26 SCIENCE AND PRACTICE OF DAIRYING. 



amount of carbonic acid is given off. At 130 C. further decomposition 

 takes place, its water of crystallization is given off and galactose is formed. 

 This brown coloration becomes more pronounced as the temperature 

 rises. Lactocaramel, which is dark brown in colour, begins to be formed 

 at 175 C., and is accompanied by the development of a characteristic 

 smell. Grape-sugar is perhaps also formed. In milk this decomposition 

 begins when the temperature rises above 70 C., and is rendered apparent 

 by the slightly brown coloration (more or less pronounced according to 

 the length of time the milk is heated) which the milk assumes. Three 

 different forms of anhydrous milk-sugar are known. The optical behaviour 

 of solutions of milk-sugar under the polariscope is complicated, since they 

 exhibit bi-rotation and half rotation. 



It is not as yet certain whether milk-sugar is rendered anhydrous, 

 or retains part or the whole of its water of crystallization, when it is 

 heated in the process for the determination of its total solids; or whether, 

 indeed, under the varying circumstances under which such desiccation 

 may take place, it behaves always in the same manner. It would seem 

 probable that this is not the case, since, as is well known, the total solids 

 in milk do not admit of such accurate determination as is the case with 

 the milk-fat. 



Solutions of milk-sugar, at ordinary temperatures, reduce alkaline 

 copper solutions. Treated with yeast or dilute sulphuric acid, galactose 

 and grape-sugar are formed. Galactose, an isomere of grape-sugar, and a 

 direct product of the fermentation of the sugars, can be obtained in small 

 white plate-shaped crystals. If milk-sugar be warmed with nitric acid, 

 mucic and oxalic acids are formed, and also saccharic and tartaric acids. 

 With bases milk-sugar forms saccharates. Galactose yields, when boiled 

 with nitric acid, double the amount of mucous acid yielded by milk- 

 sugar when treated in the same way. When heated with hydrochloric 

 acid it yields laevulin acid. When heated with chalk, milk-sugar 

 yields isosaccharine and metasaccharine. Although a molecule of milk- 

 sugar and a molecule of water contain the elements of four molecules of 

 lactic acid (C 3 H 6 3 ), in the case of ordinary lactic fermentation, decom- 

 position never takes place so completely and exactly that the milk-sugar 

 is entirely converted into lactic acid. Small quantities of a number of 

 other products in addition to lactic acid are formed, possibly from the 

 milk-sugar and possibly also from the nitrogenous matter of the milk. 

 The most extensive and thorough of recent researches on lactic fermenta- 

 tion have been carried out by Hueppe. His pupil Scholl has isolated and 

 given an exact description of ten different kinds of bacteria. The facul- 

 tative lactic bacteria are not of immediate importance since they are 

 rarely found in milk. The same applies to the few moulds (yeast) which 



