Food Properties
The functional properties of food are the physical and chemical changes that occur during food storage, preparation and presentation.
Carbohydrates
Carbohydrates are found in foods containing large amounts of sugar, fibre or starch. Cereal products, vegetables and fruit are the best sources of carbohydrate. Carbohydrates are involved in the following reactions:
Functional Property: Caramelisation
Definition/Explanation of Property: Caramelisation is the chemical reaction in which monosaccharides and disaccharides turn brown with the application of heat (i.e. any product containing sugar may caramelize upon heating.) This occurs when products containing fruits, honey, milk, sugar cane, maple syrup and cereals come in contact with heat. Although not often recognized, Caramelisation is responsible for many browning processes. A good example of this the colour of toffee.
Examples of practical applications:
The degree of Caramelisation that occurs varies according to:
Definition/Explanation of Property: Caramelisation is the chemical reaction in which monosaccharides and disaccharides turn brown with the application of heat (i.e. any product containing sugar may caramelize upon heating.) This occurs when products containing fruits, honey, milk, sugar cane, maple syrup and cereals come in contact with heat. Although not often recognized, Caramelisation is responsible for many browning processes. A good example of this the colour of toffee.
Examples of practical applications:
- Caramelisation occurs in:
- Browning of biscuits
- Cakes and other baked products
- Commercial milks
- Ice-creams
- Honeycomb (Violet crumbles)
- Crème Caramel
The degree of Caramelisation that occurs varies according to:
- the amount of sugar used
- the length of heating time
- the type of sugar
- the addition of other ingredients
- the temperature the sugar reaches
Functional Property: Dextrinisation
Definition/Explanation of Property: Dextrinisation is the process involving the browning of starch foods when subjected to dry heat. It is defined as the breakdown of starch into dextrin’s (disaccharides.) It is a non-enzymatic browning and chemical change which is easily digested as partial breakdown is complete. The characteristics of colour, taste, aroma and flavour may change as a result of this process.
Examples of practical applications
· Toasting bread
· Baked goods
· Brown gravies and sauces
· Toasted breakfast cereals, Formation of baked crusts on vegetables e.g. potatoes, pumpkin and onions
Factors affecting functional property
The degree of Dextrinisation is determined by:
· the length of timethe product isheated;
· the temperature,
· the type of starchin the product;
· addition of other ingredients;
· the action of certain enzymes,
· the action ofacids; and
· the amount of exposure to dry heat the product encounters.
Definition/Explanation of Property: Dextrinisation is the process involving the browning of starch foods when subjected to dry heat. It is defined as the breakdown of starch into dextrin’s (disaccharides.) It is a non-enzymatic browning and chemical change which is easily digested as partial breakdown is complete. The characteristics of colour, taste, aroma and flavour may change as a result of this process.
Examples of practical applications
· Toasting bread
· Baked goods
· Brown gravies and sauces
· Toasted breakfast cereals, Formation of baked crusts on vegetables e.g. potatoes, pumpkin and onions
Factors affecting functional property
The degree of Dextrinisation is determined by:
· the length of timethe product isheated;
· the temperature,
· the type of starchin the product;
· addition of other ingredients;
· the action of certain enzymes,
· the action ofacids; and
· the amount of exposure to dry heat the product encounters.
Functional Property: Geletinisation
Definition/Explanation of property:
The process wherein starch granules form a suspension in cold water. When heated in the presence of water, these swell and thicken and a gel results. The cellulose wall of the starch ruptures when swollen granules bump into each other and water is absorbed. This process is known as Gelatinisation.
Examples of practical applications
Factors Affecting Functional Property
Definition/Explanation of property:
The process wherein starch granules form a suspension in cold water. When heated in the presence of water, these swell and thicken and a gel results. The cellulose wall of the starch ruptures when swollen granules bump into each other and water is absorbed. This process is known as Gelatinisation.
Examples of practical applications
- Lemon Meringue Pie (filling)
- Roux
- Cheese Sauce
- Custard
Factors Affecting Functional Property
- Temperature (control of, to prevent burning whilst ensuring boiling point is reached);
- Ratio of starch to liquid (in accordance with use and type of starch used.
- Length of time product is heated;
- Degree of agitation (i.e. constant, steady stirring is required for effective gelatinisation.
- Addition of other ingredients e.g. acids , stabilizing agent, sugar.
Functional Property: Crystallisation
Definition/Explanation of property:
Crystallisation is the result of the cooling of a supersaturated solution (very concentrated) where solid crystals form. This occurs after substances separate from solutions or where a change from a liquid to a solid causes crystals. The result will occur only at very high concentration levels and is seen in the main in sucrose (and sometimes lactose and maltose. )
Examples of practical applications
The size of crystal formation is dependent on these factors:
Definition/Explanation of property:
Crystallisation is the result of the cooling of a supersaturated solution (very concentrated) where solid crystals form. This occurs after substances separate from solutions or where a change from a liquid to a solid causes crystals. The result will occur only at very high concentration levels and is seen in the main in sucrose (and sometimes lactose and maltose. )
Examples of practical applications
- Fudge
- Toffee
- Caramel
- Fondant
The size of crystal formation is dependent on these factors:
- · the rate of the formation of nucleii.e. the bases of crystal growth; the rate of growth of the crystals.
