Starch

Gelatinisation Success Rate

1. The type of starch used and the proportion in relation to the liquid. 2.The temperature of liquid 3.Other ingredients added. Acids reduce the thickening ability , and large quantities of sugar soften the starch gel.

Gelatinisation Process

1.Starch particles do not dissolve in liquid, instead they form a suspension. 2.Stirring or agitating liquids keep the starch particles suspended. 3. If the suspension is not stirred, the particles sink to the bottom and stick together, forming lumps. 4.When liquid reaches 60C, the starch grains begin to absorb liquid and swell. The granules will swell to more than five times their normal size. 5.80C the particles break open and release starch, making the mixture thick and viscous. This forms a gel within the liquid called Gelatinisation. 6.Gelatinisation is completed when the liquid reaches 100C. The thickened liquid now forms a gel. On cooling the gel solidifies. 7. When reheated the sauce reverts back to its liquid state.

Other Thickening Starch Foods

1.Swede & Sweet Potatoes will thicken soups and stews 2.Potato Flour - Used to thicken sauces, soups and casseroles as the starch is released from the potatoes into the cooking liquid. 3.Rice Flour - Thicken sauces, suitable for use in gluten free and wheat free diet. Thickens milk puddings such as rice pudding, used to thicken dishes such as risotto.

Sauce Making Faults

1.Thick Sauce - Inaccurate weighing of thickening agent or liquid. 2.Lumpy Sauce - Insufficient agitation, liquid added too quickly, additional flour added to mixture or heated too quickly. 3.Poor Colour - Sauce burnt in pan 4.Poor Flavour - Insufficient flavouring and seasoning or mild cheese used. Floury taste - insufficient cooking of the fat and flour when mixing roux sauce.

Gels

A gel is a solid, jelly like substance. Gels are mostly liquid, but behave like solids due to the gelling agent holding the liquid in place. Gels form when starch is heated in a liquid and cooled. White Sauce - Flour Custard & Lemon Meringue Pie Filling - Corn Flour Jam - Pectin Flan Glaze - Gelatine

Solution

A solution is formed when a liquid is dissolved into another liquid for example fruit squash in water. A solid is dissolved into a liquid, like sugar in a cup of tea. Solutions will not separate if left to stand.

Suspension

A suspension forms when solid particles are added to liquid but do not dissolve. Starch particles, such as flour don't dissolve in a liquid, but they form a suspension.

Starch

Cornflour - Fine powder obtained from maize kernels. It blends to a smooth cream with liquid. Arrow Root - Maranta Plant used to glaze tarts and flans. Wheat Flour - Thickening Agents - Taste floury and therefore needs to be cooked.

Ingredients Function

Flour - When mixed with the liquid and heated the starch granules thicken (gelatinise) the mixture. Salt & Pepper/Herbs/Spices - Improves the flavour in the sauce. Fat - Adds flavour which is absorbed by the flour when the sauce is heated. Liquid - Main ingredient, the liquid is required for the gelatinisation of starch. Can improve the nutritional value of sauce. Flavouring - Cheese, Chilli, Soy Sauce, Parsley, Mushrooms & Mustard for example improve the colour, texture and flavour of sauce.

Foams

Gas mixed into a liquid giving a light texture eg ice cream. Meringues are a foam made by whisking air/gas into egg white/liquid. When you bake them the air expands and the egg coagulates to give a solid structure.

Key Terms - Gelatinisation, Suspension, Gel & Modified Starch

Gelatinisation - When heated, starch granules absorbs liquid and swell and then burst to thicken a liquid. Suspension - A solid held in a liquid. Gel - A small amount of a solid mixed in a large amount of liquid that then sets. Modified Starch - Starches that have been altered to perform additional functions.

Emulsions

Liquids that will not mix together are immiscible eg oil and water. When shaken together they form an unstable emulsion, which separates if left standing. A mixture only remains stable if an emulsifier is used eg lecithin in egg yolk is an emulsifier. Egg yolk is used in the preparation of mayonnaise, where it holds oil and vinegar together. It helps the fat in cakes mix with the egg white.

Smart/Modified Starches

Manufacturers use a large number of starches which have been altered to react to different processes. 1.Pregelatinised Starch - Allows liquid to thicken instantly. It's used to thicken instant desserts without heat. A cold liquid can be added and the dessert will thicken when stirred or whisked eg Angel Delight. Other examples include packet custard, cup a soup and pot noodles. 2.Used to thicken condiments and low fat desserts such as low calorie salad dressing - To stop them separating. 3.Some modified starches allow sauces to be reheated with no synerisis eg Lasagne. Syneresis - Prevents sauces from separating in ready meals.

Sauces

Sauces are used to add colour, flavour, moisture and nutritional value to food. There are many different flavours and types, such as cook in or pour over. The properties and characteristics of sauces are influenced by the way they are made and the proportion of ingredients. Sauces can be made by the blended method, the roux method or the all in one method. Blended Sauces - Custard, Sweet & Sour and Gravy Roux Method - Cheese & Parsley Sauce All In One Method - White & Parsley Sauce (Pouring, Coating or Binding)

Starch - Used in food production obtained from cereals, root vegetables and fruit.

Used to thicken liquids eg Cheese Sauce. Adding acid such as lemon juice will thin the sauce. When cold the starch forms a gel.