4 Starches as Thickeners Cereals that are common sources of starch are:WheatRiceCornRoot starches include:PotatoesArrowrootCassava (tapioca)Other sources of complex carbohydrates are:Dried beansPeasSago palm
6 Starches as Thickeners Starch is a polysaccharide consisting of long chains of repeating units of glucose molecules linked together either in the form of:Amylose, which is made up of largely linear molecules.Amylopectin, whose molecules are highly branched.
7 Most starch contains 75% amylopectin and 25% amylose Most starch contains 75% amylopectin and 25% amylose. All starches contain some amylopectn, but a few consist entirely of amylopectin and these are known as waxy starches. It is the varying amount of anylose content that causes texture differences in starch containing foods.
8 Starch Characteristics Starches have the capacity to go through the processes of:Gelatinization: The increase in volume, viscosity, and translucency of starch granules when they are heated in a liquid.Gel formationRetrogradationDextrinizationHydrogen bonds holding starch together weakens allowing water to penetrate the molecule and causing them to swell until their peak thickness is reached. The swelling of the starch granules increases their size many times over. The increased volume and gumminess associated with gelatinzation radically changes the texture of many foods./ Sauces. Puddiongs
9 Starch Characteristics Gelatinization is dependent on a number of factors, including:Amount of waterTemperatureTimingStirring…and the presence of:AcidSugarFatProteinSufficient water is needed for the starch to absorb. Need lots of water when cooking pastaTemperature – larger granules gelatinize at lower temps, potato starch, smaller at higher temps wheatTiming – if heat beyond gelztiniztion viscosity decreases. Granules break apart.Sirring. Stir early to form paste or gelatinizing the starch mixture, continued stirring may cause granules to rupture.acid=- bleow 4.0 decreases viscosity. Needs to be added after gelatinization has occurred.Sugar – sugar competes with water and delays onset of gelatinization. Too much sugar inhibits complete gelatinization and results in a thick runny paste.Fat/protein. Delays gelatinization by coating the starch granules and preventing absorption of water.
10 Starch Characteristics Gel formation-requirementsGelatinizationAmyloseCoolingFor a gel to happen the starch first has to undergo gelatinization – the swelling of the starch granuleThe starch MUST contain amylose. Amylose, which is linear, will form strong bonds and become semi solid whereas amylopectin which is branched will not provide any rigidity.Cereal starches contain the most followed by root starches.Cornstarch contains 2x as much as floor. So, if a recipe calls for 2 T cornstarch and you don’t have any, use 4 T flour.Upon cooling get will set up.
13 Starch Characteristics Retrogradation: The seepage of water out of an aging gel due to the contraction of the gelDextrinization: The breakdown of starch molecules to smaller, sweeter-tasting dextrin molecules in the presence of dry heat.Retrogradation: The seepage of water out of an aging gel due to the contraction of the gel (bonds tighten between the amylose molecules).Also known as syneresis or weeping.Dex- because starch molecule has broken down, you will need more to thicken, say gravy.
16 Starch Characteristics Modified StarchesFor food industry useCrosslinked starchOxidized starchInstant or pregelatinized starchThe modifications may affect the starch’s:GelatinizationHeating timesFreezing stabilityCold water solubilityViscosityThree types of modified starches include:Crosslinked starch treated chemically to link the starch molecules together with crossbridges. This makes it more heat resistant. Less likely to lose viscosity when exposed to heat. Ideal for use in cooked or canned foods. soupsOxidized starch-exposed to chemical oxidizeers. These become less viscous than corsslinked starches but are clearer and more appropriate for emulsion stabilizers and thickeners. Ideal for dusters such as for marshmallows and chewing gumInstant or pregelatinized starch these do not have to be heated inwater to expand and gel. Already heated and dried. Expand when exposed to cold water. Instant puddings.
17 Starch Characteristics Crosslinked starch, one of the more commonly used modified starches, has been treated chemically to link the starch molecules together with crossbridges.Crosslinking makes a starch more heat resistant.
18 Sauces Cheese sauce White sauce Some gravies The major sauces used in food preparation are:Thickened sauces, including:Cheese sauceWhite sauceSome graviesUnthickened sauces, including:Other graviesHollandaiseButterFruitBarbecueTartarTomato sauces
21 Sauces-thickeners White Blond Brown Roux: A thickener made by cooking equal parts of flour and fat.There are three types of roux that serve as the foundation in making thickened sauces:WhiteBlondBrownUsually use wheat flour in a roux. Hot liquid is gradually added to the cooked flour and butter and this combination is cooked until it reaches the desired consistency.Variations in the heating times of the fat-flour combination cause the differences in the colors and flavorsAs the roux cooks it becomes darker and its stasrchy taste lessens but its abilty to thicken is also reduced as the starch molecules are broken down. Thus the darker the roux the more of it will be needed to added to the liquid for thickening purposes
22 Sauces-thickenersButter and flour and NOT cooked. It iswhisked in , bit by bit to a simmering sauce until it reaches its desired thickness.. Pot of stew.Beurre manié (pronounced burr mahn-YAY): A thickener that is a soft paste made from equal parts of soft butter and flour blended together.
23 Sauces-thickenersSlurry: A thickener made by combining starch and a cool liquid.Made by gradually mixing COLD water which will not cause the astarch to expand into either cornstach or flour to make a thin liquid. This slurry may then be mixed gradually into a simmering liquid saued. Under the heat the starch granules then expand and the sauce thickens. Pan gravies
24 No lumps Lump-free sauces Fat and flour thoroughly mixed before adding liquidSmall amount of starch mixed with cold water before addingSugarPrinciple is to separate the starch granules from each other to prevent them from being trapped in a ball surrounded by a film of gelatinized starch.Fat and flour smooth. If flour is coated with fat it will not form lumps when it contacts the liquidStarch. Mix vigoruosly with cold water in an enclosed jar before incoporating it into the rest of the liquid to be added to the rouxSugar – will separate starch granules. Too much will make runny.
25 SaucesGravy is made from the juices or drippings remaining in the pan after meat or poultry is cooked.The drippings can be served thickened and with added seasonings or unthickened.Au jus: Served with its own natural juices; a term usually used in reference to roasts.White sauces and gravies most common use of roux.Once roux has been prepared by melting the fat, mixing in the flour and gently heating the mixture until smootha dn cooked to the desired degree of doneness, the next step is to combine the liquid with the roux. Amount of liquid depends on the desired thickness of sauce.
26 SaucesDeglaze: Adding liquid to pan drippings and simmering/stirring to dissolve and loosen cooked-on particles sticking to the bottom of the pan.Reduction: To simmer or boil a liquid until the volume is reduced through evaporation, leaving a thicker, more concentrated, flavorful mass.
28 Storage of Starches and Sauces The quality of dry starches deteriorates with improper storage.Thickened sauces should also be prepared, served, and stored with caution.The quality of dry starches deteriorates with improper storage.Like any other grain product, they should be kept in airtight containers and stored in a cool, dry place away from moisture, oxygen, light, and pestsThese products should be stored in the refrigerator and never left to sit for long at room temperature.