Transcript PPTX - Bonham Chemistry

Brewing Science
Flavor and the Origins of Flavor
Beer Styles
What is a flavor?
• A combination of taste, odor, and other
sensory input
– Includes mouth feel (tactile), visual, kinetsthetic,
temperature, pain (nocioception), and other
senses (carbonation!)
• The largest contributors are taste and smell
Taste
• The taste buds are clusters of approximately
100 taste cells that occur as protuberances,
called papillae, on the tongue
• The arrival of a chemical stimulant on the
surface of a receptor temporarily modifies the
cell wall and produces an electrochemical
impulse
Smell
• perceived by neurons in the olfactory
epithelium (skin cells) of the upper respiratory
passage
• Some molecules also reach this olfactory
ephithelium by way of the back of the mouth
during swallowing; this is known as gustatory
aroma perception
Other Senses
• Tactile sensations such as viscosity and the prickle from dissolved
carbon dioxide, for example, are determined by the physical
composition of the beer and also play an important role in
zymological evaluations.
• Temperature is extremely important for all aspects of flavor
perception. Warmer temperatures tend to emphasize the aromatic
components of the beer, while lower temperatures suppress them.
It is therefore imperative to serve beer at the proper temperature
for the style.
• Psychological factors or the senses of vision and hearing, which may
indirectly affect the results of a beer evaluation. A trained taster
should be able to minimize the influence of these external factors
while performing a sensory analysis.
How do we measure Flavor?
• Meilgaard system: concentration relative to
sensing threshold value
• Beer Flavor Wheel
• “False” measures: IBU and Color
• Strength / Alcohol Content
• Others
Meilgaard Thresholds
Primary Flavor Constituents (>2 FU)
All Beers
Ethanol
Hop bittering compounds
Carbon dioxide
Specialty Beers
Hop aroma compounds
Caramel and roasted flavor compounds
Esters and alcohols (high gravity beers)
Short-chain acids
Defective Beers
2-trans-nonenal (oxidation)
Vicinal diketones (diacetyl)
Sulfur compounds (H2S, DMS)
Acetic acid (contamination)
3-Methyl-2-butene-1-thiol (lightstruck)
Others (contamination)
Secondary Flavor Constituents (0.5-2 FU)
Volatiles
Banana esters (e.g., isoamyl acetate)
Apple esters (e.g., ethyl hexanoate)
Fusel alcohols (e.g., isoamyl alcohol)
C6, C8, C10 aliphatic acids
Ethyl acetate
Butyric and isovaleric acids
Phenylacetic acid
Nonvolatiles
Polyphenols
Various acids, sugars, and hop compounds
Tertiary flavor constituents (0.1-0.5 FU)
2-Penethyl acetate, o-amino acetophenone
Isovaleraldehyde, methional, acetoin
4-Ethylguaiacol, g-valerolactone
Background flavor constituents (< 0.1 FU)
Remaining flavor compounds
International Bittering Units
• Distinct from Flavor
profile
• Based on UV/Vis
measurement of
extracted iso-alpha acids
Color
• Degrees Lovibond is derived
from comparison of color to
standardized scale, largely
replaced by other methods
(Standard Reference Method)
that give approximately equal
results
• SRM measures light at 430
nm:
SRM = 12.7 x dilution factor x Abs430
Malt Analysis
Color
• Traditional Method developed by Lovibond. The
scale is implemented by comparing colored slides
or glasses to a sample to visually see which slide
agreed with the color of the sample
• Current standards for measuring color
– Standard Reference Method (SRM) developed by
American Society of Brewing Chemists (ASBC)
– European Brewing Convention (EBC) color rating
– The two methods can be compared by the equation
EBC = 1.97 * SRM
Provided by Ken Woodson & the North Texas Home Brewers Association
Malt Analysis
Color
• The current methods use spectrophotometers
• All three scales goes from low to high, with
lower numbers assigned to light colors
• For light colored beers the SRM method is
very close to the Lovibond scale
Provided by Ken Woodson & the North Texas Home Brewers Association
Malt Analysis
Alpha-amylase (Dextrinizing Units)
• ASBC metric that measures dextrin units per 100 grams
• Over modified malt normally has lower dextrin units.
For less modified malts, the dextrinizing units needs to
be greater to apply an infusion mash.
• Typical ranges for 100 grams:
–
–
–
–
Six row malt 35-45
American two row malt 40-50
Pilsener malt 44-48
Vienna malt 40-45
Provided by Ken Woodson & the North Texas Home Brewers Association
Malt Analysis
Diastatic Power (Degrees Linter)
• Measures the enzyme content of the malt. Specifically,
the enzyme strength to convert starch to sugar
• Higher diastatic power malts convert starches faster
than lower diastatic power malts
• Well modified malts with low protein content typically
have a diastatic power between 35 and 40. On the
other hand, it can be as high as 160 for six row brewers
malt.
• Diastatic power decreases as malt color increases.
