Helle Nygaard Lærke

Physical, microscopic and chemical characterisation of industrial rye and wheat brans from the Nordic countries

Background Epidemiological studies show inverse relationship between intake of wholegrain cereals and several chronic diseases. Components and mechanisms behind possible protective effects of wholegrain cereals are poorly understood. Objective To characterise commercial rye bran preparations, compared to wheat bran, regarding structure and content of nutrients as well as a number of presumably bioactive compounds. Design Six different rye brans from Sweden, Denmark and Finland were analysed and compared with two wheat brans regarding colour, particle size distribution, microscopic structures and chemical composition including proximal components, vitamins, minerals and bioactive compounds. Results Rye brans were generally greener in colour and smaller in particle size than wheat brans. The rye brans varied considerably in their starch content (13.2–;28.3%), which reflected variable inclusion of the starchy endosperm. Although rye and wheat brans contained comparable levels of total dietary fibre, they differed in the relative proportions of fibre components (i.e. arabinoxylan, β-glucan, cellulose, fructan and Klason lignin). Generally, rye brans contained less cellulose and more β-glucan and fructan than wheat brans. Within small variations, the rye and wheat brans were comparable regarding the contents of tocopherols/tocotrienols, total folate, sterols/stanols, phenolic acids and lignans. Rye bran had less glycine betaine and more alkylresorcinols than wheat brans. Conclusions The observed variation in the chemical composition of industrially produced rye brans calls for the need of standardisation of this commodity, especially when used as a functional ingredient in foods.

REVIEW: Rye Arabinoxylans: Molecular Structure, Physicochemical Properties and Physiological Effects in the Gastrointestinal Tract

ABSTRACT Arabinoxylans (AX) are the main dietary fiber (DF) polysaccharides in rye where they represent ≈55% of the total polysaccharides. Rye AX consist of a backbone of (1→4)-β-d-xylopyranosyl residues (X) mainly substituted with α-l-arabinofuranosyl residues (A) to varying degrees at the O-2 position, the O-3 position, or both. The A/X ratio of total AX is 0.49–0.82 and extractable AX ratio is 0.34–0.85 in different studies. AX also contain small amounts of ferulate residues bound to arabinose as esters at its O-5 position. The weight average molecular weight varies from 40,000 to 900,000 with an average of ≈200,000. AX influence physiology in different segments of the gastrointestinal tract. The complex molecular structure of rye AX makes them resistant against microbial modification in the small intestine; consequently, rye AX have a much higher influence on the viscosity in the small intestinal digesta than does β-glucan from oats and barley. In spite of that, it has not been possible in studies wit...

Roughages for Growing Pigs, with Emphasis on Chemical Composition, Ingestion and Faecal Digestibility

Two experiments, each with 10 gilts of 30 kg initial bodyweight, were set up to gain experience in feeding three roughages under controlled experimental conditions. The experiments were designed to establish what proportion of the total diets the roughages can make up without refusal, and to get preliminary results on the apparent faecal digestibility of diets containing three kinds of roughage. In experiment 1 (exp. 1), the roughage consisted of either fresh or frozen (thawed) clover-grass. In experiment 2 (exp. 2), clover-grass silage and whole-crop pea-barley silage was studied. The faecal digestibility of gross energy (GE), dry matter (DM), organic matter (OM), dietary fibre (DF) and crude protein (CP) were measured for pigs fed diets including these roughages. The three roughages, leaves and stems of clover-grass and the basal diets were also tested for in vitro OM digestibility. Roughage intake was similar in both experiments. The average proportion of roughage ingested was 18-19% of DM. There were ...

Resistant starch and arabinoxylan augment SCFA absorption, but affect postprandial glucose and insulin responses differently

The effects of increased colonic fermentation of dietary fibres (DF) on the net portal flux (NPF) of carbohydrate-derived metabolites (glucose, SCFA and, especially, butyrate), hormones (insulin, C-peptide, glucagon-like peptide 1 and glucose-dependent insulinotropic peptide) and NEFA were studied in a healthy catheterised pig model. A total of six pigs weighing 59 (SEM 1·6) kg were fitted with catheters in the mesenteric artery and in the portal and hepatic veins, and a flow probe around the portal vein, and included in a double 3 × 3 cross-over design with three daily feedings (at 09.00, 14.00 and 19.00 hours). Fasting and 5 h postprandial blood samples were collected after 7 d adaptation to each diet. The pigs were fed a low-DF Western-style control diet (WSD) and two high-DF diets (an arabinoxylan-enriched diet (AXD) and a resistant starch-enriched diet (RSD)). The NPF of insulin was lower (P= 0·04) in AXD-fed pigs (4·6 nmol/h) than in RSD-fed pigs (10·5 nmol/h), despite the lowest NPF of glucose being observed in RSD-fed pigs (203 mmol/h, P= 0·02). The NPF of total SCFA, acetate, propionate and butyrate were high, intermediate and low (P< 0·01) in AXD-, RSD- and WSD-fed pigs, respectively, with the largest relative increase being observed for butyrate in response to arabinoxylan supplementation. In conclusion, the RSD and AXD had different effects on the NPF of insulin and glucose, suggesting different impacts of arabinoxylan and resistant starch on human health.

