Proximate Analysis and Nutritional Evaluation of Twenty Canadian Lentils by Principal Component and Cluster Analyses.

Proximate composition and starch nutritional properties of twenty cooked lentils were assessed to identify unique varieties that could be used in value added foods. Significant variations exist among the lentil varieties (p < 0.05) with respect to their energy, fat, protein, carbohydrate, and dietary fiber content, and these are related to lentil type and seed size. Dazil and Greenstar were unique for their high resistant starch content (RS) and lower area under the starch hydrolysis curve (SHAUC) while Proclaim was opposite. SHAUC was positively correlated (p < 0.001) with rapidly digestible starch (RDS) content (r = 0.626) but negatively correlated with RS content (r = -0.635). Principal component analysis showed that the first three principal components accounted for 62.8% of the total variance and the contribution of SHAUC was 33.2%. These results confirm that in vitro SHAUC and a combination of RDS and RS may be predictive of the digestibility profile of cooked lentils.

Cooked Red Lentils Dose-Dependently Modulate the Colonic Microenvironment in Healthy C57Bl/6 Male Mice.

Dietary pulses, including lentils, are protein-rich plant foods that are enriched in intestinal health-promoting bioactives, such as non-digestible carbohydrates and phenolic compounds. The aim of this study was to investigate the effect of diets supplemented with cooked red lentils on the colonic microenvironment (microbiota composition and activity and epithelial barrier integrity and function). C57Bl/6 male mice were fed one of five diets: a control basal diet (BD), a BD-supplemented diet with 5, 10 or 20% cooked red lentils (by weight), or a BD-supplemented diet with 0.7% pectin (equivalent soluble fiber level as found in the 20% lentil diet). Red lentil supplementation resulted in increased: (1) fecal microbiota α-diversity; (2) abundance of short-chain fatty acid (SCFA)-producing bacteria (e.g., Prevotella, Roseburia and Dorea spp.); (3) concentrations of fecal SCFAs; (4) mRNA expression of SCFA receptors (G-protein-coupled receptors (GPR 41 and 43) and tight/adherens junction proteins (Zona Occulden-1 (ZO-1), Claudin-2, E-cadherin). Overall, 20% lentil had the greatest impact on colon health outcomes, which were in part explained by a change in the soluble and insoluble fiber profile of the diet. These results support recent public health recommendations to increase consumption of plant-based protein foods for improved health, in particular intestinal health.

In vitro assessment of oat ß-glucans nutritional properties: An inter-laboratory methodology evaluation.

The purpose of this inter-laboratory study was to test the repeatability and reproducibility of an in vitro method aimed at analyzing the physicochemical properties under physiological conditions of ß-glucans from foods. After evaluating ß-glucans molar mass and quantification methods using five ß-glucan controls, four laboratories ran six oat-based products through in vitro digestion, measured ß-glucans solubility and viscosity and molar mass of solubilized ß-glucans. The determination of the molar mass of ß-glucan controls, their viscosity in solution and ß-glucans content in food samples exhibited relative standard reproducibility of 20.9-40.9%, 10.2-40.9% and 2.3-14.8%, respectively. After in vitro digestion, relative standard reproducibility ranged 12.1-60.0%, 12.2-64.3% and 9.7-36.3% for molar mass of extracted ß-glucans, their viscosity and their solubility, respectively. Although the characterization methods were satisfactory within the limits of current technology, the in vitro extraction contributed significantly to the uncertainty of final characterization.

Textural and Rheological Properties of Oat Beta-Glucan Gels with Varying Molecular Weight Composition.

