Transcript Complex Carbs

Complex Carbs
Ch 9 Day B
Functions of complex carbohydrates
• Structure- in baked goods and other products
• Cellulose forms the framework for fruits and veggies
• Pectins and gums provide texture for jelly and gummy candies, ice cream etc
Starch
• Polymers of glucose (>500 glucose molecules)
• Linked by alpha-1-4
• Digestible
Starch
• Present in plant materials as “starch granules”
• Starch molecules in the form of densely packed bundles
• Visible in sliced potato with food color
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Linear
Alpha 1,6
Branched
Amylose
• Molecules contribute to gel formation:
• Linear chains
• Orientation parallel to each other
• Moving close enough together to bond ( hydrogen bonds)
Amylopectin
• Branched molecules give viscosity to cooked paste
• Side chains /bulky shape
• Keep them from bonding together
• Not contribute to gel formation
• Doesn’t get as organized as amylose,
• It thickens but does not gel
• (Tumbleweed analogy)
Starch granules
Contain both linear amylose and branched amylopectin
Eg) corn starch, 1,3 amylose: amylopectin
( ratio depends on type of starch)
Starch
• soluble in cold water…..but
• Gelatinization
• Heat + water
• Starch granules swell and eventually burst
• Starch molecules absorb water
• Examples:
• Raw vs cooked
• Potato, rice, pasta
Gelatinization
• Raw STARCH
Heat and Water
When starch is heated in water the bonds joining amylose and amylopectin are weakened
That allows water molecules to move in and form “H” bonds
( water pushes the Hydrogen bonds apart)
• Starch = alpha -1,4,1-6= digestible
• Cellulose = beta-1,4= indigestible
• Cows can digest this….people cannot
• Both are linear chains of glucose units
Functions of complex carbohydrates
(polysacchr)
• Bind, Stabilize
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Hold batters to foods when deep fried
Carageenan- stabilizes cocoa in chocolate milk
Guar and xanthan gums improve consistency of gluten free baked goods
Keep compounds, mixtures and solutions from changing state
• Fat replacers
• Regular vs light mayo
Functions of complex carbohydrates
• Thicken- Starch
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Starch must be heated to allow starch to swell and take up water
Heating breaks intermolecular bonds exposing polar structures that attract water.
Gelatinization- thickening a liquid with starch
Gelatinization point- temperature of maximum swelling
• Holds the most water
• Has greatest thickening power
• Too much heat will break down (hydrolyze) the starch
• Too high heat
• Heating too long
• Salt and sugar will interfere with gelling
• Sugar decreases strength and viscosity
• Salt has different effects on different starches
Functions of complex carbohydrates
• Pectins
• Used to thicken jams and jellies
• Found in skins of fruits and vegetables
• Sold as powder or liquid
Thickened Starch Mixtures
Types
• Sol—a thickened liquid
• Paste—thickened starch mixture that has little fl ow but is
spreadable
• Gel—a rigid starch mixture
Properties
• Retrogradation—gel becomes firm as it cools (Lemon pie)
• Syneresis—water leaks out of gel during storage
• Viscosity—resistance to flow
• Gelatinization—starch granules absorb water and swell,
causing thickening of liquids
Retrogradation
• After gelatinization= upon cooling and storage
• Linear amylose- chains orient back to crystalline zones ( intermolecular H-bonding)
• Syneresis (loss) of water
• Toughening food, gritty texture
• eg stale bread, gritty starch pudding
• Can be partially reversed by heating
• Especially mashed potatoes
• Will not completely return like original due to starch molecule explosion
• Better to store bread in freezer than refrigerator. Freezer locks in moisture
• Stability- ability of a thickened mixture to remain constant over time
and temperature changes.
• Waxy maize starch is as thick when hot as it is cold
• Corn starch has more thickening power than flour, but unstable with
prolonged heat
• Flour might be better choice for gravy not served right away
Starch appearance
• Opacity- how much something blocks light
• Translucency- how much light passes through something
• Translucent: corn starch, potato starch, arrowroot
• Good for fruit sauces
• Wheat flour good for white foods.
Starch texture
• FDA does not require identification of sources of modified starches
• wheat,corn, or soy ( corn most common in US)
• Most modified by hydrolysis
• Cross linked starch- designed to be more resistant to acids and
separation in the freeze / thaw process
• Used in baby foods, salad dressings , cream corn, fruit pie fillings
• Modified starches- stabilize condiments, sauces and relishes
Thickening Sauces with starch
Avoiding lumps:
• Cold water paste:
• Slurry- uncooked liquid and starch
• Starch and Fat
• Roux- cooked fat and starch paste
• Beurre manie- equal parts butter and flour
• Starch and Sugar
• Starch and sugar then add liquid
• Used in sweet sauces and puddings
Nutrition of Complex Carbs
= digestible starches and
4 cal/g
Most abundant/ economical
Should provide ½ + daily cal
Glucose is only energy brain can use
Excess CHO stored as glycogen
Body uses stores w/in 2hrs heavy exercise
Skipping meals slows brain and organ stores
If no carbs… body goes into ketosis
Ketosis- elevated ketones damages kidney
indigestible fiber
beta glucose= fiber
most abundant
feel full, aids elimination
lowers risk of colon cancer
plant cell wall material
linear glucose chains
Nutritional Functions of CHO
• Provide energy
• Bulk for digestion
• Tie up bile acids( decreasing reabsorption)
• Lowers cholesterol levels in the blood
• Promotes utilization of fat
• Half of carbs should be whole grain sources