Beer, Wine, Cider and Vinegar

Question 1

Give a definition to beer and brewing

Answer 1

Beer: Is a solution of water, alcohol and carbon dioxide that is flavored by carbohydrates, proteins, minerals, and different aromatic compounds that it acquires from malt, hops, and yeast.

Brewing: Is 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 carbohydrate is converted to ethanol and carbon dioxide

Question 2

What is wort?

Answer 2

Wort (/ˈwɜːrt/) is the liquid extracted from the mashing process during the brewing of beer or whisky. Wort contains the sugars, the most important being maltose and maltotriose,[1] that will be fermented by the brewing yeast to produce alcohol.

Question 3

What is gravity density of the wort? How it is expressed? How you can calculate alcohol content out of it?

Answer 3

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)

Gravity can be expressed in degrees Plato or Original Gravity (OG) (aka Starting Gravity SG)

Original Gravity is expressed as a ratio of density relative to pure water.

Example 1.040 wort is 1.040 times as dense as pure water

Although, a number of variables will affect the final alcohol content the general rule of thumb is that the significant digit is an estimation of the final alcohol content

Example 1.040 = 4.0% Alcohol By Volume (ABV)

Question 4

What is Hydrometer?

What is refractometer?

What is terminal gravity?

How to calculate ABV

Answer 4

Gravity is normally calculated using either a hydrometer or a refractometer.

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 readings

Terminal Gravity 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)

ABV = (OG - TG) * 131.25

Question 5

How the color of the beer is measured?

How the bitterness is measured and on what does it depend?

Answer 5

Light/ dark measurements are acquired by measuring the beer in a spectrophotometer. Tristimulus (red/green/blue system) are used to assess colour.

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

Question 6

What is attenuation? How it is measured? What is apparent attenuation? How it can be altered? What does low or high attenuation means

Answer 6

Attenuation is a way to measure how complete a fermentation process is.

Apparent Attenuation=(OG-TG)/OG

Attenuation can be altered by sugar type, mashing method, composition of the wort, or type of yeast.

High apparent attenuation signifies a dry beer,(because all the sugar has been converted to alcohol) while low apparent attenuation signify a sweet beer

Question 7

What is malting? Why?

Answer 7

Malting: Is the process of allowing the grain to germinate (usually by soaking them in water)

In theory you could produce beer from barley, wheat, or oats (the ancient brewers did), but it quickly became apparent that barley was the easiest to work with in this process.

• The aim of malting is to transform the food reserves in the grain into substrates that are convenient for fermenting in the brewery
• It is a controlled germination process that is not the same as natural sprouting of the seeds in the filed would be (all of the energy would go into seedling growth)

Need to stop malting before rooting, so the energy is not wasted there

Question 8

How malting is done in detail done?

Answer 8

• The moisture content of the grains at the start and during storage should be no higher than 20%
• To commence the malting the grains are soaked in water to start germination (happens when the grains are at 42-46% moisture)
• The water is not left on the grains there are intermittent periods of drainage when air is blown though
• CO2 is dispersed and this promotes germination
• Air is blown through the germinating grain bed, and grains are turned slowing in drums or by automated turning arms

CO2 promotes germination

Question 9

What is milling? Why it is done? What are the two types of mil? What is done after it?

Answer 9

• Milling is a process that breaks down the malt into smaller more fermentable sizes, also breaks own particles in a particular size helps to control the run-off speed at subsequent steps
• There are two types of mill:

Wet milling

Dry milling

•After milling the malt grist is classified via a sieve analysis

Question 10

What is mashing? How it is done? What do you get in the end?

Answer 10

• 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
• The temperature of the brewing water is important, and the ideal temperature will depend on the type of beer being made. Temperature is important from batch to batch, to result in the same taste and alcohol content (make different amount of sugar to dissolve)
• The composition of the water is also important for different beer styles
• It generally takes about 3 hours
• After mashing wort is produced

Question 11

Where hops originated? What are the types of hops? Why they are used? when they are added

Answer 11

• Hops was first cultivated in Bavaria (or possibly Scandinavia)
• Hops can be used fresh, dried, in pellets, or in the form of extracts
• Hops come in three varieties according to their function in the brew house

a) Aroma Hops (smell)
b) Alpha Hops (flavour)
c) Dual Purpose Hops (both)

• Wort is boiled with hops for a bit over an hour before being cooled down and yeast is added
• Hops add a bitterness to the beer, but can also add a floral taste or fruity or citrusy flavours or aromas

Question 12

What is the approximate composition of beer? What are top 6 sugars present there

Answer 12

Question 13

What is fusel alcohol? Why they are relevant to beer?

