SUGAR AS A PRESERVATIVE 183 



yeast life, and it occasionally happens that materials pre- 

 served by it will ferment. But this does not commonly 

 occur if the percentage of sugar is high, i.e. 4056 to 50^. 

 The use of sugar as a preservative is adopted in a 

 number of well-known products. Fresh fish is occasion- 

 ally preserved by rubbing with sugar. Condensed milk is 

 preserved by the addition of 30^ to 40^ of it. It changes 

 the nature of the milk, rendering it somewhat less digest- 

 ible, but does not materially injure it as a food product: 

 Jellies are also preserved from bacterial action, though 

 not wholly from fermentation, by the large amount of sugar 

 which they contain ; for decay would take place quickly 

 if it were not present. It has been used for a long time 

 to protect fruits, in making what are known as preserves. 

 Almost any kind of fruit may be preserved by stewing it 

 with a large amount of sugar, equal parts by weight of fruit 

 and sugar being commonly used. At a moderate heat the 

 fruit is so thoroughly impregnated with the preservative 

 that no putrefactive organisms are subsequently able to 

 grow in it, and it may then be preserved almost indefinitely. 

 Marmalades are also preserved by the same preservative. 

 This is also, in a measure, as we have seen, the reason for 

 the preservation of raisins, figs, plums, etc., which are pre- 

 served partly by drying and partly by the presence of sugar. 

 In these cases the fresh fruit contains so much of it that 

 none is artificially added. But most fruits contain too 

 little to be preserved without the special treatment above 

 described. There are of course decided limitations to the 

 use of sugar for this purpose, for the flavors of most of our 

 fruits are changed when mixed with a great deal of it. 

 They cease to have fruit flavors and become a sort of 



