| Abstract
| - Electron spin resonance (ESR) spectrometry has been adapted to accelerated (light and temperature)storage experiments with processed cheese comparing the spin trapping technique with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as spin trap added to the cheese and the spin labeling technique with2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) as spin label added to the cheese. Bothmethods showed that light was the more important factor compared to temperature for early stages(up to 11 days) in the formation of radicals in processed cheese. For the spin labeling techniqueother, unidentified reactions interfered during the early stages of the accelerated storage, indicatingthat longer reaction times are required for the evaluation, and the spin trapping technique isrecommended. As a third method, direct measurement of free radicals formed in processed cheesestored for 15 months and subsequently freeze-dried showed that for longer storage, temperature ismore important for the steady-state concentration of radicals than light exposure. In agreementwith this result, formation of secondary lipid oxidation products determined as thiobarbituric acidreactive substances was found to correlate with the direct ESR measurement. Keywords: Processed cheese; oxidative stability; ESR; spin labeling; spin trapping; radicals
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