Section III, ISSY. [ 61 ] Trans. Roy. Soc. Canada. 



VIII. — TJie Digestibility of Certain Varieties of Bread : an Experimental Stachj of the 

 Alum Question. By E. F. Ruttan, B.A., M.D. 



(Read May 27, 1887, and communicated by Mr. Thos. Macfarlane.') 



Few questions that have arisen from the investigation of adulterated food, have excited 

 so much public interest, and given rise to opinions so diverse among experts, as what is 

 commonly known as the " Alum Question." 



For many years, alum in some form has been largely used in the manufacture of bread 

 and similar forms of food. It is added, generally speaking, in one of two ways : either 

 simply mixed with flour as alum, or compounded with a variety of other substances to 

 form a baking powder, the latter being mixed with the flour as a substitute for yeast. 

 Alum acts as the acid principle of the powder, decomposing the bicarbonate of sodium 

 and generating the reqiiired carbonic acid gas. Alum is added to flour directly to check 

 or prevent fermentation in damp or damaged flour, or with the object of giving whiteness 

 to yeast bread by checking the fermentation of the gluten that normally goes on during 

 the process of raising. It has also been added with the view of increasing the amount of 

 water in the bread, thus enabling the baker to defraud his customers by selling water 

 instead of bread. Dr. Odling, however, has shewn ' that this is a fallacy. Alumed bread 

 is not particularly hygroscopic, as in eighteen alumed and seven non-alumed loaves 

 examined by him, he found that the average was 43.68 p.c. of water in the former and 

 42.*78 in the latter ; "the difference being quite insignificant as compared with the differ- 

 ence between the different loaves whether alumed or not." 



Besides being iised to disguise the inferior quality of damaged flour, alum is very 

 largely employed in this country and in the United States in combination with other 

 substances in the form of baking powder. Alum baking powders have largely replaced 

 the older mixtures, which were made of tartaric acid or acid tartrate of potassium and 

 bicarbonate of sodium, for several reasons : a good alum baking powder makes a whiter 

 and more porous loaf, it reqtiires less skill in its use, and above all it is far less expensive 

 than the tartaric acid powders. The almost universal use of baking powders in this 

 cotintry, and the fact that alum powders are gradually driving all others out of the mar- 

 ket, make the question of their influence on digestion one of the highest importance. 



It is beyond the scope of this paper to discuss the alum question in its many bear- 

 ings, but it may be as well to note briefly the present state of the discussion before intro- 

 ducing into it any new elements. Considered wholly apart from its effect on the system, 

 it is very generally admitted by all parties that, inasmuch as alum will disguise a dam- 

 aged flour, and enable an unscrupulous baker to produce from such flour an apparently 

 pure loaf of bread, its use in the manufacture of bread should not be tolerated. If, 



' Journal of the Society of Arts, April, 1858. 



