Rum

This article deals with rum made from molasses. We look at the sugar cane and its further processing in the sugar mill, then consider fermentation, distillation, maturation and blending, and briefly summarise the different styles of rum.

What is rum?

Rum is a spirit produced by fermenting sugar cane products, for example molasses or sugar cane juice. It does not have to be produced in the country where the sugar cane grew and can therefore be produced anywhere in the world. ^{[4b] [4i]} There may be different regulations in different countries, but for us the European spirit regulation is interesting. It defines rum as follows: ^[1]

1. Rum

a) Rum is:

i) a spirit drink produced exclusively by alcoholic fermentation anddistillation, either from molasses or syrup produced in the manu-facture of cane sugar or from sugar-cane juice itself and distilled atless than 96 % vol. so that the distillate has the discernible specificorganoleptic characteristics of rum, or

ii) a spirit drink produced exclusively by alcoholic fermentation anddistillation of sugar-cane juice which has the aromatic character-istics specific to rum and a volatile substances content equal to orexceeding 225 grams per hectolitre of 100 % vol. alcohol. Thisspirit may be placed on the market with the word‘agricultural’qualifying the sales denomination‘rum’accompanied by any ofthe geographical indications of the French Overseas Departmentsand the Autonomous Region of Madeira as registered in Annex III.

b) The minimum alcoholic strength by volume of rum shall be 37,5 %.

c) No addition of alcohol as defined in Annex I(5), diluted or not, shalltake place.

d) Rum shall not be flavoured.

e) Rum may only contain added caramel as a means to adapt colour.

f) The word‘traditionnel’may supplement any of the geographical indi-cations mentioned in category 1 of Annex III where the rum is producedby distillation at less than 90 % vol., after alcoholic fermentation ofalcohol-producing materials originating exclusively in the place ofproduction considered. This rum must have a volatile substancescontent equal to or exceeding 225 grams per hectolitre of 100 % vol.alcohol and must not be sweetened. The use of the word‘traditionnel’does not prevent the use of the terms‘from sugar production’or‘agri-cultural’which may be added to the sales denomination‘rum’and togeographical indications.This provision shall not affect the use of the word‘traditionnel’for allproducts not covered by this provision, according to their own specific criteria.

Furthermore, the regulation defines:

Other spirit drinks

1. Rum-Verschnittis produced in Germany and obtained by mixing rum andalcohol, whereby a minimum proportion of 5 % of the alcohol contained inthe final product must come from rum. The minimum alcoholic strength byvolume ofRum-Verschnittshall be 37,5 %. As regards the labelling andpresentation of the productRum-Verschnittthe wordVerschnittmust appearon the description, presentation and labelling in characters of the same font,size and colour as, and on the same line as, the word‘Rum’and, in the caseof bottles, on the front label. Where this product is sold outside the Germanmarket, its alcoholic composition must appear on the label.

Rum production

Rum is produced by fermenting a sugary liquid with yeast and then distilling it. There are numerous influencing factors, for example the type of yeast used, how long and under which conditions fermentation takes place, which distillation apparatuses are used, whether and how long the distillate is matured in wooden barrels and under which conditions. The finished product is correspondingly diverse and different. ^[5a] The production itself can be subdivided into four basic processes, namely fermentation, distillation, ageing and vatting. ^[4b] efore we go into this in more detail, we would like to say a few introductory words about rum made from molasses and about the steps before fermentation.

Rum from molasses

In this post, we want to talk specifically about rum made from molasses. This style of rum originated around 1640, when people in Barbados began distilling rum from molasses. ^[2] Molasses is the waste product from sugar production. Today, rum is usually no longer distilled in sugar mills. Rather, distillers purchase molasses that has accumulated in the sugar mills. It is often said that the origin of the sugar cane has no influence on the flavour of the rum. But this statement is not true; the origin, the terroir, does influence the taste. ^[5b]

The sugar cane harvest

The sugar cane is planted using cuttings. The first harvest takes place after 9 to 24 months. ^[3] In the West Indies, the harvest season begins in January and ends in May or June. After harvesting, new shoots grow back and the sugar cane can be harvested for up to seven years. Traditionally, people burned the sugarcane fields before harvesting to remove leaves and hornets.^[4g] However, the cane must then be processed within 24 hours, otherwise the sugar content decreases and dextrins form, long-chain sugar molecules from which no sugar crystals can be obtained. ^{[4g] [5c]} In addition, the risk of bacterial infection increases. ^[5c]

Normally, up to 125 tonnes of sugar cane can be harvested from one hectare of land, from which theoretically about twelve tonnes of sugar and 1600 litres of molasses with up to 60% sugar content can be produced. From this amount of molasses, up to 600 litres of pure alcohol can be distilled. However, the actual yield depends on the soil, the climate and the cultivation methods. ^{[4h] [4i]}

The production of sugar and molasses

In the sugar mill, sugar is extracted from the sugar cane. Molasses is produced as a by-product. The sugar cane contains about 75% water, 10-16% sugar and 10-16% fibres. The latter, also known as “bagasse”, can be used as fuel for sugar production. ^[4g]

The sugar cane is first chopped, then the sweet juice is squeezed out. To remove unwanted solids, the juice is clarified with the addition of calcium hydroxide and then processed into a syrup with about 30% sugar content. Tiny sugar crystals are added to this syrup as nuclei. This mixture of nuclei and syrup is cooked under vacuum and the sugar crystals start to grow. The vacuum avoids high temperatures during the cooking process and the resulting caramelisation of the sugar. Once the crystals have reached the desired size, the mass is cooled for six to eight hours. The crystals are then separated by centrifuge. The remaining liquid is boiled again to extract more crystals.^{[4g] [5d]}

