their association with bread‐baking quality of whole grain wheat flour (WWF) were investigated with bran obtained from Quadrumat milling of 12 U.S. wheat varieties and Bühler milling of six Korean wheat varieties. Bran was characterized for composition including protein, fat, ash, dietary fiber, phenolics, and phytate. U.S. soft and club wheat brans were lower in insoluble dietary fiber (IDF) and phytate content (40.7–44.7% and 10.3–17.1 mg of phytate/g of bran, respectively) compared with U.S. hard wheat bran (46.0–51.3% and 16.5–22.2 mg of phytate/g of bran, respectively). Bran of various wheat varieties was blended with a hard red spring wheat flour at a ratio of 1:4 to prepare WWFs for determination of dough properties and bread‐baking quality. WWFs with U.S. hard wheat bran generally exhibited higher dough water absorption and longer dough mixing time, and they produced smaller loaf volume of bread than WWFs of U.S. soft and club wheat bran. WWFs of two U.S. hard wheat varieties (ID3735 and Scarlet) produced much smaller loaves of bread (<573 mL) than those of other U.S. hard wheat varieties (>625 mL). IDF content, phytate content, and water retention capacity of bran exhibited significant relationships with loaf volume of WWF bread, whereas no relationship was observed between protein content of bran and loaf volume of bread. It appears that U.S. soft and club wheat bran, probably owing to relatively low IDF and phytate contents, has smaller negative effects on mixing properties of WWF dough and loaf volume of bread than U.S. hard wheat bran.     

Influence of straw size on activity and biomass of soil microorganisms during decomposition

This study relates to the pattern of activity and biomass of soil microorganisms due to varying residue particle sizes during incubation. Wheat straw (8 t ha^–1) of different sizes (powdered, 0.9 cm, 1.8 cm, 2.9 cm and 4.4 cm) was incubated for 90 days at 50% water holding capacity in a loamy sand soil of Typic Camborthid. Dehydrogenase activity, an indicator of the total microbial activity, and microbial biomass were influenced by straw sizes during incubation. The peak dehydrogenase activity was recorded 21 days after incorporation of residue and it was highest in the powdered straw and decreased with increase in the straw length. The maximum biomass C build up was observed between 15 (< 1 cm) and 45 (> 1 cm) days after incorporation. The C:N ratio in the soil after 90 days of residue incorporation varied, with increase in straw size, between 12.1:1 and 20.8:1. The results reveal that for faster decomposition the length of the wheat straw should not exceed 1 cm.     

Significance of Wheat Flour Particle Size on Sponge Cake Baking Quality

We evaluated the effect and magnitude of flour particle size on sponge cake (SC) baking quality. Two different sets of wheat flours, including flours of reduced particle size obtained by regrinding and flour fractions of different particle size separated by sieving, were tested for batter properties and SC baking quality. The proportion of small particles (<55 μm) of flour was increased by 11.6–26.9% by regrinding. Despite the increased sodium carbonate solvent retention capacity, which was probably a result of the increased starch damage and particle size reduction, reground flour exhibited little change in density and viscosity of flour‐water batter and produced SC of improved volume by 0.8–15.0%. The volume of SC baked from flour fractions of small (<55 μm), intermediate (55–88 μm), and large (>88 μm) particles of soft and club wheat was in the range of 1,353–1,450, 1,040–1,195, and 955–1,130 mL, respectively. Even with comparable or higher protein content, flour fractions of intermediate particle size produced larger volume of SC than flour fractions of large particle size. The flour fractions of small particle size in soft white and club wheat exhibited lower flour‐water batter density (102.6–105.9 g/100 mL) than did those of large and intermediate particle fractions (105.2–108.2 g/100 mL). The viscosity of flour‐water batter was lowest in flour fractions of small particle size, higher in intermediate particles, and highest in large particles. Flour particle size exerted a considerable influence on batter density and viscosity and subsequently on SC volume and crumb structure. Fine particle size of flour overpowered the negative effects of elevated starch damage, water absorption, and protein content in SC baking.     

麦麸结构层粉体的电特性研究

为了确定麦麸结构层粉体静电场分离的可行性,该文以高纯度麦麸糊粉层和外果皮粉体为原料,研究其介电性、导电性和电晕带电特性的差异。结果表明,麦麸粉体的介电常数随频率的增加而降低,最终趋于一致;当频率较低时,外果皮的相对介电常数明显低于糊粉层;当频率为300 MHz时,两者的介电常数之比最大达5.3;麦麸粉体的导电性差,糊粉层粉体的电阻率为2300MΩ/cm,为外果皮电阻率的5倍;经正电晕带电后,糊粉层粉体所获电荷量约为外果皮的1.7倍,具有明显差异;单位质量麦麸粉体所获电荷量随电晕电压的增加而增加,而随麦麸粉体的含水率和粒径的增大而减小。总之,麦麸结构层粉体的介电性、导电性和电晕带电性均存在明显差异,可以利用介电泳和电晕带电后的静电场分离技术对麦麸结构层进行分离纯化。     

