CARBOHYDRATES

SUGARS, STARCHES, PECTINS, AND OTHER CARBOHYDRATES

CHARACTERISTICS

 Organic compounds  Carbon, Hydrogen, Oxygen  Simple or complex  Source of energy or fiber  Important food CHOs - Sugars, dextrins, starches, celluloses, hemicellulose, pectins, gums

FUNCTIONS

 SWEETENERS  THICKENERS  STABILIZERS  GELLING AGENTS  FAT REPLACERS

MONOSACCHARIDES

 SIMPLE SUGARS  MOST COMMON - 5 OR 6 CARBON

GLUCOSE

 Dextrose  Naturally present in fruit  Basic unit for starches  Less sweet than fructose  Used in food industry because of water holding properties and ability to control crystals  Food for yeast

FRUCTOSE

 Levulose  Part of sucrose  Sweetest of all sugars  In many fruits  Very soluble  Not easily crystallized  Glucose isomerase to change glucose to fructose

GALACTOSE

 Part of lactose – milk sugar  Basic unit of pectic substances  Building block of many vegetable gums

COMMON MONOSACCHARIDES

DISACCHARIDES

 Two monosaccharides  Glycosidic bonds-readily hydrolyzed by heat, acid, enzymes

SUCROSE

 Table sugar  From sugar cane or sugar beet  Glucose + fructose  Invert sugar important in controlling crystallization  Most common disaccharide

MALTOSE

 Glucose + glucose  Product of starch breakdown  Corn syrup  Flavoring and coloring agent in beer, candies, shakes

LACTOSE

 Glucose + galactose  Milk sugar  Extracted from solutions of whey  Not broken down or fermented by yeast  Does not react in batter leavened with baking soda or baking powder  Available for Maillard reaction so added to bakery products for browning

DISACCHARIDES

PROPERTIES OF SUGAR

SOLUBILITY

       Solution in foods Varying degrees of solubility for monosaccharides and disaccahrides As temperature increases  greater the amount of sugar that dissolves Slow heating increases the solubility As concentration increases  increases boiling point Each gram molecular weight of sucrose increases boiling point 0.94

0 F (0.52

0 C) Can use temperature to determine sucrose concentration

SATURATION

 Unsaturated – small amount of sugar in water, can hold more sugar  Saturated – no more sugar can be dissolved  Supersaturated – holds more than what is usually soluble at a certain temperature  Supersaturation – heat to high temperature and cool slowly

CRYSTALLIZATION

 Cool supersaturated solution  Formation of closely packed molecules from the solidification of dispersed elements in a precise orderly structure  Arranged around a nuclei   Size of crystal depends on rate of formation of nuclei and rate of growth Crystals form too soon  only a few  crystals too large, continue to grow, candy grainy

MELTING POINT/HEAT DECOMPOSITION

 Apply dry heat  state sugars melt to liquid  Sucrose melts and forms liquid that turns brown  Carmelization – nonenzymatic browning, flavors food  Noncrystalline

HYGROSCOPICITY

 Ability to absorb moisture  Responsible for lumpiness (sugar)  Decreases staling in bread  Gives stickiness for high moisture characteristics to foods  Fructose most hygroscopic

INVERT SUGAR

 Acid hydrolysis of disaccharide sucrose  Heat increases hydrolysis  Glucose and fructose in equal amounts (equimolar)  Resists cyrstallization and retains moisture  Add cream of tartar, vinegar, molasses (acids)  Enzyme hydrolysis with invertase

TYPES OF SUGARS

CRYSTALLINE AND NON CRYSTALLINE

GRANULATED SUGAR

  Crystalline – table sugar Sugar cane or sugar beet   Affects texture of baked goods Improves body and texture of ice cream   Fermented by yeast Retards growth of microorganisms   Raw sugar banned by FDA Turbinado –raw sugar separated in centrifuge, washed with steam  Retailed as fine or extra fine

POWDERED SUGAR

 Pulverized granulated sugar  Add cornstarch to prevent caking  X designates fineness

