270 UNSWEETENED CONDENSED MILK DEFECTS 



Gritty Plain Condensed Bulk Milk. 



General Description. Grittiness in the unsweetened goods 

 appears usually only in the plain condensed bulk milk. It is a 

 defect which renders the product undesirable for ice cream 

 making. 



Causes and Prevention. The chief cause of this defect is 

 too great concentration. Plain condensed bulk milk which is not 

 condensed over 3.5 parts of fresh milk to 1 part of condensed milk 

 does not become gritty. When the concentration exceeds 4:1, 

 the milk sugar begins to crystallize out, making the product 

 gritty. Milk sugar requires about six times its weight of water 

 for complete solution in cold water. When condensed at the 

 ratio of 4:1 or over, the plain condensed bulk milk contains con- 

 siderably less than five parts, by weight, of water to one part 

 of milk sugar. This high concentration, together with the prac- 

 tice of storing this product at refrigerating temperatures in order 

 to preserve it, is responsible for the grittiness. This trouble can, 

 therefore, easily be prevented by not condensing to quite as high 

 a degree of concentration. 



Metallic Evaporated Milk and Plain Condensed Bulk Milk. 



General Description. Both, evaporated and plain condensed 

 bulk milk may show a metallic and puckery flavor, though this 

 defect is rather rare. 



Causes and Prevention. The metallic flavor may be due 

 to the same cause as metallic sweetened condensed milk, i. e., an 

 unsanitary condition of the vacuum pan, in which case its recur- 

 rence can be readily avoided by thoroughly cleaning all parts of 

 the pan including the dome and the goose neck, and rinsing down 

 the whole pan thoroughly with clean water each morning before 

 operations begin. 



Unsweetened condensed milk made by the use of the "Con- 

 tinuous Concentrator" may have a metallic flavor when the 

 scrapers in this machine are improperly adjusted, causing them 

 to cut into the copper walls and thereby incorporating metallic 

 copper in the product. This source of metallic flavor can be 

 removed by proper adjustment of the revolving spider and its 

 essential parts. 



