This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
Conventional-sponge. Cakes made of oil by the conventional method always have a large portion of the oil dispersed as an oil-in-water emulsion. See Fig. 65. Nearly the same result was obtained when soft, grainy lards were used. Since this distribution of the fat results in a tougher, less desirable cake than when the major portion of the oil or fat forms a thin film at the air/crumb interface, methods of mixing to obtain the latter distribution of the fat seemed desirable. It was noted that a spice cake made from soft, grainy lard, but with no egg, had excellent, very velvety texture. Then it was observed that after the egg was added to the cake batter the tendency to disperse the soft fat as an oil-in-water emulsion was increased. From this premise Martin developed several methods of mixing to use with lard in cake. When the egg was thoroughly mixed with the milk and the milk added as usual the texture of the cakes improved. The conventional-sponge method gave still better results.
Fig. 64. - The above cake is made by method shown in Figs. 61 and 68. The flour and milk were added in the same manner as for the cakes shown in Figs. 57 and 63.
The conventional-sponge method has been used in a series of studies by McLean, Stone, Buel, Minard, and Myers. The recipe used for this method is Formula I. with 1/2 cup of fat and 1 1/2 cups of sugar. But a good creamed
Fig. 65. - Photomicrograph of cake made with oil. Left, conventional; right, conventional-sponge method. Temperature for combining 25°C. There is more tendency for the oil to be distributed at the crumb/air interface by the latter method. Magnification approximately x 350, except center, which is x 70. Center is same as right. Because of the thickness of the section and the consequent diffraction, the crumb appears fluid at 350 magnification but shows better at 70 magnification.
Fig. 66. - Cake batter. The temperature of all the ingredients was 40°C. when mixed. At this temperature the butter was melted. When stirred a partial or complete oil-in-water emulsion was formed. The small dark spheres are butter. Because of the high magnification necessary to show the fat spheres, the layer of batter appears very thick. Magnification approximately x 400.
Fig. 67. - Showing the distribution of fat (butter) in cake as influenced by method of mixing and temperature of ingredients when combined. At the lower temperature the fat (black in the photomicrographs) is at the surface of the cake crumb, but the layer is more uneven in the conventional than for the conventional-sponge method. At the higher temperature the fat is softer and is distributed within the cake crumb, which results in a cake of poorer texture. Magnification approximately x 350.
Upper left: Conventional method, ingredients mixed at 25°C.
Upper right: Conventional-sponge at 25°C.
Lower left: Conventional at 30°C.
Lower right: Conventional-sponge at 30°C. (Myers) volume is not obtained with these proportions because the ratio of sugar to fat is too large. Hence when Martin creamed the fat with one-half the sugar the volume of the creamed mixture increased. A very small amount of flour was folded into this creamed mixture, then the remainder of the flour and the milk were added in any manner desired. The other half of the sugar was beaten with the whole egg until the mixture was thick, fluffy, and spongy, resembling a sponge cake batter in texture. This was then quickly folded into the cake batter.
The conventional-sponge method is the only method used in the author's laboratory that gives an excellent textured cake when oil is used. Although developed to use with soft lard it has been found equally good to use with butter and hydrogenated fats. The chief advantage of this method is the increased velvetiness of the crumb, which may be related to the fat distribution.
That the method and order of mixing and combining ingredients has an effect on the fat distribution is shown in Fig. 67.
Temperature of the ingredients when the cake batter is mixed. At higher temperatures the fat becomes softer, more mobile, and is easier to emulsify. When a temperature at which the major portion of the fat is emulsified is reached, i.e., when very soft or entirely melted, the cakes are poorer in texture and resemble those made from oil by the conventional method. See Figs. 65 and 67.
The extent the batter should be mixed depends to a certain degree upon the temperature of the ingredients. If the ingredients are warm, the flour proteins absorb more water and at a quicker rate than at low temperatures. The sugar dissolves better, and the fat is distributed more readily. Mixing should be shorter when the temperature of the ingredients is high and longer when the temperature is low. But, since the fat creams better at 24° to 28°C, it is preferable to mix the ingredients at these temperatures. When the temperature of the ingredients drops to 18° to 19°C. the texture of the cake is not as nice as at 24° or slightly higher, even if creamed thoroughly on a machine.
A microscopic study of the distribution of fat in cake batters shows that a very important factor in obtaining velvetiness is the way the fat is distributed throughout the batter. If the fat forms an oil-in-water emulsion the cake is not velvety, for the spheres of fat or oil being surrounded by egg and flour cannot impart the softness called velvetiness to the cake. When the fat is distributed in rather thick layers, the cake is not velvety, for there is not the degree of separation of the other ingredients of the cake by the fat to impart this texture. For a velvety texture in the cake the major portion of the fat in the batter is distributed in very thin films or sheets around the sugar crystals, the air bubbles, and between the other ingredients of the batter. The distribution of the fat in thin films is most readily obtained when the fat is most plastic.