Application of Doehlert matrix for determination of the optimal conditions of hydrothermolysis of rapeseed meal in subcritical water

The hydrothermolysis of rapeseed meal components, i.e. the protein and the lignocellulosic fractions, was carried out in a batch reactor in subcritical water. The optimal experiment design methodology was used for modelling and optimizing the yields of amino acids and saccharides: xylose and glucose. In good agreement with experimental results, the model predicts an optimal yield of amino acids (approx. 32.8% in relation to the content of the total protein fraction in the rapeseed meal) at a temperature and a time of about 205 °C and 51 min. The optimal yields of xylose (49.5% in relation to the content of hemicellulose in the rapeseed meal) and of glucose (19.4% in relation to the cellulose content in rapeseed meal) require higher temperatures but shorter reaction times. The further increase in reaction temperature and time would lead to secondary undesirable reactions of amino acids and saccharides.