Food Functions Jan 2012

This presentation looks at the following food functions: Because of their physical and chemical properties, foods perform different functions which can be used in the production of food products.

How do these work? Set How do you set? Blend cornflour with a little milk and sugar to a smooth paste, gradually add to hot milk, stir and heat to boiling point - allow to cool. Why does it set? The corn starch grains swell and rupture, releasing starch which absorbs the liquid, the mixture sets on cooling.

How these work? do Glaze How do you glaze? Brush beaten egg over the surface of the sausage roll before baking. Why does it glaze? The surface of the sausage roll takes on a shiny golden brown appearance due to coagulation of egg proteins and the Maillard browning reaction.

How do these work? Thicken How do you thicken? Blend the flour with melted fat, gradually add the liquid, stir and heat to boiling point. Why does it thicken? Starch granules in the flour swell, rupture and release starch which absorbs the liquid causing the mixture to gelatinise.

How do these work? Bulk How do you bulk? Boil sugar with fruit juice, reduce mixture to thickness required, add prepared fruit, assemble pie and bake. Why does it bulk? Water evaporates and the mixture caramelises producing a syrup or a thick puree.

How do these work? Bind How do you bind? Combine yogurt with main ingredients and stir. Why does it bind? Liquid present in yogurt is absorbed by the starch granules and hydrates proteins in the flour to form a network.

How do these work? Aerate How do you aerate? Whisk egg white to produce a foam. Fold foam with other ingredients to create light mixture, e.g. sugar. Why does it aerate? Protein in egg white denature and trap air in a stable network.

Video clips on manufacturing processes http://www.youtube.com/watch?v=-i1oMwNgH2Q How to make fortune cookies

Protein and its functional properties in food products Protein is made up of chains of small units called amino acids. Proteins perform different functions in food products depending on their physical shape and chemical structure. The structure of protein changes due to heat, salts, pH and mechanical action. This process is called denaturation.

Protein and its functional properties in food products When proteins unfold from their coiled state and form a solid network, they coagulate, or set, e.g. a boiled egg. The amount and type of protein present in flour determines its suitability for use in different products, e.g. bread required strong flour with a high protein content. Meringue, cheese, bread and jelly are examples of food products which use the functional properties of protein. Key terms – coagulate , denature

Fat and its functional properties in food products Fats are made up of fatty acids and glycerol. Fats are often described as saturated or unsaturated, depending on the proportion of the different types of fatty acids they contain. Fats that are liquid at room temperature are called oils. Key terms – Melt Moisten

Fat and its functional properties in food products When fats absorb oxygen they spoil and become rancid. Fats have many different functions in food: produce short textures in biscuits and pastry/ melt over a range of temperatures, which allows margarine to spread straight form the fridge / allow air to be whisked into a cake mixture. All fats and oils have a different taste and smell, e.g. olive oil (suitable for a salad dressing) and lard (suitable for pastry).

Carbohydrate and its functional properties in food products Carbohydrates cover a wide range of natural compounds, such as starches and sugars, which are based on monosaccharides. Carbohydrates are divided into 3 main groups according to their size: monosaccharides, e.g. glucose disaccharides (two monosaccharides), e.g. maltose polysaccharides (many monosaccharides), e.g. starch

Carbohydrate and its functional properties in food products Carbohydrates perform different functions in food products. They help cause the colour change of bread, toast and bakery products; contribute to the chewiness, colour and sweet flavour of caramel; thicken products, such as sauces and custards. Sugars contribute to the flavour of many products, and can act as preservatives, e.g. jam. Key terms - sweeten, caramelise, maillard, gelatinisation

Functions of Colloidal Systems in Food Products Colloidal systems give structure, texture and mouthfeel to many products, e.g. jam. Colloids are formed when one substance is dispersed through another: gels - a liquid held in a solid network, e.g. jam or jelly emulsions - oily and watery liquids mixed together, e.g. milk and butter / foams - bubbles of gas trapped in a liquid, e.g. whisked egg white or whipped cream solid foam - bubbles of gas trapped in a solid, e.g. meringue, cake, bread

Functions of Colloidal Systems in Food Products An emulsion may separate, so an emulsifying agent may be used to help the oil and water phases to mix permanently. If a gel is allowed to stand for a time it may start to 'weep'. This loss of liquid is know as syneresis.

For further information, go to: www.nutrition.org.uk