Barley beta-glucans varying in molecular mass and oligomer structure affect cecal fermentation and microbial composition but not blood lipid profiles in hypercholesterolemic rats.

There is an unmet need for appealing and functional barley ß-glucan (BG) food matrices that can provide sufficient and active BG doses to consumers. We investigated how molecular mass and oligomer structure important for BG food and health properties affected plasma lipids and gut parameters in hypercholesterolemic rats. Following 3 weeks on a high-cholestrol diet, rats were given a high-cholesterol diet supplemented with either cellulose (control) or purified barley BGs with low (100 or 150 kDa; glucagel or lowBG, respectively) or medium (530 kDa; mediumBG) molecular masses varying in cellotriosyl/cellotetraosyl oligomer ratio for 4 weeks. All four diets (control, glucagel, lowBG or mediumBG) reduced plasma triacylglycerol and cholesterols from week 3 to 7. The BG diets increased cecal production of short-chain fatty acids (SCFAs) compared to the control diet. The glucagel and lowBG diets stimulated the number of Bifidobacterium in the cecum, whereas the mediumBG diet reduced numbers of both Bacteroides/Prevotella and Lactobacillus in the cecum compared to the control diet. In conclusion, barley BGs at 6.5-7.5% of the diet independent of molecular mass and oligomer block structure showed no additional effect compared to the control treatment on blood cholesterol and triacylglycerol levels in this hypercholesterolemic rat model. Furthermore, the cecal fermentation pattern and microbial composition did not seem to affect plasma lipid composition.

All-natural bio-plastics using starch-betaglucan composites.

Grain polysaccharides represent potential valuable raw materials for next-generation advanced and environmentally friendly plastics. Thermoplastic starch (TPS) is processed using conventional plastic technology, such as casting, extrusion, and molding. However, to adapt the starch to specific functionalities chemical modifications or blending with synthetic polymers, such as polycaprolactone are required (e.g. Mater-Bi). As an alternative, all-natural and compostable bio-plastics can be produced by blending starch with other polysaccharides. In this study, we used a maize starch (ST) and an oat ß-glucan (BG) composite system to produce bio-plastic prototype films. To optimize performing conditions, we investigated the full range of ST:BG ratios for the casting (100:0, 75:25, 50:50, 25:75 and 0:100 BG). The plasticizer used was glycerol. Electron Paramagnetic Resonance (EPR), using TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) as a spin probe, showed that the composite films with high BG content had a flexible chemical environment. They showed decreased brittleness and improved cohesiveness with high stress and strain values at the break. Wide-angle X-ray diffraction displayed a decrease in crystallinity at high BG content. Our data show that the blending of starch with other natural polysaccharides is a noteworthy path to improve the functionality of all-natural polysaccharide bio-plastics systems.

Molecular structure of large-scale extracted ß-glucan from barley and oat: Identification of a significantly changed block structure in a high ß-glucan barley mutant.

Health effects of ß-glucan are typically related to dose, size and viscosity without taking the specific molecular structure into account. High ß-glucan mutant barley, mother barley and oat ß-glucans were large-scale extracted by comparable protocols using hot water, enzyme assisted hydrolysis and ethanol precipitation leading to similar molecular masses (200-300kDa). Multivariate data analysis on all compositional, structural and functional features demonstrated that the main variance among the samples was primarily explained by block structural differences as determined by HPSEC-PAD. In particular the barley high ß-glucan mutant proved to exhibit a unique block structure with DP3 and DP4 contributions of: 78.9% and 16.7% as compared to the barley mother (72.1% and 21.4%) and oat (66.1% and 29.1%). This unique block structure was further confirmed by the (1)H NMR determination of the ß-1,4 to ß-1,3 linkage ratio. Low solubility of the barley samples was potentially an effect of substructures consisting of longer repetitive cellotriosyl sequences. FT-Raman and NMR spectroscopy were useful in measuring sample impurities of α-glucans and prediction of ß-linkage characteristics.

Flaxseed dietary fibers lower cholesterol and increase fecal fat excretion, but magnitude of effect depend on food type.

BACKGROUND: Dietary fibers have been proposed to play a role in cardiovascular risk as well as body weight management. Flaxseeds are a good source of dietary fibers, and a large proportion of these are water-soluble viscous fibers. METHOD: Here, we examine the effect of flaxseed dietary fibers in different food matrices on blood lipids and fecal excretion of fat and energy in a double-blind randomized crossover study with 17 subjects. Three different 7-d diets were tested: a low-fiber control diet (Control), a diet with flaxseed fiber drink (3/day) (Flax drink), and a diet with flaxseed fiber bread (3/day) (Flax bread). Total fat and energy excretion was measured in feces, blood samples were collected before and after each period, and appetite sensation registered 3 times daily before main meals. RESULTS: Compared to control, Flax drink lowered fasting total-cholesterol and LDL-cholesterol by 12 and 15%, respectively, (p < 0.01), whereas Flax bread only produced a reduction of 7 and 9%, respectively (p < 0.05). Fecal fat and energy excretion increased by 50 and 23% with Flax drink consumption compared to control (p < 0.05), but only fecal fat excretion was increased with Flax bread compared to control (p < 0.05). CONCLUSION: Both Flax drink and Flax bread resulted in decreased plasma total and LDL-cholesterol and increased fat excretion, but the food matrix and/or processing may be of importance. Viscous flaxseed dietary fibers may be a useful tool for lowering blood cholesterol and potentially play a role in energy balance. TRIAL REGISTRATION: ClinicalTrials.gov: NCT00953004.