Dietary Fiber Flashcards
Dietary Fibre
Lignin and plant polysaccharides that are resistant to hydrolysis by the digestive enzymes in man
Plant cell wall
Middle lamalla: Pectic substance & lignin
Primary cell wall: Cellulose in network
Secondary cell wall: Cellulose in parallel
NSP
non- starch polysaccharide
two types of NSP
Cellulose :
Cellulose
Carboxymethylcellulose
Non- cellulose polysaccharide (NCP): Hemicelluloe Pectins Plant gums & mucilages Inulin Guar
Principal sugars present in cellulose ?
Food souces?
Glucose
All cell walls
Principal sugars present in pectic substance ?
Food souces?
Galacturonic acid
Arabinose/ Galactose
Mainly in fruit & veg
Principal sugars present in hemicellulose?
Food souces?
Arabinose /Xylose - Cereals
Glucoronic Acid /Arabinose/ Xylose- Cereals
Glucoronic Acid /Xylose- Fruit & Veg
Xylose / Glucose
Principal sugars present in Gums Mucilages. Storage polysaccharides?
Gum: Glucose - Fruit & Veg & cereals
Storage: Wide range - seeds & fruits
Lignin is a polysaccharide? T/F
T
dietary insoluble fiber
it is a complex polymer of aromatic alcohols
Energy value of NSP
depending on fermentation ~ 0-3Kcal/g
mean 2 Kcal/g (with ~ 70% fermentation)
Good source of NSP
> 4g / portion
peas, beans, wholemeal, rye , Bran flakes, muesli
Moderate source of NSP
1-4g/ portion
Most veg & fruit, nuts, Brown rice, porridage
Poor source of NSP
Lettuce, grapes, white rice, biscults, cakes, corn flakes
Nutrient content of bran & germ
High [Vit B] - thiamin, riboflavin, pantothenic acid
Minerals - P, Na, K , Fe, Mg, Ca
Elevated levels of basic amino acids- arginine & lysine
Phytochemicals - phytates, oxalates & phenolics
NSP & micronutrients absorption
Bio- availability of some minerals may be reduce in present of NSP
Minerals bind to CHO structure, phytates, tannins & oxalates
Wheat bran most potent dietary inhibitor of
Calcium
Iron
Zinc
High NSP impair ? absorption
Vit D & B12
NSP in ____ diets doesn’t compromise micronutrient status long term
mixed or vegetarian
Due to NSP viscosity in solution, affects on miacronutrient utilisation by__(3)
Results in ?
inhibit gut movement
delay delivery of liquid from stomach
slow food mixing and digestive juices
> increase delivery iower small intestine
and reduce absorption in gut
Example of soluble fiber
oat, barley, rye legumes bananas/ apples, berries nuts alliums (onions, garlic, leeks) root veg
example of insoluable fibre
Bran whole grain seeds fruit skin beans Cauliflower celery
Crude fiber
residue after boiling defatted food with diluted alkali and then acid.
The methods recovers 50 -80% cellulose, 10- 50% lignin and 20% of hemicellulose
NSP (Englyst)
The CHO plant cell wall that originally called dietry fiber, less the lignin
Dietary fiber (Southgate)
The sum of lignin nad polysaccharides that are not hydrolysed by the endogenous secretions of Gastric tract
Unavailable carbohydrate
polysaccharides that are not hydrolysed by digestive tract (including lignin)
Resistance starch
physically inaccessible - locked way in food matrix
highly crystalline - raw food ; cooled food
poorly hydrolysed in small intestine
fermentable
Functionally very similar to NSP
Examples of oligosaccharides
Fructooligosaccharides- Inulin; Raftilose
Galactooligosaccharides- Raffinose
Mannan- oligosaccharides - Guar gum
CODEX ALIMENTARIUS’ definition of dietary fiber
CHO polymers with 10 or more monomeric units, which are not hydrolysed by the endogenous enzymes in the small intestine of human and belong to the catergories
CODEX ALIMENTARIUS’ defined dietary fiber catergories
- Edible CHO polymers naturally occur in food
- CHO polymers which obtained from raw material by enzymetic, physically or chemical means; have shown physiological benefit to heath and has scientific evidence that is generally accepted by competent authorities
- synthetic CHO polymers that have shown physiological benefit to heath and has scientific evidence that is generally accepted by competent authorities
- Dietary fiber may contain fraction of other compounds (that associated with the CHO in cell wall) when derived from plant. Certian analytical method may measure the other compounds as dietary fiber, excepted those if they have been extracted or re- introduced in food
- National authorities can decide whether to include CHO with 3 -9 monomeric units as dietary fiber