Carbohydrate composition and in vitro digestibility of dry matter and nonstarch polysaccharides in corn, sorghum, and wheat and coproducts from these grains

The objectives of this work were to determine carbohydrate composition and in vitro digestibility of DM and nonstarch polysaccharides (NSP) in corn, wheat, and sorghum and coproducts from these grains. In the initial part of this work, the carbohydrate composition of 12 feed ingredients was determined. The 12 ingredients included 3 grains (corn, sorghum, and wheat), 3 coproducts from the dry grind industry (corn distillers dried grains with solubles [DDGS] and 2 sources of sorghum DDGS), 4 coproducts from the wet milling industry (corn gluten meal, corn gluten feed, corn germ meal, and corn bran), and 2 coproducts from the flour milling industry (wheat middlings and wheat bran). Results indicated that grains contained more starch and less NSP compared with grain coproducts. The concentration of soluble NSP was low in all ingredients. Cellulose, arabinoxylans, and other hemicelluloses made up approximately 22, 49, and 29% (DM basis), respectively, of the NSP in corn and corn coproducts and approximately 25, 43, and 32% (DM basis), respectively, of the NSP in sorghum and sorghum DDGS. Cellulose, arabinoxylans, and other hemicelluloses made up approximately 16, 64, and 20% (DM basis), respectively, of the NSP in wheat and wheat coproducts. The concentration of lignin in grains was between 0.8 and 1.8% (DM basis), whereas coproducts contained between 2.2 and 11.5% lignin (DM basis). The in vitro ileal digestibility of NSP was close to zero or negative for all feed ingredients, indicating that pepsin and pancreas enzymes have no effect on in vitro degradation of NSP. A strong negative correlation ( = 0.97) between in vitro ileal digestibility of DM and the concentration of NSP in feed ingredients was observed. In vitro total tract digestibility of NSP ranged from 6.5% in corn bran to 57.3% in corn gluten meal. In conclusion, grains and grain coproducts contain mostly insoluble NSP and arabinoxylans make up the majority of the total NSP fraction. The in vitro digestibility of NSP depends on the amount and type of NSP and degree of lignification in the feed ingredient. The NSP composition of grains and grain coproducts plays an important role in determining the extent of fermentation of NSP; therefore, NSP composition influences the energy value of grains and grain coproducts.

Effects of concentrated arabinoxylan and β-glucan compared with refined wheat and whole grain rye on glucose and appetite in subjects with the metabolic syndrome: a randomized study

Background/objectives:Several studies emphasise that arabinoxylan and β-glucan have more beneficial effects on glucose metabolism than low-dietary fibre (DF) meals. Less attention has been paid to the effects of concentrated DF compared with whole grain. We compared the effects of DF and whole grain on glucose, hormone responses and appetite in subjects with the metabolic syndrome (MetS).Subjects/methods:Fifteen subjects with MetS participated in this acute, randomised, cross-over intervention study. The test breads provided 50 g of digestible carbohydrate: wheat bread with concentrated arabinoxylan (AX) or β-glucan (BG), rye bread with kernels (RK) and wheat bread (WB) as control. Blood samples were drawn for 270 min to determine glucose, insulin, glucagon-like peptide-1, glucose-dependent insulinotropic peptide (GIP) and ghrelin. Appetite score was addressed every 30 min. Ad libitum energy intake (EI) was measured 270 min after test meals.Results:Compared with WB, BG and RK induced lower initial glycaemic responses (P<0.001), whereas AX only reduced the glucose peak value (P<0.001). RK reduced insulin (P<0.001) and GIP responses (P<0.001) compared with the other breads. BG lowered insulin responses more than AX (P<0.001). AX, BG and RK increased satiety feeling (P<0.001) more than WB, but did not differ significantly in terms of subsequent EI (P=0.089).Conclusion:BG and RK had beneficial impact on the glucose response, whereas AX had only effect on the postprandial glucose peak. The impact of the AX bread was influenced by higher protein content. Whether the metabolic effects of the breads are still present to mixed meals remains to be tested.

Postprandial effects of test meals including concentrated arabinoxylan and whole grain rye in subjects with the metabolic syndrome: a randomised study.

