Not only does it vary much in freedom from acid and rancidity, but is frequently adulterated.
The most common defect known is that usually referred to as rancidity.
It is the casein which is the objectionable ingredient, and the presence of which is usually the cause of rancidity.
This change is usually a rancidity that is observed in all stale products of this class.
Liquid petrolatum has the advantage over these of being devoid of tendency to rancidity.
Practically, rancidity is held in check by storing butter at low temperatures where germ growth is quite suspended.
Formerly, the acidity of a fat was looked upon as the direct measure of its rancidity.
rancidity in neutral oils and fats is one of the problems the soap manufacturer has to contend with.
Butyric acid, on the presence of which rancidity depends, is freely soluble in fresh milk.
Moisture, air, light, enzymes (organized ferments) and bacteria are all given as causes of rancidity.
1640s, from Latin rancidus "rank, stinking, offensive" (also source of Italian rancido, Spanish rancio), from rancere "be spoiled or rotten," of unknown origin. German ranzig is from French rancide. Related: Rancidness.
rancid ran·cid (rān'sĭd)
Having the disagreeable odor or taste of decomposing oils or fats.