BROWN SUGARS

 From cane sugar – late stages of refining  Crystals of sugar coated with molasses  Contains invert sugar  Sold in grades  More refined  lighter color, less flavor, lower grade – for baking – less flavor  Higher, darker grades more flavorful and suitable for cooking strong flavored foods

CORN SYRUP

 Acid and high temperatures to hydrolyze corn starch  Varying degrees of sugars  High fructose corn syrup (HFCS) from high glucose corn syrup – use enzyme glucose isomerase  Significant use in food industry

MOLASSES AND SORGHUM

 By-product of sugar production from sugar cane  Mineral content varies  Bitterness increases as refinement continues – blackstrap molasses  Treacle – dark fluid left after sugar cane is processed  Sorghum – from cane sorghum, similar to molasses

MAPLE SYRUP AND HONEY

 Maple syrup from sap of mature maple trees  Water evaporated, organic acids cause flavor  Honey flavors according to flower nectars  USDA has standards for grades of honey

ALTERNATIVE SWEETENERS

 Non-nutritive – high intensity sweeteners  Approved saccharin, aspartame, acesulfame-K, sucralose, neotame  Except for sucralose not enough bulk to substitute in recipes  Cyclamates – banned  Sugar alcohols - polyols – improve bulk, mouthfeel, and texture

SUGAR COOKERY

CANDIES

CRYSTALLINE CANDIES

 Generally soft  Smooth, creamy with tiny crystals that cannot be detected with the tongue  Fondant and fudge  Use interfering agent to prevent early crystallization  Must concentrate solution-test temperature to determine concentration  Complete solution of crystalline sugar

INTERFERING AGENT

 Interfere with size or rate of crystal growth  Contribute to viscosity of syrup and elevate the boiling point  Examples – milk, butter, cream, eggs, chocolate, cocoa, proteins, fats, dextrins, invert sugar, corn syrup

NON-CRYSTALLINE CANDIES

 Amorphous  No definite crystalline pattern  Cook to very high temperature  Adding large amounts of interfering agent     Combination of methods Hard – brittles, high temperature, low moisture Chewy – caramels, high interfering agent Aerated – marshmallows, air trapped in protein foams and interfering agent

POLYSACCHARIDES

 Complex carbohydrate polymers  Properties depend on sugar units, glycosidic linkage and degree of branching  Starches, Pectins, Gums most important  Hydrocolloids – water loving colloidal substances

STARCH

 Plant polysaccharide - linked glucose monomers  GRANULES - formed in cells, grow by adding on layers  Long-chain glucose polymers  Insoluble in water  Form temporary suspension

SOURCES

 Characteristic of finished food depends on starch source  Seeds, roots and tubers  Cereal grains - wheat, corn, rice, oats  Roots and tubers - potatoes, arrowroot, cassava

STRUCTURE

AMYLOSE AND AMYLOPECTIN

AMYLOSE

 Straight chain or linear fraction  1/4 of all starch  Thousands of glucose units  Forms thick gels-hold shape when molded, rigid

AMYLOPECTIN

 Highly branched  3/4 of starches  Thickens but does not gel  Proportion of amylose:amylopectin influences cooking qualities and keeping characteristics of finished food product

AMYLOPECTIN

STARCH CHARACTERISTICS

    Ability to absorb water limited In uncooked stage is insoluble in cold water - forms temporary suspension because polymer is too large Doesn’t change boiling point or freezing point of liquid Reversible

EFFECTS OF HEAT

DRY HEAT

 Heating - increases uptake of water  Dextrinization  Color and flavor changes  Reduced thickening power  Nonenzymatic browning  Dry flour browned

MOIST HEAT

 Complete absorption as heat increases permanent swelling, irreversible  Sol - as starch continues to come out of granules  Viscosity-thickness, thinness of liquid  Translucency increases during heating

GELATINIZATION

 Sum of changes in first stages of moist heating of starch granules  Gelatinized granules = opaque, fragile, ordered structure disrupted  Temperature of gelatinization differs for each starch  Short chains of amylose come out of the granules  Irreversible changes

