The Fermenting Strength of Yeast.
The best manner for the baker to test the strength of yeast is to take equal parts of the samples of the various yeasts, about 10 g.; dissolve in 100 g. of water at 85 degrees F., and make a dough with equal amounts of the same bread flour (about 1990 g.).
Fig. 9.
In order to prevent transferring of any one yeast sample to either of the other doughs, it is advisable to thoroughly wash the hands between each mixing. Place the doughs in glass jars of equal dimensions, and allow them to raise at an even temperature. It goes without saying that all ingredients must be weighed exactly alike, and the temperatures in all cases be the same. The yeast which gives the greatest expansion of the dough has the preference.
Another simple manner to test the strength of yeast is to drop a piece of the dough into tepid water (85 degrees F.), and observe the time consumed between immersion and when the piece of dough rises to the surface of the water. The dough which rises in the shortest time contains the strongest yeast.
Of course, in technical schools yeast strength is determined along different lines. A Hayduck carbonic acid measuring apparatus is used for this purpose, and is shown in cut ([Fig. 9]). It consists of two connecting glass tubes fastened against a board. The wider of the tubes has a capacity of 500 cc., and ends at the top in a narrow glass tube, to which rubber tubing may be attached, and is graduated in cubic centimetres. The other narrow tube ends at top funnel-shaped.
Through the funnel the apparatus is filled with water, colored blue to make observations easily. In order that the water may not absorb any of the carbonic acid gas, which would tend to make the test inaccurate, on top of the water in the wider tube a thin layer of petroleum is poured.
In gas generating flasks (A) a suitable “wort” and a definite amount of yeast, to be tested, is dissolved and placed in a water bath. (B) is a second flask for the next following test. (C) is a pinch-cock, which is left open so long as (D) is kept closed. The generated carbonic acid gas forces the water out of the wide tube and is caught up at (G). The yeast which has the ability to displace the largest amount of water at stated periods is considered the best fermentation inciter. Before any readings are taken the water in both tubes is brought to the same level by means of cock (E).
If care be taken to use the exact proportions of materials in each test at even temperature, reliable conclusions are obtained from each individual yeast sample.
Water.—Next to flour, water is the most abundant compound used by the baker. It is the great solvent of Nature. Pure water is composed of the two gases, hydrogen and oxygen, in proportions of 1 to 8. It is colorless and tasteless.
Water as found in nature is never pure. Owing to its action as a solvent, it contains bodies like lime, magnesia and potash in solution, besides air, carbon dioxide and other mineral matters. Hard water is such as contains more than seven grains of mineral salts per gallon.
The hardness due to bicarbonate of lime may be neutralized by boiling. Other mineral salts are penniment.
In general, soft water is more adaptable for bakers’ use, as hard water retards fermentation and somewhat checks the softening changes going on in the dough during fermentation.
Doughs made with hard water require to lay longer to properly mature.
It is for this reason that the baker will find it necessary at equal dough temperatures to modify his methods when using hard or soft waters to get uniform results.
It is of the utmost importance that water used in the bakery be free from organic matter that is detrimental to health, as many such organisms have a tendency to set up putrefactive fermentation in doughs.
In a broad sense, however, water that is declared fit for drinking purposes can be safely employed in bread work.
Salt.—Chemically known as chloride of sodium. It is produced from three different sources: Bay or sea salt, rock or mine salt, and natural brine or pit salt. Of these the refined product of natural brine or pit salt is to be preferred by bakers.
It should be dry, to insure uniform results, as wet salt contains a large percentage of water, which interferes with obtaining accurate and uniform quantities needed in the doughs.
It is added to doughs in varying amounts, from 1½ to 4 pounds per barrel of flour, and gives bread flavor and taste. When working with soft water more salt is required than in hard water. While salt gives the bread flavor, it also retards fermentation. It is especially of import by keeping in check lactic and butyric fermentation, causing sour bread. Authorities claim that salt in all proportions from 1.4 per cent. upwards retards fermentation and diminishes the speed of gas evolution, the raising of the dough.
Milk.—Is largely used in bread making. Dry milk on account of its convenience, has supplanted fluid milk in a large measure in the bakery.
Although not universally accepted, the writer is of the opinion that dry milk containing pure butter fat will add equal flavor to bread in which fluid milk is used.
Besides giving flavor and nourishing properties to bread, on account of its dryness it has water absorptive qualities that are of economic value to the baker.
Dry milk also contains soluble extracts that have an invigorating influence on yeast growth, i. e., fermentation, and improves and gives a better bloom in the crust of the bread.
In point of economic value, the baker should determine, by making small trial doughs, the increased volume obtained by reason of the extra moisture absorbing properties of dry milk when used in doughs.
Fat.—Lard, compound lard and cotton-seed oil are the fats generally employed in bread making. The use of fats effects a finer texture in the bread.
A colorless shortening assists in producing a whiter crumb, and also by coating the cells of the loaf retains the moisture of the baked bread. Doughs containing large amounts of shortening, under best and equal conditions, will stand a larger amount of proof, as part of the shortening in a well mixed dough has combined with the gluten of the flour used, allowing it to stretch further and become more elastic and still hold the increased amount of gas generated by the heat of the oven, and produces a loaf of greater volume.
