436 CHAPTER XXI 



the sugars were infected artificially. This limit is evidently connected with 

 the quantity of molasses adhering to the crystal and with the water in the 

 molasses, and is not to be considered as an absolute limit. If, in the sugar 

 they examined, the quantity of adhering molasses were halved and the per- 

 centage of water in the molasses doubled, the water in the sugar would remain 

 the same, but the film of molasses would now form a very suitable habitat 

 for the growth of bacteria. Similarly, a sugar of lower grade containing 

 much more molasses will have a much greater percentage of water while 

 still maintaining so concentrated a solution that micro-organic activity is 

 inhibited. These conditions have been combined into a " factor of safety," 

 due to the Colonial Sugar Refining Co. of Australia. This may be expressed : 



water 



When , < 0-333, the sugar will not deteriorate. This factor has been 



100— pol. ^^^ ^ 



critically examined by Browne,^^ who, in one series found that sugars with a 



factor lying between 0'3i3 and 0-346 deteriorated, while others with a factor 



lying between 0-253 ^^d 0-289 did not deteriorate. The exact value of the 



factor is evidently connected with the concentration at which activity 



begins, and a different factor will obtain dependent on whether the organisms 



present are bacteria, yeasts, or moulds. Another point developed by 



Browne^2 is that when sugars deteriorate in a sealed container the factor 



must decrease until the safety point is reached, and experimentally he has 



found that this is the case. A cessation of activity may also be due to a 



toxic action exerted by the products of decomposition. In warehouses, 



however, conditions are different and the decomposition products are free 



to escape and the sugars may absorb water. 



The prevention of deterioration is based on the following points : — 



1. One class of organisms to which deterioration is due enters with the 

 cane. These organisms are not destroyed in the ordinary process of manu- 

 facture. The temperature and period of exposure in a pre-evaporator as 

 usually operated is, however, just sufficient to cause their destruction. 

 Thus Deerr^" found that certain very destructive bacteria common in 

 Hawaiian sugars were destroyed by 20 minutes' exposure at 110° C, in 10 

 minutes at 115° C, and almost instantaneously at 125° C. 



2. Avoid washing in the centrifugals in order not to dilute the film of 

 molasses, but, if washing is necessary, use aseptic water. Every factory has 

 a surplus supply of condensed water which is organically pure. 



3. Concentrate the film of molasses by passing the sugar through a 

 dryer. As generally operated, the temperature and period of exposure, 

 while not sufficient to give a sterile sugar, will concentrate the film so that the 

 safety limit is reached. Also, as Owen has shown, the dangerous Aspergillus 

 is very largely destroyed in the process. 



4. Avoid processes which tend to form hygroscopic substances in the 

 juice. Such are the use of an excess of lime, especially in the presence of 

 much reducing sugar, whereby hygroscopic lime-glucose decomposition 

 bodies are formed. 



5. Produce large-grained sugars, since in these the surface area is a 

 minimum and the water absorbed in wet weather is consequently small. 



6. Construct tight warehouses and open the doors only in dry weather. 

 Provide means for ventilation in the warehouses so that the temperature 

 may be controlled. Raise the floor of the warehouse two or three feet above 

 the ground level, and keep the surroundings well drained. 



