Effect of Oat Hull Fiber on Human Colonic Function and Serum Lipids

Oat hull fiber is an insoluble source of dietary fiber, derived from the outermost layer of the oat grain. The effect of oat hull fiber on colonic function and serum lipids was investigated by conducting a controlled study on 10 healthy males, aged 20–37, who ate, for two three-week periods, a controlled low fiber diet (13.1 g of nonstarch polysaccharide [NSP]/day), and the same diet with 25 g of oat hull fiber per day incorporated into foods, providing 17 g of NSP/day. Fecal weight increased from 113 ± 10.4 to 155 ± 10.8 g/day (P < 0.001) with no change in transit time or serum lipids. Fermentation of oat hull fiber was studied by analysis of feces for NSP. Excretion of NSP increased from 2.0 g/day excreted to 19.7 g/day, indicating that no degradation had occurred. Oat hull fiber is therefore resistant to fermentation in the human colon, has no effect on serum lipids, and provides no energy to the body     

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.     

Solution Viscoelastic Properties of OATRIM-10 and Cooked Oat Bran

The solution rheological behaviors of OATRIM-10 and cooked oat bran were investigated. The rheological properties of the materials were investigated using both thixotropic loop and small-amplitude oscillatory shear experiments. The cooked oat bran exhibited shear-thinning behavior during a thixotropic loop experiment over a shear rate range of 0–250/sec. The shear-thinning behavior was reproduced during the measurement of a second thixotropic loop. In contrast, OATRIM-10 exhibited an unexpected region of shear-thickening behavior at 20–80/sec. The shear-thickening and subsequent shear-thinning regions for OATRIM-10 could be described by a transient network model indicating that the shear-thickening behavior is caused by a shear-induced entangled network that is partially disentangled at higher shear rates. Subsequent thixotropic loop experiments displayed the shear-thickening region for OATRIM-10, indicating that the network structure can be reformed during the imposition of a shear field. Small-amplitude oscillatory shear data for cooked oat bran can be described reasonably well using a generalized linear viscoelastic (GLV) model. The oscillatory shear data obtained for OATRIM-10 could not be described by the GLV model. OATRIM-10 exhibited a distinctive plateau centered at 10/sec, and the low frequency response of storage modulus G′ decreased with a much larger slope in frequency than was predicted by the GLV model.     

Accumulation of Oxygenated Fatty Acids in Oat Lipids During Storage

Oxygenated fatty acids were identified in oat grain by gas chromatography‐mass spectrometry. We hypothesized that most of these were the results of lipoxygenase activity. This hypothesis was tested by measuring concentrations of these compounds after hydrothermal treatments and storage of oat groats or oat flour for 22 weeks at 37°C and 65% relative humidity. Steam treatments inactivated lipases, whereas roasting at 106°C did not. Free fatty acids accumulated quickly in untreated or roasted flour, but not in steamed flour or groats. A total of six hydroxy and epoxy fatty acids were identified. Oxidized fatty acids were found in both esterified lipids and free fatty acids, indicating that lipase action was not necessary for lipid oxidation. More oxidation products were found in flour than in groats, and less were found in the steamed treatments. Lipoperoxygenase appeared to be involved in the formation of oxidation products, although nonenzymatic mechanisms may also operate. Hydroxy‐fatty acids are associated with strongly bitter flavors and are undesirable. Results indicate the importance of enzyme inactivation before storage of processed oat products.     

Effect of Nutrim Oat Bran and Flaxseed on Rheological Properties of Cakes

Cake shortening contents were replaced with Nutrim oat bran (OB) and flaxseed powder, and the effects of these substitutions on the physical and rheological properties of cakes were investigated. Cakes with shortening replaced up to 40% by weight possessed a volume similar to that of the control cake produced with shortening. Replacement using Nutrim OB and flaxseed powder revealed significant color changes in both the cake crust and crumb. At high levels of substitution, the cake crust became lighter, while the crumb darkened. At >40% by weight substitution with either Nutrim OB or flaxseed, the cakes displayed increased hardness; however, cohesiveness and springiness increased gradually with increasing substitution. Increased substitution with Nutrim OB caused an increase in the measured shear viscosity and oscillatory storage and loss moduli of the cakes. Increased substitution with flaxseed caused decreases in these rheological parameters. Additional rheological experiments were performed to elucidate changes in the formulations during the baking process and indicated an increase in the elasticity of the baked batter with decreasing shortening.     

