Editing Rancidification (section)

==Oxidative stability measurement==
Oxidative stability is a measure of oil or fat resistance to oxidation. Because the process takes place through a [[chain reaction]], the oxidation reaction has a period when it is relatively slow, before it suddenly speeds up. The time for this to happen is called the "induction time", and it is repeatable under identical conditions (temperature, air flow, etc.). There are a number of ways to measure the progress of the oxidation reaction. One of the most popular methods currently in use is the Rancimat method.

The Rancimat method is carried out using an air current at temperatures between 50 and 220&nbsp;°C. The volatile oxidation products (largely [[formic acid]]<ref name="Allen94">{{cite book|title=Rancidity in Foods|last1=Allen |first1=J.C. |last2=Hamilton |first2=R.J. |year=1994 |publisher=Springer-Verlag GmbH |isbn=978-0-8342-1287-9 |page=47 |url=https://books.google.com/books?id=lcMgZHWIRUsC}}</ref>) are carried by the air current into the measuring vessel, where they are absorbed (dissolve) in the measuring fluid ([[distilled water]]). By continuous measurement of the conductivity of this solution, oxidation curves can be generated. The [[Cusp (singularity)|cusp point]] of the oxidation curve (the point where a rapid rise in the conductivity starts) gives the induction time of the rancidification reaction,<ref name="nut">{{cite book|title=Tree nut oils: chemical characteristics, oxidation and antioxidants|author=Miraliakbari, H.|year=2007|publisher=Library and Archives Canada|isbn=978-0-494-19381-5|url=https://books.google.com/books?id=Elz09NWHTBcC|page=31}}{{Dead link|date=March 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> and can be taken as an indication of the oxidative stability of the sample.

The Rancimat method, the oxidative stability instrument (OSI) and the oxidograph were all developed as automatic versions of the more complicated AOM (active oxygen method), which is based on measuring peroxide values<ref name="nut" /> for determining the induction time of fats and oils. Over time, the Rancimat method has become established, and it has been accepted into a number of national and international standards, for example [[American Oil Chemists' Society|AOCS]] Cd 12b-92 and ISO 6886.