Background/objectives:Prospective studies have shown an inverse relationship between whole grain consumption and the risk of type 2 diabetes, where short chain fatty acids (SCFA) may be involved. Our objective was to determine the effect of isolated arabinoxylan alone or in combination with whole grain rye kernels on postprandial glucose, insulin, free fatty acids (FFA), gut hormones, SCFA and appetite in subjects with the metabolic syndrome (MetS).Subjects/methods:Fifteen subjects with MetS participated in this acute, randomised, cross-over study. The test meals each providing 50 g of digestible carbohydrate were as follows: semolina porridge added concentrated arabinoxylan (AX), rye kernels (RK) or concentrated arabinoxylan combined with rye kernels (AXRK) and semolina porridge as control (SE). A standard lunch was served 4 h after the test meals. Blood samples were drawn during a 6-h period, and appetite scores and breath hydrogen were assessed every 30 min.Results:The AXRK meal reduced the acute glucose (P=0.005) and insulin responses (P<0.001) and the feeling of hunger (P=0.005; 0–360 min) compared with the control meal. The AX and AXRK meals increased butyrate and acetate concentrations after 6 h. No significant differences were found for the second meal responses of glucose, insulin, FFA, glucagon-like peptide-1 or ghrelin.Conclusions:Our results indicate a stimulatory effect of arabinoxylan on butyrate and acetate production, however, with no detectable effect on the second meal glucose response. It remains to be tested in a long-term study if a beneficial effect on the glucose response of the isolated arabinoxylan will be related to the SCFA production.

Dietary fibers as immunoregulatory compounds in health and disease

Many nonstarch polysaccharides (NSPs) classified as dietary fibers have been reported to possess immunoregulatory properties. The fibers reported to activate or by other means modulate immune responses originate from both plant, fungal, and microbial sources and constitute highly distinct structures. In order to enhance our understanding of factors important for the immunoregulatory activities, this article addresses the importance of chemical structure, origin, and purity of fibers for their capacity to interact with key regulatory immune cells. Furthermore, we assess bioavailability, and discuss possible mechanisms involved. The binding of some NSPs to carbohydrate receptors on immune cells is well established and this event leads to activation or other changes. Especially, certain β‐glucans and some mannans have demonstrated immunomodulatory capacity with the specific structure being important for the activity. Within β‐glucans the activity varies according to structure, molecular weight, and solubility. As many of the preparations tested constitute crude extracts or partly purified NSPs, the risk of contaminants holding immunoregulatory activities should not be ignored. To what extent NSPs enter systemic circulation has been difficult to assess, partly due to lack of sensitive analytical methods. The presence of NSPs in blood and Peyers patches in the gut has been demonstrated, supporting encounter between NSPs and immune cells, but bioavailability studies still constitute a major challenge. Studies demonstrating in vivo effects of β‐glucans on microbial infections and cancer treatment strongly indicate an immunoregulatory mechanism behind the effects. However, the potential of NSPs as immunoregulatory food ingredients is still far from fully explored.

NMR‐based metabonomics reveals that plasma betaine increases upon intake of high‐fiber rye buns in hypercholesterolemic pigs

This study presents an NMR-based metabonomic approach to explore the overall endogenous biochemical effects of a rye versus wheat-based fiber-rich diet in hypercholesterolemic pigs. The pigs were fed high-fat, high-cholesterol rye- (n = 9) or wheat- (n = 8) based buns with similar levels of dietary fiber for 9-10 wk. Fasting plasma samples were collected 2 days before and after 8 and 12 days on the experimental diets, while postprandial samples taken after 58-67 days, and( 1)H NMR spectra were acquired on these. Principal component analysis on the obtained NMR spectra demonstrated clear effects of diet on the plasma metabolite profile, and partial least squares regression discriminant analysis on the spectra revealed that the intensity of the spectral region at 3.29 ppm dominated the differentiation between the two diets, as the rye diet was associated with higher spectral intensity in this region. The 3.29 ppm signal is ascribed to N(CH(3))(3) protons in betaine, which may be an important contributor to the health promoting effects of rye.

Effects of Isolated and Complex Dietary Fiber Matrices in Breads on Carbohydrate Digestibility and Physicochemical Properties of Ileal Effluent from Pigs

To assess the effects of content and structure of dietary fiber (DF) on the carbohydrate digestibility and physicochemical properties of ileal digesta, five bread diets were studied in an experiment with ileum-cannulated pigs in a crossover design. The diets consisted of two experimental breads based on white wheat flour with added wheat arabinoxylan (AX) or with added isolated oat β-glucan (BG), which were compared with a low-DF commercial white wheat bread (WF) and two commercial high-DF, dark ground rye bread (GR) and rye bread with kernels (RK) as positive controls. There was no profound effect of either DF content, structure, viscosity, or water-binding capacity on the ileal digestibility of starch, which was almost completely digested in the small intestine. Arabinoxylan and β-glucan were 11 and 81% degraded in the ileum, respectively, which resulted in a significant increase and decrease of ileal extract viscosities, respectively. It is concluded that the viscosity-elevating properties of soluble DF in breads and ileal digesta are strongly dependent on the content and structure of DF and degree of resistance toward microbial enzymes.