Effects of Natural Chelating Agents on the Solubility of Some Physiologically Important Mineral Elements in Oat Bran and Oat Flakes

The solubility of mineral elements from oat bran and flake samples was studied by a method using equilibrium dialysis after enzymatic digestion of starch and proteins. The effects of six potential chelating agents common in food were tested on the solubility of mineral elements. The minerals studied were calcium, magnesium, iron, manganese, zinc and potassium, and the chelating agents were citric, lactic, malic, and ascorbic acids, glucose and xylitol. The mineral elements were tightly bound to the dietary fiber of the samples. Bran fiber bound even the zinc and calcium contributed through the enzymes used. Adding citric, malic, or lactic acids increased the solubility of the mineral elements studied, except for potassium which was easily dialyzable as such. Iron was insoluble in all situations. Citric acid was the most efficient chelating agent in solubilizing the mineral elements. The effect of malic and lactic acids on the solubility of minerals was small. No effect was found with glucose, ascorbic acid, and xylitol. Thus, the intestinal availability of mineral elements may be affected by dietary hydroxy acids such as citric and malic acids in high dietary fiber diets.     

Glycemic Response to Extruded Oat Bran Cereals Processed to Vary in Molecular Weight

Oat β‐glucan enriched extruded cereals with molecular weights (MWs) ranging from 2,180,000 to 326,000 were produced. Test meals composed of 31 g of available carbohydrate, 8.3–8.7 grams of β‐glucan, and milk were administered to subjects and their postprandial blood glucose levels monitored for 2 hr. White bread plus milk and a control wheat bran cereal plus milk were administered, and white bread alone served as a reference food for estimation of glycemic index (GI) of the cereals, after adjusting for the effect of adding milk to white bread. Both oat bran and wheat bran cereals significantly reduced peak blood glucose rise (PBGR) and area under the curve (AUC) versus white bread alone or white bread plus milk. There was a significant inverse relationship between AUC and log₁₀[weight average MW] (r² = 0.96, P = 0.0192). There was a significant inverse relationship between PBGR and log₁₀[viscosity] of in vitro extracts from all cereals, including the wheat control (r² = 0.96, P = 0.0031). However, no significant differences in glycemic responses among the oat bran cereals were found with pairwise comparisons. All cereals were low GI (<55) and were significantly lower than white bread alone or white bread plus milk. Among the oat bran cereals, palatability was positively correlated with MW (r² = 0.98, P = 0.0110).     

Reducing Beta-Glucan Solubility in Oat Bran Muffins by Freeze-Thaw Treatment Attenuates Its Hypoglycemic Effect

The viscosity of soluble fibers such as β-glucan depends on their concentration in solution and molecular weight (MW) distribution. We investigated whether freezing treatment of oat bran muffins affected the physicochemical properties of β-glucan, and its physiological effectiveness in lowering postprandial blood glucose response. A controlled range of β-glucan solubility was achieved by subjecting oat bran muffins containing two levels of β-glucan to repeated freeze-thaw temperature cycling. β-Glucan solubilized by in vitro digestion extraction was measured by flow-injection analysis. MW distributions of β-glucan were analyzed using size-exclusion chromatography. β-Glucan solubility decreased as the number of freeze-thaw cycles increased, while MW distribution of β-glucan decreased slightly. Peak blood glucose rise (PBGR) after fresh muffins (8 and 12 g of β-glucan/serving) was significantly lower than that after muffins (8 and 12 g of β-glucan/serving) treated with four freeze-thaw (FT) cycles (1.84 ± 0.2 vs. 2.31 ± 0.1 mmol/L, P = 0.007). Compared with the control whole wheat muffins, the reduction in incremental area under the glucose response curve (AUC) after fresh muffins (8 and 12 g of β-glucan/serving) was nearly twice that after 4 FT cycles (43.3 ± 4.4% vs. 27.0 ± 5.4%, P = 0.016). A significant inverse linear relationship was found between the log [concentration] of extractable β-glucan and PBGR (r² = 0.85, P = 0.01), and AUC (r² = 0.71, P = 0.03). The results show that reduction of β-glucan solubility in foods attenuates its physiological effectiveness in lowering postprandial glycemia.     