- The rate of crystal growth can be affected by: The concentration of sugar in the solution.
- The concentration of sucrose (disaccharide which increases rate of Crystallisation)
- The temperature of the solution;
- Stirring the solution causes a grainy textured product as Crystallisation occurs too fast;
- Addition of additives such as fats, honey, corn syrup or cream of tartar also change the form of the product.
Proteins
There are many types of proteins. Proteins enable foods to become viscous, or to set. These properties have many applications in food preparation.
Functional Property: Coagulation, Denaturation and Syneresis
Definition/Explanation of property:
Two important processes are denaturation and coagulation. The denature means to change properties; once a protein has denatured, it cannot return to its original form. An example of this is the application of heat to egg. the second step of denaturation is coagulation, whereby protein thickens and changes into solid mass. The process of denaturation and coagulation is affected by the application of acid, alkalis, sugar and salt.
Syneresis occurs when the coagulation process continues due to heating. This is seen when the protein squeezes out the liquid in the product, for example curdling in custards, the separation of liquid from meat when it is cooked to well done and the weeping of liquid from meringue on top of a lemon meringue pie.
Examples of practical applications
Definition/Explanation of property:
Two important processes are denaturation and coagulation. The denature means to change properties; once a protein has denatured, it cannot return to its original form. An example of this is the application of heat to egg. the second step of denaturation is coagulation, whereby protein thickens and changes into solid mass. The process of denaturation and coagulation is affected by the application of acid, alkalis, sugar and salt.
Syneresis occurs when the coagulation process continues due to heating. This is seen when the protein squeezes out the liquid in the product, for example curdling in custards, the separation of liquid from meat when it is cooked to well done and the weeping of liquid from meringue on top of a lemon meringue pie.
Examples of practical applications
- Raw eggs to cooked (scrambled, boiled)
- Production of Cheese
- Baked/fried fish
- Creme Caramel
- Meringue (protein denatured during beating; heat causes coagulation)
- High Temperature - the higher the temperature, the faster coagulation will occur. Over heating causes a gel to firm.
- Agitation ( excessive mechanical action may cause over coagulation);
- The action of enzymes e.g. rennin causing milk to coagulate;
- A change in pH; and
- The addition of salt - begins the process of denaturation.
Functional Property: Aeration
Definition/Explanation of property: Foams are the process of whipping or beating air into a liquid (generally lipids.) Foams are a type of aeration. In this process, fat in the product becomes partially solidified and protein partially denatured. They are an extremely efficient way to incorporate air. They rely on the mechanicaluse of instruments to create spaces for oxygen to enter although excessive beating can cause a structural breakdown of the product.
Examples of practical applications
Factors affecting the rate and effectiveness of foaming include:
Definition/Explanation of property: Foams are the process of whipping or beating air into a liquid (generally lipids.) Foams are a type of aeration. In this process, fat in the product becomes partially solidified and protein partially denatured. They are an extremely efficient way to incorporate air. They rely on the mechanicaluse of instruments to create spaces for oxygen to enter although excessive beating can cause a structural breakdown of the product.
Examples of practical applications
- Cream
- Pavlovas
- Sponges
- Meringues
- Roulades
- Soufflés
- Mousses
- Omelette
Factors affecting the rate and effectiveness of foaming include:
- The product being beaten;
- The length of beating time;
- The severity of the beating;
- The use of additivese.g. gelatine or sugar;
- The age of the product (especially in products such as cream);
- The temperatureof the product.
Lipids
Lipids or fats and oils have many functional properties that make them a useful ingredient in food and a useful component when frying food.
Functional Property: Emulsification
Definition/ Explanation of property: Emulsification is the dispersal of fat or oil throughout a liquid. Oil and water do not mix, so emulsification requires the use of a third ingredient. If oil and water are beaten for a period of time, the oil is reduced to very small droplets that appear to be distributed in the water. However if the mixture is left to stand for a while, it will separate. An example of this is a clear salad dressing, such as french dressing. Egg yolk, salt, paprika, and mustard are emulsifying ingredients that work by wrapping around the small oil droplets, preventing them from joining back together and separating from the water on standing.
Examples of Practical Applications:
Definition/ Explanation of property: Emulsification is the dispersal of fat or oil throughout a liquid. Oil and water do not mix, so emulsification requires the use of a third ingredient. If oil and water are beaten for a period of time, the oil is reduced to very small droplets that appear to be distributed in the water. However if the mixture is left to stand for a while, it will separate. An example of this is a clear salad dressing, such as french dressing. Egg yolk, salt, paprika, and mustard are emulsifying ingredients that work by wrapping around the small oil droplets, preventing them from joining back together and separating from the water on standing.
Examples of Practical Applications:
- Mayonaise
- gravy
- cheese
TASK:
Design a series of posters to illustrate the functional properties of Carbohydrates, proteins and lipids. Use recipes, magazines, photographs and hand drawn illustrations to enhance your presentation
Design a series of posters to illustrate the functional properties of Carbohydrates, proteins and lipids. Use recipes, magazines, photographs and hand drawn illustrations to enhance your presentation