Vol. XXII. No. 12.] 



POPULAE SCTEInTCE I^EWS. 



179 



l^omc, iFarm, mn Garten, 



THE CHEMISTRY OF BEEAD-MAKING. 

 The transformation of the flour, obtained by 

 grinding wheat, into a soft, spongy, nutritious 

 mass known as bread, although a matter 

 of everj'-day occurrence, is dependent upon 

 some vei-y peculiar and important chemical 

 changes. If flour is mixed with water to form 

 a dough, and dried at the temperature of the 

 air, an unpleasant- tasting mass is obtained, 

 which contains the starch of the flour in an 

 unaltered and insoluble state, and very diffi- 

 cult of digestion ; and to obtain a nutritious 

 and palatable bread, it is necessary to induce 

 certain chemical and physical changes in the 

 flour. 



Wheat flour is principally composed of 

 starch, and contains, on an average, about 

 sixty-three per cent of that substance, with 

 fifteen per cent of water. The remainder is 

 made up of small amounts of sugar, fat, 

 casein, and a mixture of various gummj' 

 bodies, generally known as gluten. This 

 gluten is an important part of the flour, 

 giving it consistency and flavor, and also 

 rendering it more nutritious. By kneading 

 flour under a gentle stream of water, the 

 starch can be washed away and the gluten 

 separated. 



The action of the heat in baking causes 

 certain changes to take place in the starch, by 

 which it is rendered soluble, and to some 

 extent converted into another substance re- 

 sembling gum, and known as dextrine. The 

 outside of the loaf is altered to a greater ex- 

 tent, forming the crust. These changes "have 

 the effect of rendering the bread both nutri- 

 tious and palatable ; but to prevent its be- 

 coming a heavy, solid mass of dried dough, it 

 must be " raised," or inflated with gas, so as 

 to convert it into a light, spongy substance 

 which can be easily masticated and digested. 



The gas used for this purpose is always car- 

 bonic dioxide, and the best method to develop 

 it in the mass of dough is to set up a vinous 

 or alcoholic fermentation by the addition of 

 j'cast. This substance is a most remarka- 

 ble living organism, which, when introduced 

 into the dough, begins to feed upon the starcli, 

 which it changes into alcohol and carbonic- 

 acid gas. Owing to the tenacious nature of 

 the dough, the gas cannot escape, but, as It 

 expands, renders it spongj- and light. Tiie 

 heat of the baking-oven still further expands 

 the gas, and completes the process, at the same 

 time killing tlie yeast, and preventing further 

 fermentation. If the fermentation continues 

 too long, it passes over into the acetic variety, 

 the alcoiiol is changed to vinegar, and the 

 bread " sours." 



Tiie alcohol produced in the process is 

 nearly all dissipated in the baking ; but it is an 

 appreciable quantity-, and some years ago a 

 company was formed in England to introduce 

 appliances for condensing and saving it. The 

 method was found impracticable, but it created 

 considerable excitement, and one baker adver- 

 tised to sell his bread " with all the gin in it." 



When baking-powder is used as a leavening 

 agent, carbonic-acid gas is formed in the 

 dough as with yeast, only it is set free by the 

 reaction of certain chemicals upon each other, 

 forming salts which remain in the bread, and 

 none of the constituents of the flour are de- 

 composed. A process has also been tried of 

 kneading the dough in closed vessels with 

 water containing carbonic-acid gas in solution 

 under pressure, like soda-water ; the supposi- 

 tion being, that when the pressure was removed, 

 the gas would expand, and cause the dough to 

 rise. This aerated, bread, as it was called, has 

 been made both in this country and England ; 

 but the method has not been successful, and it 

 is not now in use. 



It is interesting to note that the style of 

 oven and method of bread-baking in use in 

 Euro|)e at present has undergone little or no 

 change since the earliest limes. The old-fash- 

 ioned brick oven is still used, and the fire built 

 inside until the necessary heat is obtained, 

 when it is raked out, and the loaves put in its 

 place. Altiiough the method is a clumsy and 

 wasteful one, it must be confessed that the 

 bread produced by the French and German, 

 and especially tiie Viennese, bakers, is unex- 

 ce))tionable in quality. Probably the care 

 used in mixing and kneading has as much to 

 do with the result as the baking itself. 