Composition of Oat Bran and Flour Prepared by Three Different Mechanisms of Dry Milling

Three mechanisms of oat milling were tested for laboratory-scale oat bran production. Oat bran consistent with AACC definition and commercially obtained product was generated with either roller-milling or impact-milling of groats, followed by sieving to retain larger particles. These bran preparations were enriched ≈1.7-fold in β-glucan and ash, 1.4-fold in protein, and 1.1-fold in lipid. Bran finishing made further enrichments in protein, β-glucan, and ash. Tempering oat (to 12% moisture for 20 min) improved bran yield from roller-milling nearly two-fold but had little effect on bran composition. Bran yield from the impact-type mill was significantly affected by grinding screen size. Oat bran obtained from a pearling mill was only slightly enriched in β-glucan and protein, but it was more heavily enriched in ash and oil than brans from roller or impact mills. The pearling mill isolated the outer layers of the groat directly, but because of its low β-glucan composition it did not meet the AACC definition of oat bran, indicating a relatively uniform distribution of β-glucan in the groat.     

Effect of Extrusion Cooking on Extractable Lipids and Fatty Acid Composition in Sifted Oat Flour

Sifted oat flour was processed at 25.0, 27.5, and 30.0% moisture content in a twin-screw extruder at screw speed 300 rpm. The preset temperatures of the extruder barrel were 120, 150, or 180°C. Raw material and extrudates were analyzed for the content of diethyl ether-extractable lipids, with and without hydrolysis, and the content of chloroformmethanol-water saturated butanol (C/M/WSB) extractable lipids. The lipid extracts were analyzed for fatty acid (FA) composition. Percentage distribution of palmitic, oleic, and linoleic acids were significantly different in the different lipid extracts. Extrusion processing influenced the amounts of extractable lipids, while FA composition was not affected.     

Physiological Responses of Men and Women to Barley and Oat Extracts (Nu‐trimX). II. Comparison of Glucose and Insulin Responses

This study was designed to compare the glucose, insulin, and glucagon responses to consumption of high‐soluble β‐glucan compounds from oats and barley. After an initial medical evaluation that included blood and urine testing, 11 men and 11 women, nondiabetics, 35–57 years, were selected. Subjects consumed a controlled diet for three days. On the third day of five successive periods, subjects consumed 1 g/kg of body weight of carbohydrate as glucose or 0.66 g/kg of body weight pudding (predominantly sucrose) and 0.33 g/kg of body weight as oat bran, barley flour, oat or barley extract (Nu‐trimX) in a Latin square design. Order of treatment was randomly assigned. Glycemic responses were calculated using the trapezoid method. Data were analyzed using mixed procedure analysis of variance program. Glucose responses to oats, barley, and both extracts, and areas under the curve were significantly lower than responses to the glucose solution (P < 0.0001). Insulin responses for the barley extract were lowest and were significantly lower than for glucose solution. Oat and barley extracts retain the beneficial effects of the grains from which they are extracted. High‐soluble fiber barley is more effective than standard oats. Oat and barley carbohydrate‐based fat substitutes can provide a useful addition to menus to control plasma glucose responses.     

Cholesterol Response and Foam Cell Formation in Hamsters Fed Rice Bran,Oat Bran,and Cellulose + Soy Protein Diets With or Without Added Vitamin E

Four-week-old male golden Syrian hamsters were fed diets containing cellulose (control, CC), cellulose + soy protein (CS), CS + vitamin E, (CSE), rice bran (RB), RB + vitamin E (RBE), oat bran (OB), and OB + vitamin E (OBE) for six weeks (n = 10/treatment). Diets contained (by weight) 10% total dietary fiber, 3% N, 20% fat, 0.5% cholesterol, and some diets had an additional 0.1% vitamin E. After six weeks, RB and OB diets resulted in significantly higher weight gain than the CC diet. Plasma low-density lipoprotein cholesterol (LDL-C) values and the LDL-C/high-density lipoprotein cholesterol ratio in hamsters fed CSE, RBE, OB, and OBE diets were significantly lower than in those fed CC diet. There were no significant differences in total plasma cholesterol values among the hamsters fed any of the diets. Liver cholesterol in animals fed OB and OBE diets was significantly lower than in all other groups. Foam cell areas in the inner bend of the aortic arch in animals fed all treatment diets were significantly reduced when compared with that in animals fed CC diet. The level of additional dietary vitamin E did not result in further significant reductions in foam cell area. The results of this study suggest that diets containing rice bran, oat bran, or soy protein significantly reduced the development of atherosclerosis in hypercholesterolemic hamsters.     

