A water-soluble fraction from a by-product of wheat increases the formation of propionic acid in rats compared with diets based on other by-product fractions and oligofructose

Background: Dietary fibre is fermented by the colonic microbiota to carboxylic acids (CA), with potential health effects associated in particular with butyric and propionic acid. Objective: To investigate the formation of CA in the hindgut of healthy rats fed dietary fibre from different fractions of wheat shorts, a by-product of the milling of wheat. Design: Rats were fed dietary fibre (80 g/kg feed per day for 7 days) from wheat shorts and fractions thereof (ethanol-soluble, water-soluble and insoluble fractions), oligofructose (OF) diet and a mixture of oligofructose and raffinose (OR) diet. Results: The water-soluble fraction, with a high content of arabinoxylan (AX), increased the formation of propionic acid in the hindgut and lowered the ratio of acetic to propionic acid in the portal blood of rats. High levels and proportions of butyric acid were seen in rats fed the OR diet. The pattern of CA resulting from the ethanol-soluble diet, mainly composed of fructan and raffinose, was more similar to that of the OF diet than the OR diet. Conclusions: The high formation of propionic acid with the water-soluble fraction may be attributed to the high AX content. The results also indicate that the wheat fructans produced more propionic acid and less butyric acid than oligofructose. It may furthermore be speculated that the increased formation of butyrate with the OR diet was due to synergistic effects of the components in this diet

Nutritional and physicochemical characterisation of dietary fibre in wheat fractions

Dietary fibre is fermented in the colon to short-chain fatty acids (SCFAs), of which especially butyric and propionic acid may have health-promoting effects. One source of dietary fibre may be by-products from wheat, which are currently used as animal feed. The aim of the work presented in this thesis was to perform physicochemical and nutritional characterisation of dietary fibre in waste fractions from wheat, and to examine the potential for using carbohydrate-rich fractions commercially for the design of products with specific health benefits. The dietary fibre content, including arabinoxylan (AX) and fructan, was determined in six different milling fractions, distillers’ grains (DG) from ethanol production and streams from the wet fractionation of wheat flour into starch and gluten. The highest fructan content was found in one stream from wet fractionation, while the shorts and bran fractions were the milling fractions with the highest fructan content. Using xylanase in wet fractionation decreased the molecular weight of the AX and increased the proportion of soluble AX, but did not produce significant amounts of arabinoxylan oligosaccharides or affect the fructans. Mannoproteins and (1→3) and (1→6) β-glucans from the yeast and unidentified low-molecular-weight carbohydrates mainly composed of arabinose were only found in DG. Rats were fed diets containing shorts and fractions thereof (an insoluble, a water-soluble and an ethanol-soluble fraction) and wet process fractions (DG and two fractions from wet fractionation, produced with and without xylanase), separated into supernatant and pellet fractions. The fractions with a high content of soluble AX and fructan (the water-soluble fraction from shorts and the supernatant fractions from wet fractionation), and the supernatant from DG, with a high content of dietary fibre composed of xylose and arabinose, led to the formation of higher amounts of propionic acid in the hindgut, and lower ratios of acetic to propionic acid in the portal blood of the rats, than the other diets. Particularly high proportions of butyric acid were observed with the reference diet containing a mixture of oligofructose and raffinose. The results further indicated that wheat fructans of the molecular weight studied resulted in a higher proportion of propionic acid and a lower proportion of butyric acid than oligofructose. The main differences between the wet process fractions were found between the supernatant and pellet fractions, rather than between the original fractions. Rats fed the supernatant diets generally had higher caecal pools of most SCFAs and lower ratios of acetic to propionic acid in the portal blood than rats fed the corresponding pellet diets. One important difference was the bifidogenic effect of the DG supernatant, although all supernatants led to higher caecal concentrations of Enterobacteriaceae. No effect was seen following xylanase treatment, indicating that the degree of degradation was not sufficient and/or the AX content too low to produce a measurable effect

Vegetable, fruit and potato fibres

As much as one-third of the dietary fibre intake in a normal Western diet originates from fruits and vegetables. Nutritional effects of dietary fibre can to a great extent be related to the physicochemical properties of the fibre, such as composition, solubility, viscosity, water-holding capacity and molecular weight. In fruits and vegetables the structure of the cell wall matrix (tertiary structure) is also extremely important for nutritional characteristics and texture of the product. Fruits and vegetables are often processed in some way prior to consumption. During this processing the cell wall composition and also the physicochemical properties of the plant material may be changed considerably. The effects of mechanical, chemical, enzymatic and thermal processing will be discussed in this chapter

