chapter 4
DESCRIPTION
Chapter 4. Fiber. 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. Fiber and Plants. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/1.jpg)
2009 Cengage-Wadsworth
Chapter 4
Fiber
![Page 2: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/2.jpg)
2009 Cengage-Wadsworth
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
![Page 3: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/3.jpg)
2009 Cengage-Wadsworth
Fiber and Plants• >95% of fibers from cell wall
– Primary wall– Secondary wall
• Fiber-related components– Cellulose– Hemicellulose– Lignin– Pectins– Suberin– Cutin
![Page 4: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/4.jpg)
2009 Cengage-Wadsworth
Chemistry & Characteristics of Dietary & Functional Fibers• Varieties:
– Cellulose– Hemicellulose– Pectins– Lignin– Gums -glucans
– Fructans– Resistant starch– Chitin & chitosan– Polydextrose &
polyols– Psyllium– Resistant dextrins
![Page 5: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/5.jpg)
2009 Cengage-Wadsworth
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
![Page 6: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/6.jpg)
2009 Cengage-Wadsworth
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
![Page 7: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/7.jpg)
2009 Cengage-Wadsworth
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
![Page 8: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/8.jpg)
2009 Cengage-Wadsworth
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
![Page 9: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/9.jpg)
2009 Cengage-Wadsworth
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
![Page 10: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/10.jpg)
2009 Cengage-Wadsworth
-Glucans• Dietary & functinal fibers• Homopolymers of glucopyranose
units• Water-soluble, highly fermentable• Sources: cereal brans, especially
oats & barley
![Page 11: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/11.jpg)
2009 Cengage-Wadsworth
Fructans--Inulin, Oligofructose, & Fructooligosaccharides
• Dietary fibers• Fructose units in chains of varying
length• Prebiotics• Sources: chicory, asparagus,
onions, garlic, artichokes, tomatoes, bananas
![Page 12: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/12.jpg)
2009 Cengage-Wadsworth
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
![Page 13: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/13.jpg)
2009 Cengage-Wadsworth
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
![Page 14: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/14.jpg)
2009 Cengage-Wadsworth
Polydextrose & Polyols• Polydextrose
– Polysaccharide of glucose & sorbitol units that have been polymerized at high temperatures & partial vacuum
• Polyols– Polyglycitol & malitol– Found in syrups
![Page 15: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/15.jpg)
2009 Cengage-Wadsworth
Psyllium• Functional fiber• Mucilage from husk of psyllium
seeds• Used as laxative
– Must ingest plenty of fluids
![Page 16: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/16.jpg)
2009 Cengage-Wadsworth
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
![Page 17: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/17.jpg)
2009 Cengage-Wadsworth
Selected Properties & Physiological Effects of Fiber
• Important properties include:– Solubility in water– Water-holding capacity & viscosity– Adsorption or binding ability– Degradability/fermentability
![Page 18: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/18.jpg)
2009 Cengage-Wadsworth
Solubility in Water• Classifications:
– Soluble - dissolve in hot water– Insoluble - don’t dissolve in hot water
• Water-soluble: some hemicelluloses, pectin, gums, -glucans
• Water-insoluble: cellulose, lignin, some hemicelluloses, chitosan, chitin
![Page 19: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/19.jpg)
2009 Cengage-Wadsworth
Solubility in Water• Soluble
– Delay gastric emptying
– Increase transit time
– Decrease nutrient absorption
• Insoluble– Decrease transit
time– Increase fecal bulk
![Page 20: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/20.jpg)
2009 Cengage-Wadsworth
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
![Page 21: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/21.jpg)
2009 Cengage-Wadsworth
Adsorption or Binding Ability• Diminished absorption of lipids• Increased fecal bile acid excretion• Lowered serum cholesterol
concentrations (hypocholesterolemic properties)
• Altered mineral & carotenoid absorption
![Page 22: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/22.jpg)
2009 Cengage-Wadsworth
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
![Page 23: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/23.jpg)
2009 Cengage-Wadsworth
Degradability/Fermentability• Nonfermentable fibers
– Detoxification– Increased fecal volume (bulk)
![Page 24: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/24.jpg)
2009 Cengage-Wadsworth
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
![Page 25: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/25.jpg)
2009 Cengage-Wadsworth
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
![Page 26: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/26.jpg)
2009 Cengage-Wadsworth
Recommended Fiber Intake• Adequate Intakes
– Adults: • 19-50: 25 g for women, 38 g for men• 51 or >: 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
![Page 27: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/27.jpg)
2009 Cengage-Wadsworth
Perspective 4
Phytochemicals & Herbal Supplements in Health &
Disease
![Page 28: Chapter 4](https://reader035.vdocument.in/reader035/viewer/2022062520/56815df0550346895dcc1e4a/html5/thumbnails/28.jpg)
2009 Cengage-Wadsworth
Phytochemicals & Herbals• Phytochemicals• Echinacea• Garlic• Ginkgo biloba• Ginseng• Milk thistle• St. John’s wort• Regulation of herbal supplements