Lecture 4: Beer wine and Cider Flashcards
define beer
a solution of water, alcohol, and carbon dioxide that is flavored by carbohydrates, proteins, minerals and different aromatic compounds that it aquires from malt, hops and yeast
define brewing
its the combined process of preparing beverages from the infusion of grains that have undergone sprouting and subsequent fermentation of the sugary solution produced, by yeast - where a proportion of the carbohydrates is converted to ethanol and carbon dioxide
How can you know how alcoholic your final brew will be?
gravity density of the wort. It is a measure of calculating the amount of dissolved substances, largely sugars that will be converted into alcohol.
gravity can be expressed as ____. State how you would calculate.
Plato or original gravity. Using hydrometer or refractometer
OG=ratio of density relative to pure water.
Gravity reading of 1.040 results in what %ABV
4.0% (last significant digit)
Hydrometer
a weighted glass tube with a scale on the inside which stops at the relative density of the liquid being measured
Refractometer
measures the original gravity only. based on the refractive properties of sugar. alcohol distorts the reading.
is how much gravity is left after the fermentation is finished and can be used to calculate the alcohol content of the finished beer (or wine or cider)
Terminal gravity
How do you calculate %ABV
ABV= (OG-TG) * 131.25
What 4 measurements are important in beer. Provide small defintions for each.
- ABV = % ethanol in the finished beer
- Colour; measured using spectrophotometer. Tristimulus is used to assess the colour
- Bitterness; measured in BU which relates to ppm of isomerized alpha acid
- attenuation; measures how complete a fermentation is; (OG-TG)/OG
How can attenuation in beer be altered?
- sugar type
- mashing method
- composition of wort
- type of yeast
High attenuation signifies ____ beer while ____ apparent attenuation signifies ___ beer
dry beer, low and sweet beer
Malting
the process of allowing the grain to germinate (soak in water)
what is the purpose behind malting of barley?
to transform the food reserves in the grain into substrates that are convienent for fermenting in the brewery
Explain the process of malting
- moisture content of grains at the start should not be more than 20%
- to commence the malting of the grains, are soaked –> at 42-46% moisture germination starts
- intermittent periods of drainage when air is blow through
- CO2 is dispersed to promote germination
- air blown and grains are turned slowly in drums
Define Milling.
the process that breaks down malt into smaller fermentatable sizes
What are the two types of milling
wet and dry
Define Mashing
process where ground malt is mixed with brewing water such that fermentable extract is produced that will suppport the growth of yeast.
What is produced after mashing
wort
what is added to the wort to iniate fermentation?
Saccharomyces cerevisae
What is the issue with adding too much or too little Sc to the wort?
too little = slow initial fermentation
too much = competition between yeasts and poor growth
yeast stress in beer fermentation can lead to ____
fusel alcohol production
yeasts can grow under what conditions?
- aerobically or anaerobically
- anaerobic conditions are essential for the production of alcohol by yeast, sugar up-take is diminished in the prescne of oxygen
why doesnt fermentation proceed for as long as possible in anaerobic conditions and as long as hexoses are available
- budding requires cell wall synthesis which cant happen under anaerobic conditions
- ethanol at high levels becomes toxic to yeasts
- when fermentation slows the yeast cells floculate and sediment out
what happens during the exponential growth phase
yeast density can increase 4-6 fold. at this stage yeast are at their highest level of utilizing sugars and producing ethanol + co2.
how are esters formed in beer? what kind of taste do they impart to the beer?
esterification of ethanol. they impart a fruity taste
during the exponential growth phase, a considerable amount of heat is producd and cooling is needed to keep the temp down to 20-22 deg C. What can happen if this is not respected?
high fusel alcohol will be produced –> off flavors
Post fermentation: what are 5 considerations during conditioning? (FC,C,S,C,MO)
- flavour maturation
- clarification
- stabilization
- carbonation
- minimize oxygen
Flavour maturation
yeast remove undesirable compounds like acetaldehyde, diacetyl and H2S. purging
Clarification
settle so that yeasts can be removed by sedimentation
What is done to prevent non biological precipitate to form during storage?
stabilizers are added to remove precursors of this precipitate
Oxygen is ___ in green beer.
low
T or F: Pathogens are an issue with brewing
F
T or F: wort and beer are prone to spoilage microorganisms. why or why not
T; provide nutrient rich, oxygenated environment
why isnt beer a good media for bacteria?
