A Treatise on Baking

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Sugar

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Chapter V

SUGAR

SUGAR

I. SUGARS—EXPLAINED FROM A SCIENTIFIC VIEWPOINT

A. VARIETY OF SUGARS

Sugars belong to a certain group of compounds made up of the three elements, carbon, hydrogen and oxygen, which are therefore known to the chemist as “Carbohydrates.”

A large number of different substances come under the general heading of sugars. Most of these are secured from certain sugar producing plants and are characterized by their ability to dissolve readily in water and their sweet taste. However, some kinds of sugars are vastly sweeter than others.

From a chemical standpoint, the various kinds of sugars are classified In several different divisions, but those which enter into bakery products can be confined to two groups,—namely “Monosaccharides” and “Disaccharides.”

1. Monosaccharides

These sugars are often spoken of as “simple” sugars, and are directly fermentable by yeast. While the different sugars in this group all have the same chemical composition, they vary considerably in their degree of sweetness and other physical characteristics. The principal “monosaccharides” of interest are stated below:

(a) DEXTROSE

This form of sugar is known also as corn sugar, starch sugar, or grape sugar. Together with fruit sugar, it is found naturally in fruit juices and honey. Dextrose is secured commercially by the conversion of corn starch as explained later under the heading of Corn Sugar. Dextrose is not as sweet as cane sugar.

(b) LEVULOSE OR FRUCTOSE

This form of sugar is often known as “fruit” sugar. It occurs usually along with dextrose and is present in molasses, honey, and the juice of fruits. The Jerusalem artichoke and dahlia roots are said to be quite rich in levulose. While pure levulose is sweeter than either cane sugar or dextrose, it has not been commercially practical to extract pure levulose. It is extremely difficult to get levulose to crystallize out of a syrup. Furthermore, the presence of a small amount of this sugar prevents any dextrose and cane sugar present with it from crystallizing. This peculiar characteristic possessed by levulose makes its presence valuable in fondants, cream centers for candy, jams and jellies.* The reason for the fact that molasses and honey remain fluid even on long standing is due to the presence of a small amount of levulose which prevents the other sugars from crystallizing.

(c) INVERT SUGAR

As explained in the foregoing paragraph, dextrose and levulose frequently occur together. A combination of equal parts of these two simple sugars is known as “invert sugar.” In addition to its occurrence as such in nature, invert sugar is produced by the action of heat and acid on cane sugar. In a bread dough, cane sugar is converted into invert sugar by the action of the yeast enzyme “invertase.”

2. DlSACCHARIDES

The several kinds of sugar belonging to the group known as “disac-charides” have the same chemical composition but each is different in their appearance, taste and other characteristics. There are three of these sugars of interest to the baker.

(a) CANE SUGAR OR SUCROSE

The manufacture of sucrose and sugary agents rich in sucrose are described in paragraphs which follow. Both cane and beet sugar are sucrose.

In a bread dough, sucrose is first acted on by the enzyme “invertase” present in yeast and thereby changed into “invert sugar” which is then acted on by another yeast enzyme known as “zymase” resulting in the production of the carbon dioxide gas which raises the dough.

(b) MALT SUGAR OR MALTOSE

Maltose, as the name implies, is the form of sugar present in malt. Incidentally malt not only supplies the dough with maltose to meet its sugar requirements but also furnishes other substances which greatly benefit the conditioning of the dough.

In the dough batch maltose is first acted on by an enzyme known as “maltase” which is supplied by the yeast and is thereby converted into “dextrose” which is then acted on by the enzyme “zymase” in about the same manner as invert sugar described under the preceding paragraph.

A detailed description of maltose and its use as sugary agent for baking purposes is given in Chapter VI.

(c) MILK SUGAR OR LACTOSE

Lactose is that form of sugar which occurs naturally in milk. While lactose is of good food value and aids in producing crust color, it is very low in sweetening value and is not fermentable by yeast. Therefore, this form of sugar is not used as a commercial bread sugar, although when milk is used, some lactose is thereby introduced into bakery products.

II. FUNCTION OF SUGAR IN BAKERY PRODUCTS

A. SOURCE OF FOOD SUPPORTING YEAST ACTIVITY

In order that yeast may raise and condition a dough, it requires energy food, and the primary reason for the use of sugar in a bread dough is to supply the yeast with a readily available source of energy.

B. SOURCE OF THE GAS CARBON DIOXIDE

It is the sugar of the dough which is acted on by the yeast enzymes and thereby split up into carbon dioxide gas which raises the dough and some alcohol which evaporates from the dough during baking. While flour contains a small percentage of sugars, the addition of sugar in greater or less amounts is necessary in practically all bakery products.

C. SOURCE OF SWEETNESS

An important reason for the use of sugar in bread, sweet dough and pastries is its characteristic sweetening properties.

D. SOURCE OF CRUST COLOR

The carmelization of sugar of a dough during baking is largely responsible for the golden brown color and appetizing flavor of the crust produced. Hence, if insufficient sugar is used, the resulting loaf will be pale and unattractive in appearance.

