Starches and Sauces

Starches

•Storage form of carbohydrates in plants

-Roots

-Seeds

-tubers

•Purified forms - hydrocolloids

-Pectin

-Vegetable gums

-Modified starches

Starch Purification

•Wet milling - separates starch from proteins, fiber and oil

-Grinding

-Screening

-Centrifuging

Starch Structure

•Amylose - long chain of glucose

-500 to 2000 glucose molecules

-Contributes to gelling characteristics

•Amylopectin

-Highly branched, treelike molecule

-Formed of glucose molecules

-Contributes to cohesive and thickening characteristics

Natural Starches

•Corn, wheat, rice, potato and tapioca

-16-24% amylose

-76-84% amylopectin

•Strains of corn w/o amylose

-Waxy varieties - grain has waxy appearance

-Contain only amylopectin

•High amylose strains of corn

-Amylomaize 70% amylose

-Unique ability to form films and bind with other ingredients

Modified Starches

•Chemically changed for specific functions

-High temperature

-Freezing temperature

-Low pH

-High shear

•Cross-linked

•Hydrolysis

•Substitution

•Any combination

Cross-linking

•Use of 2 chemicals to react with starch a selected points

•Create cross bonds between 2 chains of the starch molecule

•Characteristics

-Lower viscosity

-Increase stability in low pH

-Increase tolerance to heat

-Increased resistance to shearing or stirring

•Uses are in pie fillings and spaghetti sauces

Hydrolysis

•Starch and acid mixed in water

•Produces randomized breaking of the starch molecule

•Known as "thin-boiled" or "acid-thinned" starch

•Low viscosity when boiled

•Hydrates at lower temperatures

•Used mainly in the confectionary industry

•Breaks down starch to

-Dextrins - large chunks of starch molecules

-Oligosaccharide units

-Disaccharide units

-Monosaccharide units

Substitution

•Substituting the -OH at random points

•Decreases the tendency of bonding with other starch molecules

•Increases stability during freeze thaw cycles

•Improves clarity

•Reduces syneresis - weeping of liquid from a cooked starch on standing

Instant Starches

•Precooked or pregelatinized starch

-Cooked and dried

-Consists of degraded starch granule fragments

•Cold water swelling starch

-Cooked and dried

-Starch granules remain intact

-Produces foods which are more stable, clarity, smoother texture, and better appearance

•"Fat mimetics"

•Modified starch hydrolysates combined with substitution

•Binds and orients water in a way as to mimic the mouth feel of fat

Effects of Processing on Starch

•Heat

-Dry Heat - breaks starch into dextrins

-Moist Heat - increased viscosity, gelatinization, and translucency

•Agitation or stirring - too long accelerates granule breakdown and decreases viscosity

•High acidity (pH 4)- causes hydrolysis and fragmentation, decreasing viscosity

Classic French sauces (suave)

•Brown (espangole)

•White (velouté)

•Milk (béchamel)

•Tomato (sometimes)

Brown (espangole)

•A cream prepared with a browned meat or vegetable stock

White (velouté)

•A sauce prepared with veal or chicken stock

•Has no milk or cream

Béchamel

•A white sauce made with veal or chicken sauce

•Always contains milk or cream

Tomato (sometimes)

•May use tomato with other stocks or with milk or cream

•If use milk, must add tomato slowly to prevent curdling

Starch-thickened sauces

•Heating and thickening

•Cooling and coagulation

Thickness of Various Starches

Thickening vs Gelling

Emulsified sauces

• Theory

-Oil in water

-Water in oil

-Effect of eggs

-Effect of lecithin (mixture)

-Effect of pH

Emulsified Sauces

•Mayonnaise

-Prepared

- cool

-, most fat

Emulsified sauces

•Hollandaise

-Prepared warm, butter-60%

• Bernaise

-Prepared warm, butter-30%, Air

Emulsified sauces-Others

•Vinegar in oil

•Peanut butter

•Catsup

•Chocolate