Fermentation and Gut Health
Henk Schols (1)
Lecture 1: Overview upper digestive tract & Carbohydrates (structure and occurrence) 06/06/2020
Fibre recommended intake: 25-30g. Food digestion depends on age. Breastmilk has
almost no starch or fibre. Babies have almost no amylase. pH in the stomach is quite high.
The GI tract is more sterile in babies. Elderly have higher amylase levels, lower bowel
movement, reduced protease levels, different microbiota.
Intestinal Tract: ingestion, digestion, absorption and gut health (gut bacteria)
Stomach: Personal variation in acidity because the stomach pH changes between different
meals, because of pH and volume triggers from food.
Small Intestine: pancreatic enzymes and biliary mixture. Undigestible sugars are not
absorbed and will be fermented in the colon.
Colon: Fermentation happens in the colon. Fermentation starts earlier in the colon in
model animals, in the caecum already. Causes gas development. Phenolics and fibres end
up in the colon.
Macronutrient digestion: depends on the intrinsic factor (chemical structure), food
texture (water holding capacity), processing (emulsification, structure and starch
gelatinization/retrogradation and fibre), interaction with other components in food,
inhibition of digestive enzymes by food components, disorders. Digestion depends on age, babies and adults
have very different digestion due to different diet, microbiota, gut development.
- Triglycerides: triglycerides are normally broken down before the colon and absorbed in the small intestine
and don’t reach the colon at all, but if we overload our digestive tract, more triglycerides will be left undigested
and reach the colon.
- Proteins: depends on primary, secondary, tertiary and quaternary structures of proteins. Proteins are
hydrolysed in the small intestine by peptidases. The proteins that enter the colon influence the fermentation in
a non-beneficial way. A glycosylic fermentation is beneficial and proteins interfere with that. Enzymes that are
not used for digestion will also be digested to recycle amino acids.
- Carbohydrates: monosaccharides and disaccharides are small and easily dealt with by the digestive tract.
Oligosaccharides are non-digestible and are fibres that can be fermented. All the polysaccharides without the
alpha-1-4-linkage in starch are indigestible.
Digestible carbohydrates: available carbohydrates, the fraction that is digestible and available to
provide energy to the cells in our body. Small sugars and starches.
Dietary fibre: the edible parts of plants or analogous carbs that are resistant digestion and adsorption
in the human small intestine with complete or partial fermentation in the colon. Dietary fibres
promote beneficial physiological effects including laxation and/or blood cholesterol attenuation
and/or blood glucose attenuation. Not all fibres have the same effect, the chemical and physical
properties matter. Diversity is key. Non-starch polysaccharides, resistant starches and non-digestible
oligosaccharides.
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,Carbohydrates
- Monosaccharides: are all digestible. Single sugars. Glucose, Fructose, Galactose.
- Disaccharides: some are digestible and some are not. Two sugars linked together. Lactose, Sucrose, Maltose.
- Oligosaccharides: Degree of Polymerization: 3-10 (number of sugar units).
Indigestible oligosaccharides
• Fructo-oligosaccharides: a subgroup of inulin. Fruit sugars. Undigestible.
• Raffinoses: oligosaccharides in legumes, are fermented. Contain galactoses. Cause flatulence.
Dosage is important.
Digestible oligosaccharides
• Galacto-oligosaccharides: Beneficial sugars for babies that are in maternal milk. They can be
mimicked in cow’s milk with altered lactose by splitting them with galactosidases and making different
new compositions in the lab to mimic mother milk oligosaccharides. Without these oligosaccharides,
babies are more prone to diseases.
Mammal milk oligosaccharides (MMO): 150 different sugar structures present in human
milk. Sialic acid, fucose sidechains on a lactose core unit. Helps the baby to develop a good
immune system.
- Polysaccharides: Starches (digestible or resistant) and non-starch polysaccharides. Can function in food to
bind water, swell, thicken, gel, limit diffusion, exchange ions. It influences water regulation in the digestive
track, transit time, bulk volume, nutrient release and fermentation. They can also provide a feeling of satiety.
The chemical structure determines the physical properties. Polysaccharides can be extracted from plant
materials, seaweeds (other sugar composition), shrimp exoskeletons, modified isolated starches/celluloses.
