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Module 2 > Unit 5 > Flashcards

Unit 5 Flashcards

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1
Q

Define maturation

A

The sum of the chemical and physical changes that occur within the spirit between distillation and bottling.

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2
Q

Which congeners typically decrease during maturation?

A

Ethanol
Lower boiling point aldehydes

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3
Q

What congeners typically increase during maturation?

A

Esters
Acids

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4
Q

What congeners are introduced from the barrel during maturation?

A

Non-volatile compounds- sugars and tannins.
Aromatic aldehydes
Lactones

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5
Q

4 classes of change during maturation

A

Additive
Productive
Reductive
Subtractive

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6
Q

Additive changes during maturation

A

Compounds gained from the casks, usually tannins, sugars, aromatic aldehydes, and lactones.

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7
Q

Main type of tannins found in oak

A

gallic acid base
Ellagitannins.

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8
Q

What is a tannin

A

phenolic compound gives astringent character, removes off-notes, and promotes oxidation products.

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9
Q

How to tannin levels change during maturation?

A

Rise early, then decrease (after 5 years)

Hydrolyse to give usually glucose, and phenolic acid

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10
Q

Organic acid activity during maturation

A

Usually acetic acid, increases during maturation, as it is extracted from wood.

Leads to increased ester production

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11
Q

2 whisky lactones

A

cis-β-methyl-γ-octalactone and trans-β-methyl-γ-octalactone

Coconut, sweet wood, and vanilla at low sensory thresholds

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12
Q

Lactones during maturation

A

Increase

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13
Q

Carbohydrates during maturation

A

Increase, directly from the hemicellulose of the wooden casks, and also from hydrolysing tannins.

Improve sweetness and positively affect mouthfeel

Increase colour (hemicellulose)

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14
Q

Lignin activity during maturation

A

Increases in the spirit from the cask, dependent on the level of cask charring.

Increase colour & blend complexity.

Production on vanilla and oxidation products.

Hydrolysed, then oxidised, then esterification.

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15
Q

What is lignin?

A

Structural polymer found in oak

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16
Q

Phenolic aldehydes formed from heat degrading lignin?

A

Coniferaldehyde (bready)
Vanillin (vanilla)
Syringaldehyde (spicy/woody)

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17
Q

Toasting temperature for max phenolic aldehydes?

A

200 degrees (degraded when charred above 250, as most American casks)

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18
Q

Productive changes during maturation

A

Add flavours and aromas from with compounds within the spirit.

Ester formation

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19
Q

How is an ester formed?

A

Reaction between an alcohol and an organic acid.

(hydrolysation of lignin, then oxidation, then esterification)

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20
Q

Most common ester found in spirits?

A

Ethyl acetate
fruity, solvent like aroma

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21
Q

How does the charr layer contribute to flavour?

A

Burnt wood
removes off notes (rubber)

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22
Q

Reductive changes during maturation

A

Less desirable compounds are converted to something less aromatic or flavoured.

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23
Q

2 examples of reductive changes during maturation

A

Acetaldehyde (green apples) oxidised to acetic acid

Acrolein (LAB or glycerol = acrid/peppery) oxidised to acrylic acid

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24
Q

Subtractive changes during maturation

A

Total removal of compounds through evaporation or adsorption.