III. THE USE OF SUGARY AGENTS IN BAKERY PRODUCTS

The different forms of sugar used in bakery products are very few. For most kinds of bread, the sugars used either singly or combination are confined almost entirely to Cane Sugar, Beet Sugar, Corn Sugar,—and Malt Sugar as supplied in the form of a malt product such as malt extract. In special sweet goods other sugary agents such as honey and molasses find a certain limited use.

The amount of sugar to be used naturally depends on the kind of bakery product under consideration. In ordinary bread doughs the amount of sugars employed usually ranges from 1 1/2 to 4% but in yeast raised sweet doughs it is in the neighborhood of 15%. In estimating the amount of sugar to be included in any dough batch, the sugar content of any added substances such as sweetened condensed milk must be taken into consideration.

The effect of sugars on the fermentation of the dough is discussed in detail in Chapter XI—Section two. However, it may be well to repeat briefly that sufficient sugar or sugars should be used to support vigorous yeast activity throughout the entire fermentation period and to serve as an adequate source of carbon dioxide gas so that the dough may be properly raised and conditioned. At the same time, sufficient residual sugar should be left unused at the end of the fermentation process so as to produce the desired crust color and proper degree of sweetness. Doughs containing relatively low amounts of sugar should be given only a short fermentation so that enough sugar will be left to give the final baked product the required sweetness and crust color.

The presence of large amounts of sugars such as in various types of sweet doughs,—slows up yeast action and hence in these doughs, increased quantities of yeast are necessary in order to bring about the vigorous healthy fermentation which is so essential to the production of quality yeast raised goods.

The use of malt extract as a sweetening agent not only supplies the dough with malt sugar to meet its usual sugar requirements but performs other valuable functions such as promoting a vigorous fermentation process and also contributing flavor, food value and keeping qualities to the loaf.

IV. POPULAR UNDERSTANDING OF THE WORD SUGAR AND ITS USE AS A SWEETENING AGENT

Practically speaking, only a very limited number of the different kinds of sugar are used in baking and for general sweetening purposes.

Without further qualification, the single word “sugar” as ordinarily employed refers to that form of sugar secured principally from the sugar cane and sugar beet. This sugar is known chemically as “sucrose,” and may also be obtained from sorghum plant,—sugar maple and palm. Frequently, refined sucrose regardless of its source is spoken of as “cane” sugar or “common” sugar.

There is no difference between the sucrose obtained from the sugar cane and that secured from the sugar beet or other sources, provided it is refined to the same extent.

Ordinary sugar is a standardized sweetening agent for general baking purposes. While sugar is very high in sweetening value and is completely fermentable by yeast, an added advantage is gained if part of the sugar ordinarily used in a bread dough is replaced by a like amount of malt extract such as Diamalt. Due to the general use of malt extract by the baking industry, Chapter VI is devoted exclusively to the subject of Diamalt.

V. PREPARATION OF SUGAR FROM CANE AND BEET

The preparation of sugar from either the sugar cane or beet takes place in two steps, namely, the preparation of raw sugar and the refining of raw sugar.

These steps are described briefly as follows:

A. PREPARATION OF RAW SUGAR FROM SUGAR CANE

1. Growth of the Cane

Sugar cane is grown in warm moist climates having intervals of hot dry weather such as the West Indies, and certain southern sections of the United States.

2. Harvesting of Cane

. It is allowed to ripen to the proper point and is then stripped of its leaves in the fields and cut.

3. Pressing of Cane and Extraction of Cane Juice

The cane is carted to the sugar mill as soon as possible, cut up or shredded,—and the juice is pressed out by passing the stalks of the sugar cane through heavy iron rollers.

4. Purification and Clarification of Cane Juice

The waste pulp or “bagasse” is used for fuel and the cane juice is clarified by heating with lime. The impurities are thus separated in the form of a scum.

5. Evaporation of Cane Juice

The clarified cane juice is then evaporated in vacuum kettles until it is ready to grain or crystallize. It is next put in large pans called “strike” pans where the sugar crystallizes out.

6. Removal of Crystallized Raw Sugar and Molasses

The crystallized raw sugar is then separated from the syrup by centrifugal or “whizzing” machines. The sugar thus removed is known as “first” sugar. The viscous, syrupy brown liquor separated from the raw sugar is known as “first” molasses. This molasses may be sold as such or further purified to yield a cruder form of sugar called “second sugar.” The dark crude syrupy liquid secured from this separation is known as “second” molasses and is used largely for cattle feed.

B. PREPARATION OF RAW SUGAR FROM SUGAR BEETS

1. Growth of Sugar Beets

Sugar beets are grown in temperate climates in such states as Colorado, California and Michigan.

2. Extraction of Sugar Beet Juice

The beets are first washed carefully and sliced. They are then digested with hot water which dissolves out the sugar contained in the beet sap. The “spent” beet pulp or chips are separated, dried, pressed and sold as cattle feed and the sugar solution or syrup is clarified in much the same way as that from sugar cane.

