Content and Molecular Weight Distribution of Oat β‐Glucan in Oatrim,Nutrim, and C‐Trim Products

The soluble fiber, β‐glucan, in oat products is an active hypolipidemic component that is responsible for lowering plasma lipids. Quantitative analysis of β‐glucan in oat hydrocolloids such as Oatrim, Nutrim, and C‐Trim was performed to measure the total β‐glucan content and molecular weight distribution. For the measurement of total β‐glucan content, both modified flow‐injection analysis (FIA) method and the standard AACC enzymatic method were employed. FIA method uses the enhanced fluorescence produced when β‐glucan forms complexes with Calcofluor. Experimental results of both the modified FIA method and the standard AACC enzymatic method revealed very good coincidence with each other. This result confirms the applicability of either technique for the quantitative evaluation of β‐glucan in hydrocolloids. Molecular weight (MW) distribution of β‐glucan was determined by size‐exclusion chromatography with postcolumn detection. Experimental results revealed that the molecular weight of β‐glucan in the Trim products was decreased during the manufacturing process. This result was ascribed to the rigorous processing condition of jet‐cooking.     

Textural and Bile Acid‐Binding Properties of Muffins Impacted by Oat β‐Glucan with Different Molecular Weights

Water‐soluble β‐glucan (BG) extracted from a high‐BG oat line was treated with different amounts of lichenase (1→3)(1→4)‐β‐d ‐glucanase) enzyme to yield three different molecular weight (MW) BG extracts. Low (LMW‐BG, 157,000), medium (MMW‐BG, 277,000), and high (HMW‐BG, 560,000) MW BG extracts were added to plain muffin formulations at a level of 0.52% (0.42% in the batter, 0.52% in the resultant muffins) to investigate the effect of MW of BG on textural and bile acid (BA) binding properties of the muffins. In addition, treatments were prepared containing LMW‐BG, MMW‐BG, and HMW‐BG extracts in amounts providing equivalent batter firmness as determined on a texture analyzer. Resultant BG concentrations (and per serving amounts) of these muffins were 1.36% (0.81 g/60 g muffin), 1.05% (0.63 g/60 g muffin), and 0.52% (0.31 g/60 g muffin), respectively; thus, the LMW treatment complied with a U.S. Food and Drug Administration health claim requiring 0.75 g of BG per serving. The firmness, springiness, and BA‐binding capacity of the muffins were unaffected by the MW of BG. However, when added at the maximum limit for equivalent batter firmness, the LMW treatment was more firm and less springy than the HMW treatment. Furthermore, BA‐binding capacities of LMW and MMW fractions tended to be greater than that of the HMW fraction when added at the maximum limit. These results add further evidence to the importance of fine‐tuning BG structure to provide maximum health benefits while maintaining high product quality.     

Extraction of β‐Glucan from Oats for Soluble Dietary Fiber Quality Analysis

Extraction protocols for β‐glucan from oat flour were tested to determine optimal conditions for β‐glucan quality testing, which included extractability and molecular weight. We found mass yields of β‐glucan were constant at all temperatures, pH values, and flour‐to‐water ratios, as long as sufficient time and enough repeat extractions were performed and no hydrolytic enzymes were present. Extracts contained about 30–60% β‐glucan, with lower proportions associated with higher extraction temperatures in which more starch and protein were extracted. All commercial starch hydrolytic enzymes tested, even those that are considered homogenous, degraded β‐glucan apparent molecular weight as evaluated by size‐exclusion chromatography. Higher concentration β‐glucan solutions could be prepared by controlling the flour‐to‐water ratio in extractions. Eight grams of flour per 50 mL of water generated the highest native β‐glucan concentrations. Routine extractions contained 2 g of enzyme‐inactivated flour in 50 mL of water with 5mM sodium azide (as an antimicrobial), which were stirred overnight, centrifuged, and the supernatant boiled for 10 min. The polymer extracted had a molecular weight of about 2 million and was stable at room temperature for at least a month.     

