Week 2: Pot distillation, column distillation, maturation in oak and inert vessels Flashcards

1
Q

What can be used to heat a still other than steam?

A

Direct heat / open flame

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2
Q

What is the heat requirement for Cognac distillation?

A

Direct heat (better for Maillard reaction)

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3
Q

What is the first batch created by the first distillation in pot stills called?

A

Low wine or pot ale

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4
Q

What is the typical abv of the low wine?

A

25% abv

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5
Q

What are the 3 main condensers?

A
  1. Shell
  2. Coil Worm Tube
  3. Others (like the rustic design of some mezcal distillers)
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6
Q

What are the main 2 heat sources of stills?

A
  1. Direct heat
  2. Indirect steam heating (coils, jackets, external heat exchangers)
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7
Q

What are the 2 batch products of the first distillation?

A
  1. Low wine (25% abv) or pot ale
  2. Liquid waste (little ethanol and all of the non volatile fractions)
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8
Q

What are the 3 products of the second distillation?

A
  1. Heads & Tails
  2. The heart
  3. Liquid waste
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9
Q

What are the 3 challenges of pot distillation?

A
  1. High operating costs
  2. Limited rectification results (up to about 80% abv max)
  3. Group 3 fractions hard to eliminate
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10
Q

What system is used for solid state fermented base material?

A

Steam injection

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11
Q

What is the aim of the second distillation?

A

Concentrate and select the wanted fractions

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12
Q

What are the two challenges that distillers have to face when using direct heat?

A
  1. Fires are difficult to control precisely.
  2. It is difficult to maintain an even heat across the base of the pot (risk of scorching).
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13
Q

What is the most widely used method for heating a still?

A

Indirect steam heating. The steam does not come into direct contact with the liquid it is heating.

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14
Q

Name three ways indirect steam can be used to heat a still?

A

Coils

Jackets

External heat exchangers.

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15
Q

How is steam introduced in a still that uses steam injection as heat source?

A

The steam is introduced at high pressure through an inlet at the base of the still.

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16
Q

Name the three key ways reflux can be managed in a pot still?

A
  1. Still height
  2. Controlling the heat input
  3. Using dephlegmators/head condensers.
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17
Q

What are the three types of condenser used with pot stills?

A
  1. Shell and tube
  2. Worm tub
  3. ‘Bowl of water’ condensers used in some Mezcal stills.
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18
Q

In batch distillation, what is the aim of the first distillation?

A

Remove some of the water and the Group 4 fractions from the alcoholic liquid.

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19
Q

In batch distillation (Scottish model), what are the outputs of the second distillation?

A
  • Heads and tails
  • Heart
  • Liquid waste
20
Q

Typically what is the abv of the heart?

A

Typically around 70% abv (it can be higher or lower depending on operational conditions).

21
Q

What is the advantage of using pot stills?

A

Pot stills are able to produce outstanding and characterful spirits.

22
Q

What type of spirit is produced with narrow cuts?

A

These cuts exclude a greater proportion of group 1 and group 3 fractions from the spirit, resulting in a purer spirit with a smoother texture.

23
Q

What type of spirit is produced with wider cuts?

A

These cuts include a greater proportion of group 1 and group 3 fractions, resulting in a spirit with more complexity as well as textural sharpness.

24
Q

What heat sources can be used for column stills?

A
  • Direct heat
  • Indirect steam heating (reboilers)
  • Steam injection
25
Q

What is a reboiler?

A

An external heat exchanger

26
Q

What type of heat source is used in Armagnac?

A

Direct heat (legal requirement).

27
Q

What are the two main features of rectification plates?

A
  1. Force vapour and liquid to interact with each other on the plate.
  2. Allow liquid to flow down the still through a downcomer.
28
Q

Name two types of rectification plates.

A
  • Sieve plates
  • Bubble cap plates
29
Q

What are the two parts of a double column/Coffey still?

A
  • Analyser/stripper
  • Rectifier
30
Q

What are the three conditions required in a column still to maintain dynamic equilibrium?

A
  1. The temperature gradient in the still needs to be constant.
  2. The composition of the fermented alcoholic liquid entering the still needs to be always the same.
  3. The volume entering the still needs to be equal to the volume leaving the still.
31
Q

The key functions of oak vessels can be divided into two groups. What are they?

A
  • Interaction between the spirit and the oak (addition of colour/aromas/texture AND removing of fusel alcohols)
  • Interaction between the spirit and the environment (contact with oxygen AND evaporation/concentration)
32
Q

What is the most commonly used species of American oak?

A

Quercus alba.

33
Q

What are two most common species of European oak used for maturation?

A
  1. Quercus petraea
  2. Quercus robur
34
Q

What factors relating to barrel design and use have an impact on the spirit?

A
  • Species of oak
  • Barrel age
  • Barrel size
  • Barrel’s previous use
  • Fill strength
  • Temperature
  • Humidity
  • Time
35
Q

To what percentage abv is a spirit typically reduced to before it is put into barrel?

A

60-63% abv.

36
Q

How do the alcohol levels of a spirit in a barrel change

(a) in drier environments
(b) in humid environments?

A

(a) The alcohol levels of the spirit will rise in drier environments.
(b) The alcohol levels of the spirit will fall in humid environments.

37
Q

What are rancio aromas?

A

Aromas of leather, tobacco, wet leaves, and forest floor that only emerge after long periods of maturation.

38
Q

What three approaches can distillers take to create diversity in their maturing spirits?

A
  • Matching spirit and wood.
  • Barrel location.
  • Re-barrelling and finishing.
39
Q

Name three oak alternatives that are used by spirit producers?

A
  • Chips
  • Cubes
  • Mini-staves/full staves
40
Q

What is the name of the glass vessel into which some spirits are sometimes decanted after a long period of oak maturation?

A

Demijohns

41
Q

What are two fundamental ways in which inert vessels differ from oak vessels?

A
  • They are airtight.
  • They do not add flavour/colour to the spirit stored in them.
42
Q

List three examples of inert vessels?

A
  1. Glass
  2. Ceramics
  3. Stainless steel
43
Q

What is the typical size of a spirits barrel?

A

Between 180 and 300L

44
Q

What are the two methods of removing visual imperfections?

A
  1. Coarse filtration
  2. Chill filtration
45
Q

What is the typical temperature a spirits is chilled to for chill filtration?

A

-10 to 4 degrees C

46
Q

How is called the filtration process of Jack Daniels?

A

Lincoln County Process