Experimental cookery

Emulsifying properties of oils. Meszaros states the size of the fat drops in an emulsion depends more on the method of preparation than on the properties of the fat. Meszaros has expressed the emulsification capacity in a number {E number) which represents the milligrams of fat which can be emulsified under certain conditions in 100 grams of water without the aid of emulsifying agents. Fats tested fall in four groups: (1) Fats which show a very good emulsification capacity {E number over 50) ; as goose fat, horse fat, lard, crude rapeseed oil (crude sunflower oil). (2) Good emulsifying fats {E number 20-50), as butter, butter fat, peanut oil, sesame oil. (3) Poor emulsifying fats {E number about 10) — coconut oil, palm-kernel oil, soybean oil, beef tallow. (4) Very poor emulsifying fats {E number 10) — illipe fat, hardened train oil. The method of mixing. Kilgore, Corran, and Hall and Halstrom 278 EMULSIONS emphasize the method of adding the oil to secure a stable emulsion of desirable consistency. Hall and Halstrom found that the method they called the Compromise Method was the best. For this method a portion of the oil was added by means of a buret above or beneath the surface of the forming emulsion until optimum dispersion was obtained. They state that optimum dispersion might properly be considered the critical dispersion point. At this point maximum thickness is attained and any further addi- tion of oil results in an irrecoverable breaking of the emulsion. This oc- curred after the addition of 30 to 35 cc. of oil to 20 grams of beaten egg yolk. At this point the vinegar and spices are added. This thins the emulsion but thickening occurs again w^ith the addition of the remainder of the oil. The amount of oil added was such that the mayonnaise con- tained 89 to 93 per cent of oil. For the method which Hall and Halstrom called American, the vinegar and spices were added to the egg yolk. After blending of these ingredients the oil was added in the same manner as for the compromise method. Their results follow : TABLE 40 Stability of Mayonnaise {Hall and Halstrom) Method Manner in which oil was added Stability of emulsion after storing at 8°C. for 2 years Compromise Compromise American American Above surface Beneath surface Above surface Beneath surface Fragile, partially separated No separation Complete separation No visible separation, but fragile The emulsifying constituent of egg yolk. In starting their investi- gation, Snell, Olsen, and Kremers added lecithin to egg yolk in making mayonnaise. They acted under the general assumption that lecithin is the constituent of egg yolk which is effective in producing emulsions. Hence it was thought that the addition of more lecithin should increase the stability of the mayonnaise. But all the mayonnaises so produced had poor consistency. Next they studied the effect of each of the known major con- stituents of egg yolk on mayonnaise. It was found that none of these sub- stances was capable of producing the consistency derived from the whole egg yolk. This led to the Investigation which demonstrated that egg yolk owes its emulsifying action to an unstable complex containing both lecithin and protein, which they called "lecitho-protein." This lecitho-protein consti- tuted about 32.5 per cent of the salted yolks. THE METHOD OF MIXING 279