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Functional Properties of Food

by Rachel Lorizio
by

Rachel Lorizio

on 23 June 2011

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Transcript of Functional Properties of Food

Functional Properties By Rachel Lorizio The main nutrients that exist within food, including proteins, carbohydrates and fats, undergo many changes which we can call functional properties of foods. This occurs when the nutrient is changed in order to enable it to be used in different forms and with different textures, tastes and appearances. What are Functional Properties? What are the recipes? What properties can be found in these recipes? In the two recipes to make Lemonade Scones and Pavlova, several functional properties can be identified. These include: Scones:
 - dextrinisation: the process in which the polysaccharide, starch, undertakes a partial chemical breakdown former shorter glucose chains called ‘dextrins’
- gluten formation: the process in which proteins, glutenin and gliadin, are moistened and combined with fat to stretch and form gluten strands Pavlova: - aeration: the process in which air is added to a substance
- denaturation: the process in which the bonds holding together the helix shape of the protein molecules are broken causing strands of the helix to separate and unravel
- malliard reaction: (if pavlova is overcooked) the process in which dry heat is applied to a substance containing sugar and protein forming a dark yellow or brown looking crust Three particular functional properties occurring within these recipes are dextrinisation, gluten formation and aeration. These three properties are particularly important within our recipes to produce the desired appearance, taste, texture and even aroma of the foods we will prepare. AERATION Aeration of egg whites is an important functional property evident in the preparation of pavlova. The protein present in the egg is what produces this reaction. The egg whites are vigorously beaten which causes the specific protein from within the egg whites to be removed from its entirety. The egg whites denature (bonds of helix shape break and unravel), coiling and forming large, foamy bubbles as the air is engulfed within the molecules. As the mixture continues to be beaten, the bubbles become smaller creating a foamier appearance that is very white and fine. Factors that affect the aeration of the egg whites include the temperature of the eggs. For best results, egg whites should be at room temperature which are less elastic than refrigerated egg whites and all equipment used should be at a consistent room temperature. The presence of acids will result in the more gradual formation of the desired foamy texture. Agitation is required to produce a large volume of foam. The more agitated the mixture is, the more successful the foam will be. The presence of fat in the mixture will obstruct the egg white’s ability to foam. This is particularly important when ensuring that no egg yolk is accidentally present in egg white mixture. Water from a wet bowl or from wet beaters will produce a less stable foam mixture. When sugar is added to the mixture, a shinier and more stable texture is produced. DEXTRINISATION Dextrinisation is also known as the ‘browning reaction.’ When making scones, this functional property is what gives the scones their golden brown appearance. The dextrinisation that occurs within the preparation of the scones is the starch granules within the wheat in the flour being exposed to heat. The carbohydrate present within starch is what produces this reaction The dextrinisation of the scones occurs due to a number of factors. The scones are cooked in a hot oven which stimulates the chemical breakdown to form smaller chains of ‘dextrins.’ As well as this, the presence of the acid in the lemonade aids the dextrinisation process. The intensity of dextrinisation that occurs to a food item depends on the length of time the food is exposed to dry heat, the temperature of the heat, the addition of other ingredients and the action of added acids. In the making of scones, the oven temperature is quite high but the scones are only cooked for a short amount of time. This allows dextrinisation to occur, browning the exterior of the scone to perfection without a doughy or raw interior. GLUTEN FORMATION The formation of gluten is a vital property in the preparation of scones. The proteins glutenin and gliadin within gluten occurring in wheat products is what produces this reaction. When a fat is added to these two proteins, they become stretchy and are elasticised, forming gluten strands. Specifically, the thorough kneading of the scone dough combines the proteins, fats and water products with the two molecules (gliadin and glutenin) sliding past each other, attaching to fat molecules to produce gluten strands. Along with the presence of these proteins, several other factors contribute to the formation of gluten within a recipe. Agitation of the scone dough is essentially the key to strengthening the mixture. When the dough is kneaded, the gluten strands form and as the dough continues to be kneaded, it becomes less elastic. The presence of fats such as the cream in the scone recipe can restrain the connection between the glutenin and gliadin to the water content meaning gluten strands cannot be formed. A soft, crumbly texture can be achieved through the addition of sugar. Scones do not contain a large quantity of sugar so scones tend to not taste too sweet and have a soft but moist and contained texture. The formation of gluten strands within scones also allows the scones to hold their shape and rise when being cooked. When the scones are in the oven, air and water within the strands escape and rise making the dough stretch until the exterior of the scone reaches the required temperature for the proteins to denature and coagulate, hardening the outside crust. The Making Of... Time Management To assist our preparation of our two chosen recipes,
Jamie and I created an appropriate Time Management
Plan to follow. Sensory Assessment After preparing our dishes, we asked some of our peers to taste them and complete a sensory assessment. Bibliography Burnett-Fell, B. (2009). Food Technology in Action - 3rd Edition. Queensland: Jacaranda Plus
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