Glycemic Response to Oat Bran Muffins Treated to Vary Molecular Weight of β‐Glucan

Oat bran muffins, containing 4 or 8 g of β‐glucan per two‐muffin serving, were prepared with or without β‐glucanase treatment to produce a range of β‐glucan molecular weights from 130,000 to just over 2 million. Following an overnight fast, the glycemic responses elicited by the untreated and treated muffins was measured in 10 healthy subjects and compared with a control whole wheat muffin. Taken all together, the 4‐g β‐glucan/serving muffins reduced blood glucose peak rise (PBGR) by 15 ± 6% compared with the control. The 8‐g β‐glucan/serving muffins had a significantly greater effect (44 ± 5% reduction compared with the control, P < 0.05). The efficacy of the muffins decreased as the molecular weight was reduced from a 45 ± 6% reduction in PBGR (P < 0.05) for the untreated muffins (averaged of both serving sizes) to 15 ± 6% (P < 0.05) for muffins with the lowest molecular weight. As the molecular weight was reduced from 2,200,000 to 400,000, the solubility of the β‐glucan increased from a mean of 44 to 57%, but as the molecular weight was further decreased to 120,000, solubility fell to 26%. There was a significant correlation (r² = 0.729, P < 0.001) between the peak blood glucose and the product of the extractable β‐glucan content and the molecular weight of the β‐glucan extracted.     

High‐Starch and High‐β‐Glucan Barley Fractions Milled with Experimental Mills

This study focused on the performance of two hulless barley cultivars (Doyce and Merlin) and one commercial husked (hulled) sample using experimental milling. The purpose was to use experimental milling as a preliminary indicator of the milled streams with potential use for fuel ethanol production and fractions that could be used in food products. Experimental mills designed for flour production evaluation from wheat were Chopin CD1 Auto, Quadrumat Sr, Buhler, and an experimental Ross roller mill walking flow. Results indicate that the shorts had the highest levels of β‐glucan from all the mills. However, the β‐glucan content in the break flours was highest with the roller mill walking flow and the Chopin CD1 for the hulless cultivars. The lowest β‐glucan content in the break flour was found with the Buhler for Doyce. Break flour and, to a slightly lesser extent, reduction flour from all cultivars tested on all mills contained the highest starch content (up to 83%) and are therefore most appropriate for use as feedstock for fuel ethanol production. Conversely, bran and shorts from all cultivars and mills were lowest in starch (as low as 25%), making them ideal as low‐starch food ingredients.     

Molecular Weight of β‐Glucan Affects Physical Characteristics,In Vitro Bile Acid Binding,and Fermentation of Muffins

Muffins containing different amounts and molecular weights (MW) of β‐glucan were evaluated for the effect of β‐glucan on the physical characteristics of the muffins and on in vitro bile acid binding and fermentation with human fecal flora. Wheat flour muffins were prepared with the addition of β‐glucan extracts with high‐, medium‐, or low‐MW. For oat flour muffins, the native oat flour contained high‐MW β‐glucan; the oat flours were treated to create medium‐ and low‐MW β‐glucan within the prepared muffin treatments. For each 60‐g muffin, the amounts of β‐glucan were 0.52, 0.57, and 0.59 g for high‐, medium‐, and low‐MW β‐glucan wheat flour muffins, and 2.38, 2.18, and 2.23 g for high‐, medium‐, and low‐MW β‐glucan oat flour muffins, respectively. The lower the MW of the β‐glucan in muffins, the lower the height and volume of the muffins. The oat flour muffins were less firm and springy than the wheat flour muffins as measured on a texture analyzer; however, MW had no effect on muffin texture. The oat flour muffins bound more bile acid than did the wheat flour muffins. The muffins with high‐MW β‐glucan bound more bile acid than did those with low‐ and medium‐MW β‐glucan. Muffin treatment affected the formation of gas and total short‐chain fatty acids (SCFA) compared with the blank without substrate during in vitro fermentation. There were no differences in pH changes and total gas production among muffin treatments. The high‐MW β‐glucan wheat flour muffins produced greater amounts of SCFA than did the wheat flour muffin without β‐glucan and the oat flour muffins; however, there were no differences in SCFA production among muffins with different MW. In general, the β‐glucan MW affected the physical qualities of muffins and some potential biological functions in humans.     