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25
2 examples for subtractive changes during maturation
Evaporation of acetaldehyde (low boiling point) DMS (Di-methyl sulphide) dissipates from spirit into the air, there is also adsorption into the char layer.
26
Main countries supplying oak for casks
USA & France Spain, Portugal, then Eastern Europe.
27
Characteristics of Quercus alba
American Oak - Fine, tight, uneven grain. - 100-120 y/o - Rich in vanillin, lactones, coconut (cis-tannins), woody (less tannins than European oaks) - Abundant tyloses
28
Characteristics of Quercus petraea
European oak sp. -Medium large pores, coarse to tight grain. - 300 y/o - Troncais and Jupilles (France) - Rich in lactones, coconut and woody.
29
Characteristics of Quercus robur
European Oak sp. - Wide, straight grain, coarse uneven texture. - 150-200 years. - Limousin (France) - Ellagitannins produce cooked apple character, rich tannins increase smoothness.
30
*Oak Properties* Cellulose
Organic compound, forms plant cell walls. Gives barrels strength, but does not affect flavour.
31
*Oak Properties* Hemi-cellulose
Short glucose polymer 20-25% of oak matrix Easily hydrolysed into sugars. Form furfurals. Colour, mouthfeel, Sugar
32
*Oak Properties* Lignin
20-25% of oak matrix Found between and within cell walls. Undergoes thermal degradation during seasoning and toasting, producing key flavour compounds extracted during ethanolysis (guaiacol)
33
*Oak Properties* Hydrolysable tannins
Astringency & structure Gallic and Ellagic acid into spirit. Too much - over oaked
34
2 main ellagitannin isomers found in European oak?
Vescalagin Castalagin
35
Volatile compounds in oak & flavours
Oak lactones cis (coconut) and trans (spicy) Vanillin Eugenol (cloves, allspice) Guaiacol and 4-methylguaiacol (smokey, tobacco) Furfural and 5-methylfurfural (aromas - butterscotch, caramel, almonds)
36
Volatile compounds which reduce with more toasting
Vanillin (inc, then decrease) Phenolic aldehyde Furanic aldehydes
37
Volatile compounds which increase/are generated by more toasting
Guaiacol and 4-methyl guaiacol Furfural and 5-methylfurfural Eugenol
38
Coarse grain properties
<2 rings/cm More fibre = more lignins = more tannins. Fewer vessels (Summerwood) Ellagitannins = mouthfeel. Less porous. Q. robus (limousin)
39
Fine grain oak properties
5+ rings/cm Less fibre = more vessels = more nutrient, sugars, etc. More vessels (Springwood) More porous. Aromatic, lactones, eugenol. Q. alba.
40
Describe natural cask seasoning
- Staves stacked into ricks with good air flow. - Leave for 18-36 months - Expose to sun and rain first 8-10 months to leave green tannins. - Dry to 12-24% moisture. - Fungal colonies develop which can break down cellulose and tannins. - Dimensions retract. - Preferable, increases aromatic compounds (vanillin, eugenol, syringic) Cis lactone is higher in natural seasoning.
41
Name of fungal colony primarily found in natural seasoning?
Aureobasidium pullulans
42
Which phenylpropanoid units of lignin provide a wide range of congeners during seasoning/toasting/charring
Guaiacyl Syringyl
43
Describe forced drying.
Kiln for 1 month More astringency, as no leaching through sun and rainwater of ellagitannins.
44
Define a light toast
5 minutes. Internal surface is 120-180°C Modified lignin and hemi-cellulose Intact cellulose
45
Define a medium toast
200°C for 10 minutes. Hemi-cellulose and lignin disappear.
46
Define a heavy toast
230°C held for 15 minutes. Internal structure is blistered and cracked.
47
Which aromatic compounds are found in the largest amounts in medium toast?
Volatile phenols (guaiacol, eugenol) Volatile aldehydes (vanillin)
48
Which aromatic compounds are found the in largest amounts in light toast?
Ellagitannins (gallic, ellagic acid)
49
Which aromatic compounds are found in the largest amount in heavy toast?
Cis and trans lactones.
50
Reasons for charring
American oak - regulation Scotch - regeneration Increases surface area and gives active charcoal for sulphur adsorbtion. Increases lignin aromatic compounds (spice/smoke) Breaks down hemi-cellulose and cellulose = vanillin.
51
Char level 1
15 seconds wood character and campfire aromas
52
Char level 2
30 seconds caramel, vanilla, coffee
53
Char level 3
35 seconds earthy spice, wood scent, smoke, deep colour.
54
Char level 4
55 seconds aka alligator skin smoke, tobacco, heavy spice, cloves, sweet caramel notes.
55
6 types of cask
American standard barrel Hogshead Butt Puncheon Barrique Charred new barrels.
56
American standard barrel
190-200L SAVR - 100cm2/L American white oak Vanilla & caramel
57
Hogshead
225-250L SAVR - 88.5cm2/L Assembled from American white oak ex-bourbon staves.
58
Butt
450-500L SAVR - 71cm2/L Often used for sherry. Traditionally Spanish oak
59
Puncheon
450-500L SAVR - 67.5cm2/L Most common for sherry. Fatter than a butt and made from Spanish oak staves. Highly prized
