Abstract:

This work reports the use of one-factor-at-a-time combined with linear orthogonal regression design to optimize process parameters including alkali (KOH) dosage (X1), anhydrous alcohol dosage (X2) and solid-to-solvent ratio (X3) for the extraction of humulone and lupulone from hop extract by acid-alkali precipitation. The optimal conditions for separating lupulone from hop extract were determined as 6.5% (m/m) of KOH dosage, 1 mL/g of anhydrous alcohol dosage and 1:60 g/mL of solid-to-solvent ratio. KOH dosage was the most important process condition followed by solid-to-solvent ratio and anhydrous alcohol dosage. The following multiple regression model that describes fi nal lupulone content ( ) of the lupulone extract (i.e., purity) as a function of the process conditions was established by complete regression analysis: = 84.375－2.843X1－1.995X2 + 2.360X3. The optimal conditions for separating humulone from hop extract were determined as 8.5% (m/m) of KOH dosage, 1 mL/g of anhydrous alcohol dosage and 1:60 (g/mL) of solid-to-solvent ratio. Anhydrous alcohol dosage was the most important process condition, solid-to-solvent ratio was in the middle and KOH dosage was the least important one. The following multiple regression model that describes fi nal lupulone content ( ) of fi nal humulone content ( ) of the humulone extract (i.e., purity) as a function of the process conditions was established by complete regression analysis: = 82.667 + 1.515X1－2.950X2 + 2.037X3. The purities of humulone and lupulone in both extracts were as high as 86.43% and 87.12%, respectively as shown by HPLC analysis.

Key words: hop, humulone, lupulone, separation, acid-alkali precipitation method, process optimization