The impact of oat ß-glucan concentration and molecular weight (MW) on gel properties was investigated. Mixed MW gels/viscous solutions at 3, 4, and 5% ß-glucan with high molecular weight (HMW):low molecular weight (LMW) ratios of 0:100, 25:75, 50:50, 75:25, and 100:0 were evaluated. The 100:0 and 50:50 gels had the lowest tan δ values. The 50:50 gels had the highest storage moduli (G'), whereas 100:0 solutions did not gel. Peak melting temperature (TP) was highest for 0:100 gels and decreased with the addition of HMW ß-glucan. Hardness, at 40% compression, increased with concentration, and 25:75 and 50:50 gels were hardest at each concentration. Ordered microstructure, apparent in 0:100 gels, diminished with HMW ß-glucan addition. Glucose addition resulted in lower tan δ values and firmer, harder gels compared to gels without glucose. Thus, the textural properties and melting profiles of ß-glucan gels can be manipulated by adjusting the ratios of molecular weight fractions or addition of sugar for different applications.

Increasing the viscosity of oat ß-glucan beverages by reducing solution volume does not reduce glycaemic responses.

The soluble fibre (1 → 3)(1 → 4)-ß-D-glucan attenuates postprandial glycaemic responses when administered in solution. This attenuating effect is strengthened when solution viscosity is increased by increasing the ß-glucan dose or molecular weight (MW). The effect of varying solution viscosity by changing solution volume, without changing the ß-glucan dose or MW, on glycaemic responses was determined. A total of fifteen healthy subjects received six 50 g oral glucose beverages prepared with or without 4 g of high-MW (HMW, 580,000 g/mol) or low-MW (LMW, 145,000 g/mol) ß-glucan, with a beverage volume of 250 or 600 ml. Postprandial plasma glucose concentration was measured over 2 h, and the peak blood glucose rise (PBGR) and the incremental area under the glycaemic response curve (AUC) were calculated. Subjects served as their own controls. The physico-chemical properties of the beverages were measured to examine their relationship with glycaemic response results. The HMW ß-glucan beverage was more viscous and achieved greater reductions in PBGR than the glucose beverage with LMW ß-glucan (P < 0·05). At the same MW, the 250 and 600 ml ß-glucan beverages differed in viscosity (>9-fold difference) but not in PBGR (P > 0·05). No differences in AUC were detected among the beverages (P = 0·147). The effects of ß-glucan on glycaemic response were altered by changes in beverage viscosity achieved through changes in MW but not in volume. Therefore, ß-glucan dose and MW are the most vital characteristics for optimising the bioactivity of ß-glucan solutions with respect to glycaemic response.

Attenuation of glycemic responses by oat ß-glucan solutions and viscoelastic gels is dependent on molecular weight distribution.

Oat ß-glucan attenuates postprandial glycemic responses when solubilized to form viscous solutions. High molecular weight (MW) ß-glucan is associated with high solution viscosity, which is in turn associated with lower glycemic responses. However, low MW ß-glucan is also able to form viscoelastic gels. The effect of low (145,000 g mol(-1)) and high (580,000 g mol(-1)) MW ß-glucan presented as liquid drinks and gels on glycemic responses was determined. Healthy subjects (n = 15) consumed 50 g glucose drinks with no ß-glucan; 4 g low MW; or 4 g high MW ß-glucan; and gels containing 4 g low MW; 2 g low plus 2 g high MW; or 3 g high plus 1 g low MW ß-glucan. Overall, ß-glucan solutions elicited lower glycemic responses than gels. For gels, peak blood glucose rise (PBGR) decreased with increasing dose of high MW ß-glucan (r(2) = 0.976, P > 0.05), and PBGR for the gel with 3 g high-MW was lower than for the control (P < 0.05). However, ß-glucan gels retained glucose better than solutions under in vitro analysis. Observed effects were found to be related to the rheological properties of the foods. ß-Glucan solutions and not gels effectively attenuated in vivo glycemic responses.

Identification of high ß-glucan oat lines and localization and chemical characterization of their seed kernel ß-glucans.

