236 SWEETENED CONDENSED Mik DEFECTS 
stances which are highly sensitive to heat, such as albumin, 
colostrum, etc. 
Excess of Acid in Condensed Milk and Acid Flux in Tin 
Cans.—The presence in the condensed milk of organic and 
mineral acids, in excess of the amount which normal fresh milk 
contains, is conducive of the formation of lumps. 
Excessive amounts of acid in condensed milk may be the 
result of fermentations, usually due to a poor quality of sugar, 
or of the use of acid flux in the making and sealing of the tin 
cans. Condensed milk that shows acid or gaseous fermentation 
usually contains lumps. The acid which it develops as the result 
of the fermentation, curdles the casein with which it comes in 
contact. 
One of the most common channels through which condensed 
milk may become contaminated with acid mechanically, is the 
use of cans. in the manufacture and sealing of which acid flux 
was used. The acid flux generally used contains zinc chloride. 
The flux precedes the solder and some ef it is bound to sweat 
through the seams into the interior of the cans. ‘This type of 
lumps usually has a pink or brownish-red color, especially in the 
case of considerable quantities of acid flux. Zine chloride is a 
highly poisonous product and its use in the manufacture of tin 
cans, which are intended for receptacles of human food, should 
be prohibited by law. Aside from its injurious effect on the 
health and life of the consumer, its presence, even in small quan- 
tities in condensed milk, is a detriment to its market value. In 
such cans there accumulate, usully along the seams, lumps and 
smeary substances which have been found to consist of casinate 
of zinc. 
Most commercial soldering fluxes consist largely of zine 
chloride and are highly acid, although many of these are adver- 
tised as acid-free fluxes. In order to avoid the appearance in con- 
densed milk of lumps from this source, cans should be used, in the 
manufacture of which a strictly acid-free flux is used and which 
are sealed with acid-free flux. Dry, powdered resin or resin 
dissolved in aleohol or gasoline are harmless in this respect and 
are just as cffective fluxes, as acid flux, 