Bread is not often adulterated, but the defi- 

 ciencies of a poor flour are sometimes covered 

 up by the addition of alum or a minute quan- 

 tity of sulphate of copper (blue vitriol). 

 These substances render the bread whiter and 

 of a better consistency, but are not only a 

 fraud upon the purse of the- consumer, but 

 detrimental to his health .as well. Most of the 

 cheaper varieties of baking-powder contain 

 alum, and their use cannot be recommended. 



The art of bread-making has been known 

 from the earliest times, and as early as the 

 period of the Jewish exodus the process of 

 leavening was in general use. In the museum 

 at Naples there are exhibited loaves of bread 

 taken from a shop at Pompeii and stamped 

 with the name of the baker. They are perfect 

 in shape, but are quite black, probably from 

 the heat of the volcanic ashes which were cast 

 upon the city from Vesuvius. AVhen properly 

 made, bread is a most wholesome and nutri- 

 tious food, and, with the other cereal products, 

 forms the principal means of sustenance of a 

 large majoritj' of the human race. 



man, as shown in the accompanying illustra- 

 tion (from the Magasin Pittoresque). This 

 accidental resemblance gave rise to the most 

 absurd superstitions. It was said, that, when 

 the root was pulled from the ground, it gave 

 forth terrible shrieks and groans, which turned 

 to stone any one who heard them. To avoid 

 this unpleasant consequence, it was customary 

 to tie a hungry dog to the plant, and, having 

 thrown a piece of meat before him, to run 

 quickly away, and out of earshot of the botan- 

 ical lamentations. The dog, in his struggles 

 to reach the food, would uproot the much- 

 prized plant, and, it is fair to suppose, was at 

 once transformed into a canine petrifaction; 

 but, as no specimens have ever been preserved. 



tlie fate of the unhappy animal must be con- 

 sidered as doubtful. 



Tlie mandrake is a European plant; but in 

 this country the Podophyllum, or May-apple, 

 is sometimes called by that name. It belongs, 

 however, to an entirely distinct famil}'. 



TIIE MANDRAKE. 



The mandrake {Alropa viandragora) is a 

 plant which has, from ancient times, been cele- 

 brated for the resemblance of its root to the 

 human figure. Pythagoras called it the an- 

 thropomorphon, or plant of human form, and 

 in some countries it is known as the " man- 

 faced tree." Tiie plant possesses dangerous 

 narcotic properties, and was an ingredient of 

 the poisonous philters and potions of the sor- 

 cerers and magicians of the Middle Ages. 



The mandrake has a bifurcated, hairy root, 

 which, with a little alteration, can be trans- 

 formed into a very good representation of a 



A NEW METHOD OF rOTATO CULTURE. 

 The old-fashioned method of planting pota- 

 toes in hills bids fair to be superseded by the 

 " trench method " introduced the past season 

 b}- the Rural New-Yorker. It is claimed that 

 the yield is largely increased, the bad effects 

 of drought are prevented, and the tubers are 

 larger and better developed. The following 

 description of the method is taken from the 

 columns of our contemporary : : — 



The seed potatoes were spread out singly in a 

 warm room. The eyes of the "seed end" soon 

 pushed, forming short, warty shoots. The eyes of 

 the other portions of the potatoes grew but 

 slightly. The object of placing the seed potatoes 

 in a warm, light room was to secure the most vig- 

 orous "seed" for the contest plot. All potatoes 

 the eyes of which seemed dormant or feeble were 

 rejected. They were cut according to the number 

 of strong eyes developed, the object being to 

 have at least three to a piece. On April 18 the 

 trenches were dug with a spade about seven inches 

 deep and a full foot in width. As we have not as 

 yet determined whether it is better to strew the 

 fertilizer tmdtr or over the seed, it was sown 

 both under and over. Eight hundred and eighty 

 pounds were first evenly sown in the bottom of the 

 trench, and incorporated with the soil. On this, 

 an inch or so of soil was raked, and the seed-pieces 