Wet Processing of Barley Grains into Concentrates of Proteins, β‐Glucan,and Starch

An improved wet method was developed to process barley into fractions concentrated in protein, (1‐3)(1‐4)‐β‐d ‐glucan (BG), starch, or other carbohydrates (CHO). Alkaline concentration, solvent to barley flour ratio (SFR), and extraction temperature were evaluated for their effects on concentration and recovery of protein, BG, starch, oil, ash, and other CHO in each fraction type. Results show that the three parameters and their interactions all had significant effects, resulting in varying nutrient concentrations and recovery rates in each type of fractions. For protein fractions, protein content varied from 37.7 to 75.2%, protein recovery from 8.5 to 75.7%, and increasing alkaline concentration and SFR improved nutrient recovery. For BG fractions, BG content ranged from 21.5 to 87.0%, BG recovery from 28.6 to 78.0%, and increasing alkaline concentration decreased BG content but increased its recovery significantly. For starch fractions, starch content varied from 76.9 to 93.9%, starch recovery from 33.6 to 63.9%, and all parameters had little effect on the nutrient concentrations, but alkaline concentration and SFR improved recovery of starch, other CHO, and mass. Overall, the improved wet method was effective in concentrating the major nutrients from barley into their respective fractions, but process optimization through manipulating the three parameters is necessary to achieve a maximum concentration or recovery rate of a nutrient of interest in a specific fraction.     

Factors Influencing β‐Glucan Levels and Molecular Weight in Cereal‐Based Products

The beneficial role of soluble dietary fiber in human nutrition is well documented and has lead to a growing demand for the incorporation of β‐glucan, particularly from oats and barley, into foods. β‐Glucan with high solubility and high molecular weight distribution results in increased viscosity in the human intestine, which is desirable for increased physiological activity. Molecular weight, level, and solubility of β‐glucan are affected by genotype, environment, agronomic input, and the interactions of these factors and food processing methods. Available literature reveals that the level of β‐glucan in a finished product (e.g. bread, cake, muffins) depends upon several factors in the production chain, whereas food processing operations are major factors affecting molecular weight and solubility of β‐glucans. Therefore, to avail themselves of the natural bioactive compounds, food manufacturers must pay attention not only to ensure sufficient concentration of β‐glucan in the raw material but also to the processing methods and functional properties of β‐glucan, minimizing enzymatic or mechanical breakdown of the β‐glucans in end‐product and optimizing processing conditions. This review discusses the different sources of β‐glucan for use in human functional foods and factors affecting the levels and the molecular weight of β‐glucan at various pre‐ and postharvest operations.     

Comparison of Different Types of NIR Instruments in Ability to Measure β‐Glucan Content in Naked Barley

Importance of β‐glucan in human nutrition is mirrored in numerous approval applications registering β‐glucan containing products as health beneficial products in accordance with forthcoming EU Health Claims Regulation. In comparison to other cereals, barley contains considerable amounts of β‐glucan. Naked barley is of particular interest because it circumvents the costs and loss of beneficial substances related to dehusking. In this study, the potential of near‐infrared spectroscopy as an accurate, fast and economic method of determination of β‐glucan in naked barley was appraised. Four different near‐infrared instruments were used to analyze 107 barley samples, in both whole grain and milled form. Importantly, both black and purple pericarp samples, which are of additional nutritional interest due to high anthocyanin content, and waxy samples, which show an extraordinary high β‐glucan content could be analyzed within the same calibration set as the normal samples. All tested dispersive near‐infrared reflection instruments showed suitability for supervision of breeding experiments and β‐glucan monitoring in food industries (R² > 0.78). Common, industrially used near‐infrared transmission instruments also provided reasonable results, although only suitable for rough selection according to β‐glucan levels. On the other hand, the Fourier transform near‐infrared reflection instrument was able to perform analytical analyses (R² = 0.96–0.98).     

