Other Analyses Flashcards
What is Dimethyl sulphide (DMS)?
An important, and sometimes unwanted, beer flavour compound
DMS is often measured using a gas spectrometer.
How is free malt DMS measured?
By incubating milled malt in a tube at 35˚C for 30 min and analyzing the headspace
This analysis focuses on the area above the malt.
How is total malt DMS measured?
By degrading the precursor SMM to DMS using a caustic solution and incubating at 50˚C
SMM values are calculated by subtracting free DMS from total DMS.
What is the recommended level of DMS/SMM in malt specifications?
Set to provide the target level of DMS in the beer after brewing
For most beers, this value is below its flavour threshold.
What is viscosity?
The resistance of a fluid to a change in shape
High viscosities can cause problems in wort separation, whirlpool operations, and beer filtration.
How is viscosity measured?
Using a viscometer, which measures the time taken for a set volume to flow through a capillary
Results are expressed in units of centipoise (cP).
What are the ideal viscosity values for brewing?
Values should be below 1.60 cP; results lower than 1.5 cP are even better
Viscosity is sometimes reported in mPa.s (milliPascal.seconds) on analysis sheets.
What is the significance of β-glucan in malt?
It causes problems in wort separation and beer filtration
The amount depends on levels in barley and the degree of modification.
How is β-glucan analyzed?
Using flow injection analysis with calcofluor that fluoresces when binding to β-glucan
The concentration is calculated from the fluorescence measured.
What are the ideal β-glucan levels in malt?
Should ideally be below 150 mg/L; many breweries set the limit at 100 mg/L
High levels can hinder brewing efficiency.
What is the Wort Attenuation Limit (WAL)?
A test to determine how fermentable a wort is
It helps assess the reduction in gravity or extract in the wort by yeast.
What does the term ‘attenuate’ mean in brewing?
To make thin or weak, referring to the reduction in gravity or extract in the wort by yeast
This is key for understanding fermentation processes.
How is the WAL test performed?
Wort is added to a flask with yeast and kept warm to allow the yeast to consume sugar
The test is complete when the gravity of the wort ceases to fall.
What is the formula for calculating percentage apparent attenuation?
Percentage apparent attenuation = (OG - PG) / OG x 100
OG = original gravity; PG = attenuation limit test gravity.
What does the term ‘real attenuation’ account for?
It accounts for the difference in gravity caused by the increase in ethanol
It is calculated as % real attenuation = % apparent attenuation x 0.819.
If a congress wort has an OG of 11°P and a WAL gravity of 1.2°P, what is the percentage apparent attenuation?
89.09%
Calculated as (11 - 1.2) / 11 x 100.
What is the relationship between percentage fermentability and percentage attenuation?
They are the same; both describe how fermentable the wort made from malt is
The same calculations are used for both metrics.
