10 



fermentation known as decay, they also, more or less, prevent digestion after the food 

 is swallowed. Consequently their use should \te everywhere illegal, as it is in the 

 United States and, to a partial extent, in England. 



The employment of chemicals for the preservation of milk is particularly 

 undesirable, as it enters so largely into the diet of infants and invalids. It is not 

 generally known that the natural souring of milk is its own form of protection against 

 putrefaction, for the germs of decay cannot grow in acid i.e., in soured milk. 



Now, sour milk is not unwholesome, except for young children and the nick. But 

 the changes which take place in milk when, by the addition of chemicals, the normal 

 formation of lactic acid is prevented are a source of grave risk to the consumers, 

 specially so to babies. 



(6.) The Preservation of Food by chilling if to a Temperature beloir 40 Fahr. 

 Taking everything into consideration, therefore, this is quite the most satisfactory 

 method of rendering it unsuitable to the attack of any form of putrefactive germ, 

 always supposing that the process be carried on under good conditions of care and 

 cleanliness. No change in flavour, digestibility, or appearance ensues, but the food 

 must be consumed almost immediately after its removal from cold-storage, for a 

 tendency to rapid putrefaction develops when such food is brought back into warm, 

 damp air. This tendency is probably the result of the moisture which at once 

 condenses on its surface; but, whatever the cause, decay quickly ensues, whether it be 

 in meat, fish, fruit, milk, or vegetables. 



The Effect of a Loir Temperature on Food 



is to prevent the development of the germs of putrefaction, or to arrest their activity 

 if already developed. None of the organisms responsible for decay in food can develop 

 at a temperature so low as 40 Fahr. or less. Once again, however, 



Two Cautions muni be tjiren. 



Cold, even zero cold, does not destroy the source of decay if present in food. 

 The seeds of putrefaction remain merely quiescent, to quicken into active life when 

 temperature, moisture, and nutrition are once more favourable to their growth. 



The temperature of the domestic refrigerator is rarely low enough or steady 

 enough to be reliable as a certain means of food-preservation. Neither are conditions 

 of cleanliness and ventilation sufficiently understood by the ordinary housewife to 

 allow food materials to be safely stored for more than a few hours. 



For commercial purposes, and under skilled supervision, this method is rightly 

 superseding all others for the preservation of foods, whether during transpoit or while 

 awaiting distribution from market or store. 



(6.) MEANS BY WHICH FOOD MAY BE PRESERVED BY EXPOSURE TO CONDITIONS 

 WHICH WILL DESTROY MICRO-ORGAN ISMS IF PRESENT. 



Exposure to great heat, or sterilization, prolonged over a sufficient period, is the 

 only means of food-preservation which comes under this head. 



Moulds are usually destroyed by any temperature above 150 Fahr. , but nothing 

 less than boiling-point (212 Fahr.) can be relied on to destroy germs ; and even higher 

 temperatures, which cannot be secured in our kitchens, are necessary to kill the seeds 

 from which these germs grow. 



Two Great Drairbackx to Sterilization 



exist as a domestic method of food-preservation : 



(i.) All foods are bad conductors of heat, so that the deeper parts of a joint of 

 meat, for instance, never reach a high enough temperature to ensure their 

 protection from putrefaction : 