Physiological Responses of Men and Women to Barley and Oat Extracts (Nu‐trimX). I. Breath Hydrogen,Methane, and Gastrointestinal Symptoms

While consumption of diets high in fiber is perceived to result in undesirable gastrointestinal symptoms, the fermentation of undigested carbohydrate in the large intestine may, in fact, have beneficial health effects. In this study, we compared the effects of oats, barley, and their extracts with a glucose control for 24 hr on breath hydrogen and methane production as a marker of colonic fermentation and also assessed gastrointestinal symptoms. Nine men and 11 women (35–57 yr) consumed 1 g/kg of body weight of carbohydrate as glucose or 0.66 g/kg of body weight sugar and 0.33 g/kg of body weight as oat bran, barley flour, oat extract, or barley extract (Nu‐trimX) in a Latin square design. Expired alveolar breath samples were collected after instruction at fasting, 2, 4, 5, 6, 7, 8, 9, 10, and 24 hr after consumption of the test meals. All test meals increased breath hydrogen and methane (both P < 0.0001). Hydrogen, but not methane, responses to barley, oats, and extracts of each were higher (barley > oats, P < 0.05) than responses to glucose (P < 0.0001). Reported gastrointestinal symptoms were not related to specific test meals. Oats and barley, as well as their extracts, can be consumed in greater amounts by Americans to increase soluble fiber and lower fat intake, and thus lower risk factors for chronic disease.     

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 Extrusion on Hypocholesterolemic Properties of Rice,Oat, Corn,and Wheat Bran Diets in Hamsters

Brans from rice, oats, corn, and wheat were cooked in a twin-screw extruder at either high or low energy input, and their cholesterol-lowering effects were compared with those of unprocessed brans when fed to four-week-old male golden Syrian hamsters (n = 10 per treatment) for three weeks. Peanut oil was added to oat, corn, and wheat bran during the extrusion process to match the oil content of rice bran. Diets contained 10% total dietary fiber, 10.3% fat, 3% nitrogen, and 0.3% cholesterol. Plasma and liver cholesterol and total liver lipids were significantly lower with low-energy extruded wheat bran compared with unprocessed wheat bran. Extrusion did not alter the hypocholesterolemic effects of rice, oat, or corn brans. Plasma and liver cholesterol levels with corn bran were similar to those with oat bran. Relative cholesterol-lowering effects of the brans, determined with pooled (extruded and unextruded) bran data, were rice bran > oat bran > corn bran > wheat bran. Rice bran diets resulted in significantly lower levels of total plasma cholesterol and very low density lipoprotein cholesterol compared with all other brans. Total liver cholesterol and liver cholesterol concentrations (mg/g) were significantly lower with high-energy extruded rice bran compared with the cellulose control group. Plasma cholesterol and total liver cholesterol values with low-energy extruded wheat bran were similar to those with rice bran (unextruded or extruded) diets. Lowered cholesterol with rice bran diets may result in part from greater lipid and sterol excretion with these diets. Results with low-energy extruded wheat bran suggest that this type of processing may improve the potential for lowering cholesterol with wheat bran products.     

Extraction of β‐Glucan from Oat Bran in Laboratory Scale

Effects of various enzymes and extraction conditions on yield and molecular weight of β‐glucans extracted from two batches of commercial oat bran produced in Sweden are reported. Hot‐water extraction with a thermostable α‐amylase resulted in an extraction yield of ≈76% of the β‐glucans, while the high peak molecular weight was maintained (1.6 × 10⁶). A subsequent protein hydrolysis significantly reduced the peak molecular weight of β‐glucans (by pancreatin to 908 × 10³ and by papain to 56 × 10³). These results suggest that the protein hydrolyzing enzymes may not be pure enough for purifying β‐glucans. The isolation scheme consisted of removal of lipids with ethanol extraction, enzymatic digestion of starch with α‐amylase, enzymatic digestion of protein using protease, centrifugation to remove insoluble material, removal of low molecular weight components using dialysis, precipitation of β‐glucans with ethanol, and air‐drying.     