Övergången från gymnasie- till högskolestudier i kemi

Kemi läses som ämne på de högskoleförberedande naturvetenskapliga och tekniska gymnasieprogrammen, men kemiundervisningen måste även förhålla sig till den aktuella läroplanen och ta hänsyn till andra syften än det högskoleförberedande. Med utgångspunkt från detta var syftet med studien att undersöka hur studenter och lärare upplever studenternas förkunskaper i kemi i relation till högskolestudier. Arbetet innefattar dels enkätundersökningar, där studenter tillfrågades om upplevelse och värdering av sina förkunskaper vid introduktionen till högskolestudier, dels enskilda intervjuer med både högskole- och gymnasielärare. Svaren användes för att identifiera ämnesområden och förmågor som ansågs särskilt viktiga för studenter att få med sig som förkunskaper från gymnasiet inför högskolestarten. Därutöver undersöktes bakomliggande faktorer i gymnasieutbildningen, som lärarnas förhållningssätt till läroplan och läromedel samt deras kunskapssyn, vilka starkt påverkar förutsättningarna för elevernas tillägnande av kunskap. Resultaten visar att majoriteten av studenterna i undersökningen kände sig väl förberedda inför sina högskolestudier, men inom framförallt termodynamik önskades mer förkunskaper. En slutsats som kan dras av undersökningen är att det finns vissa möjligheter att underlätta övergången till universitetsstudier i kemi genom att som enskild lärare göra justeringar i innehållet i kemikurserna eller den tidsmässiga fördelningen mellan dem till förmån för de områden som nyblivna studenter upplever som särskilt problematiska

The Effect of Dietary Fiber from Wheat Processing Streams on the Formation of Carboxylic Acids and Microbiota in the Hindgut of Rats.

Colonic fermentation of dietary fiber produces carboxylic acids and may stimulate the growth of beneficial bacteria. This study investigated how byproducts of wheat processing (distillers' grains and two fractions from the wet fractionation to starch and gluten, one of which was treated with xylanase) affect the composition of the cecal microbiota and the formation of carboxylic acids in rats. Differences were mostly found between diets based on supernatants and pellets, rather than between fiber sources. Cecal pools and levels of most carboxylic acids in portal blood were higher for rats fed the supernatant diets, while cecal pH and ratios of acetic to propionic acid in portal blood were lower. The diet based on supernatant from distillers' grains gave the highest level of bifidobacteria. Molecular weight and solubility are easier to modify with technological processes, which provides an opportunity to optimize these properties in the development of health products

Characterization of Indigestible Carbohydrates in Various Fractions from Wheat Processing

Fractions rich in indigestible carbohydrates, such as fructan and arabinoxylan, are obtained as by-products when ethanol, starch, and gluten are produced from wheat flour. Today, these fractions are used as animal feed. However, these components may have positive physiological effects in humans. In this study, the content of indigestible carbohydrates in distillers' grains and process streams from the wet fractionation of wheat flour was determined. The fractions were further characterized by ethanol extractability analysis, anion-exchange chromatography, NMR, and size-exclusion chromatography. One fraction from wet fractionation contained (g/100 g, db) 6.0 ± 1.0 fructan and 10.3 ± 1.1 dietary fiber (66 ± 4% arabinoxylan), while distillers' grains contained 20.7 g/100 g (db) dietary fiber (30% arabinoxylan). In addition to indigestible carbohydrates from wheat, distillers' grains contained β-(1→3) and β-(1→6) glucans and mannoproteins from the yeast and low molecular weight carbohydrates mainly composed of arabinose. The use of endoxylanase in wet fractionation decreased the molecular weight of the arabinoxylans and increased the arabinose to xylose ratio but had no effect on the fructans. In conclusion, waste streams from industrial wheat processing were enriched in fructan, arabinoxylan, and other indigestible carbohydrates. However, the physiological effects of these fractions require further investigation

Distribution and characterisation of fructan in wheat milling fractions

Structure and health effects of inulin-type fructans have been extensively studied, while less is known about the properties of the graminan-type fructans in wheat. Arabinoxylan (AX) is another important indigestible component in cereal grains, which may have beneficial health effects. In this study, the fructan content in milling fractions of two wheat cultivars was determined and related to ash, dietary fibre and AX contents. The molecular weight distribution of the fructans was analysed with HPAEC-PAD and MALDI-TOF MS using 1H NMR and enzymatic hydrolysis for identification of fructans. The fructan content (g/100 g) ranged from 1.5 ± 0.2 in flour to 3.6 ± 0.5 in shorts and 3.7 ± 0.3 in bran. A correlation was found between fructan content and dietary fibre content (r = 0.93, P < 0.001), but with a smaller variation in fructan content between inner and outer parts of the grain. About 50% of the dietary fibre consisted of AX in all fractions. The fructans were found to have a DP of up to 19 with a similar molecular weight distribution in the different fractions

Development of an oat-based sour milk-like product

A fermented, oat-based product with properties resembling those of the traditional, Swedish, fermented milk product "filmjoelk" (sour milk) was developed. Com., mixed-strain, mesophilic starter cultures were grown in the oatbases M30, G40, and Oatly, which differed in the compn. of their carbohydrates. The exopolysaccharide-producer Pediococcus damnosus 2.6 was included to increase the viscosity of the G40 product. The CHN-19 culture chosen for the final product formulation produced a pleasant, buttery aroma, but a less sour taste than ordinary "filmjoelk". The addn. of glucose to M30 increased the acidification rate and gave a better aroma. A sensory anal. of two flavored products based on the G40 and M30 media, showed a higher acceptance of the M30 product. This study shows a potential for producing an oat-based "filmjoelk", but further work on consistency and taste is needed