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Brewing > Brewing water > Flashcards

Brewing water Flashcards

1
Q

What are the three principal sources of fresh water?

A

Precipitation, surface water, groundwater.

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2
Q

What is the specificity of precipitation water (rainfall and snow)?

A

Low pH, low organic matter, low dissolved minerals.

Less than 20ppm of dissolved solids.

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3
Q

What is the specificity of surface water (rivers and lakes)?

A

More organic matter (plankton and debris), moderate concentration of dissolved minerals and alkalinity.

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4
Q

What is the specificity of groundwater?

A

Low organic matter, high dissolved minerals, susceptible to contamination (industry, agriculture).

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5
Q

What is pH?

A

It is the measure of hydrogen ion concentration, or the acidity of a solution.

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6
Q

What is a buffer?

A

It’s a chemical compound in a solution that reacts (dissociates/associates) to the addition of another chemical to effectively resist changes in pH of the solution.

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7
Q

What is the primary buffer in brewing buffer?

A

Alkalinity.

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8
Q

What is the composition of standard dry air?

A
  • 78.1% nitrogen
  • 20.95% oxygen
  • 0.9% argon
  • 0.04% of other gases (CO2 mainly, ozone, krypton, helium…)
  • 1-4% moisture
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9
Q

What is usually the major determinant of water acidity and its resulting pH?

A

Carbon dioxide, which lowers the pH from 7 to typically 5.5.

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10
Q

What is the main cause for elevation of the ionic content of precipitation water?

A

Contamination from heavily industrialized areas.

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11
Q

What is the typical pH range of surface water?

A

Between 6 to 8.

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12
Q

What off-flavor is created by the chlorination of decaying plant material?

A

TCA (2,4,6-Trichloroanisole): earthy, mildew, wet dog.

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13
Q

What is the name of the semi-permeable layer the groundwater flows through?

A

An aquifer.

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14
Q

What is the average age of groundwater?

A

250 years.

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15
Q

What is the typical pH range of groundwater?

A

Between 6.5 to 8.5.

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16
Q

What is the specificity of the water of Burton-Upon-Trent, UK?

A

It’s the most famous hard water region of the brewing world: high hardness from gypsum and high alkalinity from the carbonate rock.

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17
Q

What measure is taken when water contains objectionable concentrations of iron or manganese?

A

The water is aerated or ozonated to oxidize soluble forms of these metals into their insoluble forms. The metals are then filtered from the water.
Water can also be filtrated through greensand to oxidize and trap those ions.

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18
Q

What measure is taken when water is excessively hard?

A

It may be softened with lime to precipitate calcium carbonate and magnesium hydroxide.

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19
Q

What are chloramines?

A

Chemical compounds, family of chlorine and ammonia, relatively stable in water supplies, stay effective longer than chlorine but less effective.

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20
Q

What is the atomic composition of the water molecule?

A

Two hydrogens, one oxygen. The two hydrogens each share an electron with the oxygen.

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21
Q

What do we mean when we say that water is a polar solvent?

A

Each water molecule has poles, charged positively (hydrogen side) and negatively (oxygen side). The polarity of the molecule allows it to attract other polar molecules such as sodium chloride or calcium sulfate.

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22
Q

Why do we call water the “universal solvent”?

A

Because it can dissolve so many substances, both polar and non-polar, the latter being performed by the process of “hydration” (water molecules fully surround the non-polar molecules).

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23
Q

Give examples of non-polar molecules being dissolved by water.

A

Carbon-dioxide, alpha-acids, benzene or iodine.

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24
Q

What is an ion?

A

An atom or a group of atoms that has net positive or negative charge, due to the gain or loss of electron(s).

25
Q

What is an ionic compound?

A

It’s a polar molecule composed of two or more ions that are held together by ionic bonds (i.e., electrostatic attraction).

26
Q

How is called a positively charged ion?

A

A cation.

27
Q

How is called a negatively charged ion?

A

An anion.

28
Q

What is the sum of the positive and negative charges for any ionization products from a single compound?

A

It is always 0.

29
Q

What is the effect of chlorine over membrane filtration equipment?

A

It will oxidize and destroy it.

30
Q

What is the principal ion that determine hardness in drinking water?

A

Calcium.

31
Q

How do the presence of calcium in the mash lower its pH?

A

It reacts with malt phosphates to precipitate calcium phosphates and release hydrogen ions.

32
Q

What is the risk of having too high calcium concentration in the wort?

A

A concentration >250ppm can inhibit magnesium uptake by the yeast and may impair fermentation performance.

33
Q

How does beerstone is created in the brewing process?

