Rancimat assay

Chemical Antioxidant Systems. The antioxidant activity of tea extracts and tea polyphenols have been determined using in vitro model systems which are based on hydroxyl-, peroxyl-, superoxide-, hydrogen peroxide-, and oxygen-induced oxidation reactions (109—113). The effectiveness of purified tea polyphenols and cmde tea extracts as antioxidants against the autoxidation of fats has been studied using the standard Rancimat system, an assay based on air oxidation of fats or oils. A direct correlation between the antioxidant index of a tea extract and the concentration of epigallocatechin gallate in the extract was found (107). 

Much work has been published on evaluations of natural flavonoids in various lipid systems, but most evaluations were done either at elevated temperatures, under AOM or Rancimat conditions, or were based on the unspecific bleaching of )5-carotene by co-oxidation with linoleic acid. Unfortunately, from the results of these assays, the usefulness of flavonoids as antioxidants is difficult to predict for foods containing mainly triacylglycerols and stored under ambient or near ambient conditions (Chapter 8). 

The induction period for formation of PBN spin adducts in milk fat, isolated from butter, is shown in Figure S. The course of radical formation resemblances that typically observed in other accelerated oxidation tests, such as Rancimat and Oxidograph methods. This ESR procedure has the advantage of milder conditions compared to other methods, combined with a short assay time. 

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