• Starches: starches are not required to be mentioned on food labels but can still provide many sugars.
More digestible starches will provide energy. Amylose (linear) and amylopectin (branched) structures
are in starches. Starches are hard to dissolve and need to be heated to dissolve. The viscosity will go
up and the starch granules take up water, then it will be broken down in to saccharose and
amylopectin. After some time, retrogradation will happen. The starch granules will start to bind again.
Digestible: digestible starch, are easily degraded to glucose in the small intestine.
Resistant: indigestible. 90% of the starch will be digested, but some parts will escape
digestion, the resistant starches. Those parts are resistant to the amylases. There are four
types that are either physically entrapped, uncooked, retrograded, or chemically modified.
• Non-starch polysaccharides (NSP): indigestible, glucans, dextrins, mannans, fructans, xylans, pectins,
NSPs. Fibres. Cause attraction of water to the small intestine, which changes absorption and
fermentation plus gas production in the colon.
Prebiotics: Dietary fibres that are selectively utilized by host microorganisms conferring a health benefit. A
selected desired effect is attained. All prebiotics are fibres. Not the other way around. This definition can
change in the future. Inulin, FOS and GOS.
Inulin: is an indigestible oligosaccharide, a polymer of glucose. Fructo-oligosaccharides are made from
inulin by hydrolysis by inulase. It is extracted from chicory roots. Ensiled (preserved) chicory root pulp
(ECRP) is easier to use in products. The composition does not change by ensiling, but the solubility
changed, differences in soluble and insoluble fibres. Especially pectin became more soluble. Increased
solubility causes easier fermentation. It
stimulates bifidobacterial and butyrate
production.
Probiotics: live bacteria
EFSA: determine the right to make health claims.
Authorization company.
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, Polymers: Glucose -> glucan (polymer form of glucose). The more charged polymers, the more soluble the
polymers will be because the negative charges disperse the polymers, making them easier to digest. Linear
sugars are less soluble because they can approach each other and make crystals. More branched sugars are
more soluble (higher substitution, more branches).
Reducing ends: free oxygen groups, at the end of the sugar polymer. The oxygens in the linkages between the
sugars are not reducing, because they are connected in a polymer chain. The ones on the ends can reduce. OH
groups can change to an open form (=O). which is reactive. Reactive oxygen can facilitate Maillard and
caramelization reactions. Reactive forms can reduce copper. Reducing sugars can switch between forms.
Cell wall: Hemicellulose, celluloses and pectins form the cell wall
structures of vegetables. They create firmness in the cell wall of the
plants. Pectins fill the gaps between celluloses and hemicelluloses. Plants
have the same building blocks, but different structure and relative
amounts, leading to different cell wall porosity, accessibility, water
binding properties etc.
- Pectins: galacturonic acid is the main residue in pectin.
Chemical structure of pectin determines the 3D structure and
functionality. Pectins make up around half of plant structural
elements. Chemical pectin degradation by cooking causes easy
digestion and chewing. It is pH dependent. At high pH, cooking
causes pectin degradation. Pectins are important for ripening
fruits and vegetables, when they are broken down they are easier
to consume. Pectins themselves give no direct energy in the small intestine, but from SCFA production
from the bacteria, energy is still gained.
Pectolytic enzymes: Pectins are processed and fermented by enzymes. The enzymes are very
specific to sugars and bonds. Specific microbiota will produce enzymes to degrade the fibres
in the food.
Galacturonic acid: sugar with an acid group. It will take a lot of effort to hydrolyse this strong
bond. It comes from galactose and is its uronic acid.
- Cellulose: Large glucose polymer, difficult to degrade.
- Xylans (Hemicellulose): cellulose backbone (glucose) with xyloses attached. Increases what flour
quality, brewing barley quality and dietary fibre. Prebiotic function, stimulate a certain family of
bacteria. They can be very linear or very branched, which have different properties. Huge variation
depending on source, type of tissue, environmental grow condition. Prebiotic function.
Galactomannans: backbone of beta-1,4-linked mannose residues. Gum present in cell walls and in many seeds
as storage polysaccharide. Galactose to mannose ratio differs greatly. The physical properties depend strongly
on the type of galactomannan. The substitution (sidechains) determine the solubility, it decreases with more
sidechains. The gelling properties improve with more side chains.
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