580 MICROBIOLOGY OF FOODS 



SUGAR* 



In the manufacture of sugar, microorganisms have no useful part 

 but many forms may be injurious and cause serious losses. The 

 juices of beets and sugar cane and the saccharine liquids obtained by 

 presses or diffusion batteries form excellent media for the multiplication 

 of many Saccharomyces and bacteria. They are controlled by cleanli- 

 ness, rapidity of handling, and sterilization by heat. They are injuri- 

 ous by destroying sugar and thereby diminishing the yield, by inverting 

 a portion of the saccharose and rendering the crystallization difficult 

 and by forming gelatinous masses in the liquids. 



Many of them are very resistant to heat. S. zopfi withstands a 

 temperature of 66 for half an hour. Streptococcus mesenterioides 

 forms chains of cocci surrounded by voluminous gelatinous sheaths 

 which unite in zoogleic aggregations sometimes very troublesome in 

 sugar factories. On account of its sheath it is very resistant to adverse 

 conditions. It retains its vitality after drying for three and a half 

 years. It is not killed by heating to 86 for five minutes and occurs 

 in the hot liquids of the diffusion batteries. 



TEA* 



In the curing of black tea several fermentation processes occur. 

 It is stated that yeasts and bacteria are of little importance in this 

 curing process under normal conditions. The most important changes 

 are brought about by enzymes and by a mold which converts the tan- 

 nic acid of the tea to gallic acid. If the fermentation is too prolonged 

 or moisture conditions improper, ^slime-forming bacteria develop, 

 resulting in injury to or complete spoiling of the product. 



* Prepared by F. T. Bioletti. 



