Rancidity is associated with characteristic off-flavor and odor of the oil. There are two major causes of rancidity. One occurs when oil reacts with oxygen and is called oxidative rancidity. The other cause of rancidity is by a combination of enzymes and moisture.
Oxidative rancidity, one of the major causes of quality deterioration in foods, is caused by the oxidative deterioration of lipids by atmospheric oxygen. Lipids oxidize through a complex series of reactions giving rise to a myriad of non-volatile and volatile compounds that are responsible for off-flavors even at concentrations in the parts-per-billion range.
Oxidative rancidity is off special interest as it leads to the development of unfavorable off-flavors that can be detected early on in the development of rancidity.
One of the most common methods for measuring the oxidative rancidity of vegetable oils is the peroxide value (PV). The PV determines the amount of peroxides formed during early oxidation stages, expressed as millimoles or milliequivalents of peroxide oxygen per one kilogram of oil.
Peroxide value (PV) is one of the most widely used quality indicators in food industry. The PV can be used as an oxidative index for the early stages of lipid oxidation, and a higher oxidative stability is usually accompanied by a slower increase in the PV.
Numerous analytical protocols have been described for the measurement of PVs. The most widely used procedure utilizes the oxidative capacity of lipid (hydro) peroxides to generate iodine from potassium iodide.
Oxidative rancidity