Not all shortenings will produce the same effect, and the baker should experiment with small batches. The points to be determined are the effect the shortening has on the crust, volume of the loaf, as well as the color.
Sugar.—Among the sugar groups used in the bakery we find cane sugar, malt extracts, glucose and yeast foods.
Each of these products have characteristic effects on fermentation and doughs, and will be treated in a later paper.
DOUGHS LEAVENED BY YEAST
BY PROF E. W. HABERMAAS
There are two distinct ways of making doughs. One way is to set a sponge first, then make the dough, and the other way is to make the dough at once. The first is called a “Sponge Dough” and the second is called a “Straight Dough.” Straight dough is so called, because all ingredients such as yeast, salt, sugar, lard, water and flour are all mixed and formed into a dough. There are various reasons for making straight doughs, a few of which we will proceed to give. In the first place, it is more convenient to make a straight dough, because it does not require as much time to make as does mixing the sponge dough, because the mixing is all done at one time. Then, again, a straight dough can be taken in a shorter time than a sponge dough. By this I mean that in case of necessity the dough can be taken, in from 1½ to 2 hours after it has been made. I do not advocate taking the dough in such a short time, but it can be done, because I have done it with good results.
Straight dough requires more yeast than doughs made from a sponge, because the yeast has not as favorable a medium in which to grow, in the straight dough as it has in the sponge dough. It is conceded by some that straight dough requires a stronger flavor than a dough made from a sponge; by others that a stiffer dough is required; by others, that the finished product has a coarse texture, and that an “yeasty” taste predominates. The author made straight doughs daily for eleven years successfully. He neither made a specially stiff dough nor did his finished product have a coarse texture nor an “yeasty” taste. Sometimes when the temperature of the shop was very high or an exceptionally weak flour was sent us, then would our product have a somewhat coarse texture, but this would soon be remedied by using less yeast and reducing the temperature of the liquid used. There are advantages in using strong flour, but they are alike in the straight and the sponge dough, and they are larger yields and larger goods, but these are not the only points to be considered.
Some bakers are partial to spring wheat flour, because the yield in bread is greater than when a blend is used.
Too often is quantity preferred to quality. It seems that most bakers are working to the one end, namely, to get the flour which yields most bread. In this endeavor they are sacrificing quality for quantity.
Spring flour containing a larger per cent. of gluten than winter wheat flour naturally takes up more moisture, producing in turn more bulk, therefore more bread.
Then again the gluten in the spring wheat flour is of a tenacious character, producing a tough elastic dough. Such a dough can resist a greater gas pressure than can one made of weaker flour, and can therefore stand more proof, thus producing a larger and better appearing loaf than one made of a winter wheat flour or a blend.
If a blend is used, we will say two parts of a high grade winter wheat, and one part of spring wheat flour, and the dough is properly worked, the bread will have a fine, smooth, soft, velvety texture, and a mild, sweet taste. The loaf will not be as large a loaf as the one made of spring wheat flour, but will remain soft and moist longer than the loaf made of spring wheat flour. The reason for this is, that winter wheat flour contains a larger per cent. of natural moisture and a smaller per cent. of gluten than the spring flour, therefore it takes up less moisture, and consequently does not lose as much by evaporation in baking; thus leaving a larger per cent. of moisture in the bread.
The chemist’s test cannot decide the true baking value of a flour. A bakeshop test, made by a practical baker, is absolutely necessary to decide this matter.
The principal points to be considered when making straight dough are these: the temperature of the ingredients, the temperature of the shop, the quantity of yeast, and the quality of the flour used. If the temperature of the shop is very high, the liquid used should be cool, and the quantity of yeast should be reduced.
The most favorable temperature for fermentation is from 80 to 90 degrees Fahr., though I prefer to have the dough 85 degrees Fahr.
Before proceeding to make the dough, take the temperature of the flour and the shop, then heat the water to a temperature which will give your dough a temperature of 80 degrees Fahr. when ready. For example, if the temperature of your flour were 5 degrees Fahr., the temperature of the water would have to be 10 degrees Fahr. Now if the temperature of the shop were 70 degrees Fahr., the temperature of the water could be raised to 110 degrees Fahr. I would advise you not to get the temperature of the dough too high, but would rather that you raise the temperature of your shop. Dough chills very quickly when it is on the bench, and after a dough is chilled it will come up very slowly. When making dough in a dough-mixer, the temperature of the water should be at least 5 degrees higher than when making it by hand, because the mixers are more or less cold, while, when dough is made by hand you have the animal heat of the hands to keep up the temperature of the dough. When the weather is very warm, the temperature of the water must be changed to suit. For example, if the temperature of your shop is 90 degrees Fahr., your flour would naturally be very near the same temperature (providing it were kept in the shop), then the temperature of the water would have to be at the utmost 75 degrees Fahr., because the temperature of the dough would continue to rise while it was in the trough or mixer.