*2.2. Steam Refining*

The process of steam refining was conducted in a 10 L defibrator (Martin Busch & Sohn GmbH, Schermbeck, Germany). The input of raw material was 200 g dry material. The four blade-refiner-system (illustrated in [28]) in the reactor was rotated only in the final 30 s of steam treatment. The severity factor was calculated with Equation (1) according to Overend and Chornet [29]:

$$\log R\_0 = \log \left( t \times e^{\frac{(T-100)}{14.75}} \right) \tag{1}$$

with time in minutes (*t*); temperature in ◦C (*T*).

For the further understanding of the used process, the different steps of the process are illustrated as a sequential process schematic in Figure 1.

After steaming and refining the raw material, the fiber fraction was washed and the yields were calculated after measuring the solid content. The liquid extract fraction including the wash water was separated and the amount of the combined aqueous extract fraction was gravimetrically measured for further calculations. For calculating the extract yield, the dilution and solid content of the combined extract were gravimetrically measured after freeze-drying. Further process steps will be explained in the following chapters. According to Equation (1), a trial design from 160 ◦C up to 210 ◦C was performed with different time steps as outlined in Table 1.

**Figure 1.** Sequential schematic of the used process. Dotted squares representing process steps, solid lines represent products.


**Table 1.** Reaction conditions and corresponding severity factors.
