CHEMICAL CHANGES IX RIPENING 33! 



heat, and not precipitated by saturation with zinc 

 sulphate or ammonium sulphate; precipitated by 

 phosphotungstic acid, tannic acid and some other 

 reagents. 



(e) Amino acids, the simplest protein deriva- 

 tives (except ammonia). 



(f) Ammonia. 



It would be beyond the scope of this book to go 

 further into the details of the chemistry of these 

 compounds, since they are very complex and require 

 a special knowledge of organic chemistry to under- 

 stand. 



The amounts of these protein-derived products vary 

 with many conditions, some of which will be con- 

 sidered later (p. 337). 



Fat. There have been numerous investigations 

 made by different workers to ascertain whether the 

 milk-fat in cheese decomposes during the ripening 

 process. The general results of these investiga- 

 tions show that cheese-fat is unchanged milk-fat and 

 that these glycerin-acid compounds (glycerids) (p. 

 140) do not share extensively in the ripening proc- 

 ess, especially in the case of hard cheese, such as 

 cheddar. In one case, it was found that from i.o 

 to 7 per cent of the cheese-fat had undergone some 

 decomposition, the higher amounts occurring in 

 soft cheese. One of the early investigators (Blon- 

 deau) made several analyses of Roquefort cheese 

 at various ages and reported that the proteins of 

 the unripe cheese changed rapidly into fat. This 

 statement, though frequently disproved later, has 

 not even yet entirely disappeared from physiologi- 

 cal literature. The conclusions were based upon 



