D. Kristensen et Lh. Skibsted, Comparison of three methods based on electron spin resonance spectrometry for evaluation of oxidative stability of processed cheese, J AGR FOOD, 47(8), 1999, pp. 3099-3104
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) a
s spin trap added to the cheese and the spin labeling technique with 2,2,6,
6-tetramethylpiperidine-1-oxyl radical (TEMPO) as spin label added to the c
heese. Both methods showed that light was the more important factor compare
d to temperature for early stages (up to 11 days) in the formation of radic
als in processed cheese. For the spin labeling technique other, unidentifie
d reactions interfered during the early stages of the accelerated storage,
indicating that longer reaction times are required for the evaluation, and
the spin trapping technique is recommended. As a third method, direct measu
rement of free radicals formed in processed cheese stored for 15 months and
subsequently freeze-dried showed that for longer storage, temperature is m
ore important for the steady-state concentration of radicals than light exp
osure. In agreement with this result, formation of secondary lipid oxidatio
n products determined as thiobarbituric acid reactive substances was found
to correlate with the direct ESR measurement.