CARBOHYDRATES 53 



Raffinose occurs normally in cotton seeds, in barley grains, and 

 in manna; also, in small quantities in the beet root, associated 

 with sucrose. It is more soluble in water than is sucrose and 

 hence remains in solution in the molasses from beet-sugar manu- 

 facture, which constitutes the commercial source for this sugar. 

 Raffinose crystallizes out of concentrated solutions, with five 

 molecules of water of crystallization, in clusters of glistening prisms. 

 It is strongly dextrorotatory, the anhydrous sugar having a specific 

 rotatory power of +185, and the crystalline form, CisH^Oie, 

 showing a specific rotation of +104.5. It does not reduce Feh- 

 ling's solution, nor form an osazone, and in its other properties it 

 closely resembles sucrose. 



The hydrolysis of raffinose presents several interesting pos- 

 sibilities. If its structure is represented as follows: 



Fructose Glucose Galactose 



Sucrose Melibiose 



it is apparent that it may break down by hydrolysis in three dif- 

 ferent ways: (1) into sucrose and galactose, (2) into fructose and 

 melibiose, and (3) into fructose, glucose, and galactose. As a 

 matter of fact, it does actually break down in these three different 

 ways, under the influence of different catalysts; invertase or 

 dilute acids break it down into fructose and melibiose, emulsin 

 hydrolyzes it to sucrose and galactose, while strong acids or the 

 enzymes of bottom-yeasts break it down into the three hexoses. 



Gentianose, a trisaccharide found in the roots of yellow gentian 

 (Gentian alutea), is a non-reducing sugar, which when hydrolyzed 

 yields either fructose and gentiobiose, or fructose and two mole- 

 cules of glucose. 



Melizitose, a trisaccharide which, in crystallized form, has 

 the formula, CigH^Oie -2H2O, occurs in the sap of Larix europea 

 and in Persian manna, and has recently been found in considerable 

 quantities in the manna which collects on the twigs of Douglas 

 fir and other conifers. When hydrolyzed, it yields one molecule 

 of fructose and one of turanose, a disaccharide containing fructose 

 and glucose linked together in a slightly different way than they 

 are in sucrose. Turanose itself is a reducing sugar, but when 

 linked with fructose to form melizitose its reducing properties are 

 destroyed. Melizitose is a very, sweet sugar. 



