332 



article of food is preserved against decomposition. On the other 

 hand, if warmth is needed for the satisfactory evolution and work- 

 ing of those inicro-organisms which cause fermentation or decom- 

 position, it may either be insufficient or too cold, and then they 

 remain inactive or dormant, or it may be in excess or too hot, and 

 in that case their life is suspended or destroyed. 



On these principles are based the keeping of meat, milk, butter, 

 etc., by freezing, or of the sterilizing of wine, with a view to their 

 better keeping, which is effected by heating them up rapidly to 150 

 F. (65 C.), and also rapidly cooling them to the normal tem- 

 perature. This process is known as "pasteurisation" after the 

 name of the scientist who first suggested it and proved its efficiency. 



By an application of the same process, we find, in canning, a 

 cheap, ready, and practical way of destroying germs of decomposi- 

 tion from the articles of food we seek to preserve. How to success- 

 fully achieve that end without materially destroying the natural 

 flavour and appearance of the goods to be preserved, constitutes the 

 art of canning. 



A little experience will in this matter bring proficiency to the 

 operator, and enable one to save much fruit that would otherwise be 

 lost. 



The materials used for canning are much too numerous to 

 enumerate, but amongst the more commonly used are fish, oysters, 

 meat, condensed milk, cream, asparagus, green peas, sweet corn, 

 tomatoes ; and amongst fruit apricots, cherries, gooseberries, 

 grapes, nectarines, peaches, pears, plums, pineapples, quinces, guavas, 

 and many other fruits which endure stewing without injury to 

 flavour or to the form of the fruit. 



Oranges, for instance, are not suitable for canning, on account 

 of the peculiar bitter flavour they develop on cooking ; while, on the 

 other hand, sour or cooking apples are also unsuitable, as they cook 

 into a pulp, and lose both their flavour and appearance on cooking. 



Besides preservation of fruit by drying or by sterilising by the 

 application of heat, there is also a third way of preventing fer- 

 mentation, and that is by heavy additions of spirits or of sugar ; 

 but these are unsuited for the purpose we have in view, and are too 

 expensive. 



All these are legitimate ways of preserving fruit almost 

 indefinitely. Another way, besides, exists which is not lawful nor 

 wholesome, and consists in the use of antiseptics which are 

 antagonistic to the development of ferments and other micro- 

 organisms, such as salicylic acid, etc. These substances are all 

 noxious poisons, which paralyse the digestion and injuriously 

 affect the health of the consumer. 



HOUSEHOLD CANNING. 



No detailed account will be given in this chapter of the process 

 of factory canning, as this constitutes an industry in it&elf, and 



