HEAT IN THE PRESERVATION OF FOOD PRODUCTS 531 



By pasteurization of the cream, the butter-maker destroys most of the 

 organisms present; and by the use of a culture starter of lactic acid 

 bacteria, he is able to control the fermentation, and is assured of a 

 uniform quality of product from day to day throughout a season. An 

 added value of pasteurization is that all pathogenic organisms are 

 destroyed, thus aiding in the prevention of such diseases as might be 

 conveyed through this product. In creameries, the usual method of 

 pasteurization is what is known as the continuous or flash process, in 

 which the milk is subjected to a momentary heating to about 85, 

 the flow of milk through the pasteurizing machine being so regulated as 

 to bring all the milk up to the desired temperature, the heating being 

 immediately followed by rapid cooling, and subsequent addition of the 

 lactic starter. 



In the pasteurization of milk for infant feeding, a lower temperature 

 is employed. A temperature sufficiently high to kill the organism of 

 tuberculosis (the standard for pasteurization) by momentary heating, 

 imparts to the milk a cooked flavor, making it less palatable, and coagu- 

 lates some of the protein constituents making it less digestible. The 

 desired end may be reached by using a lower temperature for a longer 

 period of time, and the method generally recommended is to heat the 

 milk to 60 to 65 for thirty minutes. This heating is sufficient to 

 render harmless any pathogenic organisms likely to be present in the 

 milk, without^the objectionable features attendant on heating to a 

 higher degree. 



Condensed Milk. It is commonly stated that Gail Borden invented 

 the process for preparing condensed milk, in 1856. Previous to this, 

 however, milk had been condensed in France, England and Germany 

 as early as 1825 to 1835. While he cannot, therefore, be called the 

 inventor of condensed milk, to Borden belongs the credit of having 

 first prepared it by a rational process, and in a practicable form. 



In the manufacture of condensed milk, good fresh milk is evaporated 

 in a vacuum pan similar to those used in sugar factories, at a tempera- 

 ture of 40 to 50 until the volume is reduced to a little more than half, 

 cane sugar being added so that the finished condensed milk usually 

 contains 40 per cent cane sugar. The evaporation must be conducted 

 with great care, otherwise the lactose crystallizes out, and this causes 

 the product to feel " sandy " to the tongue. When the evaporation 

 of the milk is complete, the yellowish white syrup is sealed up in tins 