Answer 13

• yeast stress can lead to undesirable fusel alcohol production
• Fusel alcohols refer to alcohols that contain more than two carbons. Ethanol is a two carbon atom molecule.

Fusel alcohols cause hangover

Question 14

What is the principal microorganism responsible for brewing? When it is added? at what conditions? what is the lag time?

Answer 14

• Saccharomyces cerevisiae is the yeast of choice, and there are specific brewers yeast that are used in beer making
• Sc is added to the wort in a very specific amount, adding too little leads to very slow initial fermentations, adding to much leads to competition between yeast and poorer growth
• Temperature is also important. If the wort is more than 5C cooler than the yeast ‘cold-shock’ will result and this will result in a prolonged lag period
• A normal lag phase is 6-15 hours
• For industrial fermentations, it is important that the microbe starts growing as quickly as possible, so that other microorganisms are discouraged

Question 15

At what air conditions yeast can grow? What conditions are needed during beer making? Does the reaction is endless? What are the limitations

Answer 15

• Yeast can grow aerobically or anaerobically
• Anaerobic conditions are essential for the production of alcohol by yeast, sugar up-take is diminished in the presence of oxygen
• Theoretically, then fermentation should proceed for as long as anaerobic conditions are available and there are hexoses in the media, this does not happen in practice
• Budding requires cell wall synthesis which cannot happen in anaerobic conditions, therefore eventually growth must cease
• Eventually the level of ethanol present becomes toxic to yeast
• When fermentation slows the yeast cells flocculate and sediment out (which causes growth to slow even further)

Question 16

Draw an approximate chart of how sugars are utilized by yeast during beer fermentation, what are four stages of growth? What max temperature during brewing? can you avoid fusel alcohols?

Answer 16

Fusel alcohol will be produced any ways, but want to minimize it

You do not want to go higher than 20C

• The lag phase is followed by a short phase of exponential growth
• During the exponential growth phase the yeast density can increase by four- to six-fold
• During exponential growth yeast are at their highest level of utilizing sugars and producing ethanol and carbon dioxide
• Exponential growth lasts for 48-60 hours, after which growth is decelerated before the cells reach stationary phase

Question 17

Why do we need to control the temperature of brewing? What molecules impart fruity flavor in the beer and how it is produced

Answer 17

• A considerable amount of heat is also produced, and cooling is usually needed to keep the temperature down to 20-22C
• If the temperature gets too high higher (fusel) alcohols (propanol, iso-amyl alcohol, or iso-butyl alcohol) will be produced, and this will impart off-flavours
• Esters cause a fruity flavor, and produced during fermentation. They can create a taste and aroma like pears, roses, bananas or other light fruits. In very high concentration esters can create a solvent-like flavor. Esters are formed in beer by the “esterification” of ethanol.

Question 18

What is happening when the final gravity is reached? How it is called?

Answer 18

• Once a beer has been fermented down to its final gravity, it is chilled to 9-11C
• Immediately after the fermentation beer is called ‘green beer’ and must still be conditioned before packaging

Question 19

What are five considerations during conditioning?

Answer 19

1. Flavour Maturation: The yeast remove undesirable compounds such as H2S, acetaldehyde, and diacetyl. This process is called purging.
2. Clarification: Green beer can contain 1 x 10^7 cells per mL(will block any filter). This would block your filter during filtration. Thus, the beer is allowed to settle so that yeast can be removed by sedimentation.
3. Stabilization: To prevent a non-biological precipitate to form during storage. Stabilizers are added to remove the precursors of this precipitate.
4. Carbonation: CO2 is more soluble at reduced temperatures, so a top pressure of CO2 is maintained in conditioning tanks.
5. Minimize Oxygen: Oxygen is low in green beer. If O2 finds its way back in, antioxidants are added

Question 20

Are pathogens an issue in brewing? then what should we be aware of? how to contain it?