3. Evaporation of Syrup, Crystallization and Separation of the Raw Sugar

The sugar syrup secured as described above from the sugar beet is evaporated and the sugar crystallized therefrom in practically the same manner as that secured from the sugar cane. The molasses secured along with the raw sugar secured from the beets is not used for edible purposes as such but is usually treated still further to remove much of its sugar content.

C. REFINING OF RAW SUGAR

The raw sugar obtained from either the sugar cane or beet, in the manner just described contains substances which impart to it a dark color and a characteristic flavor. It must be refined to produce the pure white sugar generally used.

This is done by dissolving the raw sugar in hot water. Impurities are precipitated out and removed by filtering. The sugar syrup is decolorized by passing it thru a “charcoal” filter. It is then evaporated down until the sugar crystallizes out. This is separated from the residual syrup by centrifuging or “whizzing” in a machine designed for this purpose. The sugar is then placed in hot revolving cylinder or “granulator” which dries the sugar thoroughly and prevents the sugar crystals from sticking to each other.

The granulated sugar thus produced is very familiar to everyone. It is snow white, and at least 99.5% sucrose.

VI. MISCELLANEOUS SUCROSE PRODUCTS

A. BROWN SUGARS

This form of sugar has been mentioned under the foregoing description of the manufacture of cane and beet sugar. It represents sugar which has received little or no refinement and contains in the neighborhood of 85 % to 92 % sucrose. The characteristic flavor and color of brown sugar is due to the caramel and other substances present in the natural sugar syrup before refining. Brown sugar is not as sweet as refined granulated sugar, but finds some use in dark colored cookies and other baked goods where its characteristic flavor is desired. A light yellow colored sugar familiarly known as “C” sugar also is used to some extent in cakes and cookies.

B. MOLASSES

As explained previously, molasses is the viscous sugary liquor left after the greater part of the sugar has been recrystallized out from the original brown sugar.

The brown color and characteristic flavor of molasses are due to the caramel and other substances derived from the original cane or beet sap in the process of extracting the sugar.

There are, of course, different grades of molasses which vary somewhat in composition. In general, molasses contains approximately 35 to 50% sucrose, and about 15 to 30% invert sugar, about 20% to 25% water, and 4 to 6% ash, or mineral matter. For baking purposes, molasses is mostly used in certain dark types of cakes, cookies and “brown” bread.

C. MAPLE SUGAR

Maple sugar is the raw sugar obtained by the evaporation of the sap of the sugar maple tree. It is not refined because in so doing the characteristic maple flavor would be eliminated. Maple sugar is used as a confection and only to a limited extent in the manufacture of certain types of sweet goods.

D. SYRUP

Syrups in general are understood to be more or less concentrated sugar solutions, made by purifying and evaporating the juice of sugar producing plants without the removal of the sugar present. Various types of sugar syrups including maple syrup are employed mainly for table use.

VII. MALT SUGAR

Malt Sugar is not manufactured and sold commercially as such. However malt sugar represents the major constituent of malt extract which is described in detail in the following Chapter VI, entitled Diamalt.

VIII. CORN SUGAR

A. DEFINITION

The corn sugar of commerce refers to dextrose which is manufactured from corn starch. Because of this, corn sugar is often spoken of as Starch Sugar. It is directly fermentable by yeast and is a suitable sugary agent for yeast raised doughs. As in the case of cane sugar however, the use of malt extract in conjunction with corn sugar is very desirable.

B. PREPARATION OF CORN SUGAR

The kernels of corn or maize are usually first soaked so as to soften the hard outer layer of the kernel. This is then removed along with the “germ” of the kernel. The corn is then ground,—the starch is removed and washed. The corn starch is then heated under pressure in large digesters containing a certain amount of acid. This causes the starch to be converted into dextrose or corn sugar usually together with some dextrin and other impurities. The acid is neutralized and the sugar solution thus prepared is carefully purified, and evaporated until it becomes very thick or viscous. The dextrose crystallizes out and is separated from the mother liquor by centrifuging or pressing. It is then thoroughly dried. Various grades of commercial corn sugar can be produced having a dextrose content of from 80 to over 99% on a dry basis.

C. GLUCOSE SYRUP

“Commercial” glucose syrup which contains various mixtures of dextrose, dextrin, maltose, water and mineral matter is often spoken of as glucose syrup “mixing glucose,” “confectioner’s glucose” or merely “glucose.” Commercial glucose syrup should not be confused with purified corn sugar which is often termed “glucose” by the scientist.

Ordinary glucose syrup is not as sweet as either cane sugar or pure corn sugar and is not used to any great extent in bread making as the sole sweetening agent inasmuch as it contains a large percentage of dextrin which will tend to make the loaf soggy and gummy.

IX. HONEY

Honey was one of the first sugary agents known to man. The honey formed by the bee is separated from the wax comb in the form of a syrup which contains about 15 to 25 percent water. The remainder of the honey is mainly “invert” sugar together with a very small amount of sucrose.

Honey of course, is expensive but like butter it possesses a natural characteristic delicious flavor and because of this is used to a limited extent in the manufacture of special sweet goods.