Essential Oils Flashcards
What are essential oils in hops also known as?
Hop oils
What percentage of the hop cone do hop oils typically constitute?
0.5-3%
How many components can be found in hop oil?
Over 1000 components
What are the three categories of components in hop oil?
- Hydrocarbons
- Oxygenated fraction
- Sulphur compounds
What is odour/flavour activity?
How aromatic a compound is
Which type of oil components generally have the highest odour/flavour activities?
Sulphur containing oil components
What are hydrocarbons made of?
Hydrogen and carbon
Why are hydrocarbons significant in dry hopped beers?
They are very volatile and easily oxidised and polymerised
What are terpenes and terpenoids?
- Terpenes: hydrocarbons
- Terpenoids: include oxygen-containing compounds
What is the most abundant hydrocarbon component in hop essential oil?
β-myrcene
What aroma does β-myrcene contribute to hops?
Green resinous
Which monoterpenes are important for dry hop aroma?
- α-pinene
- β-pinene
- Ocimene isomers
- ρ-cymene
What is a characteristic ratio of α-humulene to β-caryophyllene in noble hops?
3:1 or above
What happens to β-myrcene levels during the hop ripening period?
Rises rapidly from nearly zero up to 36%
What does the oxygenated fraction of hop oil consist of?
Hydrocarbons with oxygen added
What is the aroma of linalool?
Floral and spicy
What compound imparts a green and grassy note in beer?
Hexanal
Which esters are found in relatively high concentrations in late and dry hopped beers?
- Isobutyl isobutyrate
- Isoamyl isobutyrate
- 2-methylbutyl isobutyrate
- 3-methylbutyl isobutyrate
What is the role of yeast in the biotransformation of hop compounds?
Encourages the formation of esters from precursors
What is the minimum concentration at which the taste or aroma of a substance can be perceived called?
Flavour threshold
What are polyfunctional thiols known for?
Imparting fruity and tropical aromas in beer
What is a common descriptor for the polyfunctional thiol 3M4MPol?
White wine, tropical fruit, grapefruit
What compound is known to impart a pineapple aroma?
S-methyl thiohexanoate
What is the main challenge with sulphur compounds in beer?
They are extremely flavour active with low flavour thresholds
What happens to certain compounds during normal brewing processes?
Most are lost
What should brewers be cautious about regarding small amounts of certain compounds?
They can have a large effect on flavour and aroma
