What is Emulsion?

What is an Emulsion.

    An emulsion is the even distribution of one liquid in another liquid with which it does not readily mix. When ingredients are used that do not mix, termed immiscible, such as oil and water, it is often necessary to force them to form a stable mixture, termed homogeneously.

     If the oil and vinegar are simply poured into the same bowl with no whisking, agitation, the oil will rise to the top and the vinegar will settle to the bottom. If oil is placed in the bowl first and is whisked vigorously while the vinegar is added, the result is the distribution of the vinegar in the oil. The mixture is thicker than either the oil or the vinegar individually.

Emulsion Sauce.

     They are hot and cold emulsion sauces. The hot emulsion sauces are such as Hollandaise, Bearnaise, Beurre Blanc and the cold emulsion sauces, basic French dressing, mayonnaise, and dessert sauces such as Sabayon. These sauces have a common factor for each is that they are based on the suspension of oil in liquid or liquid in oil.

• Hollandaise and Bearnaise are the mixtures of egg yolk, butter, and acid.
• Beurre Blanc is a combination of butter, a liquid such as wine or meat juices, and often acid.
• French dressing is a combination liquid, generally vinegar, and oil. 
• Mayonnaise is a combination of eggs, oil, and acid.
• Sabayon is a combination of egg yolks, wine, and sugar.

In the preparation of each of these sauces the mixing procedure, temperature and balance of ingredients must be correct in order to achieve a smooth stable blend of the ingredients.

Emulsion stabilized.

    Pooling and separation are the focus of proper preparation of all sauces. There are several methods used to prevent the liquid that has been distributed from pooling and some of them work better than others. It is the natural tendency of like molecules to attract each other as if by magnetism. For instance, the vinegar was blended into the oil while whisking vigorously a temporary emulsion was created. As the mixture sets without whisking, the drops of oil in the jar slowly (at first) begin to attract each other. As the drops get bigger they grow faster, incorporating more drops of oils until there is only one very large drop of oil. The oil gathers at the top of the bowl and the vinegar at the bottom.

    The way to make a more stable emulsion is to physically prevent the drops from being able to join together. This is accomplished in one of the several ways. The use of emulsifiers, very finely ground (powdered) solids, polysaccharides, and proteins, or even thick liquids can help stabilize and emulsion. Each of these ingredients can be important in different situations.

Emulsifiers.

Hydrophilic / Lipophilic 

    The emulsifiers most commonly used in the kitchen include egg yolks, finely ground dried herbs such as thyme and oregano and finely ground spices such as mustard seed, paprika, turmeric, cumin, ginger, and pepper. 

Polysaccharides

     Pectins, a type of polysaccharide that is a gummy, water-soluble dietary fiber is used both in food processing and the commercial kitchen in jams, jellies, and other fruit products. While pectins are not usually thought of as an emulsion stabilizer, they can act as such. Agar gum is also known as kosher gelatin. Locust bean gum is also known as carob.

    These gums work by interfering with the pooling process of the distributed liquid or by forming a matrix that traps the distributed droplets. Many of these are found in processed foods and are used infrequently in today's kitchens.

Starch Gelatinization

    Flour is one of the more common starches used in sauce preparation. All-purpose flour is composed of approximately 74% carbohydrates (Starch). When the flour is used in a roux the roux is cooked. As the roux is cooked the starch granules, when toasted slowly, begin to unwind a bit.

     The toasting of the starch granules in fat allows complete separation of the granules, thereby maximum exposure for maximum absorption. What is created is a mass capable of absorbing six times its own weight of liquid when cooked. The toasting must be just that, toasting, not burning. Burnt starch absorbs water, creating gel much less effectively.

Protein

    Proteins that are naturally present in foods can make very effective emulsifiers because they too have hydrophilic and lipophilic properties. Gelatin is an example of a protein that can act as a stabilizer. Since proteins are such large molecules they also interfere with the pooling. It is a protein that is responsible for holding the fat in suspension in the meat emulsions in bologna and frankfurters. Salad dressings can be stabilized by using egg whites in the same way one would make mayonnaise because of the protein albumen in the egg whites.

Thick Liquid

    Another method of stabilizing an emulsion is to add thick liquid to the two immiscible liquids. A fruit salad dressing may contain citrus juice, oil, and herbs but it will form only a very temporary emulsion when mixed. By adding honey the mixture is sweetened and more stable. The addition of pureed fruit, such as strawberries, will add flavor and make the mixture more stable.

The reason of Emulsion breakdown.

 

    There are three main reasons that emulsions break, separate, or never form in the first place.

1.    The liquid is added too quickly.

2.    The mixture becomes saturated.

3.    Temperature.

Liquid adding

    When the liquid that is to be dispersed and the discontinuous phase is added too quickly, the emulsion may never form or quickly separate. This occurs because there is not sufficient time for the liquid to fully disperse. The tiny drops cannot form, and instead, pools of the liquid are created. This is why the recipes for mayonnaise and hollandaise call for the oil to be added in a slow, thin stream. As the old chef said, if too much butter is added too fast the eggs will be swimming in it, not gathering it up.

    There are two solutions for this problem. One is to slow down the stream of liquid, giving it time to disperse into the continuous phase. Secondly, it may be necessary to increase the speed of mixing the item.

Saturation

    When an emulsified mixture becomes saturated it is similar to when the liquid is added too quickly. However, the difference is that no amount of whisking will incorporate all of the liquid. For example, in the first instance, the oil in the mayonnaise never had a chance to disperse. In the second instance, there is simply too much oil. 

    The basic ratio for an emulsion using egg yolk as the emulsifier is 1 large egg for each 6 ounces of oil for melted fat( butter). This is true for emulsions such as mayonnaise and hollandaise. 

    A towel can only hold a certain amount of water without dripping. When it becomes totally saturated with water it begins to release some. This is exactly what happens in an emulsion when too much of the liquid to be dispersed is added.

    When saturation occurs the solution is to put some of the continuous ingredients into a separate mixing bowl and slowly add the broken emulsion to it. In the case of mayonnaise or hollandaise, place some beaten egg yolk in a mixing bowl and begin to whisk the broken emulsion into it. This decreases the proportion of dispersed phase, oil or butter, to the water and water-soluble solids contained in the egg yolk.

Temperature

    Temperature abuse is a major cause of broken emulsions. In the kitchen, the most common emulsion is between oil or fat, and a water-based solution (vinegar, fruit juices, wines, stock, etc). Often the emulsifier is a protein or is part of a protein system.

    Excess heat or agitation or acid can catalyze chemical reactions that can destroy the protein molecule in terms of its emulsifying properties. Furthermore, the energy input (heat and agitation) in the presence of acids can also act to destroy some of the other emulsifiers such as the lecithin in egg yolk. This is why it is important to know when to be careful when making an emulsion and to learn to recognize the warning signs of imminent breakage.

    Another problem is that of thickness. When oil gets cold, it gets thick; when it gets hot it becomes thin. water does not do this to any noticeable extent. This presents a problem in making an emulsion because not only are you trying to combine two immiscible substances, you are often trying to mix two solutions that are of different thicknesses.