CONTINUED HEATING

 Gelatinization requires addition of heat  Cooking develops flavor  Pasting occurs  Granules swell  Granules of starch swell independently

PASTE CHARACTERISTICS

 Concentration of starch affects consistency  Clear thickened gel made from root starches or waxy versions of starches  Cloudy gels from cereal starches

FACTORS AFFECTING GELATINIZATION

ACID

 Fragments (hydrolyzes) starch molecule = thinner hot paste and less firm product  Hydrolysis = less hydration of starch  Add acid after gelatinization and after starch has cooked  Applicable - lemon juice, vinegar, tomatoes

AGITATION

 Over-stirring causes granules to burst, empty bound water = gel will thin  Creates more uniform mixture

OTHER FACTORS

 FAT AND PROTEIN- coats (adsorbs) to surface of granule = delays hydration Fat in pie crust to prevent clumping  SUGAR - competes for liquid = delays absorption by granule = thinner mixture Elevates temperature for gelatinization  ENZYMES - hydrolyze starch molecules

TIME AND TEMPERATURE

 Lengthen heating time = causes granules to rupture - thins product  More rapid heating = smoother paste  Bring to boil over direct heat

GELATION

  Formation of a gel when gelatinized starch is cooled Strong amylose bonds   Elastic solid Retrogradation-reverting to crystalline state  Syneresis - water loss during retrogradation, “weeping”-as water evaporates dried out rubbery matrix of starch  Non-pourable, highly viscous

SEPARATING AGENTS

 DEFINED - ingredients or additives which physically separate starch granules during hydration, allowing maximum hydration  Prevents lump formation  FAT -ROUX- forms film around granule = each granule swells independently of others  COLD WATER- SLURRY-physically separates granules (hot water causes partial gelatinization)  SUGAR-LIAISON - physically separates

MODIFIED STARCHES

 Defined-starches which have been chemically altered to produce physical changes  Will improve stability, convenience, performance during food processing  Use acids or oxidizing agents  FDA-regulations governing modification

EXAMPLES

 PREGELATINIZED STARCH - gelatinized, dried, can reconstitute without heat (instant potatoes, hot cereal)  Acid-modified starch - treated with acid slurry, forms strong gel upon cooling  Cross-linked starches - acid resistant, resists rupture  Cold water-swelling - instant starch that remains intact

FUNCTIONS OF MODIFIED STARCHES

 Increase acceptability of product flavor and consistency  Prevent retrogradation  Stabilizers in conjunction with emulsifiers  Improve freeze-thaw stability  Prolong shelf life of frozen food by preventing oxidation

WAXY STARCHES

 Commonly used in pie fillings  Made from natural starches  Practically no amlyose  Thicken at lower temperature but no gelling  Less retrogradation  Barley, corn, rice, sorghum

HIGH AMLYOSE STARCHES

 Genetic manipulation  Form films and bind other ingredients

PECTINS AND GUMS

 Polysaccharides  Plant tissue  Used as gelling agents, thickeners, stabilizers

PECTIC SUBSTANCES

 Part of primary cell wall  Hold cells together, hold skin on fruit  Protopectin - immature fruits  Pectinic acid- mature fruit, includes pectins  Pectic acid - over ripe fruit

PECTIN

 Dispersible in water  Forms a sol  Can be converted to a gel in the presence of water with addition of sugar or acid  Attraction to water is decreased  Pectin under skin of fruits melts with heat application (peel tomatoes, etc)

PECTINS

 Commercially extracted from apple cores and skins; form white inner skin of citrus fruits  Boiling too long - depolymerization occurs, gel may not set  Boiling too short - insufficient invert sugar formed, sucrose may crystallize

GUMS

  All are colloidal polymers (too large to dissolve) All are very hydrophilic     All are thickeners in water dispersions Galactose most common sugar All are polysaccharides – EXCEPT for gelatin Examples: Guar gum, gum arabic, carob bean gum, carageenan, agar, xanthan gum

USES

 Thickening agents replacing starch  Stabilizers of emulsions  Maintain smooth texture of products like ice cream  All do not form gels