low ph, ethanol concentration and largely devoid of nutrients
T or F: spores can make it into canned beer and germinate
F; they will not likely germinate
cause turbidity, acid notes and unwanted flavours in Beer
LAB; pediococcus and lactobacillus
Effect of zymonas in beer
infects cask-conditioned beers resulting in cider sickness, where there is secondary fermentation with much frothing, a loss of sweetness and off-odours due to hydrogen sulfide and acetaldehyde production
effect of megasphaera
produces hydrogen sulfide in beer producing rotten egg smell. cannot tolerate more than 2.8% abv so only effects low alcohol beers
effect of pectinatus in beer?
rapidly converts finished beer into propionic acid, acetic acid, succinic acid, lactic acid and hydrogen sulfide given beer rotten egg smell
aerobic beer spoilers mainly include
AAB (acetobacter and gluconobacter)
oxidize ethanol into acetic acid. This results in a raft; surface growth in the beer that will lead to generalize turbidity and ropiness quality.
What is added to most fruit wines
sugar cane
what are superior wines?
They are vintage wines and cannot be blended with other wines. non vintage wines are generally blended so that wine makers can still have an acceptable product even in bad years
Explain the simple/general wine making process
sampling –> harvest –> crushing –> fermentation –> blending –> stabilization –> aging –> filtration — bottling
Explain the process for making red wine
- crushing + adding sulfur dioxide –> obtain juice and skins
- innoculate with yeast
- maceration and partial fermentation
- pressing
- completion of alcoholic fermentation followed by racking off yeast lees
- wine –> malolactic fermentation
- aging in oak barrels
- finding, clarification and packaging
Explain the process for making white wine
- crushing –> addition of sulfur dioxide
- pre-fermentation treatments settling
- pressing (removal of skins)
- juice
- inoculation with yeasts optional
- racking off yeast lees
- malolactic fermentation oak barrels
- aging
- fining, clarification and packaging
explain the fermentation (phases) involved in wine fermentation
lag phase –> few hours
short growth phase
long stationary phase during which most of the alcohol is converted to sugar
what is malolactic fermentation?
- its not important in all wines but it helps in the taste development. during this process L-malic acid is converted is converted into L-lactic acid and carbondioxide. Several LAB can carryout this reaction but commercial strains of oenococcus onesie are generally used
what are the management conditions used to make sure brewing Sc dominate the fermentation and other yeasts are removed in wine
- sulfiting
- anerobic conditions
- rapid and complete exhaustion of sugars
what is the purpose of adding sulfur dioxide to wine?
kill natural species and allow wine specific Sc (which is resistant to sulfur dioxide_ to carry out fermentation.
It can inhibit growth of microbes by rupturing disulfide bridges in proteins and reactions with cofactores. It can also deaminate cytosine to uracil which increases the likelihood of fatal mutations.
what leads to sulfite resistance in wine yeast?
reciprocal translocation between chromosome 8-16.
translocation results in dominant allele sulfite pump –> SSU!-R1 which is expressed at high level and leads to sulfite resistance
what is the function of campden tablets?
- sterilize wine –> sodium metabisulfite
- eliminate free chlorine
- antioxidizing agent when transferring wine between containers (sodium metabisulfite traps oxygen and prevents harm)
what is the function of potassium sorbate in wine?
halt yeast and preserve wine
what is a stuck fermentation?
problem during wine fermentatiwhere there in premature cessation of alcohol production in the fermentation
causes of stuck fermentations?
- nutrient deficiency
- inhibitory substances
- killer toxins
- low ph
- pesticides
- temp (too low or too high)
why compound is produced by LAB in wine which may indicate signs of spoilage at high concentrations?
diacetyl
what are 3 signs that wine has been spoiled?
- mold growth
- slime and ripiness
- taste like vinegar (AAB)
what is added to cider to prevent contamination with AAB?
sulfur dioxide
what is malt vinegar
is made from malting barley which results in the conversion of starch to maltose. the maltose is converted to ale and then turned into vinegar which is then aged. it is typically light brown in color
what is cider vinegar
- made from apple juice through a double fermentation with alcohol and acetic acid fermentation in the same barrel by naturally occuring yeast and acetic acid bacteria
process of making traditional balsamic vinegar?
is made only in modena italy with cooked grape; 3 step process
- conversion of sugars to ethanol by yeast
- oxidation of acetic acid by AAB
- 12 years of aging in a barrel
- final product = dense, dark brown and sweet/sour taste
rice vinegar
made from fermented rice wine
produced via static surface fermentation
acidity = 10%
Acetobacteria
3 types of rice wine vinegar (KKK)
- komesu
- kurosu
- kasuzu
