scope it appears as a fine network of mostly colorless parenchyma cells, containing globules of fat (Fig. 67). Some of the cells are circular, others considerably elongated, and some contain a deep-brown coloring matter, which, with ammonia, become violet-red, changing to red with acid. Occasionally the cell walls appear of a dark color. If flour containing ergot be treated with a very dilute solution of anilin violet, the stain will be practically absorbed by the damaged particles of the grain, and resisted by the normal granules. A hot, alcoholic extract of flour containing ergot is colored red when treated with dilute sulphuric acid.

FIG. 67.-A, Transverse Section of the Ergot of Wheat under the Microscope; B, Powdered Wheat Ergot. (After Villiers and Collin.)

Adulteration of Flour.-Besides the substitution of cheaper or inferior grades for those of higher quality, the fraudulent admixture of corn flour to wheat flour was at one time extensively practiced. This adulterant is best detected by the microscope (p. 317).

Rye flour has been adulterated with cheap grades of wheat flour cr middlings. These admixtures are detected by the Bamihl test (p. 330) and by microscopic examination of the residue after boiling with dilute acid (page 315), noting especially the cross cells.

Much of the so-called buckwheat flour formerly contained large amounts of wheat or corn flour, or both. Rice flour is also used in pancake flours, although probably not to cheapen the product. Self-raising pancake

flours are usually mixtures of two or more flours with leavening material. The microscopic characteristics of the starch grains and tissues serve to identify the different flours present in such mixtures.

In England so-called "improvers," notably calcium acid phosphate and other soluble phosphates and potassium persulphate, have come into use to correct certain defects of flour made from native wheats. The addition of phosphorus trichloride and pentachloride and various phosphorus and sulphur compounds has also been proposed.

Alum in Flour.-Alum was formerly used in Europe, both by miller and baker, to improve the appearance of inferior or slightly damaged flour, but now is rarely if ever employed, and the presence of notable quantities of aluminum compounds in flour or bread is usually due to alum baking powder.

Bleaching of Flour.-In 1908 about 80% of the flour produced in the United States was bleached by nitrogen peroxide, but as a result of the enforcement of the federal law the practice has been largely discontinued. The gas is generated by electrical, chemical, or electro-chemical means, and is diluted with air before treatment of the flour. In the Alsop process, which is most commonly employed, it is formed by a flaming discharge of electricity, which causes the nitrogen and oxygen of the air to combine.

Nitrogen peroxide destroys almost immediately the yellow color which is associated with the fat of the flour, thus increasing the whiteness of the product. It also forms with the moisture of the flour nitrous and nitric acids, the former (free or combined), being easy of detection. A considerable part of the nitrous nitrogen remains in yeast bread after baking and nearly all of it in soda biscuit. Bleaching also diminishes the iodine number of the fat, affects the quality of the gluten, and injures the flavor of the bread.

Recently bleaching with chlorine has come into use.

Aging versus Bleaching.-Storage under proper conditions slowly whitens flour, improves its baking properties, increases its organic acidity, diminishes its water-content and brings about other changes not well understood. Nitrogen peroxide immediately whitens flour but does not improve its baking properties, increase its organic acidity nor appreciably affect its water-content. It does, however, introduce nitrous and nitric acids. Often 2 parts of nitrous nitrogen per million are recoverable and sometimes 6 or 7 parts, but this gradually disappears so that after some months hardly a trace remains.

The extent to which typical flours are whitened by aging and by bleaching so as to contain 2 parts of nitrous nitrogen per million is apparent from the gasoline color values in the following table by Winton:

INSPECTION AND ANALYSIS OF FLOUR.

In some of the larger cities, authorized inspectors are appointed by boards of trade to pass upon the quality of flour. To such inspectors dealers submit samples, which are gauged as to color, soundness, weight, ctc., comparing them usually with a series of graded samples, and stamping or branding them officially with the date as well as the grade. Market quotations also are based on the standard terms adopted. The names of the various grades differ with the locality. In St. Louis, the following names are adopted in order of the quality, viz., Patent, Extra Fancy, Tancy, Choice, and Family.

The grade or quality of flour is determined largely by its color, fineness, odor, absorption, and dough-making properties. Baking tests are also relied on to a considerable extent by millers and buyers.

Of the chemical methods those for ash, protein, gluten, acidity, fat, and fiber are of chief importance.

Fineness. The granulation is determined by rubbing the flour between the thumb and fingers. A gritty flour is one that feels rough and granular, due to aggregates of cells with contents intact. Smooth flour, on the other hand, feels soft and slippery. It is so finely ground that the cells are isolated and often ruptured, thus liberating the contents.

