Technical Brewing
Beyond Lovibond — Understanding Beer Color
Bob Hansen - Technical Services Manager
4.18.08
Color and Light
What is light?
Electromagnetic wave spectrum.
[]. Retrieved April 13, 2008, from Encyclopædia Britannica Online: http://www.britannica.com/eb/art-70892
1
Color and Light
What is color? What causes color?
2
Visible spectrum of light
100100
100
100
100
100
90
90 90
9090
90
80
80 80
8080
80
70
70 70
7070
70
60
60 60
6060
60
50
50
50
5050
40 50
40 40
40
40
3040
30 30
30
30
2030
20
2020
20
10 20
1010
10
01010
00 00
400
0
400
400
400
400
400
3
450
450
450
450
450
450
500
500
500
500
500
500
550
550
550
550
550
550
600
600
600
600
600
600
650
650650
650
650
700
700
700
700
750
750750
750
Reflection, Absorption and Transmittance
Colored light can come to the eyes in one of three ways:
Primary Source
• Directly from a light source
Secondary Sources
• Light reflected off an object
• Light transmitted though an object
For Secondary Sources, Interaction of Primary Light and
Secondary Source is Very Important
4
Beer’s color is Transmitted
White light is transformed to yellows as blues are absorbed.
100
90
80
70
60
50
40
100
30
90
20
10
80
70
0
400
60
450
500
50
40
100
30
20
90
80
10
70
0
400
450
500
550
600
650
700
750
60
50
40
30
20
10
0
400
5
450
500
B
E
E
R
550
550
600
600
650
650
700
700
750
750
Measuring beer color
Many means have been used to measure and predict a beers color:
• Visually-the original and obvious way
• Using a machine
• Using a more expensive machine
6
Measuring Transmitted Light
P0
P
Transmittance = P/ P0
7
Measuring Transmitted Light
% trans
•
Beer transmittance vs wavelength
Transmittance measures the % age of light reaching the eye.
As
100the photo response in our eye is proportional to the light it
90
receives,
transmittance represents most closely light or color
80
intensity.
70
60
50
40
30
2
10
20
10
20
30
0
400
450
500
550
600
nm
8
650
700
750
Absorbance vs. Transmittance
Absorbance = Log 10 1/T
Absorbance = Log 10 1/(P/P0)
Absorbance = Log 10 (P0/P)
Beers Law A= eBC
9
Absorbance vs. Transmittance
30
3
25
2.5
20
2
Abs or SRM
15
10
1
5
0.5
0
0
10
20
30
40
50
% trans
10
1.5
60
70
80
90
0
100
Abs
SRM
Absorbance
Log 10
1/T
SRM
and Abs= vs.
Transmittance
Wort preparation for color
- Measured using a mash with a grain bill of
50 grams/ 450 grams (11.1% )
- Similar concentration to brewers rule of thumb, 1 lb/gallon (10.7%)
- Corresponds to a wort of roughly 8 Plato or 1.032
- Beer / Wort normally diluted to get absorbance below 2.0
- Specialty malts mashed with base malt as needed
11
Transmission Spectrum of Specialty malts
%trans
Transmission at 20 SRM
100
90
80
70
60
50
40
30
20
10
0
400
Special Roast
Caramel 60
Caramel 120
Extra Special
2-Row Dark
Roasted Barley
Black Malt
aromatic
450
500
550
600
nm
12
650
700
750
800
Caramel Malt Transmittance
% trans
100
90
80
70
60
50
40
2
30
20
10
10
0
30
20
400
450
500
550
600
nm
13
650
700
750
trans
Black Malt Transmittance
100
90
80
70
60
50
40
30
20
10
0
2
10
20
30
400
450
500
550
600
nm
14
650
700
750
A whiter shade of pale? 2 SRM
15
A whiter shade of pale?
Tranmittance spectrum at 2 SRM
100
90
80
% trans
70
60
50
40
30
Caramel (90%)
20
Black (87%)
10
0
400
450
500
550
600
nm
16
650
700
750
Orange or Tan 10 SRM
17
Orange or Tan
Transmittance at 10 SRM
100
90
80
% trans
70
60
50
40
Caramel (68%)
30
Black (57%)
20
10
0
400
450
500
550
600
nm
18
650
700
750
Red or Brown-20 SRM
19
Red or Brown- 20 SRM
Transmittance spectrum at 20 SRM
100
90
80
% trans
70
60
50
40
Caramel (53%)
30
Black (40%)
20
10
0
400
450
500
550
600
nm
20
650
700
750
Mahogany or Black-30 SRM
21
Mahogany or Black-30 SRM
Transmittance spectrum at 30 SRM
100
90
80
% trans
70
60
50
40
Caramel (44%)
30
Black (30%)
20
10
0
400
450
500
550
600
nm
22
650
700
750
Spectrum of Same Color Worts
23
Summary-Specialty Malt Color
Caramel Malt
24
Black Malt
10 SRM
Orange
Tan
20 SRM
Red
Brown
30 SRM
Mahogany
Black
Summary-formulating for color
25
•
A beers color is caused by the selective transmission of light
•
Light source, path length and concentration are important to measuring and
viewing a beers color
•
Current SRM is good for measuring batch to batch variability within the
same recipe
•
Current SRM color rating is ineffective for describing the actual color of
darker colored beers.
•
Absorption of light by different classes of malt is mostly equivalent across
the spectrum of visible light
Summary-formulating for color
26
•
At equivalent SRM the color from different malts within the same class will
be the same, though flavor may vary.
•
Dark roasted malts absorb more strongly across the spectrum, leading to
darker beers and browner tones at equivalent SRM.
•
Full spectrum analysis can give a truer picture of beer color.
•
True perceived beer color could be predicted from recipe.
•
Tools could be developed to be both predictive and descriptive of
true beer color.
Questions?
27
Thank You!