Effects of β‐Glucan Content and Pearling of Barley in Diet‐Induced Obese Mice

The effects of the β‐glucan content and pearling of barley on abdominal obesity and the proinflammatory state were investigated in diet‐induced obese mice. Male C57BL/6J mice were randomly divided into four groups and fed either a high‐fat diet containing high‐β‐glucan barley (Beau Fiber [BF]) or a high‐fat diet containing β‐glucan‐free barley (Shikoku‐hadaka 84(bgl ) [BGL]) as whole grain flour or 60% pearled flour for 12 weeks. The weights of mesenteric fat, serum total and low density lipoprotein cholesterol levels, serum insulin and fasting glucose levels, oral glucose tolerance test results, and messenger RNA (mRNA) expression of proinflammatory markers in epididymal fat in both BF groups were significantly lower than those of both BGL groups. The abundance of Bacteroides in both BF groups was significantly higher than that in both BGL groups, whereas the abundance of Clostridium clusters in both BF groups was significantly lower than that in both BGL groups. No significant differences between the whole grain and pearled flours were observed. These results suggest that high‐β‐glucan barley attenuates the progression of abdominal obesity and the proinflammatory state in diet‐induced obese mice compared with β‐glucan‐free barley, possibly by modifying insulin secretion and the microbiota.     

Prediction of β‐Glucan Concentration Based on Viscosity Evaluations of Raw Oat Flours from High β‐Glucan and Traditional Oat Lines

Rheological properties of raw oat flour slurries were determined in experimental high β‐glucan (≤7.8%) and traditional oat lines (4–5% β‐glucan) grown in two consecutive years. Three different media were used to disperse oat flours: deionized water, silver nitrate solution (to inactivate endogenous enzymes), and alkali solution (to solubilize both water‐soluble and water‐insoluble β‐glucans). Significant correlations (P < 0.05) between viscosity of slurries and β‐glucan concentration obtained in either deionized water (r = 0.833), silver nitrate (r = 0.940), or alkali (r = 0.896) solutions showed that β‐glucans were the main contributor to oat extract viscosity. The highest correlation was obtained in silver nitrate solution, suggesting that inactivating endogenous enzymes is important to obtain high correlations. Predictive models of oat β‐glucan concentration based on the viscosity profile were developed using partial least squares (PLS) regression. Prediction of β‐glucan concentration based on viscosity was most effective in the silver nitrate solution (r = 0.949, correlation coefficient of predicted vs. analyzed β‐glucans) and least effective in the alkali solution (r = 0.870). These findings demonstrate that the β‐glucan in oat could be predicted by measuring the viscosity of raw flours in silver nitrate solution, and this method could be used as a screening tool for selective breeding.     

Development of an Orange‐Flavored Barley β‐Glucan Beverage

Barley β‐glucan concentrate shows great potential as a functional food ingredient, but few product applications exist. The objectives of this study were to formulate a functional beverage utilizing barley β‐glucan concentrate, and to make a sensory evaluation of beverage quality in comparison to pectin beverages and to assess shelf stability over 12 weeks. Three beverage treatments containing 0.3, 0.5, and 0.7% (w/w) barley β‐glucan were developed in triplicate. Trained panelists found peely‐ and fruity‐orange aroma and sweetness intensity to be similar (P > 0.05) for all beverages tested. Beverage sourness intensity differed among beverages (P ≤ 0.05). Panelists evaluated beverages containing 0.3% hydrocolloid as similar (P > 0.05), whereas beverages with 0.5 and 0.7% β‐glucan were more viscous (P ≤ 0.05) than those with pectin at these levels. Acceptability of beverages was similar according to the consumer panel. Shelf stability studies showed no microbial growth and stable pH for all beverages over 12 weeks. Colorimeter values for most beverages decreased (P ≤ 0.05) during the first week of storage, mostly stabilizing thereafter. With an increase in concentration, β‐glucan beverages became lighter in color (P ≤ 0.05) and cloudier, but these attributes for pectin beverages were not affected (P > 0.05). β‐Glucan beverages exhibited cloud loss during the first three weeks of storage. β‐Glucan can therefore be successfully utilized in the production of a functional beverage acceptable to consumers.     