Oat, (Avena sativa) is an excellent source of mixed linkage ß-glucans ((1→3)(1→4)-ß-D-glucan), a dietary fibre with cholesterol lowering properties. Using a mutagenized oat-population we screened 1700 different lines and identified ten lines that displayed ß-glucan levels above 6.7% and 10 below 3.6%.The extreme values were 1.8% and 7.5%. We chose six lines with an increased- and four lines with a reduced ß-glucan content for further study. By longitudinal- and cross-sections of seeds it was shown that localization of ß-glucan varied between the different lines. In addition, ß-glucan quality parameters like molecular weight and solubility were also determined. Although the selection was designed for quantitative differences, qualitative differences between the ß-glucans from the different lines were found. The high and low ß-glucan lines will now be used as a model system to study molecular regulation of ß-glucan biosynthesis as well as possible links between fibre quality and biological activity.

Nutritional Profile and Carbohydrate Characterization of Spray-Dried Lentil, Pea and Chickpea Ingredients.

Although many consumers know that pulses are nutritious, long preparation times are frequently a barrier to consumption of lentils, dried peas and chickpeas. Therefore, a product has been developed which can be used as an ingredient in a wide variety of dishes without presoaking or precooking. Dried green peas, chickpeas or lentils were soaked, cooked, homogenized and spray-dried. Proximate analyses were conducted on the pulse powders and compared to an instant mashed potato product. Because the health benefits of pulses may be due in part to their carbohydrate content, a detailed carbohydrate analysis was carried out on the pulse powders. Pulse powders were higher in protein and total dietary fibre and lower in starch than potato flakes. After processing, the pulse powders maintained appreciable amounts of resistant starch (4.4%-5.2%). Total dietary fibre was higher in chickpeas and peas (26.2% and 27.1% respectively) than lentils (21.9%), whereas lentils had the highest protein content (22.7%). Pulse carbohydrates were rich in glucose, arabinose, galactose and uronic acids. Stachyose, a fermentable fibre, was the most abundant oligosaccharide, making up 1.5%-2.4% of the dried pulse powders. Spray-drying of cooked, homogenized pulses produces an easy to use ingredient with strong nutritional profile.

Processing affects the physicochemical properties of beta-glucan in oat bran cereal.

The tendency of mixed linkage oat beta-glucan to form viscous solutions is generally assumed to be related to its ability to lower serum cholesterol levels in humans. However, the association has not been clearly demonstrated. To conduct a clinical trial showing the relationship between LDL-cholesterol levels and viscosity, a series of extruded oat bran cereals were prepared in which the beta-glucan had a range of molecular weights and modified solubility. An extraction protocol using physiological enzymes at 37 degrees C was used to estimate the effect that the cereals would have on gut viscosity. By reducing the molecular weight from 1,930,000 to 251,000 g/mol, the apparent viscosity in the physiological extract dropped from 2900 to 131 mPa.s (at 30 s(-1)). Microscopic examination showed that as the extrusion conditions were made more severe, to cause depolymerization, the integrity of the cell walls was lost and beta-glucan dispersed throughout the cereal. Differences in the hardness and density of the extruded cereals were also evident as the molecular weight was reduced.

Effect of blood sampling schedule on the ability to discriminate between postprandial glycemic responses.

OBJECTIVE: The blood glucose responses elicited by foods are often determined using blood samples taken at 15-min intervals. Our objective was to see whether taking blood samples at 10-min intervals affected the results. METHODS: Overnight-fasted healthy subjects (n=11) were studied on nine different occasions with seven different test meals. Blood samples were obtained at fasting and at 10, 15, 20, 30, 40, 45, 50, 60, 90, and 120 min after starting to eat. Peak rise, incremental area under the curve, and relative glycemic response were calculated using the 10- and 15-min sampling schedules. RESULTS: With 10-min intervals, peak rise was 4% greater than with 15-min intervals (P<0.001), but sampling interval did not significantly affect mean incremental area under the curve or relative glycemic response. The 10-min blood sampling schedule had a slightly greater ability to discriminate between foods and between subjects for peak rise and relative glycemic response. CONCLUSIONS: We conclude that the blood sampling schedule used may influence the accuracy and precision of measurements of glycemic response; however, the difference between taking blood samples at 10-min and 15-min intervals is quite small.