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preserver has to contend with, and in order to purge the liquid of 

 them two ways present themselves one chemical and one physical. 

 The chemical methods consist in paralysing the microscopic cells of 

 the agents of fermentation by means of antiseptic substances. This 

 method is prohibited wherever a Pure Food Act is enforced, and 

 moreover, on hygienic grounds it is strongly to be deprecated, for 

 the reason that such toxic substances which silence and paralyse 

 the living cells of organisms in the sweet juice, on the other hand 

 also happen to injuriously affect those other micro-organisms which 

 accompany and foster digestion. Their use is to be deprecated, and 

 should be prohibited by law. 



The physical methods are, on the other hand, safe, and yield 

 results which are quite satisfactory. These are purely mechanical, 

 such as filtering, or both mechanical and biological, such as those 

 methods in which heat, cold, or electricity play the leading part. 

 Of these, heat is, up to the present, both the cheapest and the most 

 reliable. 



The germs figured in the chapter on " Ferments and on Diseases 

 of Wine " consist of translucent gelatinous cells which at even a 

 moderate temperature coagulate and perish. The temperature at 

 which these micro-organisms perish is called " the death point" of 

 these microbes. This point is several degrees lower in slightly acid 

 liquids, such as grape or other fruit-juice, than it is in neutral liquids. 

 Time is also a factor which in a measure influences this death 

 point. For instance, a micro-organism which would only perish if 

 heated for half an hour at, say, 60deg. C. (140deg. F.) would probably 

 survive the treatment if the period of heating was only a quarter of 

 an hour. Then again, micro-organisms occur in two states : an active 

 or growing state, consisting of a fragment of protoplasma, encased in 

 a cellulose covering, and a resting or spore state, the spores being 

 minute nuclei embedded into the body of the micro-organism and 

 endowed with greater resistant properties. This being so, a degree 

 of heat which would coagulate and kill the micro-organism in its 

 gellified or growing state would probably only cause passing dis- 

 comfort to the more hardened resting spores. As a rule, it requires 

 about 5deg. C. (9deg. F.) additional above the death point of the 

 growing micro-organism to kill the same organism in its resting 

 state. In practice it is found that grape-must is sterilised by 

 heating up to 65deg. to 75deg. C. (149deg. to 167deg. F.). It is 

 essential not to raise the temperature too high, so as not to 

 affect the delicacy of taste or colour of the liquid operated upon, 

 and for that purpose it is essential not to exceed 85deg. C. 

 (185deg. F.). 



Whilst it is known that germs of fermentation and of other 

 decomposition organic liquids are destroyed at a comparatively low 

 temperature when immersed in a liquid, these same germs, when 

 desiccated, can tolerate a much higher temperature with impunity. 

 It is important to bear in mind this fact when bottling the sterilised 

 liquid, as any germs which may be resting on the dry neck of the 



