Vol. VIII. No. 194. 



THE AGRICULTURAL NEWS. 



.307 



SUGAR INDUSTRY. 



Bacteria and the Deterioration of Sugars. 



The subject of the deterioration of sugars through the 

 jvction of bacteria is dealt with in an excellent manner in 

 Bulletin No. 9 of the 1 )ivision of Pathology and Physiology 

 of the Hawaiian Sugar Planters' Association, entitleil Tlu- 

 lUu-terial Flora ot Haimiiaii Sti,/iir.i, by L. Lewton-lirain 

 (sometime Mycologist to this Departnjent) and Noel Deerr. 

 The results of experiments showing the influence of moisture 

 and of the time of storage in respect to the fall in polariza- 

 tion of sugar."^, which are also dealt with in this Bulletin, 

 were given on page 301 of the last issue of the Agricultural 

 Korx. The following facts are taken from that part of the 

 publication which treats more particularly of the character- 

 istics of the bacteria which are instrumental in causing the 

 change. 



The need for the enquiry arose from the fact that sugars 

 in storage, and especially in transit from Honolulu to New 

 "^'ork round Cape Horn, showed by test a lo\\er i^iercentage 

 of sucrose after time had elapsed while they were in store or 

 on the voyage. An investigation as to the cause of this was 

 made, and it was found to be due to the action of the bacteria 

 where a minimum of 1 per cent, of water was present. 

 (Bulletin No. 24 of the Division of Agriculture and Chemis- 

 try of the above Association.) The connexion of micro- 

 organisms with such loss has already been indicated by 

 Shorey and Grieg Smith, and the subject is advanced much 

 further in the present [uiblication. 



Five forms of bacteria were isolated from the sugars 

 with which experiments were made, and exhaustive investiga- 

 tions of the behaviour of these on various solid culture media, 

 in liquid media containing a known percentage of sugar and 

 i>n commercial sugars, completed, together with the necessary 

 control experiments. The chief changes due to the action 

 of the bacteria that were demonstrated in the case of the 

 ticpiid media were the destruction of sucrose, the formation 

 of invert sugar and the production of gums. The first 

 two of these were also shown to take place in the case 

 of the sugars : imdoubtedly the third occurs as well, 

 but, in the light of the second series of experiments, there 

 was no need to take special measures to elucidate this 

 fact. Two of the bacteria (or, more correctly, bacilli) caused 

 a very small amount of gum formation, and at the same time, 

 the destruction of sucrose by them was smaller than that 

 effected by the other three. The destruction of sucrose and 

 formation of invert sugar was greatest in the case of these 

 three bacteria, thus it appears 'that a faculty of rapidly in- 

 verting sugar is associated in liquid cultures with the formation 

 of gums '. In one of these three types, the total of gums and 

 reducing sugars formed was approximately equal to the 

 original amount of cane-sugar present ; in the other two, it 

 was less, showing that other compounds beside invert sugar 

 and gums were formed. 



Where inversion took place to any great extent, it was 

 invariably rapid, and in the case of two of the bacterial forms, 

 had alw.ays reached its limit by the fifth day. As the licjuid 

 media became acid while the inversion proceeded, there was 

 a probability that this was the cause that prevented further 

 action of the bacteria, especially on account of the fact that 

 neutral or alkaline sugars are usually regarded as having 

 a better keeping quality than those which are acid. In order 

 to obtain definite information on this point, the experiments 

 were repeated with one of the more active of the bacteria, 

 using an alkaline instead of a neutral liquid culture medium, 

 with the usual controls. In the result, it was found ' that it 



is not the acids produced that inhibit the activity of the bac- 

 teria, but probably some of the other by-products '. 



The experiments with the sugars are specially intere-;ting. 

 Here it was found that one sterilization of thirty minutes, at 

 100" C, of the material both for control and inoculation, was 

 sufficient for the purposes of the investigation; heating for 

 longer periods caused caking of the sugars through the 

 condensed steam that ran down inside the Hi.sks. The 

 cultures of the liacteria under examination were intro- 

 duced into the flasks containing sugar for inoculation 

 in the form of a liquid spray, driven under the same 

 pressure and for the same time in each case. Before this, the 

 controls had been treated in exactly the same way, with the 

 substitution of sterilized water for the cultures. In this way, 

 the condition as regards infection in the several inoculated 

 flasks, and as regards moisture in all instances, were made as 

 nearly alike as possible. The results obtained agree with 

 those given by the liquid cultures containing sugar: the 

 three gum-forming bacteria ettected the largest destruction of 

 cane-sugar and the greatest formation of reducing sugar. 



In agreement with the results obtained by keeping 

 sugars containing difterent percentages of water and deter- 

 mining the polarization from time to time (see the table 

 reproduced from this bulletin on page 301 of the last issue of 

 the Agricultural News), it was found that the amount of 

 deterioration became greater with the percentage of water 

 that was present, up to 5 per cent., the destruction of total 

 sugars calculated on dry weight increasing with the greatness 

 of the moisture content. At incubator temperature (30" C.) 

 the process was much more rapid than at room temperature 

 (2-5' C). At 17' C, the gro\\th of colonies of the bacteria 

 was very slow, and it is probable that this would be the same 

 with deterioration. 



Preliminary work has been done in the direction of 

 determining at what part of the proce.ss the introduction of 

 bacteria takes place and the ways in which this may be 

 avoided as far as possible. In a factory representing the 

 older type of sugar-house design, it was found that a small 

 part of the bacteria in the original juice survived its passage 

 through the heaters, and that those which did so were also 

 unattected by the passage through the evaporators and pans, 

 and appeared in the syrups and massecuites. A large 

 infection took place at the centrifugals, through the water 

 (though this was only a very small quantity) which was used 

 Biainly to wash down the spouts of the pug mills and the 

 spindles of the centrifugals. Reinfection also took place 

 through the reintroduction of low sugars, and the surface 

 layers of the molasses and massecuite tanks always contained 

 bacteria in large numbers. 



The conclusions aie finally reached that all means to 

 prevent deterioration of sugars while in transit or in storage 

 are only palliative at the best, and that the best remedies for 

 it are the keeping of the factory in as aseptic condition as 

 possible, the avoidance of the use of unclean water in or 

 about the centrifugals, and the disinfection of the factory 

 during the ofl' sea.son. 



To Hasten the Germination of Hard Seeds. 



The seeds are placed in a small sieve, or pocket, of wire gauze 

 a few at a time, which is ])lunged into boiling water for 

 a period of 10 to 20 seconds, depending on the hardness of the 

 seed In the case of small seeds, the sieve is plunged into cold 

 water immediately after being taken out of the boiling water. 

 The object of dealing with a few seeds only, at a time, i.s_to 

 ensure that the boiling water shall have the full eftect. By thi.'s 

 means, hard seeds were made to sprout in 10 days. 

 {Le Jardin, Vol. XXII, No. 1.5.5.) 