Answer 20

• Pathogens are not an issue with brewing. Any pathogen are not resistant to even 4-10% ALCOHOL
• Both wort and beer are prone to spoilage organisms (particularly wort since it provides a nutrient rich, oxygenated environment)
• Process control is the best way to prevent contamination (mash should pass straight into copper for boiling, which sterilizes it)
• Beer isn’t a good growth media for bacteria because it has a low pH, a good ethanol concentration, and is largely devoid of nutrients
• Certain spores can survive the whole process and make it into canned beer, but they will likely not germinate

Question 21

Who are included in potential anaerobic beer spoilers?

Aerobic?

Answer 21

Aerobic: LAB (Pediococcus and Lactobacillus), Zymomonas,Megasphaera, Pectinatus

Aerobic:AAB (Acetobacter and Gluconobacter)

Question 22

How LAb, zymomonas, megasphaera and pectinatus can spoil beer

Answer 22

Anaerobic Beer Spoilers can include LAB (Pediococcus and Lactobacillus) which cause turbidity, acid notes, and unwanted flavours

Zymomonas: 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.

Megasphaera: Produces hydrogen sulfide in beer producing “rotten egg” smell. Cannot tolerate more than 2.8% ABV so only affects low alcohol beers.

Pectinatus rapidly converts finished beer into propionic acid, acetic acid, succinic acid, lactic acid, and hydrogen sulfide giving the beer a “rotten egg” smell

Question 23

How aerobic beer spoilers can harm beer

Answer 23

Aerobic Beer Spoilers are primarily AAB (Acetobacter and Gluconobacter) they will result in the oxidization of ethanol to acetic acid. There will be a “raft” of surface growth in the beer that will lead to generalize turbidity, and the infected beer may have a “ropiness” quality

Question 24

What is wine? Other names of wine alterations? How the climate is responsible for wine quality and what are vintages vs regular wine

Answer 24

• Wine is an alcoholic beverage made from grapes fermented without the addition of sugars, acids, enzymes, water, or other nutrients (Grapes is the only fruit that has enough sugars for fermentation without addition of sugar)
• Different varieties of grapes and strains of yeast will produce different styles of wines
• Variation is a result of complex interactions
• Wines not made from grapes can include sake (rice wine), mead (honey), or fruit wines (plum, cherry, elderberry, strawberry)
• Cane sugar must be added to most fruit wines
• Climate has a huge impact on the quality of the wine, and the same vineyard can produce very different wines from year to year
• Superior wines are known as vintages and cannot be blended with other wines
• Otherwise non-vintage wines are generally blended so that wine-makers can still have an acceptable product even in bad years

Question 25

What are the main steps in wine making process?X

Answer 25

Question 26

What is the difference between white and red wines except for grape types

Answer 26

Red wines - the skin is not removed, white wines-pre-fermented and the skin is removed

Question 27

What is the most abundant sugar in grape must?

Answer 27

Glucose and fructose

Question 28

What are the main phases in wine fermentation? What is the most desirable outcome?

Answer 28

• Wine fermentation typically comprises a lag phase which lasts a few hours, a short growth phase (24-36 hr), and a long stationary phase during which most of the sugar is converted into alcohol
• During the stationary phase the yeast activity continually decreases, although viability remains around 90% until the sugar is depleted
• The most desirable outcome is complete degradation of sugars into ethanol, and CO2 to provide metabolites and aroma compounds that positively impact the sensory balance of the wine

Question 29

What is malolactic fermentation? in what types of wine it is important, and what type of microorganisms is used for it?

Answer 29

• Malolactic fermentation is important to some wines (Chardonnay), but not all wines
• Malolactic fermentation is also important in the taste development of wine
• During this process L-malic acid is converted into L-lactic acid and CO2
• Several LAB can carryout this reaction but commercial strains of Oenococcus onesie are generally used

Question 30

How microorganisms end up in wine? how they are selected, what type of organism does the fermentation

Answer 30

• At the start of the wine making process grapes are crushed and the grape must contains a yeast flora similar in numbers and composition of the grapes pre-harvest
• Several genera and species of yeast are present
• Sound management conditions are required to make sure that brewing Sc dominate the fermentation, and other yeast are removed:
• Sulfiting
• Anaerobic conditions (many spoilage organisms rely on oxidative metabolism)
• Rapid and complete exhaustion of sugars
• Sulfur dioxide is added to kill natural species and allow wine specific Sc (which are resistant to sulfur dioxide) to carry out the fermentation, but despite the addition of sulfur dioxide several different species of yeast participate in the process

