RAFFINASE. 



535 



ledge of the characteristics of the various sugars will be found 

 by referring to BAU (XVII.) and E. O. VON LIPPMANN (V.). 



Raffinose is a trisaccharide, i.e., it consists of three simple 

 sugars of the C 6 group, namely r-fructose, (Z-glucose and rf-galac- 

 tose. The two latter are in a more intimate state of mutual 

 combination they form melibiose (seep. 526, vol. ii.) than that 

 uniting them with the rZ- fructose. This latter is readily detachable, 

 dilute acids (even weak acetic acid) sufficing to set up hydrolysis 

 resulting in the separation of the trisaccharide into d-fructose and 

 melibiose, according to the equation : 



CisHaA,, + H 2 = C 6 H 12 6 + C 12 H 22 O n . 



The quantitative determination of raffinose in presence of 

 saccharose is effected by several methods, which can be found in 

 handbooks on the testing of sugar ; and BAU (XIII. and XXV J I.) 

 employed a method, based on fermentation physiology, whereby 

 raffinose can also be detected in mixtures with other sugars. By 

 the fermentation method he succeeded in determining the raffinose 

 contained in beet-sugar molasses ; but the process requires so 

 much time that it is only suitable for scientific investigations, 

 and not for the practical conditions of the sugar industry. 



Raffinose is fermented by the great majority of yeasts that are 

 able to ferment saccharose (see 327). The fermentation of this 

 trisaccharide is either complete as with bottom yeasts or else 

 only about two-thirds of it are fermented, as is the case with 

 most top-yeasts and a few other kinds, a fission-product, melibiose, 

 being left behind (see p. 528, vol. ii.). 



It was assumed that raffinose needed to be split up by a 

 special yeast enzyme before it could be fermented; but this 

 opinion was opposed by BAU (XXX.), who asserted that 

 fZ-fructose combines with melibiose to form raffinose, in exactly 

 the same manner as it does with cZ-galactose to form saccharose. 

 The method of combination is shown below, Formula I. represent- 

 ing raffinose, and II. saccharose : 



II 



CH..OH 



(CHOH). 



CH 

 CH 2 OH 



(CHOH) 2 



The fructose group on the right in these formulae is combined 

 in an identical manner with the melibiose group in the one case 



