CHAPTER IV 

 THE PECTIC SUBSTANCES 



OCCURRENCE AND PROPERTIES OF PECTIN 

 AND PECTASE. 



IN a very great number of fruits and fleshy tissues in general 

 there exists a substance which is ordinarily soluble, but is 

 precipitated as a gelatinous mass on the addition of alcohol. 

 This is known as pectin, and was first fully described by 

 Fremy (1840), though Bracannot (1825) had previously 

 obtained it. From its relationship to the material which 

 forms the middle lamella of cell walls, it is clear that it 

 must be of considerable physiological importance. In 

 many fruit juices as well as in the sap pressed from woody 

 stems, gelatinization takes place on standing, this being 

 due to the action of an enzyme, pectase, upon the pectin 

 of the juice. 



The extensive literature of the subject has been sum- 

 marized by Czapek (1913), whilst the common properties 

 and reactions of these bodies have been described in the 

 recent publications of Molisch (1913), Browne (1912), 

 Euler (1912), and of Haas and Hill (1913). There is, 

 therefore, no need to give more than an outline here, to 

 serve as an introduction to the study of the action of 

 pectase by viscosity measurements which was carried 

 out by Ball (1915). 



A survey of the work done so far upon the pectic sub- 



63 



