Maturation/Clarification Flashcards
What is the reaction to form acetaldehyde?
What causes acetaldehyde in the final beer?
CH3CHO
Pyruvate is decarboxylated to acetaldehyde which is the precursor to ethanol
Acetaldehyde in the final beer is caused by early flocculation of yeast not allowing the acetaldehyde to convert to ethanol
What are the 2 Vicincal Diketones?
What causes Vicinal Diketones in the final beer?
Diacetyl (flavor threshold - 0.1 mg/L)
Pentanedione (flavor threshold - 0.9 mg/L)
VDKs are produced during fermentation but will be consumed as long as yeast does not floccuate early
What causes Hydrogen Sulfide in the final beer?
If the fermentation is not vigorous enough to purge off all volatiles
What are the 3 reasons for Cold Conditioning?
- Precipitation of undesirable materials
- Preparing the beer for filtration
- Preparing the beer for carbonation
What is the typical Cold Conditioning temp?
-1°C (30°F)
What factors affect the freezing point of beer?
Each 1% increase in alcohol content lowers the FP by 0.42°C
Each 1°Plato in gravity lowers the FP by 0.04°C
FP = -[0.42 x A + 0.04 x E + 0.02]
What is the flow requirement of a Plate HX?
Turbulent flow > 2 m/s
Issues with HXs
Requires maintenance to prevent holes where glycol can contaminate the beer
Requires cleaning to prevent microbiology forming in beer
Carbonation Levels of Various Beer
What is the typical level of residual air in CO2?
Even 0.05% residual air in CO2 can add 200 ppb O2 to the beer when it is force carbonated
This is enough to reduce the flavor stability of the beer
Ideally you want <20 ppb O2 in the beer
What is the effect of temperature on carbonation?
The colder the better!
What is the effect of pressure on carbonation?
The higher the better!
Follows Henry’s Law
What is the effect of pH on carbonation?
Has no effect when working in the pH range of beer (4-5)
What is the most common method for carbonation of beer?
Inject CO2 inthe the liquid in-line or in a pressure vessel. This method greatly increases the surface area for the interaction of gas and liquid
What are the 4 methods for producing deaerated water?
- Using a hydrophobic membrane system
- Vacuum deaeration
- Gas stripping
- Packed bed gas stripping
What are the 3 advantages of a Centrifuge?
- Rapid lowering of the amount of suspended solids with little damage to the soluble components
- Low waste
- Low beer losses
What are the 5 disadvantages of a Centrifuge?
- Potential for oxygen pickup
- High running costs - powerful motor
- Noisy
- High shear forces can cause unraveling of B-glucans
- Produces temperature through friction
Darcy’s Law Equation
Rate of Liquid Flow = pressure x bed permeability x filter area
bed depth x beer viscosity
Typical particle sizes in green beer
3 types of beer filter
- Powder
- Sheet
- Membrane
What are the 4 important parameters to monitor in a filter?
- Flow rate
- Pressure
- Temperature
- Clarity
Rate of filtration depends on what 2 factors?
- Clarity - how many particles need to be removed
- Viscosity (pentosans and arabinoxylans will affect beer viscosity more than B-glucans)
Powder Filtration
What is Diatomaceous Earth?
Filter aid, naturally occurring sedimentary rock, considered the “gold standard” of filter aids
What is Perlite?
A filter aid made from volcanic material
What are 3 types of powder filter?
- Plate and frame filter
- Candle filter
- Leaf filter
What is the benefit of crossflow filtration?
- Does not build up with material on the membrane so it filters faster
- Does not require a filter aid
Sheet Filtration
