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Fiber

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... Chitosan Chitin Amino-polysaccharide polymer containing 1-4 linked glucose units Cells walls of some lower plants Chitosan Deacetylated form of chitin; ... – PowerPoint PPT presentation

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Title: Fiber


1
Chapter 4
  • Fiber

2
Definitions of Dietary Fiber Functional Fiber
  • Dietary fiber - nondigestible CHO lignin that
    are intact intrinsic in plants
  • Functional fiber - nondigestible CHO that are
    isolated, extracted, or manufactured known to
    have physiological benefits

3
Fiber and Plants
  • gt95 of fibers from cell wall
  • Primary wall
  • Secondary wall
  • Fiber-related components
  • Cellulose
  • Hemicellulose
  • Lignin
  • Pectins
  • Suberin
  • Cutin

4
Chemistry Characteristics of Dietary
Functional Fibers
  • Varieties
  • Cellulose
  • Hemicellulose
  • Pectins
  • Lignin
  • Gums
  • ?-glucans
  • Fructans
  • Resistant starch
  • Chitin chitosan
  • Polydextrose polyols
  • Psyllium
  • Resistant dextrins

5
Cellulose
  • Dietary functional fiber
  • Long, linear polymer of ? 1-4 linked glucose
    units
  • Main component of plant cell walls
  • Sources bran, legumes, nuts, peas, root
    vegetables, cabbage family, outer covering of
    seeds, apples

6
Hemicellulose
  • Dietary fiber
  • Heterogenous group of polysaccharide substances
  • Sugars in backbone side chains
  • Xylose, mannose, galactose (backbone)
  • Arabinose, glucoronic acid, galactose (side
    chains)
  • Sources bran, whole grains, nuts, legumes, some
    vegetables fruits

7
Pectins
  • Dietary functional fiber
  • Complex group of polysaccharides called
    galacturonoglycans
  • Backbone galacturonic acid
  • Cell wall middle lamella in plants
  • Water-soluble, gel-forming
  • Sources apples, strawberries, citrus

8
Lignin
  • Dietary functional fiber
  • Highly-branched polymer composed of phenol units
    with strong bonding
  • Structural components of plants - found in stems,
    seeds, bran layer
  • Sources wheat, mature root vegetables, fruits
    with edible seeds

9
Gums (Hydrocolloids)
  • Dietary functional fibers
  • Group of substances secreted at site of plant
    injury
  • Tree exudates gum arabic, gum karaya, gum ghatti
  • Shrub exudate gum tragacanth
  • Composed of sugars derivatives
  • Sources oatmeal, barley, legumes

10
?-Glucans
  • Dietary functinal fibers
  • Homopolymers of glucopyranose units
  • Water-soluble, highly fermentable
  • Sources cereal brans, especially oats barley

11
Fructans--Inulin, Oligofructose,
Fructooligosaccharides
  • Dietary fibers
  • Fructose units in chains of varying length
  • Prebiotics
  • Sources chicory, asparagus, onions, garlic,
    artichokes, tomatoes, bananas

12
Resistant Starch
  • Starch that cannot be digested by humans
  • Types
  • RS1 - plant cell walls
  • RS2 - ungelatinized starch granules
  • RS3 - retrograde starch from cooking cooling or
    extruding foods
  • RS4 - chemically modified starch
  • RS1 RS2 dietary fibers, RS3 RS4
    functional fibers

13
Chitin Chitosan
  • Chitin
  • Amino-polysaccharide polymer containing ? 1-4
    linked glucose units
  • Cells walls of some lower plants
  • Chitosan
  • Deacetylated form of chitin polysaccharide made
    of glucosamine N-acetyl glucosamine

14
Polydextrose Polyols
  • Polydextrose
  • Polysaccharide of glucose sorbitol units that
    have been polymerized at high temperatures
    partial vacuum
  • Polyols
  • Polyglycitol malitol
  • Found in syrups

15
Psyllium
  • Functional fiber
  • Mucilage from husk of psyllium seeds
  • Used as laxative
  • Must ingest plenty of fluids

16
Resistant Dextrins
  • Functional fibers
  • Generated by treating cornstarch with heat acid
    then with amylase
  • Glucose polymers containing ? 1-4 ? 1-6
    glucosidic bonds ? 1-2 ? 1-3 bonds

17
Selected Properties Physiological Effects of
Fiber
  • Important properties include
  • Solubility in water
  • Water-holding capacity viscosity
  • Adsorption or binding ability
  • Degradability/fermentability

18
Solubility in Water
  • Classifications
  • Soluble - dissolve in hot water
  • Insoluble - dont dissolve in hot water
  • Water-soluble some hemicelluloses, pectin, gums,
    ?-glucans
  • Water-insoluble cellulose, lignin, some
    hemicelluloses, chitosan, chitin

19
Solubility in Water
  • Soluble
  • Delay gastric emptying
  • Increase transit time
  • Decrease nutrient absorption
  • Insoluble
  • Decrease transit time
  • Increase fecal bulk

20
Water-Holding/Hydration Capacity Viscosity
  • Ability of fiber to bind water
  • Delayed (slowed) gastric emptying
  • Reduced mixing of gastrointestinal contents with
    digestive enzymes
  • Reduced enzyme function
  • Decreased nutrient diffusion rate--attenuation of
    the blood glucose response
  • Altered small intestine transit time

21
Adsorption or Binding Ability
  • Diminished absorption of lipids
  • Increased fecal bile acid excretion
  • Lowered serum cholesterol concentrations
    (hypocholesterolemic properties)
  • Altered mineral carotenoid absorption

22
Degradability/Fermentability
  • Fermentable fibers
  • Fermentable fibers as prebiotics
  • Short-chain fatty acid generation
  • Increased water sodium absorption in the colon
  • Mucosal cell proliferation
  • Provision of energy
  • Acidification of luminal environment

23
Degradability/Fermentability
  • Nonfermentable fibers
  • Detoxification
  • Increased fecal volume (bulk)

24
Roles of Fiber in Disease Prevention Management
  • Hypoglycemic hypolipidemic effects of soluble
    fibers
  • For diabetes high serum cholesterol
  • Insoluble, nonfermentable fibers for GI diseases
  • Diverticular disease, gallstones, IBS,
    constipation
  • Health claims for fiber

25
Roles of Fiber in Disease Prevention Management
  • Mechanisms
  • Adsorb bile acids, promote excretion
  • Increase fecal bulk
  • Provide fermentable substrates for bacteria in
    colon
  • Shortened fecal transit time
  • Decreases interluminal pH
  • Fermentation may release fiber-bound calcium
  • Butyric acid appears to hinder cancer cells
  • Insoluble fibers bind carcinogens

26
Recommended Fiber Intake
  • Adequate Intakes
  • Adults
  • 19-50 25 g for women, 38 g for men
  • 51 or gt 21 g for women, 31 g for men
  • Children
  • 1-3 19 g 4-8 25 g
  • Girls 9-18 26 g
  • Boys 9-13 31 g boys 14-18 38 g

27
Perspective 4
  • Phytochemicals Herbal Supplements in Health
    Disease

28
Phytochemicals Herbals
  • Phytochemicals
  • Echinacea
  • Garlic
  • Ginkgo biloba
  • Ginseng
  • Milk thistle
  • St. Johns wort
  • Regulation of herbal supplements
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