Wednesday, October 20, 2021

Oxidative rancidity

Rancidity can occur in many products or ingredients during storage. It affects taste and odor, and can have an impact on nutritive value. Exposure to light, pro-oxidants and elevated temperature will accelerate the reaction. Rancidity is associated with characteristic off-flavor and odor of the oil.

There are two basic types or causes of rancidity that cause and/or contribute to the degradation of foods: oxidative and hydrolytic. 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. It is the reaction of double bonds in unsaturated fatty acids with 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.

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.
Oxidative rancidity

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