60
Barrique
225L Wine, European or American oak.
61
Charred new barrels
190-200L ASB Used for bourbon.
62
3 main cask 'type' categories
Virgin First fill Refill
63
Virgin casks
Usually American heavy (3-4) char High extraction (fast but intense) Good physical shape, but expensive. Primarily bourbon, but also cognac.
64
First fill
Primary whisky maturation (first re-fill) Attention paid to previous fill (wine - sulphur) 1/3 price of virgin casks lower extraction
65
Refill casks
Refilled by the distillery with their same spirit. Oxygenation still occurs, even if cask is exhausted for extraction. Oxidation, evaporation (congeners, alcohol) Concerns - leaking, rusting, extraction.
66
Cons of smaller casks
expense space higher evaporation losses productive and reactive reactions are not increased by surface area to volume ratio. Therefore - hot/astringent/immature spirit character.
67
Typical Scotch filling ABV
63-64%
68
Water soluble compounds
Glycerol, tannins, sugars
69
Alcohol soluble compounds
lactones (cis and trans)
70
Higher barrel fill strength =?
Lactone extraction Lower colour extraction Lower volatile acids Overall slower uptake of maturation character
71
Lower barrel fill strength =?
Extraction of wood sugars and tannins. More colour extraction. More volatile acids.
72
What is saponification?
Fatty acid reacting with a base to create a salt of the fatty acid. (heat speeds up this reaction)
73
How do higher temperatures affect maturation?
Faster extractions and chemical reactions (some) Oxygen less dissolvable, however increased evaporation = more head space for air/liquid interaction. Losses 4-10% per year.
74
How does humidity affect maturation?
High humidity = more alcohol evaporation Low humidity = more water evaporation.
75
Factors affecting warehouse matuaration
Temperature Humidity Type and nature of construction materials
76
Maturation conditions in Scotland
Low temp and high humidity, 2% alcohol loss per year. Long times
77
3 types of warehouse organisation
Rick Dunnage Palletised
78
Rick warehouses
7-9 stories of wooden shelves with casks rolled on. 20 000 casks 55% on level 1 to 72.5% on level 9 hot and dry at the top cool and humid at the bottom different maturation at different points.
79
Dunnage warehouse
long rows of 2-3 barrels high. less space efficient earth floors to increase humidity and consistent temperature.
80
Pallet warehouse
Good for space and easy to move with machinery. Some concerns regarding airflow.
81
Solera systems
Higher, younger barrels top up lower older barrels. Consistency of spirit produced.
82
Effects of oxygen during maturation
- polymerise tannins = soften astringency. - Helps form aromatic compounds from lignin degradation by-products - Oxidise hydrogen sulphide - Oxidises compounds into carboxylic acids which combine with alcohol to form esters.
83
Log cutting technique for French Oak Implications?
Hand split along medullary grain. less tysoles. Lower yield = expensive.
84
Log cutting technique for American Oak? Implications?
Quarter-sawn against grain. More tysoles = watertight. Higher yield = cheaper.
85
Springwood vs Summerwood
Springwood - rich wide vessels, constant width Summerwood - variable width, small vessels.
86
How are staves seasoned?
- Stacked in outdoor ricks for 18-36 months. - First 8-10 months, rainwater leaches green ellagitannins (soluble) and astringent phenols. - Fungal colony - enzymes break down cellulose and tannins. - Wood reaches 12-14% moisture, contracts allowing swelling when filled.
87
Notable macromolecules in oak
Cellulose Hemicellulose Lignin Hydrolysable tannins
88
Volatile compounds in oak
Lactones (cis and trans) Vanillin Eugenol Guaiacol and 4-methylguaiacol Furfural and 5-methylfurfural.
89
How to ensure a cask is watertight?
Add 5-10L of 50 degree water. Seal with silicone bung. Roll barrel then remove bung. Vacuum = watertight.
90
Receiving new barrels
Fill within 3 months (stored inside) Check for aroma Check watertight Repair as needed
91
Receiving old barrels
Store outside (rainwater risk) Wine = low ABV (12-14) + oxygen = bacteria risk. Some might be sulphured and need rinsed + aired. Fortified wine = higher ABV.
92
Effect of Oxygen on spirit during maturation
Polymerise tannins = soften astringency. Oxidise hydrogen sulphide (removes negative aroma) Role in aromatic compound formation from lignin degradation. Oxidised carboxylic acids - combine with alcohols to form esters.
93
What compounds decrease in concentration in spirit during maturation?
Aldehydes
94
What can be done to favour lactone extraction?
Use a higher ABV spirit
95
What characteristics does a coarse grain give spirit?
Full mouthfeel, and high levels of tannins.
96
What wood treatment is responsible for spirit colour?
Charring
96

Module 2 (7 decks)

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