Effects of Resistant Starch and Fiber from High‐Amylose Non‐Floury Corn on Tortilla Texture

A high‐amylose, non‐floury corn, a floury corn, and a 1:1 blend were made into masa and then tortillas. The masa flour made with the high‐amylose corn had a greater amount of resistant starch (RS 28.8%) and a greater amount of total dietary fiber (TDF 42.1%) than that with the floury corn (RS 2.9%, TDF 9.6%), producing a high‐fiber tortilla. The masa was evaluated for pasting properties using a Rapid ViscoAnalyser (RVA). The high‐amylose masa slurry gelatinized little at 95°C. The floury masa had the greatest peak viscosity, whereas the 1:1 blend was intermediate in value. Sensory evaluations of the tortillas for the textural attributes showed the floury tortillas to be chewier, more rollable, and grittier than the high‐amylose tortillas, whereas the blend tortillas were intermediate for most attributes. The cutting force of the high‐amylose tortillas, measured on a texture analyzer, was very low; the blend and floury tortillas required more force. Chewiness was correlated to rollability (r = 0.99, P = 0.05). The %RS and %TDF were correlated to rollability (r = –0.99), and cutting force (r = 0.99). The floury and blend tortillas had firm textures expected of desirable tortillas, whereas the high‐amylose tortillas broke under little force, and would not roll. The high‐amylose tortillas had high amounts of RS and TDF but poor texture. The blend tortillas retained most floury tortilla textural properties, making them suitable products for consumer use.     

Physical and Sensory Characteristics of Extruded Products Made from Two Oat Lines with Different β‐Glucan Concentrations

The impact of extrusion on physical and sensory properties and on the in vitro bile acid (BA) binding was examined for N979 and Jim oat (Avena sativa) lines with 8.1 and 4.8% β‐glucan, respectively. Based on hardness and edibility of products made from Jim oats, moisture concentrations of 16–25% and temperatures of 165–180°C were selected for N979 extrusion. Jim‐based cereal had a significantly greater (P < 0.05) expansion ratio than did N979‐based cereal at most moistures. N979 cereal was browner, but not harder, than Jim cereal. Extruded products from N979 and Jim oats had 5.29–5.99% and 3.38–3.94% β‐glucan, respectively. Changing extrusion temperature or moisture content did not affect β‐glucan concentration in the products. N979 cereal made at 165°C and 16% moisture had greater BA binding than at other conditions, and had crunchiness comparable to cereals made at other conditions. BA binding of Cheerios brand breakfast cereal was close to that of N979 cereal made at 180°C and 18% moisture, but lower than cereals made at other conditions. Cereals made from Jim and N979 oats were browner, harder, coarser, and crunchier than Cheerios breakfast cereal. Proper processing and preparation techniques should be considered when producing extruded products from high β‐glucan oats.     

Molecular Weight Distribution of β‐Glucan in Oat‐Based Foods

Oats, different oat fractions as well as experimental and commercial oat‐based foods, were extracted with hot water containing thermostable α‐amylase. Average molecular weight and molecular weight distributions of β‐glucan in extracts were analyzed with a calibrated high‐performance size‐exclusion chromatography system with Calcofluor detection, specific for the β‐glucan. Oats, rolled oats, oat bran, and oat bran concentrates all had high Calcofluor average molecular weights (206 × 10⁴ to 230 × 10⁴ g/mol) and essentially monomodal distributions. Of the oat‐containing experimental foods, extruded flakes, macaroni, and muffins all had high average molecular weights. Pasteurized apple juice, fresh pasta, and teacake, on the other hand, contained degraded β‐glucan. Calcofluor average molecular weights varied from 24 × 10⁴ to 167 × 10⁴ g/mol in different types of oat bran‐based breads baked with almost the same ingredients. Large particle size of the bran and short fermentation time limited the β‐glucan degradation during baking. The polymodal distributions of β‐glucan in these breads indicated that this degradation was enzymatic in nature. Commercial oat foods also showed large variation in Calcofluor average molecular weight (from 19 × 10⁴ g/mol for pancake batter to 201 × 10⁴ g/mol for porridge). Boiling porridge or frying pancakes did not result in any β‐glucan degradation. These large differences in molecular weight distribution for β‐glucan in different oat products are very likely to be of nutritional importance.     

