Experimental cookery

The making of mayonnaise, HoUandaise sauce, gravies, and other sauces in which an emulsion is formed comes under dispersion methods, for although the dispersed phase is not sufficiently small to class the product as a sol, the dispersed phase must be broken into many particles. Bancroft states that one means of dispersion is by the addition of a peptizing agent. He says that peptization is always due to adsorption. "If an adsorbed film has a low surface tension on the water side, it will tend to scrunch up and to peptize the solid as internal phase. If the reverse is the case, the solid will tend to form the external phase." If the word oil is substituted for solid in the foregoing quotation, an excellent picture of the formation of mayonnaise emulsion is obtained. For example, if one-fourth cup of oil is I 276 EMULSIONS added to a cup or more of well-emulsified mayonnaise, the oil may be stirred slowly a few times with a spoon, 15 to 20, and presto, it is all emulsified. The stirring could not possibly break the oil into thousands of small particles. Hence, the function of the stirring is to increase the area for adsorption to occur and the squeezing effect of the adsorbed egg yolk breaks the oil into many spheres. For the first addition of oil in making mayonnaise great care must be taken, but large quantities of oil may be added rapidly in the last part of the process. Investigations on Mayonnaise and Emulsions Air film on the oil phase. Hall and Halstrom have reported that the presence of an air film on the oil phase, as it is introduced into the emul- sifier and forming emulsion in making mayonnaise, results in a less stable, inferior emulsion with lower specific gravity than in mayonnaise prepared with oil having no such air films. For the emulsions having air films on the oil, the oil was added from a buret at a definite rate, the point of the buret being six inches above the surface of the forming emulsion. For oil having no air film the buret point was lowered so that the oil was injected beneath the surface of the forming emulsion. They add, "Clayton pre- dicted that when the dispersed phase is injected into the continuous medium below the surface, intermittent injection would confer no advantage." From their results Hall and Halstrom felt that Clayton's prediction was a sound one. Water-holding capacity o£ emulsifier. Kilgore states that preserved yolks are available in five main conditions : frozen salted, frozen sugared, fresh refrigerated, especially treated, and dried. This is also the order of their volume consumption by the mayonnaise trade. Kilgore emphasizes that the starting mixture to which the oil is added should not contain too much *'free" water. It should have enough **free" moisture to start emulsi- fication yet have a heavy body, like a thick paste, smooth in texture. Frozen and treated yolks, because they have more bound and less '"free" water than fresh yolks, are excellent for starting mayonnaise to secure a fine "grain." Yet more of the frozen than of fresh yolks are necessary for an emulsion of good consistency. Kilgore adds that de-fatted mustard flour is an excellent water-holding ingredient ; hence it gives a heavy paste and also has decided emulsifying powers.