Experimental cookery

Emulsions stabilized by colloids. So many of the emulsifiers are colloidal in nature that this group is the most important In food prepara- tion. The following are commonly used : eggs, gelatin, flour, starch, and milk. Gum arable, gum tragacanth, Irish moss, and other substances are used less frequently. Pectin is being used to some extent. Gum arable and gum tragacanth are used principally in cookery of diabetic foods, the Irish moss in puddings. Stabilization by powders. Finely ground particles or powders such as lampblack, mustard, and paprika are a third class of substances used for emulsifying agents. The best examples of this type of emulslfier in prepared foods are the French dressings. At the present time several brands are on the market that are fairly stable. All are deep red in color, so that the 274 EMULSIONS emulsion must be partially and probably wholly stabilized with particles of paprika and mustard. This kind of emulsion is formed by the powder film around the drops of oil which keeps them from coalescing. Clayton reports the results of using finely divided solids as emulsifiers by Bechhold, Dede, and Reiner. "They found that the formation of emulsion depends upon: (1) the grain size of the powder. The smaller the grain the better the emulsion, until an optimum is reached, after which smaller grains have inferior emulsifying properties. (2) The quantity of powder. The more powder there is available the more globules there can be covered, provid- ing the powder is sufficiently fine." They report that zinc dust, iron powder, clay, Kieselguhr, and yeast made very efficient emulsifiers. The Making o£ Emulsions To make an emulsion it is necessary to break or separate the dispersed phase into small globules. The work for this separation can be done in dififerent ways. Machines of different types are used for making commercial emulsions. They are all designed to break the liquid into globules, either by a rotary motion, pressure, or by some other means. Agitation is used in all of these. Homogenization is used by most commercial firms for making mayonnaise. In making emulsions in the home, different methods are fol- lowed. For mayonnaise, an egg beater is often used, French dressing is often shaken, and gravy and sauces are made by stirring, usually with a spoon. Optimum degree of agitation for each emulsion. Clayton says it is well known that agitation can both break and make an emulsion. The amount of agitation required for a given emulsion depends upon the par- ticular emulsion being made and the kind of mixing utensil used. Clayton states: "It is quite reasonable to believe that for any given emulsifying apparatus there exists an optimum speed or degree of agitation or mixing, and an optimum time of mixing or running, whereby the most perfect emulsion can be obtained in a given system. Experiments prove this."