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.     

REVIEW: Oat and Rye β‐Glucan: Properties and Function

Over the years, the β‐glucan of oats and barley has been the subject of study either because of the importance of the cholesterol‐lowering potential to health claims (FDA 1997, 2005) or, in the case of barley, because of the role of β‐glucan and β‐glucan‐rich endosperm cell walls in malting and brewing. β‐Glucan is also present in rye and in much lesser amounts in wheat. The most striking difference in these latter two sources is the difficulty in extractability; alkali rather than water is required for significant release from the cell walls. This review will discuss physicochemical properties of oat and rye β‐glucan and, where information allows, relate these to physiological effects. Viscosity, or more generally rheology, plays a central role in discussions of cereal β‐glucan functionality and physiological effects and will be the focus of this review.     

Distribution of β‐Glucan in the Grain of Hull‐less Barley

Nine hull‐less barley (HB) containing waxy (0–7% amylose), normal (≈25% amylose), or high amylose (≈42% amylose) starch with normal or fractured granule make‐up and 4–9% (1→3)(1→4)‐β‐d ‐glucans (β‐glucan) were pearled to remove 70% of the original grain weight in 10% intervals. The pearled fractions were analyzed for β‐glucan distribution within HB grain. Protein content of the pearled fractions indicated that the three outermost fractions contained pericarp and testa, aleurone, and subaleurone tissues, respectively. For all HB, β‐glucan and acid‐extract viscosity were very low in the outermost 20% of the kernel. For low β‐glucan HB, β‐glucan content was the greatest in the subaleurone region and declined slightly toward inner layers. For high β‐glucan HB, however, more than 80% of grain β‐glucan was distributed more evenly throughout the endosperm. Acid extract viscosity was significantly (P < 0.01) correlated with total (r = 0.75) and soluble (r = 0.87) β‐glucan content throughout the kernel of all HB. Growing conditions, location and year, had significant effects on the concentration of protein, starch and β‐glucan. However, protein, starch, and β‐glucan distribution patterns were not affected by growing conditions. The difference in β‐glucan distribution between low and high β‐glucan HB may explain the difference in milling performance of HB with low or high β‐glucan.     

Thermal Decomposition of Corn Starch with Different Amylose/Amylopectin Ratios in Open and Sealed Systems

Thermal decomposition of corn starches with different amylose to amylopectin ratios (0:100 waxy, 23:77 maize, 50:50 Gelose 50, 80:20 Gelose 80) were studied by thermogravimetric analysis (TGA) in an open system and differential scanning calorimetry (DSC) in a sealed system using stainless steel high‐pressure pans with varying water content (9–75%). The initial water content did not affect the decomposition temperature in the open system because all water evaporated from samples before reaching the decomposition temperature. The sequence of decomposition temperature of different starches is waxy > maize > G50 > G80 in an open system. The moisture content in starch remains constant during the degradation process in a sealed system. Two decomposition temperatures were observed in the sealed system: the first at lower temperature represents long chain scission and the second at higher temperature involves decomposition of the glucose ring. The sequence of the first degradation is waxy > maize > G50 > G80. There is no observable difference of the second degradation for the samples containing different amylose to amylopectin ratios. The higher the moisture content, the lower the second decomposition temperature. Decomposition of glucose was used to confirm the mechanisms proposed for the starch degradation.