Analysing Hops Flashcards
What must all hops purchased be analyzed for?
Parameters that affect yield and beer quality.
How do large breweries analyze hops?
In house.
How do smaller breweries analyze hops?
Rely on the suppliers’ results.
What is the recommended sample size for whole hops according to EBC?
10-15 g samples from every bale.
What is the method for sampling a set number of bales?
The square root of the total number of bales.
If a batch contains 64 bales, how many bales should be sampled?
8 bales.
What percentage of the sample should come from the surface layer?
Less than 10%.
For hop products, what is the recommended sampling method?
Random 100 g samples from 0.2% of the packages with a minimum of 3 samples.
What is the purpose of measuring α-acids?
To determine the level of α-acids in hops.
What analysis uses lead conductance value (LCV)?
To measure α-acids level.
How does lead acetate react with α-acids?
Forms a precipitate, affecting conductivity.
What is the process for measuring LCV?
Titrate acidified lead acetate solution into the hop solution.
What wavelengths are used for UV light absorbance spectrophotometry?
325 nm, 355 nm, 275 nm.
What does the absorbance at 325 nm measure?
α-acids.
What does the absorbance at 355 nm measure?
β-acids.
What is the formula for calculating concentration of α-acids?
73.79A325 – 51.56A355 – 19.07A275.
What is the formula for calculating concentration of β-acids?
55.57A355 – 47.59A325 + 5.10A275.
What units are used to report bitterness levels in beer?
Bitterness units (BU) or international bitterness units (IBU).
What is the method to measure bitterness in beer?
Extract beer with iso-octane and measure absorbance.
What is the equation for calculating IBU or BU?
Factor x Absorbance.
What is the factor for whole hops added to the kettle?
50.
What is the factor for pre-isomerised pellets added to the kettle?
55 - 58.
What is the factor for pre-isomerised extract added post fermentation?
65 - 70.
What is the factor for reduced iso-α-acids?
70 - 73.
What is the role of high pressure liquid chromatography (HPLC)?
To separate and measure hop acids.
What is injected into the HPLC column?
A solution of hop acids in di-ethyl ether.
What is measured at 314 nm in HPLC?
Absorbance of hop acids.
What does HPLC allow for each hop variety?
Creates a fingerprint of bitter acids.
What is steam distillation used for?
To analyze total essential oil content.
How much water is used in steam distillation for hops?
3 litres.
What is the method for analyzing essential oil components?
Gas chromatography with flame ionisation detection (GCFID).
What is mixed with distilled essential oil for GC analysis?
Pentane or hexane.
What happens to the sample in gas chromatography?
It is vaporised and carried through the column.
How is the electrical current measured in GCFID?
By passing the gas through a flame ionisation detector.
