ESR spin trapping for in situ detection of radicals involved in the early stages of lipid oxidation of dried microencapsulated oils

•Oxidative events during oil microencapsulation can be detected by ESR spin trapping.•Susceptibility to oxidation of dried microencapsulated oils can be quantified in situ.•Higher levels of radicals by spin trapping do not necessarily mean higher oxidation.•Oxygen availability affects the rates of radical trapping and spin-adduct quenching.•Accumulation of radicals is the result of faster trapping than spin-adduct quenching. Different studies have shown that detection of free radicals by ESR spin trapping provides useful information on the susceptibility to oxidation of bulk oils and accordingly on the oxidative stability of different samples for comparative purposes. With the same goal, ESR spin trapping was evaluated in this work for in situ detection of radicals in dried microencapsulated oils (DMOs). By testing different oils, encapsulation matrices and oxidation conditions, results showed that ESR spin trapping can be useful to evaluate the oxidative susceptibility of DMOs, but ESR data should be interpreted cautiously, as the great complexity of the reactions involved may lead to data misinterpretations. Conditions for oxygen availability can have important impacts on the rates of both spin trapping and spin-adduct quenching affecting the levels of radicals observed. The kinetics of oxidation, spin trapping and spin-adduct decay should be known first in bulk oils for correct data interpretation in DMOs.