Func%onal Proper%es of Carbohydrates

Func%onal Proper%es of Carbohydrates

What are Carbohydrates? Carbohydrates are a main nutrient needed by the body as they provide energy and fibre. There are THREE types of carbohydrate found in foods: polysaccharides, monosaccharides and disaccharides.

What are Carbohydrates? There are three types of carbohydrates in foods. These are: 1. Polysaccharides 2. Disaccharides 3. Monosaccharides Polysaccharides = Starches, Pec%ns and Dietary Fibre Monosaccharides & Disaccharides = Sugar

Func%onal Proper%es of Starch Starch is a common polysaccharide found in grains such as rice and wheat and in vegetables such as potatoes.

Func%onal Proper%es of Starch Starch molecules are made up of two substances: Amylose and Amylopec5n. Starches containing more amylose produce semi- solid, opaque gels whereas higher propor%ons of amylopec%n produce clearer, thicker gels.

Those starches with higher levels of amylopec%n produce clearer gels that are more a thick liquid (viscous) than solid. Wheat flour contains a high propor%on of amylose and produces thick but cloudy gels.

Func5onal Proper5es of Carbohydrates 1. Gela5nisa5on of Starch What is Gela5nisa5on? Starch can thicken mixtures by absorbing liquid in the presence of heat. This process is called gela5nisa5on. Plain wheat flour, corn flour and arrowroot are the most common ingredients used to thicken liquids (thickening agents) in a domes%c kitchen. Food manufacturers use a variety of modified starches.

Video: Gela%nisa%on of Starch

Factors that Affect the Gela%nisa%on of 1. Temperature: Starch Gela%nisa%on requires warm, moist condi%ons. In order for starch to absorb liquid, the outside of the starch granule needs to be sovened by hea%ng. These starch granules soven at 64-72 degrees celsius. When the temperature reaches 86-90 degrees celsius, the swollen starch granules burst and the amylose and amylopec%n they contain capture the liquid, causing it to thicken. When a gela%nised mixture cools, it forms a more rigid gel.

2. Agita%on: Agita%on is essen%al for the crea%on of a smooth, gela%nised sauce. It helps to prevent lumps forming in a sauce thickened with starch. Other ways to prevent lumps, include; Mix flour with cold water in a cup rather than adding dry flour to a warm mixture. The mixture should be s%rred immediately before adding it to the warm liquid, because starch is insoluble in cold water and se_les to the bo_om of the cup. Add only cold liquid to a starch mixture. Adding a hot liquid causes starch to gela%nise on contact, forming lumps. S%r roux mixtures constantly from the %me the liquid is added un%l the sauce boils. If the mixture is not s%rred, the starch closest the bo_om of the pan gela%nises before those at the top.

Importance of Agita%on Making a White Sauce

3. The Impact of other Ingredients and ph: The gela%nisa%on process can be affected by several ingredients, including sugar and acid. Sugar: Sugar competes with the starch for water, so not as much water is available for the starch to absorb. Also, the sugar raises the temperature at which the starch granules start gela%nising and causes the mixture to become more liquid and less likely to remain stable and is also sover. For example; sugar is added to make custard. Acids: In the presence of heat, acids break down the large starch molecules into smaller molecules of dextrin, which have less thickening power. When preparing a starch- thickened sauce that requires the addi%on of acid, add the acid to the starch paste aver gela%nisa%on has occurred.

Func5onal Proper5es of Carbohydrates 2. Dextrinisa5on of Starch Browning Reac5on What is Dextrinisa5on? Dextrinisa%on is defined as the process in which starch breaks down into dextrins. For example; when bread is toasted. The polysaccharide starch can undergo a par%al chemical breakdown into shorter glucose chains called dextrins. Starch (Polysaccharide) à Dextrins à Maltose (Disaccharide) à Glucose (Monosaccharide) 1. Starch does not dissolve in cold water but dextrins do. 2. Starch has a floury taste, and dextrins are sweet. 3. Starch gela%nises, but dextrins are poor thickening agents.

The process of dextrinisa%on is the reason for: Bread turning brown during toas%ng. Toasted commercial breakfast cereals being brown and having a sweet taste. The brown crust forming when bread or pastries are baked. Gravies being brown. The brown crust forming on potatoes.

Func5onal Proper5es of Carbohydrates 3. Func5onal Property of Pec5n Pec%n is a polysaccharide found in the liquid extract of many fleshy fruits. It is used to create fruit gels such as; jams and jellies. Fruits with a high pec%n content include; lemons, limes, apples, blackberries, cranberries, grapes, sour plums. Fruits with a moderate pec%n content include; oranges. The more overripe a fruit is, the more pec%n it contains. Acids must be present for pec%n to gel.