Activation of Foam Positive Proteins Flashcards
(18 cards)
What is beer foam composed of?
Bubbles of gas surrounded by beer
The foam’s stability is influenced by amphiphilic substances in beer.
What are the two proteins identified as particularly good at stabilizing beer foam?
- Protein Z
- Lipid transfer protein one (LTP1)
These proteins help maintain the structure of foam in beer.
What percentage of non-dialysable protein does protein Z account for in beer?
10-25%
Protein Z is the first protein identified as foam positive.
What is the molecular weight of protein Z?
Around 45 kDa
This characteristic is important for its function in beer.
What reaction is thought to glycate protein Z?
Maillard reaction
Glycation involves the attachment of carbohydrates to the protein.
How does glycosylated protein Z compare to non-glycosylated protein Z in terms of foam promotion?
Glycosylated protein Z is much more effective at promoting foam
This enhancement is crucial for beer foam stability.
What is the role of LTP1 in barley?
Transfers lipids and protects barley from microbial pathogens
This function is essential for the barley’s health.
What happens to LTP1 when it is denatured during wort boiling?
It becomes more hydrophobic
This change allows it to associate with gas in foam bubbles.
What is the effect of boiling wort under pressure at 103°C on foam stability?
Results in poor foam stability
This highlights the importance of temperature control during boiling.
How does a 102°C boil compare to a 96°C boil in terms of foam stability?
102°C boil produced poorer foam stability than 96°C boil
The level of lipids in the beer influences this outcome.
What is the purpose of adding antifoam during boiling?
To minimize foam production in the kettle
This prevents the loss of compounds that support foam and reduces the risk of overflow.
What is the most popular antifoam used in brewing?
Dimethylpolysiloxane
It is added at a rate of a few mg/L before the boil.
What is trub formation in the brewing process?
Protein coagulation and flocculation
Trub formation is influenced by temperature, time, and vigour.
What is the mechanism behind bitterness extraction during boiling?
α-Acid extraction and isomerisation
This process depends on temperature, vigour, and time.
What processes contribute to flavour and colour development in beer?
- Maillard reaction
- Strecker degradation
- Caramelisation
- Hop aroma extraction
These reactions are affected by temperature, time, and pH.
What is the role of denaturation of enzymes during boiling?
Stabilisation
It also contributes to sterilisation and trub removal.
What compounds are removed during the volatile removal process in brewing?
- DMS
- Worty/grainy aldehydes
- Maillard products
This process is influenced by vigour, time, and temperature.
What happens during concentration in the boiling process?
Evaporation of water
This process is also dependent on vigour, time, and temperature.
