*2.3. Acid Hydrolysis of the Extract and Fibers*

The acid hydrolysis of the freeze-dried extracts was conducted as a one-step hydrolysis. One hundred milligrams of dry extractive material were suspended with ultrasound in 10 mL deionized water. Then, 1.8 mL 2N H2SO<sup>4</sup> were added and the suspension was hydrolyzed for 40 min at 120 ◦C and 0.12 MPa.

For carbohydrate analysis of fibers after steam refining, a two-step hydrolysis (see Section 2.1.) was performed on air-dried and fine milled samples.