Pekar Color-test.-Place 10-15 grams of the flour on a rectangluar glass plate, about 12 cm. long and 8 cm. wide, and pack on one side in a

straight line by means of a flour trier. Treat the same amount of the standard flour used for comparison in the same manner, so that the straight edges of the two flours are adjacent. Carefully move one of the portions so as to be in contact with the other, and "slick" both with one stroke of the trier, in such a manner that the thickness of the layer diminishes from about 0.5 cm. on the middle of the plate to a thin film at the edge, and the line of demarcation between the two flours is distinct. Cut off the edges of the layer with the trier, so as to form a rectangle, and compare the color of the two flours. The difference in color becomes more apparent after carefully immersing the plate with the flour in water, and still more apparent after drying.

Gasoline Color Value.-Winton Method.-Place 20 grams of the flour in a wide-mouthed glass-stoppered bottle of about 120 cc. capacity and add 100 cc. of colorless gasoline. Stopper tightly and shake vigorously for five minutes. After standing sixteen hours, shake again for a few seconds until the flour has been loosened from the bottom of the bottle and thoroughly mixed with the gasoline, then filter immediately through a dry 11-cm. paper, previously fitted to the funnel with water and thoroughly dried, into a flask, keeping the funnel covered with a watch-glass to prevent evaporation. In order to secure a clear filtrate, a certain quantity of the flour should be allowed to pass over on to the paper and the first portion of the filtrate passed through a second time.

Determine the color value of the clear gasoline solution in a Schreiner colorimeter, using for comparison a 0.005% water solution of potassium chromate. This solution corresponds to a gasoline number of 1.0 and may be prepared by making 10 cc. of a 0.5% solution up to one liter. The colorimeter tube containing the gasoline solution should first be adjusted so as to read 50 mm., then the tube containing the standard chromate solution raised or lowered until the shades in both tubes match. The reading of the chromate solution, divided by the reading of the gasoline solution, gives the gasoline color value.

Absorption and Dough Test.-Stir 30 grams of the flour in a heavy coffee cup with 15 cc. of water by means of a spatula until a smooth ball of dough has been formed. If after standing two minutes, the amount of water proves insufficient to thoroughly dough up the flour, repeat the operation, using 15.5 cc. of water, and, if necessary, continue to repeat until the quantity is found that will yield a stiff, but thoroughly elastic dough. From the results of this test, calculate the absorption of 1000 grams of flour in terms of cc. of water.

The physical characters of the dough, such as color and elasticity, furnish valuable indications of the quality or grade of the flour.

Expansion of Dough.-Rub to a smooth paste 3.5 grams of granulated sugar, 1.2 grams of salt, and 3 grams of compressed yeast, and thoroughly mix with 60 cc. of water at 35° C. Warm 100 grams of the flour in a shallow pan to 35° C., add to it the yeast mixture, mix with a spatula, and knead with the fingers until a smooth ball of dough has been formed. Drop the dough into a graduated, 500-cc. cylinder, pat down so as to force out the air, and note the volume of the mass. Place in a raising closet kept at 35° C. Read the volume at the end of the first hour and every half hour thereafter until the maximum is reached.

Baking Tests. These should be carried out in such a manner as to produce the best results with the kind of flour used and the purpose for which it is intended-whether for yeast bread, soda-biscuit, pastry, or crackers. Only tests for bread flours are here taken up, although methods for flours designed for other purposes may be easily devised to suit the conditions.

In judging the loaf the chief points are volume, shape, flavor, odor, texture, and color.

Two types of bread baking tests are in general use, (1) the long fermentation, or more accurately the short sponge, straight dough method, and (2) the straight dough method, best known in the form described by John Koelner of Milwaukee who also supplies a special kneader and other apparatus.

Apparatus.-1. The Proofing or Raising Closet is a kind of incubator with double doors, provided with one or more electric lamps or other heating device to keep the temperature at about 32° C.

2. Kneader.-Hand kneading is recommended for the long fermentation process. The combined mixer and kneader supplied by Koelner

is used with his process.

3. Baking Tins for the long fermentation method are 16.8×8.8 cm. at the top, 14.9 × 6.9 cm. at the bottom, and 13.9 cm. deep (inside measurements) with aprons on both sides to prevent the falling over of the loaf. Those for the Koelner method are 27X6.3 cm. at the top, 25.4×5 cm. at the bottom, and 8.8 cm. deep (inside measurements) and do not have aprons.

4. Oven.-The best form is an electric oven provided with three heats (low, medium, and full); a gas or kerosene oil oven may also be used.