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Nutritional and physicochemical characterisation of dietary fibre in wheat fractions

Haskå, Lina LU (2011)
Abstract (Swedish)
Popular Abstract in Swedish

Arbetet visar att restprodukter från fraktionering av vete är rika på kostfiber med olika funktionella och nutritionella egenskaper. Biprodukterna används för närvarande inte för vidare exploatering utan har endast användning som djurfoder. Ett ökat intag av kostfiber är önskvärt ur folkhälsosynpunkt, och det kommersiella värdet av restprodukterna skulle öka betydligt om de i stället kunde utnyttjas för att utveckla produkter med hälsomervärden. De kostfiberkomponenter som främst studerades var fruktan och arabinoxylan, eftersom tidigare studier har visat att dessa kan ha positiva hälsoeffekter. Fruktan från cikoriarot kan t.ex. bidra till ökat upptag av kalcium och minskad inflammation i tarmen,... (More)
Popular Abstract in Swedish

Arbetet visar att restprodukter från fraktionering av vete är rika på kostfiber med olika funktionella och nutritionella egenskaper. Biprodukterna används för närvarande inte för vidare exploatering utan har endast användning som djurfoder. Ett ökat intag av kostfiber är önskvärt ur folkhälsosynpunkt, och det kommersiella värdet av restprodukterna skulle öka betydligt om de i stället kunde utnyttjas för att utveckla produkter med hälsomervärden. De kostfiberkomponenter som främst studerades var fruktan och arabinoxylan, eftersom tidigare studier har visat att dessa kan ha positiva hälsoeffekter. Fruktan från cikoriarot kan t.ex. bidra till ökat upptag av kalcium och minskad inflammation i tarmen, och både fruktan och arabinoxylan kan öka koncentrationen av hälsosamma bakterier. Innehållet av fruktan var speciellt högt i en restfraktion i processflödet från framställningen av gluten och stärkelse, men denna fraktion innehöll också förhållandevis mycket lösliga arabinoxylaner. Det högsta fruktaninnehållet i malningsfraktioner från vete hittades i fodermjöl och kli, dvs. i de yttre delarna av vetekärnan. Dranken, en biprodukt från produktionen av etanol, bestod av jästceller och den del av vetemjölet som inte brutits ner under jäsnings- och destillationsprocessen. Denna fraktion innehöll även en stor andel av en oidentifierad löslig kostfiberkomponent bestående av arabinosenheter.



De nutritionella effekterna (främst bildningen av kortkedjiga fettsyror) från de kostfiberrika fraktionerna från fodermjöl, drank och från processflödena vid produktionen av stärkelse och gluten studerades också. När de odigererbara kostfibrerna når tjocktarmen produceras bakteriella nedbrytningsprodukter, s.k. kortkedjiga fettsyror, främst ättiksyra, propionsyra och smörsyra, där framför allt smörsyra och propionsyra har satts i samband med en rad fysiologiska effekter. Av speciellt intresse är därför att identifiera fraktioner som ger mycket smörsyra och propionsyra. Sammansättning, typ av kolhydratbindningar, molekylvikt och löslighet är faktorer som påverkar produktionen av kortkedjiga fettsyror. För att kunna studera effekten av olika kostfiberkomponenter delades vetefraktionerna upp ytterligare baserat på löslighet i vatten och/eller etanol. Fraktioner som innehöll mycket fruktan och lösliga arabinoxylaner ledde till att mycket propionsyra bildades. Även lösliga kostfiber från dranken gav en hög bildning av propionsyra. Fruktaner från cikoriarot som användes som jämförelse gav däremot mycket smörsyra, framförallt i kombination med raffinos (en kostfiber som också finns i vete). De lösliga kostfibrerna från dranken ökade också koncentrationen av gynnsamma bakterier i tjocktarmen. I en av fraktionerna från framställningen av stärkelse och gluten hade arabinoxylanerna delvis brutits ner med hjälp av tillsatt enzym. Detta ökade visserligen andelen lösliga arabinoxylaner, men inga skillnader beträffande bildning av kortkedjiga fettsyror kunde ses jämfört med när fraktioneringen gjorts utan enzym. (Less)
Abstract
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... (More)
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. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Amado, Renato, Institute of Food Science and Nutrition, ETH Zürich
organization
publishing date
type
Thesis
publication status
published
subject
keywords
dietary fibre, fructan, arabinoxylan, wheat, distillers' grains, short-chain fatty acids, microbiota
defense location
Lecture hall B, Center of Chemistry and Chemical Engineering, Getingevägen 60, Lund University Faculty of Engineering, Lund
defense date
2011-03-31 09:15
ISBN
978-91-7422-266-1
language
English
LU publication?
yes
id
b1100e06-f136-4480-a844-abe72bf450fa (old id 1782414)
date added to LUP
2011-03-08 09:52:05
date last changed
2016-09-19 08:45:19
@misc{b1100e06-f136-4480-a844-abe72bf450fa,
  abstract     = {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.<br/><br>
<br/><br>
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.<br/><br>
<br/><br>
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.<br/><br>
<br/><br>
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.},
  author       = {Haskå, Lina},
  isbn         = {978-91-7422-266-1},
  keyword      = {dietary fibre,fructan,arabinoxylan,wheat,distillers' grains,short-chain fatty acids,microbiota},
  language     = {eng},
  title        = {Nutritional and physicochemical characterisation of dietary fibre in wheat fractions},
  year         = {2011},
}