Transcript Beyond Lovibond—Understanding Beer Color

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
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Color and Light
What is color? What causes color?
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Visible spectrum of light
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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
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Beer’s color is Transmitted
White light is transformed to yellows as blues are absorbed.
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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
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Measuring Transmitted Light
P0
P
Transmittance = P/ P0
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Measuring Transmitted Light
% trans
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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
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receives,
transmittance represents most closely light or color
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intensity.
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Absorbance vs. Transmittance
Absorbance = Log 10 1/T
Absorbance = Log 10 1/(P/P0)
Absorbance = Log 10 (P0/P)
Beers Law A= eBC
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Absorbance vs. Transmittance
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Abs or SRM
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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
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Transmission Spectrum of Specialty malts
%trans
Transmission at 20 SRM
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Special Roast
Caramel 60
Caramel 120
Extra Special
2-Row Dark
Roasted Barley
Black Malt
aromatic
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Caramel Malt Transmittance
% trans
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Black Malt Transmittance
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A whiter shade of pale? 2 SRM
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A whiter shade of pale?
Tranmittance spectrum at 2 SRM
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% trans
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Caramel (90%)
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Black (87%)
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Orange or Tan 10 SRM
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Orange or Tan
Transmittance at 10 SRM
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% trans
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Caramel (68%)
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Black (57%)
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Red or Brown-20 SRM
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Red or Brown- 20 SRM
Transmittance spectrum at 20 SRM
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Caramel (53%)
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Mahogany or Black-30 SRM
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Mahogany or Black-30 SRM
Transmittance spectrum at 30 SRM
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Caramel (44%)
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Spectrum of Same Color Worts
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Summary-Specialty Malt Color
Caramel Malt
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Black Malt
10 SRM
Orange
Tan
20 SRM
Red
Brown
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Mahogany
Black
Summary-formulating for color
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A beers color is caused by the selective transmission of light
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Light source, path length and concentration are important to measuring and
viewing a beers color
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Current SRM is good for measuring batch to batch variability within the
same recipe
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Current SRM color rating is ineffective for describing the actual color of
darker colored beers.
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Absorption of light by different classes of malt is mostly equivalent across
the spectrum of visible light
Summary-formulating for color
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At equivalent SRM the color from different malts within the same class will
be the same, though flavor may vary.
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Dark roasted malts absorb more strongly across the spectrum, leading to
darker beers and browner tones at equivalent SRM.
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Full spectrum analysis can give a truer picture of beer color.
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True perceived beer color could be predicted from recipe.
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Tools could be developed to be both predictive and descriptive of
true beer color.
Questions?
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Thank You!