Question 31

How sulfur dioxide is used in food and what is its reaction principle

Answer 31

• Sulfur dioxide is widely used in the food industry as well as in wine making for its antioxidative and antimicrobial properties
• Once dissolved in water, sulfur dioxide exists in equilibrium between its molecular species

SO2 H2O readily enters the cell and undergoes rapid pH-driven dissociation to bisulfite and sulfite

SO2 can inhibit the growth of microbes by rupturing disulfide bridges in proteins, and reactions with cofactors. It can also deaminate cytosine to uracil which increases the likelihood of fatal mutations

Question 32

How wine yeasts we made sulfite resistant?

Answer 32

• In wine yeast, but in no other yeast, there is a reciprocal translocation between chromosome 8 and 16
• This translocation resulted in a dominant allele of the sulfite pump, SSU1-R1, which is expressed at much higher levels than SSU1 and confers a very high level of sulfite resistance
• Other translocations that confer higher sulfite resistance have also been found
• The first translocation (chromosome 8 and 16) was mediated through homology between the promoters ECM34 and SSU1
• Several 76bp repeats were found in the promoters of non-recombinant ECM34 and recombinant SSU1-R1
• There is a direct relationship between the number of repeats and sulfite tolerance
• There is a second translocation resulting in SSU1-R2 that is increased in expression during the first hours of a wine fermentation

Question 33

What is Campden tablet, why it used, principle of action

Answer 33

•Campden Tablets are used to sterilize wine, cider, and beer by amateur brewers, since it allows the easy measurement of very small quantities of sodium metabisulfite

•

• Campden Tablets can also eliminate free chlorine from water solutions (i.e. if you use water from a municipal source)
• Campden Tablets are also used as an antioxidizing agent when transferring wine between containers. The sodium metabisulfite in the Campden tablets traps the oxygen that enters the wine, and prevent it from doing any harm
• Potassium sorbate must be used to halt the yeast and preserve the wine

Question 34

What is a stuck fermentation and why it is caused?

Answer 34

• A significant problem that can arise during wine fermentation can be a stuck fermentation, which is when there is a premature cessation of alcohol production in the fermentation
• A stuck fermentation can be caused by any of the following:
• 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 too low (<3)
• Pesticides remain on grapes from field
• Temperature (too low at the beginning, or too high during the ferment)

Question 35

What are the spoilage bacteria for wines

Answer 35

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.

One of the most important odor compounds produced by LAB is diacetyl, which has a “buttery” aroma that at low concentrations is described positively as “nutty” but at high concentrations is considered spoilage.

Both heterofermentative and homofermentative LAB can produce diacetyl

AAB results in the oxidation of ethanol to acetic acid, and produces odors and off flavors for wine

Question 36

Why cider is prone to AAB, and how to cope with it

Answer 36

Cider is particularly prone to contamination with acetic acid bacteria (as apples are covered in them) so it is important to add sulfur dioxide at the initial fermentation step,

Question 37

What is malt vinegar

what is cider vinegar

Answer 37

Malt vinegar

• 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 to vinegar, which is then aged
• It is typically light-brown in color

Cider vinegar

Cider vinegar is made with apple juice through a double fermentation with alcohol and acetic acid fermentation in the same barrel by naturally occurring yeasts and acetic acid bacteria.

Question 38

How traditional balsamic vinegar is made

Answer 38

• Traditional balsamic vinegar is made only in Modena, Italy with cooked grape must through a three-step process
• Conversion of sugars to ethanol by yeast
• Oxidation of acetic acid by acetic acid bacteria
• At least 12-years of aging by sequential transfer from a larger barrel into a smaller barrel
• The final product is highly dense dark-brown in color and has a sweet and sour taste, and is complex in flavor

Question 39

What is rice vinegar, final acidity, dominant AAB, other types of rice wine vinegar

Answer 39

• Rice vinegar is made from fermented rice wine (sake)
• Rice vinegar is produced via a static surface fermentation
• The final acidity is usually about 10%
• The dominant acetic acid bacteria are usually Acetobacteria
• There are three types of rice wine vinegar:
• Komesu is produced from polished rice grains, is pale amber in color, and is used 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