Introductioin

Cake is often the dessert of choice for meals at ceremonial occasions, particularly weddings, anniversaries, and birthdays. There are countless cake recipes; some are bread-like, some rich and elaborate and many are centuries old. In this chapter we talk about the raw materials needed to make a good cake and how to make it.

The definition of muffin here is the American muffin i.e. a small individual cakes baked in paper cups. An English muffin, which predates by far the American muffin, is a type of light bread leavened with yeast. The English muffin will be discussed in another chapter.

Cake flour

Soft wheat as the term indicates, is soft to the bite, low in protein, and starchy white when a cross section of a kernel of wheat is looked at. Conversely, the hard wheat is hard to the bite, high in protein, vitreous and glossy looking when examining a cross section of the kernel

Soft wheat flours are used in many products such as cakes, pastries, cookies, crackers, pretzels, ice cream cones, gravies, biscuits, batter and breading, and in industrial use as glue extenders.

Soft wheat flours are generally low in water absorption, do not require harsh mixing or long mixing time when working with a batter or a dough system. The resulting products possess qualities such as tenderness, softness, crispness, and good texture.

Cake flour is usually a short patent flour of low ash and protein content. In the USA the flour is often treated with chlorine to an optimum pH level for best cake bake performance. Patent flour is defined, in milling technology of soft as well as hard wheat, as highly refined flour which is extracted from the centre of the kernel of wheat. In the milling process, flour streams can be grouped together and fall into one of the following categories: very short, short, medium, long, and very long patent flour. Each one of these categories is only a certain percentage of the total flour produced. The shorter the patent, the more refined the flour will be. Going back to cake flour, a powdered bleaching agent is added to the flour for carotene colour removal or creamy colour removal, which is important if the flour is intended for white cake production. The bleaching agent can also be an enzyme. The following general specifications are typical for cake flour:

The first major type of cake is the white, yellow, spice, chocolate and devil's food, which may be baked in layer, loaf or sheet form, or as cup cakes. The second major type is the foam cake which depends primarily on the whipping capacity of eggs and the air incorporated therein for structure and volume. Usually foam cake or angel food cake flours are fancy short patent of fine granulation and contain slightly less ash and protein than flours used in the layer-type cakes.

I believe the pH is the most important factor in the cake flour specifications, and the moisture level becomes of great importance in the case of dried flours used in prepared mixes. The pH is critically important because without chlorinating cake flour to a certain pH level, the cake volume, as well as the external and internal cake characteristics, will suffer tremendously. The following basic cake formula is used by some cereal chemists since it is designed to test flour performance in high-ratio white layer cakes. The ingredient percentages are based on flour.

ingredient

percentage

cake flour

100,0

granulated sugar

140,0

shortening

50,0

dried skimmed milk

12,0

dried egg whites

9,0

baking powder

6,0

salt

2,0

water

145,0

Baking powder

The word "leavening" comes from the Latin word "levo" meaning "to rise" or "making light."

Generally, baked products become light by the expansion of carbon dioxide evolved within the dough or batter during the preparation stage and during baking. Carbon dioxide can be produced by either live yeast or by the reaction of an acid with sodium bicarbonate.

The resulting cellular structure in the baked product not only adds a pleasing appearance, but also contributes to texture, and aids digestion by extending the surface area to the action of enzymes in the digestive system.

The first known leavening, of course, was the action of yeast and it was known to the Egyptians as early as 2000 B.C. Mummified loaves of yeast-leavened bread were, in fact, found in early Egyptian tombs as well as in the Roman ruins of Pompeii.

Late in the 18th century, chemical leavening first made its appearance when sodium bicarbonate was recognized as a source of carbon dioxide which could be released by the action of an acid. The lactic acid in sour milk or buttermilk serves this purpose very well and there is some evidence that sodium bicarbonate was used along with sour milk in baking as early as the Renaissance period.

The use of chemicals to leaven or raise baked products was proposed over a century ago by Liebig, a German chemist.

The first record of a chemical leavening dates back to about 1835, when cream of tartar (potassium hydrogen tartrate or potassium tartrate, (KHC4H4O6), obtained from the lees and argots of wine during the winemaking process, was used in combination with bicarbonate of sodium bicarbonate for leavening cakes. Cream of tartar is a convenient acid in solid form, and when mixed with sodium bicarbonate, is relatively stable when kept dry.

Early experimentation with cream of tartar and sodium bicarbonate indicated that two parts of cream of tartar to one part of sodium bicarbonate made the best combination for releasing the desired amount of carbon dioxide. The first commercial baking powder, based on these two ingredients, was marketed in 1850.

Later, corn starch was added as an inert vehicle to carry the active agents and to disperse them to prevent the premature release of gas in the package.

