202 



♦ KNOWLEDGE . 



[Sept. 28, 1883. 



superior to any bread I have ever obtained in the South. 

 The particular bread referred to was obtained from an 

 ordinary baker's shop, and was light, white, of most deli- 

 cious flavour, and even after keeping some days, showed 

 not the slightest taste or smell of acidity. Without a 

 greater knowledge of local facts, it is difficult to give the 

 reasons for this superiority. Without doubt, in the 

 first place, the baker must be a master of his trade. But 

 in addition to this, flour of the best quality must be used ; 

 it is possible that Liverpool, being one of the principal 

 English ports to which flour and grain are shipped, and 

 these from some of the best wheat-growing countries, that 

 better flour can be there obtained for the same price as 

 that asked for an inferior quality where aji additional 

 •charge for carriage is incurred. Be this as it may, for 

 reasons laid down in oiu- last article, good flour is an indis- 

 pensable requisite for the production of good bread. 

 Unfortunately nature, in yielding us the fruits of the earth, 

 does not always yield them in the best possible condition ; 

 rain and want of adequate sunshine may cause the wheat 

 crop to be poor and the grain damp and not thoroughly 

 ripened. Under these adverse circumstances the problem 

 to be faced is how to make the best bread possible from 

 the unsound flour obtainable. The great difficulty with 

 such flour is the tendency of the gluten to convert the 

 starch into sugar ; there is further the danger of lactic 

 fermentation and consequent sourness. 



Certain mineral substances possess the power of arrest- 

 ing the action of the gluten of damp flour on its starch ; 

 among these alum has been long employed by the bakers. 

 Alum is a double sulphate of alumina and potash, having 

 the formida ALK„(S0j)4. A flour which, under ordi- 

 nary circumstances, produces a bread unfit for consump- 

 tion can be made by the addition of a small quantity of 

 alum to yield a white bread of fair quality. If an infu- 

 sion of bran be made and added to some boiled starch, the 

 starch is rapidly converted into dextrin and sugar, and 

 the mixture gives no colouration with iodine tincture ; but 

 if to a second quantity of boiled starch a little alum is 

 added before the infusion of bran, the conversion is either 

 altogether stopped or proceeds very slowly. In the 

 same way the alum prevents the decomposition of 

 starch in the operation of bread-making. It is also 

 claimed for alum that it prevents bread becoming 

 sour or mouldy. Both these changes, in common with 

 ■ordinary fermentation, are produced by the growth of 

 organisms, and the action of alum may be explained by 

 stating that its presence is injurious to these bodies ; that 

 it is, in fact, to them, a poison. Hence alum also tends to 

 prevent fermentation proper (or alcoholic fermentation), 

 but its presence is not so inimical to these particular germs 

 as to those producing lactic acid and ordinary mould. So 

 far we have been dealing with the advantages resulting 

 from the use of alum ; and there is no doubt that in many 

 ways its action is beneficial. There is, however, another 

 side to this question, and that relates to the conse- 

 quences resulting from a continual absorption into the 

 system of alum, even in small quantities. Opinion is here 

 divided, but an undoubted result is the production of con- 

 stipation and the symptoms of ill-health following in its 

 train. It acts in yet another manner ; in very much the 

 same fashion as it prevents the decomposition of starch 

 during the time the bread is " put to soak," so, too, it 

 tends to retard the digestive action of the fluids of the 

 stomach on the bread ; much of the nutriment contained 

 in the flour being thereby wasted. It has also been 

 asserted that bread which has been alumed retains a much 

 larger quantity of water than it otherwise would do. 

 Chemical analysis does not, however, bear out this state- 



ment, for on examination some alumed loaves were found 

 to contain 43 68, and others without alum 42 78 per cent, 

 of water. This diflerence is less than the variation between 

 the limits of percentage of water in loaves of the one 

 class only. 



Other substances are or have been suggested as substi- 

 tutes for alum. Among these, the least injurious is lime- 

 water. This substance is stated to be equally efficacious 

 in preventing the decomposition of starch ; while, as the 

 yeast fermentation proceeds, the carbon dioxide gas that is 

 evolved combines with the lime and produces chalk (car- 

 bonate of lime), a substance having but little action on the 

 organs of digestion. Among other proposed substitutes 

 for alum, sulphate of copper is said to have been used. 

 This body is so poisonous that its employment in even the 

 smallest quantities is extremely reprehensible. 



Hitherto, the only means considered for the production 

 of carbon dioxide within the bread has been the use of 

 yeast or leaven for the purpose of causing fermentation. 

 The employment of alum and other substances of similar 

 properties is simply to prevent injurious changes pro- 

 ceeding simultaneously with the fermentation, unsound 

 flour being particularly liable to such alteration. 



Although it is still almost universally the custom for 

 dough to be raised by the use of yeast or leaven, there have 

 been from time to time other methods devised than that 

 which depends on the production of carbon dioxide gas by 

 the decomposition of a part of the flour itself. Among 

 these other methods the use of " baking powder " is the 

 best known. This substance consists essentially of bi- 

 carbonate of soda and tartaric acid. If a pinch of the 

 powder is put into some water, the same reaction takes 

 place as when water is added to " sherbet " or " citrate of 

 magnesia." All these mixtures contain the two bodies 

 above-mentioned, and when moistened the tartaric acid 

 immediately combines with the soda and liberates the 

 carbon dioxide : — 



H0C4H4O6 + 2NaHC03 = Na.,CjH406 -H 2H2O + 2C0- 

 Tartaric Bicarbonate Tartrate of Carbon 



acid. of soda. soda. Dioxide. 



The baking powder in making bread is mixed with the dry 

 flour, which is then made into a dough with water, cut 

 into loaves and then baked in a quick oven. The bicar- 

 bonate of soda is sometimes used alone, as the heat of the 

 oven is competent to eflect its decomposition into normal 

 carbonate of soda and carbon dioxide thus : — 



Although not strictly connected with our present subject, 

 it may be of service to mention, in passing, the diflerence 

 between the bicarbonate and normal carbonate of soda. 

 The above formuhe show that the carbonate contains twice 

 as much sodium. Carbonic acid, H,CO;„ contains two atoms 

 of hydrogen, which require two atoms of sodium in order 

 to displace them ; when only the one atom is displaced, a 

 bi- or half- salt is formed. Carbonate of soda is but little 

 used for domestic purposes, as it is more powerfully 

 alkaline and exerts an injurious action on the coats of the 

 stomach. 



Our next article will deal specially with the properties of 

 aerated bread. 



Life of the Edison Lamp. — It is stated, says the 

 Electrician, that some Edison lamps in a mill at Phila- 

 delphia have lasted on an average 3,886 hours, and are 

 still going. 