A

Oxalate is present in barley malt and reacts with calcium to form beerstone.

34
Q

Why can beerstone be a particular problem when it precipitates in the beer package?

A

Because the calcium oxalate crystals act as gas nucleation sites and cause foaming and gushing.

35
Q

What is temporary hardness?

A

Hardness that can be removed by boiling or lime softening where it combines with bicarbonate to precipitate as calcium carbonate.

36
Q

What is the role of magnesium in the yeast cell metabolism?

A

It is an important nutrient for yeast pyruvate decarboxylase metabolism and should be present in the wort at a minimum level of 5ppm.

37
Q

What is the definition of total alkalinity?

A

It is defined as the amount of strong acid (in milliequivalent per liter) required to convert the carbonate and bicarbonate in the sample to carbon dioxide at 4.3pH.

38
Q

How do we define the carbonate alkalinity when the pH is higher than 8.3?

A

If the water pH is higher than 8.3, the carbonate alkalinity is defined as the amount of acid required to titrate to pH 8.3. It is measured using phenolphtalein solution, and is referred to as P Alkalinity.

39
Q

How do we define the bicarbonate alkalinity when the pH is less than 8.3?

A

When the pH is less than 8.3, the carbonate contribution is not significant and the sample is typically titrated using methyl orange indicator. This bicarbonate dominated portion of the titration is referred to as M Alkalinity.

40
Q

What are the most prevalent hardness constituents in drinking water?

A

Calcium and Magnesium.

41
Q

How many atoms are in a mole?

A

6.02 x 10^23 atoms.

42
Q

What is an isotope?

A

An isotope of an element has the same number of protons in its nucleus, but a different number of neutrons in the nucleus.
For exemple all carbon atoms have 6 protons, but Carbon 12 has 6 neutrons and Carbon 14 has 8 neutrons.

43
Q

What is the difference between hardness and alkalinity?

A

Hardness is the sum of the multivalent metal ions in solution, whereas alkalinity is a measure of the solution’s ability to neutralize acids (sum of hydroxide, carbonate, and bicarbonates).

44
Q

What is the only buffer in potable brewing water?

A

Alkalinity via carbonate and bicarbonate equilibrium.

45
Q

What buffer comes from the malt?

A

Phosphate.

46
Q

What interaction determines how hard we have to work to change the mash pH?

A

The interaction between the two buffer systems (in malt and brewing water) and calcium and magnesium.

47
Q

What is the optimum mash pH range at room-temperature?

A

Between 5.2 to 5.6.

48
Q

What are the major pH factors in most potable waters?

A

Partial pressure of CO2 and the resultant carbon dioxide/carbonate equilibrium.

49
Q

What determines the alkalinity of water?

A

It is determined by the carbonate content, which is formed when acidic groundwater reacts with chalk (CaCO3) of dolomite (CaMg(CO3)2).
The amount of carbonate that can bu dissolved into the water depends on the partial pressure of carbon dioxide that in turn determines the amount of carbon dioxide dissolved into the water : dissolved carbonate and dissolved carbon dioxide are always in equilibrium.

50
Q

How much phosphate can be found in barley?

A

About 1% by weight, and this is one of the keys to reducing the mash pH to the range favored by the enzymes.

51
Q

What is the pathway of pH reduction in the mash?

A

Malt phosphate react with dissolved calcium to precipitate calcium phosphates, releasing hydrogen ions that react with dissolved carbonate (alkalinity) to form water and CO2 gas, thereby reducing the alkalinity of the system.
The reduction of alkalinity is usually limited by the amount of calcium available in the mash.

52
Q

According to Kolbach, how much calcium is needed to neutralize water alkalinity?

A

3.5 equivalent of calcium react with phosphate to neutralize 1 equivalent of alkalinity.

53
Q

What is residual alkalinity?

A

It is the alkalinity that remains in the water after calcium has reacted with phosphate, causing the mash pH to be higher than it would be using distilled water.

54
Q

What are the consequences of low wort pH?

A

It reduces hop utilization, expression and bittering.

55
Q

What is the pH range of beta amylase?

A

5 to 6 pH.

56
Q

What are the consequences of high residual alkalinity wort?

A

It can result in a mash pH exceeding 6, leading to increased tannin and silicate extraction, has hop bitterness and beta amylase impairment.

57
Q

What acid buffers are contained in the malt; and where do they come from?

A

Melanoidins and organic acids contained in the malt neutralize acidity and lower the mash pH. They are created by Maillard reaction during kilning and roasting.

58
Q

What is the typical pH range of base malts?

A

Between 5.6 to 6.

Brewing (3 decks)

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