At about this time, 1856, Eben Horsford received a patent on a new baking powder derived from monocalcium phosphate (calcium dihydrogen phosphate, Ca(H2PO4)2.H2O. This baking powder was based on a mixture of rather impure phosphates and sodium bicarbonate.

In 1885, sodium aluminium sulphate was used as an acid component for a baking powder. However, its reaction with sodium bicarbonate was very slow, making it unsatisfactory as a single-acting system. About 15 years later, the slow acting sodium aluminium sulphate was combined with the faster acting monocalcium phosphate to yield the first double-acting baking powder. Several such commercial baking powders are still being marketed today.

The next major advance in leavenings occurred about 1902, when a German chemist over-dried a batch of mono-sodium phosphate and found he had produced sodium acid pyrophosphate. This material was found to be an excellent leavening agent. Initially, its aftertaste and slow rate of reaction in cakes precluded its use as a household baking product. Later, technological developments overcame this fault and several types are now made for use in the baking industry.

As I indicated earlier, the mechanism of chemical leavening occurs when carbon dioxide is produced by the reaction between an acid and sodium bicarbonate (sodium bicarbonate) when they are dissolved in water. The fundamental reaction, that of neutralizing a basic material with an acidic material, is measured by what is sometimes called its "neutralizing value" or "neutralizing strength." This value has been defined as the parts by weight of sodium bicarbonate that 100 parts by weight of an acid leavener will neutralize, i.e., convert to carbon dioxide gas.

Typical neutralizing values for the most common food leavening agents can be seen in the following table. To calculate the amount of leavening acid required to neutralize a known amount of sodium bicarbonate, we substitute these values into the following formula:

Amount of acid = (amount of sodium bicarbonate x 100)/neutralising value

Acid

Neutralising value

Grams of acid to
neutralise 100 g of sodium bicarbonate.

Final pH of baked goods

Monocalcium Phosphate Monohydrate (MCP)

80

125.0

7.1 to 7.3

Monocalcium Phosphate Anhydrous (AMCP)

83

120.0

7.3 to 7.5

Sodium Acid Pyrophosphate (SAPP)

72

138.9

7.7 to 8.3

Sodium Aluminium Phosphate (SALP)

100

100.0

7.2 to 7.4

Sodium Aluminium Sulphate (SAS)

100

100.0

7.3 to 7.6

Potassium Acid Tartrate

50

200.0

7.2 to 7.5

Glucono-delta-lactone (GDL)

45

222.2

-

Dicalcium Phosphate Dihydrate (DCP)

33

303.0

-

A few baked products are improved by a slightly alkaline or slightly acid final pH. For example, chocolate cakes may be made alkaline with formulations containing additional amounts of sodium bicarbonate to give a pleasing, dark mahogany coloured cake crumb. Similarly, the crumb colour in white cakes may be improved by slight increases in the acid component of a balanced leavener during production.

Leavening rate of reaction

Normally, sodium bicarbonate will dissolve almost immediately when water is added and, thus, the rates of dissolution of the acid component of a leavener will determine the rate of reaction of a particular leavener. Leaveners are, therefore, characterized by this rate of reaction and are formulated to take this reaction rate in account.

In order to determine the rate of reaction of a particular acid leavener, a simple dry biscuit mix or cake batter mix is placed in a closed system. The vessel is attached to a device that measures the gas evolved by means of either volume or pressure increases. Water is added and stirring is initiated. The amount of gas evolved is determined.

The amount of carbon dioxide evolved is converted to a percentage of the total sodium bicarbonate present and this is plotted against time. The information thus obtained provides a convenient tool for comparing the reactivity of different leavening acids.

Note that the sodium bicarbonate reacts quickly with the acids in the flour and milk, even when no leavening acids are present, evolving about 25 percent of the total potential carbon dioxide.

The particle size of both the sodium bicarbonate and the acid leavener will influence the rate of reaction. In general, the coarser the granulation of the sodium bicarbonate, the slower it will react. Therefore, tailoring the particle size of commercial baking powder is required for optimum performance.

Potassium acid tartrate or cream of tartar, reacts very fast, probably too fast for modern baking methods. Nearly all of the carbon dioxide is liberated during mixing of the batter or dough, leaving only the entrapped gas and air for expansion in the oven. Its high cost coupled with its low efficiency has led to its replacement.

Monocalcium phosphate monohydrate is also sometimes too fast to be used alone, but it is used in combination with slower acting leavening acids to give the "so-called" double-acting baking powder. In production, this quick reaction rate gives initial nucleation which increases the viscosity of the batter and lowers its density so that proper pan fill can be achieved.

