to 
aN 
(oe) 
SWEETENED CONDENSED Mik DEFrEcTS 
under average conditions. A higher per cent of sucrose would 
naturally intensify the preservative action and inhibit the growth 
of the bacteria normally present more completely; but if enough 
sugar were added to also inhibit the growth of and make harm- 
less those violent gas-producing butyric acid bacteria and yeast 
cells, which thrive in sweetened condensed milk containing 40 
per cent sucrose, the product would be objectionable from the 
consumer’s point of view. ‘The logical avoidance of “swell 
heads” as the result of these undesirable germs, therefore, must 
ever lie in prevention, rather than cure. The sanitary standard 
of production on the farm and of the process in the factory must 
be raised to and maintained on a level where the milk is pro- 
tected from contamination with these micro-organisms. 
The writer! has isolated yeast from fermented sweetened 
condensed milk that produced vigorous gas formation in media 
containing as high as &5 per cent sucrose (600 grams sucrose in 
100 ce. whey bouillon). 
Effect of Too Thin Condensed Milk.—Condensed milk that 
is too thin is, also, prone to start fermenting, since it is deficient 
in the chief preserving agents, 1. e., density and per cent of 
sucrose. It is not safe to put goods on the market, with a ratio 
of concentration much less than 2.5:1, unless the amount of cane 
added is sufficient to raise the cane sugar content of the fin- 
ished product to 44 per cent or above. 
Effect of Excessively Low Temperatures.—The cans of 
sweetened condensed milk may also bulge in the case of cans 
with non-hermetical seals, exposed successively to excessive cold 
and to room temperature. In this case, the condensed milk is 
entirely normal and unaffected, and the bulging is the result 
of mechanical contraction and expansion by cold and heat. This 
is possible only where the seal of the cans is not entirely her- 
metical. In the case of the Gebee seal with the burr cap, and 
the McDonald seal with the friction cap, the seal is not absolutely 
air-tight. While the pores between cap and can are microscopic 
in size, and not large enough to permit the contents from leak- 
ing out, they are sufficient to admit air. The cans are usually 
filled with the condensed milk at a temperature of about 70 de- 
1 Hunziker, Results not published. 
