The antinitrosating capacity of hydroxycinnamic acids and hydroxytyrosol in a cured meat model unraveled through structural and kinetic investigations

Nitrite is a widely used preservative in cured meats that provides microbiological safety and characteristic sensorial properties. However, it also drives the formation of N -nitrosamines, some of which being classified as probable human carcinogens. This study aimed to evaluate the antinitrosating capacity of hydroxytyrosol and three hydroxycinnamic acids (chlorogenic acid, caffeic acid and ferulic acid) toward N -acetyltryptophan (AcTrp) nitrosation under pH conditions relevant to meat processing and gastric digestion, i . e . pH 5 and pH 2.5. Neo-formed compounds were followed kinetically by LC-DAD-MS 2 allowing the main mechanistic pathways to be proposed. Caffeic acid and ferulic acid showed the highest inhibition rates (77-80% after 195 min at pH 5), whereas chlorogenic acid and hydroxytyrosol appeared less effective (28% and 51%, respectively). The main reaction pathways for the antinitrosating capacity of chlorogenic acid and hydroxytyrosol involved nitrite-induced oxidation of catechol units, leading to oligomerization, and further nitration of monomers and oligomers at both pH values. In addition, covalent coupling of monomers with N -acetyl- N -nitrosotryptophan ( NO -AcTrp) was observed at pH 2.5. By contrast, caffeic acid and ferulic acid underwent selective nitrosation at the C2 position of the propenoic chain, generating nitroso cations that were trapped by ( NO )-AcTrp. The antinitrosating capacity was thus reassessed based on the number of nitrite ions scavenged per phenolic compound confirming the superiority of hydroxytyrosol over chlorogenic acid at pH 5 and their similar capacities at pH 2.5, while non-esterified hydroxycinnamic acids were less efficient at both pH. Overall, the findings demonstrate that esterified hydroxycinnamic acids and hydroxytyrosol could efficiently mitigate nitrite-induced N -nitrosation in cured meat processing and early gastric digestion.