Coated, anhydrous monocalcium phosphate is slightly slower in reaction rate than monocalcium phosphate monohydrate and, because of this, can be used in single-acting baking powders for home use where there is little delay between preparation time and introduction into the oven.

Sodium acid pyrophosphates (SAPP) exhibit a wide range of reactivity. In the presence of calcium salts from milk or other ingredients, these acids are time-temperature triggered. Under constant baking preparation conditions, each grade of SAPP has a characteristic time at which it will start to dissolve and release most of the available carbon dioxide. The rate of reaction is also influenced by temperature. As the temperature is increased, the rate of activity is increased. Cake doughnuts require this type of reactivity and sodium acid pyrophosphates are generally the only acids used to leaven them.

Many commercial baking powders today contain sodium acid pyrophosphate as one of the acid components. Monocalcium phosphate monohydrate is generally used in conjunction with SAPP to provide a double-acting system.

Another area in which sodium acid pyrophosphates are used in large quantities is refrigerated doughs. Here a relatively slow SAPP is employed as the acid leavener. Biscuit doughs are mixed cold (about 15C) and the doughs are sheeted quickly and cut into small disc-shaped pieces. These are packed into foil-lined cans, sealed, and proofed at relatively high temperatures (60 to 65C) until the dough expands against the sidewalls of the can. After proofing, the canned biscuits are cooled to below 15C prior to shipping. Refrigerated dough products are generally produced in plants requiring dairy-level sanitation to obtain products having low levels of spoilage organisms.

Sodium aluminium sulphate gives little leavening reaction until heated and, therefore, is generally combined with faster acting leavening acids such as monocalcium phosphate monohydrate to provide a satisfactory baking powder combination for cakes. Some of the better known retail baking powders still use this combination of baking acids.

Glucono-delta-lactone reacts slowly but continuously with sodium bicarbonate. It is quite expensive, but has found limited use in cake doughnuts and "instant breads."

Dicalcium phosphate dihydrate is very slow acting and is triggered too late in the baking cycle (generally 60 to 65C), for most baked products. It has been used for specially formulated frozen cake batters.

Sodium aluminium phosphate is primarily triggered by temperature. The reaction is too slow to give maximum oven spring in some baked products. However, it is used widely with monocalcium phosphate monohydrate in double-acting baking powders. It yields a baked product free of leavening aftertaste and, because of this, finds broad use in many present-day baked products. Many of today's commercial cake mixes use sodium aluminium phosphate as one of their leavening acids.

In cake formulations, considerable variation exists in sodium bicarbonate levels, acid combinations and level, and in the type of inert diluting materials such as starch and calcium salts.

Each leavening combination has been developed to do a specific job and is sold at a competitive cost. Most commercial baking powders are made in modern, automated plants where great care is taken in blending, mixing and packaging. There are rigid specifications for purity, particle size and moisture control. The baking powder is usually packed in airtight cans or poly-lined, multi-walled bags for protection against moisture.

Sugar

Sugar is mainly used as a tenderiser in cakes because of the softening effect it has on the protein of the flour. Obviously it is also used for sweetness, moisture retention and crust colour. Increasing the sugar level in the recipe will raise the gelatinisation temperature of the starch and as a result the expansion time will increase. Granulated sugar will help to incorporate air into the batter. Sugar is also hygroscopic and will help with the shelf life extention (both in terms of softness and microbiological).

There are many types of sugar of course: dextrose, muscovado sugar, invert sugar, corn syrup, molasses etc. Muscovado sugar or "Barbados sugar" or "moist sugar", muscovado is very dark brown and slightly coarser and stickier than most brown sugars. Muscovado takes its flavor and color from its source, sugarcane juice. It offers good resistance to high temperatures and has a reasonably long shelf life. It is commonly used in baking recipes and making rum. Muscovado sugar can be used in most recipes where brown sugar is called for, by slightly reducing the liquid content of the recipe. Muscovado sugar has 11 calories per 4 grams. When produced under regulated conditions, it is nutritionally richer than other brown sugars or refined sugar, and retains most of the natural minerals inherent in sugarcane juice.

These different sugars ar used either for the particular flavour they impart to the cake or as moisture retaining agents. Glucose syrup for instance can be used to replace partily the vegetable oil in muffins.

Sugars tend to make the batter softer and thinner. It is also important to remember that these various sugars have a different level of sweetness as granulated sugar as can be seen from the following table. It is custom to give a value of 100 to sucorse (25 parts of sucrose in 100 parts of water).

type of sugar relative sweetness type of sugar relative sweetness
sucrose
100
fructose
140
high fructose corn syrup
100 - 160
high fructose corn syrup 42 %
100
glucose
70 - 80
lactose
30 - 50
invert sugar
50
sorbitol
50 - 70
saccharin
300
honey
97
molasses
74
aspartame
180

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