38 LUTHER BURBANK 



How SUGAR AND LYE COOPERATE 



It may seem rather curious at first glance that 

 a high sugar content should be essential to the 

 preservation of the prune, when we reflect that 

 sugar is a very fermentable substance. Everyone 

 knows, for example, that starch is transformed 

 into a form of sugar before it is fermented in the 

 manufacture of alcohol. How, then, does the 

 sugar in the prune prevent the fermentation of 

 the fruit and insure its preservation? 



The answer is that sugar ferments only under 

 influence of certain living microorganisms, and 

 that these microorganisms cannot work in a too 

 concentrated solution of sugar. There are myr- 

 iads of the microbes spread broadcast everywhere 

 on the wind, and of course they find lodgment 

 on the skin of the prune as on every other ex- 

 posed surface. 



But the alkali bath to which the prune is 

 subjected, destroys these germs at the same time 

 that it cracks the skin of the fruit. 



Other germs would find lodgment, however, 

 and set up fermentation, were it not that the 

 cracked skin permits a very rapid evaporation of 

 the water content of the fruit. This quickly 

 brings the sugar content to a degree of concen- 

 tration that makes it a powerful antiseptic that 