Phenolic Content and Antioxidant Activity of Pearled Wheat and Roller‐Milled Fractions

Wheat contains phenolic compounds concentrated mainly in bran tissues. This study examined the distribution of phenolics and antioxidant activities in wheat fractions derived from pearling and roller milling. Debranning (pearling) of wheat before milling is becoming increasingly accepted by the milling industry as a means of improving wheat rollermilling performance, making it of interest to determine the concentration of ferulic acid at various degrees of pearling. Eight cultivar samples were used, including five genotypes representing four commercial Canadian wheat classes with different intrinsic qualities. Wheat was pearled incrementally to obtain five fractions, each representing an amount of product equivalent to 5% of initial sample weight. Wheat was also roller milled without debranning. Total phenolic content of fractions was determined using the modified Folin‐Ciocalteau method for all pearling fractions, and for bran, shorts, bran flour, and first middlings flour from roller milling. Antioxidant activity was determined on phenolic extracts by a method involving the use of the free radical 2,2‐diphenyl‐l‐picrylhydrazyl (DPPH). Total phenolics were concentrated in fractions from the first and second pearlings (>4,000 mg/kg). Wheat fractions from the third and fourth pearlings still contained high phenolic content (>3,000 mg/kg). A similar trend was observed in antioxidant activity of the milled fractions with ≈4,000 mg/kg in bran and shorts, ≈3,000 mg/kg in bran flour, and <1,000 mg/kg in first middlings flour. Total phenolic content and antioxidant activity were highly correlated (R² = 0.94). There were no significant differences between red and white wheat samples. A strong influence of environment (growing location) was indicated. Pearling represents an effective technique to obtain wheat bran fractions enriched in phenolics and antioxidants, thereby maximizing health benefits associated with wheat‐based products.     

Antioxidant Capacity of Water‐Extractable Arabinoxylan from Commercial Barley,Wheat, and Wheat Fractions

The objective of this research was to analyze the antioxidant capacity directly of water‐extractable nonstarch polysaccharides (NSP) and feruloylated arabinoxylans (WEAX) following their characterization. NSP were isolated from barley, wheat, and wheat fractions (germ, bran, and aleurone). WEAX were extracted only from wheat fractions. Antioxidant capacity of NSP measured with the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid (ABTS), and oxygen radical absorbance capacity (ORAC) assays was 24.0–99.0, 40.0–122.0, and 140.0–286.0μM Trolox equivalents (TE)/g, respectively. The antioxidant capacity of WEAX was 75.7–84.0, 58.0–105.0, and 110.0–235.0μM TE/g for those three assays. DPPH and ABTS were highly correlated to xylose content (R² = 0.85), degree of substitution (R² = −0.99), total phenolic acids (R² = >0.73), total phenolic content (TPC) (R² = >0.78), and ferulic acid content (R² = >0.86). ORAC was only influenced by TPC (R² = 0.63). By taking yield and antioxidant capacity into account, NSP would provide about 0.4–4.2, 0.6–5.1, and 2.8–12.0μM TE/g of flour of radical scavenging activity as measured by DPPH, ABTS, and ORAC, respectively, compared with WEAX (0.4–1.0, 0.3–1.3, and 0.6–2.8μM TE/g). Our results suggest that NSP or WEAX may play a role in protection against free radicals in a food matrix and likely in the gastrointestinal tract.     

超微粉碎对青稞麸皮粉微观结构及功能特性的影响

为研究超微粉碎对青稞麸皮表观结构及物化特性的影响,探究青稞麸皮超微粉作为食品辅料的可行性。该研究以青稞麸皮为原料,通过气流超微粉碎处理得到青稞麸皮微粉,并比较青稞麸皮粗粉与微粉的微观结构及功能特性。结果表明,青稞麸皮粗粉经超微粉碎20、40 min后获得了平均粒径为72.52和22.69μm的粉体。随着粉体粒径的减小,粉体更加细腻,分布更均匀,色泽更白亮;且对青稞麸皮的营养成分有较好的保留;但超微粉碎并未对粉体的微观结构产生较大影响。与青稞麸皮粗粉相比,2种微粉的休止角与滑角均变大;水溶性增加,持水力和持油力减小,膨胀力和振实密度、堆积密度显著降低(P<0.05);对阳离子交换能力减小,但胆酸盐的吸附能力增强;显著(P<0.05)增加了青稞麸皮微粉的峰值黏度、谷值黏度、最终黏度、崩解值,降低了其回生值;青稞麸皮微粉(平均粒径72.52μm)的膨胀力、持水力、持油力、阳离子交换能力、胆酸盐吸附能力均优于微粉(平均粒径22.69μm)。研究为青稞麸皮的深加工利用提供一定的理论依据。     

Influence of Added Enzymes and Bran Particle Size on Bread Quality and Iron Availability

