Hop bitterness analysis

ref : ASBC methods of Analysis, 8th Edition, 1992.

Transcribed by Dan McConnell (danmcc@umich.edu)

Hop bitterness in beer (ASBC Method)

BU= Abs @275*50

Example: Abs =0.622 -- 0.622*50= 31.1 BU

Notes:

  1. isooctane should have an Abs@275 <0.005.
  2. readings should be done ASAP due to decomposiotin by UV light

Alpha and Beta acids in hops: ASBC MoA Method

Calculations

dilution factor, d= (volume dil A x volume dil B)/ (500 x aliq extract A x aliq dil A)

% alpha acids= d x (-51.56 A355+ 73.79 A325-19.07 A275)

% beta acids= d x (55.57 A355-47.59 A325 + 5.10 A275)

Example:

Alpha and Beta acids in hops by HPLC: ASBC MoA Method

detector:
capable of 314 nm
column:
C18 (they recommend 250x4mm, 5 um ODS, RP18, Nucleosil-5)
Mobile phase:
MeOH: H2O: HPO4 (85%) /85:17:0.25 (v/v)
Conditions:
isocratic
Flow:
0.8 mL/min
Temp:
ambiant
Sample:
10 uL

Method:

  • add 20 mL MeOH to 10.0 gr finely ground hops
  • add 100 mL diethyl ether- stopper and shake for 30 min.
  • add 40 mL 0.1M HCl
  • stopper and shake for 10 min.
  • allow to stand for 10 min to separate the phases
  • pipette 5.0 mL of the supernate to a 50 mL volumetric flask
  • bring to volume (50 mL) with methanol
  • filter before injecting (sample is stable 24 hours)
  • calculate based on a known calibration standard as follows

    Calculations:

    Response Factor, RF= [mass of calib extr (gr) x conc of component in calib extr (%)] / area.

    Component %= (2 x average sample peak area of component x RF) / mass of sample

    Typical Retention times:

    cohumulone
    16 min
    n- + ad-humulone
    19 min
    colupulone
    27 min
    n- + adlupulone
    34 min

    Back to the Beer Page.

    Spencer W. Thomas (spencer@umich.edu)