Provided by Ken Woodson & the North Texas Home Brewers Association
Malt Analysis
Protein Percent
• Equals 6.25 times the total nitrogen content
• The protein percent for Barley malt should be
9 to 11%
• Enzymes are proteins, so higher protein levels
correspond to higher enzymatic strength.
Provided by Ken Woodson & the North Texas Home Brewers Association
Malt Analysis
Soluble Nitrogen/Total Nitrogen Ratio
• The ratio of soluble nitrogen to total nitrogen
is a measure of malt modification. A higher
ratio indicates higher malt modification
• For lager malts, 30-33% indicates under
modification and 37-40% indicates over
modification.
• For infusion mashing, the ratio should be 3842%
Provided by Ken Woodson & the North Texas Home Brewers Association
Malt Analysis
Mealy Percent
• Malt is characterized as mealy, half-glassy, and
glassy. Mealy malt is very chewable, whereas,
glassy malt is very hard.
• Well modified malt is mealy.
• For infusion mashing, the malt should be at
least 95% mealy. Malt should be at least 92%
mealy for decoction and step mashes.
Provided by Ken Woodson & the North Texas Home Brewers Association
Malt Analysis
Example
Let’s review a typical malt analysis from Briess
Malt and Ingredients Co.
http://www.briess.com/brew/products.shtml
Provided by Ken Woodson & the North Texas Home Brewers Association
Beer Strength
• Most accurate (but time-consuming) method
would be distillation and measurement of
alcohol content
• Instead, Density is usualy used as an
approximation
• Specific Gravity: density relative to pure water
• Water is 1.000, pure alcohol is 0.789
Beer Strength
• Original Gravity (OG) is specific gravity
BEFORE fermentation (also called original
extract)
• Final Gravity (FG) is specific gravity AFTER
fermentation
• ABV% ≈ (105 x (OG-FG)) / (0.79 x FG)
Beer Strength
• Many systems for measurement of density:
points, brix, degrees Plato, etc
• Points is simply the thousands of a specific
gravity: SG 1.020 = 20 points
• British Brewers often use degrees Plato, which
is roughly: points / 4
(so SG 1.020 ≈ 5 degrees Plato)
Beer Styles
• The idea of distinct, recognizable styles is
mostly a modern invention (1977+), but has
become big business
• Style can include measurables such as color,
flavor, strength, but also includes intangibles
such as production method, history, or
country of origin
Beer Styles
• Divided traditionally between Ale and Lager
styles
Types of Beer
•
Ales
– Use “top-fermenting” yeast which is unable to metabolize certain sugars. This results in
a fruitier, sweeter beer. Top fermenting yeast rises to the top of the vessel during
fermentation.
– Fermented at higher temperatures than lager beer (15–23°C )
– Ale yeasts at these temperatures produce significant amounts of esters resulting in a
flowery, fruity aroma
• Pale ale
– Brewed using a pale barley malt. Hop levels can vary.
• Dark ale
– Brewed using dark roasted barley malts. Also called stout.
• Irish red ale
– The red colour comes from the use of roasted barley. Has a malty, caramel flavour.
• Cream ale
– Brewed to be light in colour, hop and malt flavour is subdued.
• Brown ale
– Brewed with a darker barley malt, lightly hopped and fairly mildly flavoured with a slightly nutty taste.
Ale Styles
Top
Fermenting
Wheat
Beers
Pure
Yeast
Belgian
Witbier/
White/
Blanche
South
German
Weissbier/
Weizen
Lactic
Fermentation
Berliner
Weisse
Sweet
Stout
Spontaneous
Fermentation
Lambic
Porter
Ale Types
Oatmeal
Stout
American
Ale
Dry
Stout
Cream
Ale
Imperial
Stout
Pale
Mild
Dark
Mild
Bitter
Best
Bitter
Light
Ale
Pale
Ale
Strong
Bitter
Gueuze
So English
Brown
Ale
No English
Brown
Ale
Old
Ale
Pale/Dark
Barley
Wine
Faro
DunkelWeizen
Kriek
Irish
Red Ale
Strong
Scotch Ale
Belgian
Brown/”Red”
India
Pale Ale
Belgian
Ales
Altbier
Weizenbock
Frambooise
American
Hefeweizen
Other
Fruit
Beers
Saisons
Trappisten
Types of Beer
• Lager
– The most commonly consumed style
– Fermentation occurs at around 7-12°C using a “bottom fermenting”
yeast
• “Fermentation phase”
– Then cooled at 0-4°C
• “Lagering phase”
• The lager clears and mellows
• Inhibits the production of esters, resulting in a “crisper” (less fruity)
tasting beer
– Has more fizz than ale
– Premium Lager? No such thing.
Lager Styles
Bottom
Fermenting
Vienna
Type
Lager
Pilsener
Dortmunder/
Export
Strong
Lager
American
Malt Liquor
Marzen/
Oktoberfest
Munich
Type
Pale
Dark
Pale
Bock
Rauchbier
Pale/Dark
Double Bock
Dark
Bock