Chapter 9 - The complex carbohydrates: starches, cellulose, gums, and pectins

In food preparation, complex carbohydrates provide

- structure - bind other products together - thicken

3 basic methods for combining a liquid and start with the goal of preventing lumps which depends on

- the dish - the desired flavor - personal preference

Functions of complex carbohydrates in food preperation

1. provide structure 2. act as binding agents 3. complex carbohydrates thicken liquids

Starches

> Are molecules of 100 to several thousand glucose units linked in chains > are polymers of sugar found in wheat, flour, rice, corn, potatoes, oats, sorghum, soy, rye, tapioca, and arrowroot

Roux

> a gravy made from starch heated in fat until the starch turns a reddish brown - adds distinctive flavors to gravies and sauces - requires low heat and constant stirring

Complex carbohydrates act as binding agents examples

> amylose molecules work best at binding batters to meat, fruit, vegetable pieces for deep frying > the gum carrageenan stabilizes cocoa in milk, dairy products, and ice cream > guar gum and xanthan gums improve the consistency of gluten free baked goods.

modified starches

> are changed structurally by chemical or mechanical means - are often made from wheat, corn, or soy - can be made to exact specification - can have their sweetness, viscosity, mouthfeel, and appearance modified

carbohydrate gums

> are polysaccharides that are soluble in water and extracted from plants > thicken and stabilize mixtures > trap color and flavor > are in salad dressings and gummy candies

Complex carbohydrates provide structure examples

> flour provides most of the structure of baked goods and other food products > starch thickens when heated and gels when cooled > cellulose forms the structure of fruits and vegetables > Pectins contribute structure to jams and jellies

carbohydrate pectins

> found in plant cells and made of sugar acids > a key component in jams and jellies

cellulose

> is a polysaccharide made from large amount of beta-glucose > humans like the enzyme needed to digest it. > it is also known as fiber in the diet

indigestible fiber

> is called fiber, bran, or bulk on food labels > gives crispiness and mouthfeel to many foods > aids in digestion and the elimination of waste > helps maintain a feeling of fullness > is added to commercial break products to slow staling and improve loaf volume

cross linked starch

> is changed chemically so bonding takes place between molecules - forms a molecular network that is more stable during freezing and thawing - is more resistant to acids - is used for baby foods, salad dressings, cream style corn, and fruit pie fillings

Retrogradation

> is the firming of a gel during cooling and standing > it is desirable when it causes thickening during cooling, but it may form cracks if it continues

granules

> packets in which plants produce starch > ratios of amylose to amylopectin within them cause a starch to prefeorm differently in food mixtures

Besides providing energy for bodily functions, carbohydrates

> provide bulk for digestive processes > decrease bile reabsorption > lower cholesterol levels in the blood > promoet the utilization of fats

starch and fat method

> separate starch granules with melted fat > method uses equal amounts of fat and starch and is used for white sauce and gravy ex: beurre manie balls

Digestible starches are

> the most abundant and economical source of energy > needed in the diet to allow fat to be used for energy and prevent ketosis which produces harmful ketone bodies

waxy starches are mainly of ________

amylopectin

In most foods, starches are mixtures of _____ and ________

amylose and amylopectin

Viscosity in amyloses vs. amolyopectins

amyloses are more viscous that amylopectins

sols

are pourable thickened liquids

gels

are rigid starch mixtures in which molecules of hydrogen bond together and form a junction

pastes

are thickened starch/liquid mixtures that have very little flow

slurries

are uncooked mixtures of starch and water

Cornstarch stability vs. Flour stability

corn starch has more thickening power than flower, however, flour is more stable over time and temperature changes

Before selecting a starch for a food product, food scientists

evaluate the various properties of starches

stability

is the ability of a thickened mixture to remain constant over time and temperature EX: sauce - can be frozen and reheated with very little change in appearance or taste EX: corn starch has more thickening power than flour, however, flour is more ______ over time and temperature changes

syneresis

is the condition of water leaking from a gel over time

translucency

is the degree of how much light passes through an object ex: evident in sauces made with cornstarch

opacity

is the degree of light blockage ex: evident in sauces made with flour

texture

is the feel of graininess or smoothness of a mixture on the tongue. - ex: cornmeal or whole wheat flour is not used to thicken gravy because of its gritty mouthfeel

Viscosity

is the resistance of a mixture to flow or a measure of a starch's thickening ability - the more solids that are present --> the greater is the resistance to flow - normally a liquid's _________ changes when temperature is changed, but with corn starch its ________ changes when pressure is applied

gelatinization point

is the temperature at which maximum swelling occurs > too much heat will cause starch moelcules to break apart

Gelatinization

is thickening a liquid with starch

cold water paste

made by quickly stirring the starch while adding at least an equal amount of cold water - must be heated while stirring and stirred until smooth - liquid is added as needed for the recipe - common uses are gravy and soups

refined grains

provide vitamins and minerals should be limited due to sugar and solid fats that are often added

interference with gelling

salt and sugar compete for water, so large amounts interfere with gelling

amylopectin

starches with a branched strcuture

amylose

starches with a linear structure

starch and sugar

sugar helps separate starch granules and prevents them from sticking

complex carbohydrates thicken liquids

when heated with water, starch packets open, allowing water molecules to slide into spaces in the starch molecules

when does a corn starch's viscosity chagne

when pressure is applied

when does a liquid's viscosity change

when the temperature is changed

the bulk of carbohydrates in the diet should come from

whole grains, fruits and vegetables

Physical properties:- Types of combinations (gelling?)

- Slurries - Sols - Pastes - gels

digestible and indigestible starches come from

- grains - breads and cereals - fruits - vegetables - nuts and seeds

Complex carbohydrates are also called

- polysaccharides - macromolecules

the physical properties of starch and liquid mixtures are

- retrogradation - viscosity - stability - opacity versus translucency - texture

starch and liquid combinations can be

- slurries - sols - pastes - gels

The types of complex carbohydrates found in foods are

- starches - cellulose - gums and pectins

what is the brains energy source

Glucose is the brain's only energy source stored as glycogen when in excess quantity

Macromolecules

Molecules that contains hundreds or thousands of atoms

Polysaccharides

Many units of saccharides bonded together

why is cornmeal or whole wehat not used to thicken gravy

because of gritty mouthfeel