5- beer and wine Flashcards
What is attenuation?
is a way to measure how complete a fermentation process is.
what is a hydrometer and what does it measure?
: A weighted glass tube with a scale on the inside which stops at the relative density of the liquid being measures
What is a refractometer and what does it measure?
Measures the original gravity only, based on the refractive properties of sugar. Alcohol distorts the readings
High apparent attenuation signifies a ___ beer, while low apparent attenuation signify a ____ beer.
dry sweet
what is malting ?
Is the process of allowing the grain to germinate (usually by soaking them in water)
What is miling and what is the goal of this step?
Milling is a process that breaks down the malt into smaller more fermentable sizes
What are the two types of milling?
Wet milling Dry milling
what is mashing and what is the goal of this step?
Mashing is the process where ground malt is mixed with brewing water, such that a fermentable extract is produced that will support the growth of yeast
After mashing, the malt in name ____
wort
What are the three types of hops?
- aroma hops 2. alpha hops 3. dual purpose hops
Temperature is also important. If the wort is more than 5C cooler than the yeast a ____ will result and this will result in a _____
‘cold-shock’ prolonged lag period
how long is a normal lag phase?
6-15 hours
what is the result of adding too little yeast in the fermentation of beer?
slow initial femrentation
what is the result of adding too much yeast in the fermentation of beer?
too much competition between yeast and poorer growth and production of fusel alcohol
what is fusel alcohol ?
alcohol with more than two carbons and that don’t taste good.
T or F : Yeast can grow aerobically or anaerobically
true, but the anaerobic conditions are essential for the production of alcohol by yeast.
why do you need to control the temperature when the yeast are converting sugars to alcohol?
If the temperature gets too high higher alcohols (propanol, iso-amyl alcohol, or iso-butyl alcohol) will be produced, and this will impart off-flavours
Exponential growth lasts for ____hours, after which growth is decelerated before the cells reach stationary phase
48-60 hr
Immediately after the fermentation beer is called ____ and must still be conditioned before packaging
‘green beer’
What are the five steps of conditioning?
- flavour maturation 2. Clarification 3. Stabilization 4. Carbonation 5. Minimize O2
T or F : Pathogens are not an issue with brewing
t
In wine fermentation most of the sugars are consumed within ___ days
2
wine fermentation : Dissolved CO2 peak around _____ there shouldn’t be no dissolved CO2 when you finish your fermentation.
40 hours
why is wine yeast more resistant to sulfite?
reciprocal translocation between chromosome 8 and 16 This translocation resulted in a dominant allele of the sulfite pump
T or F : Campden Tablets can eliminate free chlorine from water solutions
t
What is a stuck fermentation?
when there is a premature cessation of alcohol production in fermentation
name the cause of stuck fermentations (6)
- Nutrient deficiency (nitrogen, vitamins, or minerals) 2. Inhibitory Substances (acetic acid, lactic acid, excessive sulfur dioxide) 3. Killer toxins (toxins produced by yeasts against other yeasts) ph to low (<3) 4. Pesticides remain on grapes from field 5. Temperature (too low at the beginning, or too high during the ferment)
Is LAB good or bad for wine fermentations?
LAB have an interesting relationship with wine. The growth of some LAB in wine produces desirable traits (malolactic fermentation), while the growth of some species just causes spoilage.
What is the compound produced by LAB that can have a buttery aroma at low concentration but a nutty aroma (spoilage) at high concentration
diacetyl compound
T or F : only heterofermentative LAB can produce diacetyl
false, also the homofermentative
what is gravity?
density of the wort, or a way of calculating the amount of dissolved substances, largely sugars that will be converted into alcohol (it is your first look at how alcoholic your final brew will be)
how can you estimate the final ABV from the original gravity?
you take the significant digit. for example 1.040 will have 4% ABV.
what are the tools used to measure the gravity?
hydrometer and refractometer
What is the terminal gravity?
it is how much gravity is left after the fermentation is finished
what is the problem of the gravity measured by the refractometer
the alcohol can distort the light
what compound causes the bitterness in alcohol?
the isomerized alpha acid
What is the bitterness?
Is the level of bitterness you taste when you drink beer. It is measured in bitterness units (BU) which relates to ppm isomerized alpha acid
What is the ABV ?
the percentage of ethanol in the finished beer
What is the formula of the ABV
OG - TG * 131.25
What is the formula of the attenuation ?
OG -TG / OG
what is the disaccharide mostly present in the wort before fermentation
maltose
What will happen if the fermentation is exposed to oxygen?
the sugar up-take is diminished
why is there still sugar that can be left after the alcoholic fermentation and why are the yeast not fermenting all the sugar into alcohol?
because in the absence of oxygen, there is no budding and so no growth of yeasts and eventually they will die because of the too high level of ethanol.
What is flavour maturation?
The yeast remove undesirable compounds such as H2S, acetaldehyde, and diacetyl. This process is called purging
what is purging?
the removl al of the undersirable compounds like H2S, acetaldehyde and diacetyl during the maturation by the yeast
What is clarification ?
the sedimentation of the yeasts in the green beer
What is the stabilization step?
To prevent a non-biological precipitate to form during storage. Stabilizers are added to remove the precursors of this precipitate
What is the carbonation step?
adding CO2 to the beer at low temperature because CO2 is more soluble at lower temp
how do they minimize the oxygen in green beer
antioxidants
What are the anaerobic beer spoilers?
LAB like pediococcus and lactobacillus
___ Infects cask-conditioned beers resulting in ‘cider sickness’ where there is a secondary fermentation with much frothing, a loss of sweetness, and off-odours due to hydrogen sulfide and acetaldehyde production. Due to failure in the cask-washing regime.
zymomonas
Produces hydrogen sulfide in beer producing “rotten egg” smell. Cannot tolerate more than 2.8% ABV so only affects low alcohol beers.
megasphaera
rapidly converts finished beer into propionic acid, acetic acid, succinic acid, lactic acid, and hydrogen sulfide giving the beer a “rotten egg” smell
pectinatus
What are the primarly aerobic beer spoilers
are primarily AAB (Acetobacter and Gluconobacter)
What are the process that happens in the wine fermentation
during wine fermentation, in which phase most of the sugar are converted into ethanol
in the stationnary phase
during malolactic fermentation, the L-malic i converted to ___and ___
L-lactic acid and CO2
what are the commercial strains that are used for the wine malolactic fermentation
Oenococcus onesie
how does the sulfure dioxide inhibits the growth of microbes?
SO2 by rupturing the disulfide bridges in proteins and between co-factors and enzymes.
It can also deaminate cytosine to uracil and increase the likelyhood of fatal mutation
What is the purpose of the campden crush tablet?
can sterilize
eliminate the chlorine
antioxidant
What is a stuck fermentation?
•when there is a premature cessation of alcohol production in the fermentation
What are the causes of stuck fermentation?
- Nutrient deficiency (nitrogen, vitamins, or minerals)
- Inhibitory Substances (acetic acid, lactic acid, excessive sulfur dioxide)
- Killer toxins (toxins produced by yeasts against other yeasts)
- ph to low (<3)
- Pesticides remain on grapes from field
- Temperature (too low at the beginning, or too high during the ferment)
•There are three types of rice wine vinegar :
- Komesu is produced from polished rice grains, is pale amber in color, and is sued for sushi and seaweed salad
- Kurosu is produced from unpolished rice grains, is dark black and is used as a table condiment or a healthy drink
- Kasuzu is produced from sake lees, 210 different acetic acid bacteria were isolated from a traditional fermentation
What is the dominant acetic acid bacteria in rice vinegar?
Acetobacteria