The aim of this investigation was to study the influence of different bran proportions and particle sizes, addition of fungal phytase, and α‐amylase addition on bread quality and phytate levels, and how these treatments affect availability of iron to intestinal epithelial (Caco‐2) cells. Potential mineral contributions to dietary reference intakes and phytate‐to‐mineral molar ratios were also evaluated. Wheat bran supplementation significantly affected bread quality. Smaller bran particle size affected crumb firmness negatively, whereas the use of α‐amylase, in some cases in combination with phytase, could improve technological bread quality. The use of phytase in the formulation significantly reduced the level of phytates, and phytate hydrolysis also led to smaller bran particle size. Increasing the bran proportion used in the bread formulation increased the iron concentration in bread samples by 18.9%. Phytase addition proved to be a useful strategy to improve iron dialyzability; however, incomplete dephytinization still had an inhibitory effect on iron uptake, with the exception of samples formulated with 10% bran. The inhibitory effect of phytate could be predicted from the values of the phytate‐to‐iron ratios. Reduction of particle size did not improve iron availability or uptake by Caco‐2 cells.     

Sequential Acid,Alkaline, and Enzymatic Modifications of Chickpea and Lentil Flours Impacted Batter Physical Properties

The effect of sequential acid, alkaline, and enzymatic treatment of chickpea and lentil flours on batter rheological properties was investigated. Substitution of wheat with disrupted chickpea and lentil flours significantly (P < 0.05) increased water‐holding capacity from 66.8% in wheat flour to more than 70.0% based on the disruption treatment, indicating an improved adhesion of coated batter. Flow behavior index of batter treatments of partially replaced wheat flour with various ratios of disrupted chickpea and lentil flours ranged from 0.88 to 1.36 and was significantly (P < 0.05) lower than the flour (i.e., 2.15) and nondisrupted control (i.e., 1.28–1.38 for chickpea and 1.22–1.28 for lentil) flours. Consistency coefficients of disrupted chickpea and lentil flours were significantly (P < 0.05) greater when replacing wheat control, indicating a best fit for the shear‐thickening model. Flour disruption decreased the treatment's pasting properties, except the setback, providing support for the significant role of proteins in dictating the pasting characteristics of batter flour treatments. Results of this study suggested a potential use for treated chickpea and lentil flours in enhancing batter rheological properties including adhesion and water‐holding capacity.     

Formation of phenolic microbial metabolites and short-chain Fatty acids from rye, wheat, and oat bran and their fractions in the metabolical in vitro colon model

Rye bran and aleurone, wheat bran and aleurone, and oat bran and cell wall concentrate were compared in their in vitro gut fermentation patterns of individual phenolic acids and short-chain fatty acids, preceded by enzymatic in vitro digestion mimicking small intestinal events. The formation of phenolic metabolites was the most pronounced from the wheat aleurone fraction. Phenylpropionic acids, presumably derived from ferulic acid (FA), were the major phenyl metabolites formed from all bran preparations. The processed rye, wheat, and oat bran fractions contained more water-extractable dietary fiber (DF) and had smaller particle sizes and were thus more easily fermentable than the corresponding brans. Rye aleurone and bran had the highest fermentation rate and extent probably due to high fructan and water-extractable arabinoxylan content. Oat samples also had a high content of water-extractable DF, β-glucan, but their fermentation rate was lower. Enzymatic digestion prior to in vitro colon fermentation changed the structure of oat cell walls as visualized by microscopy and increased the particle size, which is suggested to have retarded the fermentability of oat samples. Wheat bran was the most slowly fermentable among the studied samples, presumably due to the high proportion of water-unextractable DF. The in vitro digestion reduced the fructan content of wheat samples, thus also decreasing their fermentability. Among the studied short-chain fatty acids, acetate dominated the profiles. The highest and lowest production of propionate was from the oat and wheat samples, respectively. Interestingly, wheat aleurone generated similar amounts of butyrate as the rye fractions even without rapid gas production.     

Calcium-binding capacities of different brans under simulated gastrointestinal pH conditions. In vitro study with (45)Ca

The present study was performed to investigate calcium-binding characteristics of different brans under simulated gastrointestinal pH conditions and to explore the significance of dietary fiber, oxalate, and phytate for calcium binding. Different brans (rice, rye, soy, fine wheat, coarse wheat, and oat) and CaCl(2) solution containing (45)Ca were incubated at 37 degrees C at gastric pH (2.2) followed by buffering steps of 1 degree from pH 3.0 to pH 8.0. Total calcium binding and calcium-binding capacity of the pH 2.2 soluble bran fraction were determined. Additionally, oxalate and phytate contents of brans and solubility profiles of phytic acid were investigated. Calcium-binding capacities of brans showed a clear pH dependence. At gastric pH calcium binding was low in all brans, ranging from 0.022 to 0.040 mmol of calcium/g of bran. Soy bran, nearly phytate-free, showed higher binding values up to pH 4.0 and lower values between pH 5.0 and 8.0. In all other brans, binding values increased strongly with increasing pH in the quantitative order rice bran > coarse wheat bran > fine wheat bran > rye bran > oat bran. The solubility profiles indicate that in the cases of rye, wheat, and rice bran phytate accounts for 70-82% of their total calcium-binding capacities. The results suggest that dietary fiber makes no important contribution to calcium binding, except for soy and oat brans. Oxalate plays only a minor role in calcium binding by brans.