Lower 30 Minute Serum Insulin in Healthy Sprague‐Dawley Rats Consuming Chips from Specific Barley Flour Blends

Consumption of whole grains such as barley is known to inversely correlate with insulin resistance, type 2 diabetes, and other chronic diseases. However, data from randomized controlled trials in humans have not produced consistent results. Compositional differences between foods produced from different whole grains are likely to be a main reason for these discrepancies. The purpose of this study was to determine if varying barley flour composition achieved through milling influenced the postprandial glucose and insulin response. Specifically, this study aimed to test barley foods in the form of chips with very low hydration, thereby mimicking human snack foods. Fasted rats (N = 39) were randomized to one of four barley treatments, all produced from a single variety, Hordeum vulgare L. ‘CDC Fibar.’ The treatments used were straight‐grade flour (SGF), whole grain flour (WGF), bran flour with high β‐glucan (BF‐BG), bran flour with high insoluble dietary fiber, and wheat flour (WF) as the control. Blood was sampled over 120 min following treatment consumption to measure postprandial glucose and insulin concentrations. Our data showed that although there were no substantial glycemic or insulin effects following one‐time consumption of barley tortilla chips with specific compositions, those rats consuming WGF, SGF, or BF‐BG tended to have lower 30 min serum insulin concentrations compared with those rats consuming WF.     

籽粒苋不同富钾基因型矿质营养元素含量的研究

采用水培试验,研究了在两种供钾水平(K,0.5mmolL-1和5.0mmolL-1)条件下4个不同籽粒苋品种植株体内矿质营养元素的含量及其变化。同时,还在低钾条件下,测定了不同籽粒苋品种根、茎、叶中矿质营养成分的含量和构成情况,结果表明:(1)籽粒苋各品种氮、钾含量随着供钾水平降低而减少,一般基因型氮钾含量降幅大于富钾基因型;在相同供钾水平条件下,富钾基因型的氮钾含量均高于一般基因型,而相同基因型的不同品种间氮钾含量则相近。籽粒苋各品种氮主要分布在根和叶中,其次是茎;磷大量分布在根,其次是叶,再次是茎;钾主要存在于茎中,根和叶次之。(2)籽粒苋钙、镁、硫含量随着供钾水平的升高而降低,富钾基因型镁、硫含量低于一般基因型。籽粒苋不同品种的钙、镁主要分布在叶片中,其次是茎和根;硫在根中的分布最少,叶中最多。(3)不同品种B、Cu、Fe、Mn、Zn等微量元素含量随着供钾水平的降低而升高,灰分含量则降低。富钾基因型B、Fe、Zn及灰分含量都高于一般基因型,而Cu的含量则是一般基因型高于富钾基因型。4个籽粒苋品种的硼、铜主要存在于叶片中,其次是根,茎含量相对前两者要小;铁、锰、锌在根的含量最高,叶片次之,茎最低,根系中铁的含量分别是叶和茎的7倍左右和10倍以上。     

Determination of Bran Contamination in Wheat Flours Using Ash Content,Color, and Bran Speck Counts

A fast new method based on image analysis, ScanPro Speck Expert (SPX), to determine the bran contamination in wheat flour was studied and compared with existing methods (air-oven, ash, and color measurements) using an Agtron color meter and a Minolta chromameter. Twenty-one hard red winter wheat flour samples with ash contents of 0.30–0.58% were collected from the Kansas State University pilot mill and used for this study. Intrinsic variability in the flour sample because of randomness of bran speck orientation and distribution in the sample holder could result in variation in the speck count. Simple and multiple linear regression analyses showed that estimation of flour ash content from the SPX results (R² = 0.91) would be more accurate than the results from color measurements (R² = 0.66 [Agtron color meter] and 0.74 [L*]). The added capability of SPX image analyzer to not only count the number of bran specks but also to measure their areas probably increases the accuracy of determining the bran contamination in wheat flour by image processing.     

籽粒苋根际土壤及根系分泌物对矿物态钾的活化作用

通过大田和模拟试验等方法 ,研究了籽粒苋根际土壤及根系分泌物对矿物态钾的活化作用 ,研究结果表明 :(1)籽粒苋根际土壤的速效钾含量较非根际土增加了 1.7倍 ,缓效钾 (K)的含量也提高了 5 5 .9% ;(2 )用籽粒苋根际土壤处理后的花岗岩粉末 ,其速效钾和缓效钾含量均较对照有所增加 ,增幅分别为 2 .8%～ 2 4.7%和 15 .7%～ 44 .7% ;用籽粒苋根际土壤处理后的紫色土 ,其速效钾和缓效钾含量较对照分别增加了 18.5 %和 11.1% ;(3 )通过对y值的综合贡献率计算可知 ,不同籽粒苋模拟根系分泌物对花岗岩粉末中矿物态钾的活化能力大小依次为 :草酸 >蔗糖 >核酸 >乳酸 >柠檬酸。