522 ENZYMES DECOMPOSING SACCHARIDES. 



by digesting beer yeast with the saccharose solution at 56 C. 

 and running the inverted mixture into the hop back. 



Invertase is also utilised practically in chemical analysis, for 

 the determination of saccharose in cases where no reliable results 

 can be obtained either by direct polarisation or by the Clerget- 

 Herzfeld inversion method. According to the Convention for 

 the Uniform Examination of Foodstuffs and Delicacies, VEREIN- 

 BARUNGEN (I.), ioo c.c. of the solution under examination, e.g., a 

 10 per cent solution of honey, are treated with 50 c.c. of a solution 

 of invertase, prepared by the conventional method, the mixture 

 being allowed to stand for two hours at 5o-55 C., and the invert 

 sugar then determined either in the polarimeter or gravimetrically. 



328. Maltase. 



Whereas at one time it was thought that maltose was capable 

 of direct fermentation, we have already seen, on p. 511, vol. ii., 

 that this sugar also must be subjected to hydrolytic fission before 

 it can be attacked by alcoholase. 



Maltose, which was k first discovered by Dubrunfaut, is also 

 known as malt sugar, and, in the anhydrous condition, has the 

 same empirical composition as saccharose, namely, C^H^O^. 

 Unlike the latter, however, it is not composed of two " simple " 

 sugars, but consists of two molecules of cZ-glucose, condensed to 

 maltose by the elimination of water. It occurs in nature, usually 

 in small quantities in the leaves of various plants and, according 

 to PURIEWITSCH (VIII.), is formed during the germination of 

 seeds. It has also been found in germinated barley, and occa- 

 sionally in green and cured malt, by numerous workers, including 

 O'SULLIVAN, BROWN, and MORRIS (III.), JALOWETZ (II.), and 

 others, whereas other observers, such as DULL (III.), LINTNER 

 (IX.), and KROBLER (I.) deny or regard as doubtful its presence 

 in malt. These divergent results are explained to some extent 

 by the circumstance that some workers extract the malt with 

 water, in order to examine the sugar content, during which 

 treatment the diastase is afforded an opportunity of acting on 

 the starch, whilst others have attempted to destroy the diastase 

 previous to extraction for the practical purpose of the fermentation 

 industry ; however, it is immaterial whether maltose is already 

 contained in malt or not, since the mashing process in brewing 

 and distilling is designed for securing a more or less extensive 

 conversion into maltose of the starch contained in the cereal grains. 



In distillery work and in the manufacture of pressed yeast, 

 attention is concentrated on attaining the utmost possible saccha- 

 rification of the starch by diastase, whereas in brewing it is 

 found desirable to regulate the process of saccharification, accord- 

 ing to the type of beer required, in such a manner, by the 

 employment of more or less highly cured malt, that the wort will 



