CLASSIFICATION OF CARBOHYDRATES 193 
III. Trisaccharides 
1. Raffinose 
IV. Polysaccharides 
A. Starches 
1. Starch 
2. Glycogen 
3. Inulin 
B. Celluloses 
1. Cellulose 
2. Hemicellulose 
a. Pentosans 
Gum arabic 
b. Hexosans 
Galactans 
Agar-agar 
Action of Bacteria on Carbohydrates. This class of substances 
serves bacteria for both energy and building purposes. The action of 
microorganisms on carbohydrates is a subject too large for extensive 
treatment here.* The enzymes which will attack carbohydrates are 
widely distributed among microorganisms. Foods contaiming car- 
bohydrates are especially susceptible to attack by bacteria unless the 
sugar is too concentrated. If there is too little moisture present the 
organisms are unable to carry on their activities. 
The changes induced in sugar by bacteria may be discussed in dif- 
ferent ways. It is quite natural to discuss them on a physiological basis. 
Lactic Acid Fermentation. This is brought about by bacteria by 
first splitting the lactose into two molecules of a monosaccharide, each 
of which is further decomposed to lactic acid according to the following 
equation: 
C12H22011 + HOH = 2C6H1206¢, 
CeH1206 = C3HeQs. 
Since the lactic acid which is thus formed possesses so much latent 
energy, it may be further decomposed to other compounds such as 
butyric acid. 
The kind of lactic acid formed has been the subject of many investiga- 
tions. Four lactic acids are known, three of which have the same formula, 
* Those wishing an exhaustive treatment of the subject are referred to Kruse’s 
Allgemeine Mikrobiologie, or Lafar’s Handbuch der technischen Mycologie. 
