CHAPTER V 



THE HYDROLYSIS OF STARCH BY AMYLASE 



STARCH occurs widely in the vegetable world, being the first 

 visible product of assimilation in plants containing chlorophyll. 

 Starch is usually manufactured in Europe, from potatoes, rice, 

 wheat and maize ; and in tropical countries, from the palm 

 and from tubers of various plants. 



Examined under the microscope, starch, which in the 

 mass is a white powder, is seen to consist of small granules 

 which have the power of polarising light. Different species 

 of starch vary greatly in the size of their granules. This is 

 clearly seen in Plate I, reproduced from actual photographs, 

 the same magnification being used in every case. Under high 

 magnification, especially after treatment with dilute alkali, 

 the starch granules can be seen to consist of a series of layers 

 arranged round a nucleus. 



Starch is found to consist of several isomeric compounds, 

 the chief portion being starch proper, termed either amylum 

 or granulose, the remainder consisting of starch cellulose or 

 farinose. The starch cellulose is not readily attacked by 

 enzyme action or by acids. Soluble starch consists of granu- 

 lose from which the less soluble starch cellulose has been 

 removed. 



If a solution of starch is boiled for some time with dilute 

 acid the solution will become clear and it will be possible by 

 suitable tests to recognise the presence of a sugar in the 

 solution. The same reaction is brought about if a small 



