Mild acidolysis was performed as the described method (de Souza et al., 2018 (link); Eugene et al., 2020 (link); Lapierre et al., 2019 (link)) with slight modifications. In brief, 10 mg of CWRs was mixed with 1 ml of 50 mM TFA (Sigma‐Aldrich) and incubated at 100 °C for up to 4 h with shaking at 750 rpm. The samples were then centrifuged at 19 500 g. 400 μL of supernatant was dried and re‐dissolved in 100 μL of 80% methanol. 2 μL of them was analysed via UHPLC‐MS (ThermoFisher Scientific) as described above. For alkaline digestion, the rest 500 μL of the TFA supernatant was dried and then treated with 2 N NaOH for 24 h at RT followed by neutralization with 6 N HCl. The samples were then extracted twice with 300 μL of water‐saturated ethyl acetate containing 100 μm t‐o‐coumaric acid as the internal standard. The combined extracts were dried and resuspended in 50% methanol with 0.1% formic acid. 3 μL of each sample were analysed in UHPLC‐MS as described for wall‐bound phenolics.