Factors affecting hop utilisation Flashcards
What is the effect of pH on hop utilisation?
Hop utilisation is higher at higher pHs. A pH of 8-10 can provide 90% utilisation, while at a standard wort pH of 5.2, it is only around 35%.
Boiling at higher pHs is not always practical, but some breweries do this to isomerise hops before adding them to the main boil.
How does boil time affect hop utilisation?
The longer the wort is boiled with hops added, the greater the utilisation, up to a maximum point of around 4 hours.
What is the relationship between wort gravity and hop utilisation?
Hop utilisation is greater in lower gravity worts because it is harder to dissolve material in more concentrated solutions.
What impact does trub have on hop utilisation?
Hop acids are not completely soluble in wort and can be adsorbed on trub. More trub formation leads to greater loss, so avoiding excessive trub formation prevents low hop utilisation.
How does temperature affect hop isomerisation?
The higher the temperature of the wort, the more effective the isomerisation. Isomerisation drops significantly below 80°C.
What is the effect of pressure on hop utilisation during boiling?
Wort at a higher pressure boils at a higher temperature, increasing the rate of hop utilisation. For example, it takes 4 hours to fully utilise hops at 100°C, but only 20 minutes at 120°C.
How does hop age affect α-acid levels?
α-Acid levels decrease as hops are oxidised over time. Using old or oxidised hops is not advisable.
What is the difference in hop utilisation between hop cones and hop pellets?
The α-acids in hop cones are trapped in vegetable material, requiring more vigorous boiling to extract them. Hop pellets have better utilisation than non-pre-isomerised hops.
How does the quantity of hops added influence hop utilisation?
The more material dissolved in water, the harder it becomes to dissolve additional material. Utilisation reduction with increased bitterness units is largely linear until wort saturation.
What role does the wort boiling system play in hop utilisation?
The vigour of the boil affects the rate of hop utilisation. Systems designed to maximise boil vigour provide superior hop utilisation.
How do hop α-acid levels affect their utilisation?
Hop varieties with higher α-acid levels have higher utilisation than those with lower levels. Lower utilisation from lower α-acid hops may be due to increased trub or difficulty in extracting α-acids.
What aspects of wort composition influence hop utilisation?
Wort pH, concentration of dissolved material (gravity), and level of trub formation all affect hop utilisation.
What is the effect of foaming on hop utilisation?
α-Acids and iso-α-acids can be lost in foam formed during the boil, as the foam sticks to the vessel surface.
