The illegal additions of chemicals
in food products are serious
incidents threatening current public safety. To date, ideal methods
to determine permanent traces of prohibited chemicals in foods are
still lacking. For example, formaldehyde (FA) can be added illegally
as a food preservative. However, most current methods that are dependent
on the direct detection of FA are not able to determine if FA has
ever been added once food products are rinsed completely. Herein,
we present a novel approach relying upon protein modifications induced
by FA (PMIF) to examine FA in foods. We reveal the entire catalog
of PMIFs in food products by combining mass spectrometry analysis
with unrestrictive identification of protein modifications. Consequently,
four obvious PMIFs were identified and confirmed as markers to discriminate
the addition of FA in foods. Our study demonstrates that the approach
based on PMIFs enables detecting the imprinted trace of FA even if
the food products have been washed thoroughly. Our work presents a
novel strategy for analysis of chemical additives, offering broad
potential applications in protein analysis and food safety