CHAPTER GELATIN In this chapter you will learn to Demonstrate your knowledge and understanding of gelatin: Types of gelatin available How to use gelatin Factors to ensure a successful product 1. INTRODUCTION Gelatin is an incomplete animal protein derived from collagen that has been dried and purified. It is used in a variety of dishes such as set desserts, ice-creams, moulded salads, uncooked terrines and sweets. Some religious groups and certain vegetarians avoid using gelatin and would rather substitute it with agar-agar. Important word: Collagen: is a protein, present in the hides, bones and connective tissue of animals. Agar-agar: is a gum derived from seaweed.
2. TYPES OF GELATIN 2.1. Flavoured instant gelatin Gelatin is coloured, sweetened with sugar and flavoured with flavouring agents. It is usually manufactured so that it can dissolve in hot water without hydrating e.g. jelly powder. 2.2. Unflavoured gelatin Gelatin is colourless, odourless and almost tasteless and is available in two forms: 2.2.1 Leaf or sheet gelatin Although it is more expensive than powdered gelatin it is preferred as it gives a more consistent end product. It also dissolves more evenly and has a longer shelf life than granulated gelatin. 2.2.2 Powdered or granulated gelatin It is cheaper and more readily available than sheet gelatin. Important: carefully read the ingredient list of a recipe to see which type of gelatin is specified. Substitute the same weight of granulated gelatin with sheet gelatin called for in a recipe or use the following formula: 1 sheet of gelatin(3 g) = 5 ml granulated gelatine 3. HOW TO USE GELATIN 3.1 Phases of gel preparation/formation A three-phase process is necessary for both types of unflavoured gelatin: 3.1.1 Hydration The gelatin must first be soaked in a cold liquid in order to absorb liquid and soften. This process is called hydration. Powdered gelatin should be sprinkled over cold liquid and left to stand for two minutes or longer so that it can absorb liquid and swell. The proportion is about four times cold liquid to gelatin or 62,5 ml of liquid to 15 ml of gelatin. Sheet gelatin must be separated and soaked in cold water until very soft, at least 15 minutes. It is then removed and squeezed to remove excess water. 3.1.2 Dispersion The hydrated gelatin should be melted to become a liquid by: adding the hydrated gelatin directly to a hot liquid or base melting the hydrated gelatin over steam (a hot water bath/bain marie) or melting it in the microwave oven for a few seconds. It is then stirred into a base mixture that is warm or at room temperature. If the base is too cold, the gelatin may set into strings, on contact with the cold liquid.
3.1.3 Gelation The gelatin mixture is refrigerated to set or form a solid gel. This is a slow process that should not be hurried. 3.2 Handling of gelatin mixtures 3.2.1 Moulding Pour the gelatin mixture into a mould to set. A variety of moulds are available e.g. dariole moulds, silicone or plastic moulds. Prepare the mould by: rinsing it with cold water to which a drop of oil could be added lightly spraying it with non- stick spray lightly brushing it with oil Place the mould in the fridge to set. Gels are best served within 24 hours. After that the gel will become firmer and even rubbery as more bonds form between the gelatin proteins. Eventually water will be squeezed out in a process called syneresis. 3.2.2 Unmoulding Once a solid gel has formed, it can be served in the mould or removed from the mould. Try not to insert a knife. Pull it away from the sides with your fingertips. Use a blow-torch briefly around the outside of the mould. Put a warm cloth around the mould to facilitate unmoulding. Dip the mould for 1 or 2 seconds into hot water not long enough for the gel to start melting. Invert the mould over a plate or place a plate over the mould and flip them over together. A few drops of water on the plate will allow you to move the gel if not in the correct spot. 3.2.3 Whipping When whipped into a foam, a gelatin mixture can double or triple in volume giving it a soft, airy consistency. Allow the gelatin mixture to thicken to a thick egg white consistency, before whipping it. Whipping it too soon will result in the foam floating to the top with the rest of the gel at the bottom. 3.2.4 Adding additional ingredients Solid ingredients Pieces of fruit, vegetables, nuts or meat may be added to gelatin mixtures. Any solid ingredients should be free of liquid or else the volume / quantity of other liquids should be reduced. Only small quantities of solid ingredients should be used. Allow the gelatin mixture to thicken to a consistency of thick egg white before adding the solid ingredients (pieces) to ensure even distribution of it. Adding solid
ingredients to a runny gelatine mixture will result in the pieces floating to the top or sinking to the bottom. Whipped cream or egg white foams Again, the gelatine mixture should have the consistency of thick egg white before folding in the whipped mixture to ensure that the foam is distributed evenly. Adding the foam to a runny gelatine mixture will result in the foam floating to the top, creating two layers. Classroom activity 1 1. Explain the term aspic. 2. Explain the use of gelatin in: 2.1. Wine making 2.2. Frozen desserts
4. FACTORS INFLUENCING GEL FORMATION 4.1. Gelatin concentration The correct quantity of gelatin should be used. Too much gelatin may result in a rubbery end product and too little in a product not setting properly. The quantity of gelatin varies with each dish and its ingredients e.g. Cream and custard based gelatine desserts: 4 ml gelatin to 100 ml liquid Thin liquid based (milk, water etc) jellies or gelatin foam: 6 ml gelatin to 100 ml liquid 4.2. Temperature The faster the gelatine mixture cools, the quicker it sets. The cooling process can be accelerated by: adding crushed ice cubes as substitute of water to the dispersed gelatin placing the mould in a larger bowl with ice water placing the mould in the freezer for a short time but prevent freezing as the ice crystals will damage the gel structure cooling the ingredients and the moulds before using it Fast-setting methods may however result in gels melting quicker at room temperature. Refrigerate gelatin dishes until service to keep them firm. 4.3. Whipping the gelatine mixture The increased volume due to whipping in air decreases the firmness of the gel and extra gelatin is usually added. 4.4. Adding additional ingredients Ingredient Effect Action Sugar A large quantity of sugar will weaken the gel and retard the setting process properly Acid Enzymes Proteins and mineral salts A large quantity of acid (lemon juice, vinegar, etc.) will weaken the jelly and retard the setting process The addition of raw pineapple, figs, kiwi or paw-paw prevent gel formation due to the proteolytic enzymes present in these fruits which breaks down proteins in the gelatin Ingredients such as milk, egg, yoghurt, hard water, etc., will added to set the gel added to set the gel properly Before adding these fruits to gelatin mixtures it should be cooked to destroy the enzymes. Alternatively canned products may be used Less gelatin could be used
Solid ingredients Whipped cream or egg whites Alcohol form a firmer jelly due to the proteins and mineral salts present Pieces of fruit, vegetables, nuts or meat weaken gel formation The large quantity of air decreases the firmness of the gel The addition of alcohol will form a firmer jelly e.g. wine jelly. When more than 30% of the total jel volume consists of alcohol it may cause the gelatin to solidify into hard particles added added Always use less than 30% alcohol