*2.5. Free Amino Acid Content Determination*

A 0.5 g sample was ground in a mortar on ice with 5 mL of extracting solution containing 50% alcohol and 0.01 mol L−<sup>1</sup> of HCl. The homogenate was transferred to a centrifuge tube and sonicated for 30 min at low temperature, then centrifuged at 12,000× *g* for 5 min. Next, 1 mL of supernatant was recovered, freeze-dried, and dissolved in 1 mL of amino acid diluent. The sample was filtered through a 0.22 μm membrane filter before use. Finally, 50 μL of the filtrate was assessed in an automatic amino acid analyzer (SykamS433D, SYKAM Vertriebs GmbH, Fürstenfeldbruck, Germany) with an analysis column (LCA K07/Li, Sykam). The results were expressed as mg kg−<sup>1</sup> DW.