After the first centrifugation, a class A molasses remains, which contains around 70% sugar. After the third centrifugation, you get the so-called “blackstrap” molasses with a sugar content of 55-60%. The sugar crystals from the last centrifugation form the nuclei that are added at the beginning of sugar extraction for crystallisation. Most of the molasses left over after sugar extraction is processed into rum, ethanol or cattle feed. ^[4h]

Since molasses can be stored very well, rum can be made from molasses all year round. ^[5d]

Die fermentation

Before we go into more detail about the fermentation process, it is useful to first look at the raw materials used in fermentation. The basic ingredients for fermentation are sugar from sugar cane – although we will only go into the molasses in more detail here – water, yeast and nutrients. ^[4b]

Molasses

The intensity of a rum depends on the amount of molasses used. The more molasses is used, the higher the proportions of sugar cane components, and the more intense the rum. The level of sugar cane components is reflected in the classification of the molasses. Class A molasses contains more sugar and fewer other ingredients than blackstrap molasses, which contains less sugar and more other ingredients. The latter produces a more intense rum. To increase yield, some distillers add other sources of sugar. ^[4i]

It is important that the sugar content is reduced before fermentation. For example, normal blackstrap molasses contains up to 60 per cent sugar by weight. Since this amount of sugar is too high for fermentation, the sugar content is reduced to about 16%, which gives an alcohol content of about 7% by volume at the end of fermentation. The sugar content can only be somewhat higher if the sugar cane products used consist of less than 45% molasses. ^{[4j] [4w] [5d]} However, the sugar concentration is also adjusted depending on the type of rum to be produced. To put it simply, the lighter the rum is to be, the higher the dilution. ^[5d]

Molasses also contains ash. Ash is the term used to describe the solids in molasses that are not sugar. Ash can consist of dirt, minerals and sulphur dioxide. ^[4ae] The ash content of molasses can be up to 12%. During fermentation, this ash is undesirable because it increases the osmotic pressure on the yeast cells, hindering their activity and reducing their efficiency. Due to this ash content, an alcohol concentration of maximum 10 vol% can therefore normally be achieved during fermentation. To reduce the ash content, some distilleries add other sugar sources to the molasses. ^{[4h] [4o]} During sugar production, calcium hydroxide is often used to clarify the sugar cane juice. This ingredient also gets into the molasses. In some distilleries it is removed. ^[4w] In principle, filtering the molasses can remove unwanted substances that interfere with fermentation, leave residues in the still and thus hinder the distillation process. ^[5d]

Water

For optimal fermentation, the water is also crucial. It should be free of bacteria, have a pH around 6.5, a hardness level around 4, almost no iron, 100 ppm calcium, 50 ppm magnesium and 200 ppm sulphates. Water is also the primary source of oxygen needed by the yeasts in the initial fermentation phase. ^[4k]

Yeast

It is important that the sugar content is reduced before fermentation. For example, normal blackstrap molasses contains up to 60% sugar by weight. As this amount of sugar is too high for fermentation, the sugar content is reduced to about 16%, which results in an alcohol content of about 7 vol% at the end of fermentation. The sugar content can only be somewhat higher if the sugar cane products used consist of less than 45% molasses.

The demands on the yeast are numerous. It should not only produce enough alcohol in a reasonable time, but also a lot of flavour and an expressive ester profile, and exactly the congeners that give the distillate the character of a rum. ^[4l] Congeners are organic chemical compounds such as aldehydes, polyphenols and aromatic esters that are produced during fermentation and contribute to the aroma profile of the rum. ^[4af] In a rum with a high ester content, the yeast is said to resist a higher concentration of fatty acids. It is also said to be insensitive to a higher ash content. ^[4l]

Originally, fermentation was carried out by wild yeasts that occur naturally on the sugar cane and in the surroundings of the distillery. This type of fermentation is still done to some extent today. However, it is more complicated and difficult to control, and there is a risk of bacterial infections or undesirable flavours. Therefore, most rum producers use certain cultivated yeast strains that are added selectively to control the flavour profile. ^[5e] However, some distilleries add a small percentage of sugar cane juice to the molasses, as the bacteria and yeasts present in it usually make for a more flavourful rum. ^[4h]

A rum with a high percentage of congeners is traditionally produced with a combination of wild yeast and bacteria. For greater predictability and consistency of result, yeasts and bacteria are also selectively bred and can be purchased. It is critical when multiple styles of rum or other spirits are produced at a distillery, as the bacteria can easily spread throughout the production facility and thus contaminate the other production processes.^[4m]

Higher alcohols and acids play an important role in the production of aromas by the yeasts. The former result from the latter. In addition, esters are formed from acids and alcohols. The proportion of esters and other congeners can be increased by a longer fermentation time or by less nutrients in the substrate. ^[4n]

Some yeast strains take twice as long to ferment as others. The yeasts are also sensitive to heat, so cooling is required during fermentation. The yeast strains used must be strong enough to displace unwanted wild yeasts and bacteria, although a good rum will tolerate a certain level of bacteria in the fermentation. It should be remembered, however, that some bacteria normally found in molasses contribute to the flavour. ^[4n]

Yeast dies at alcohol levels above 20 vol%, ^{[4n] [4o]} likewise at temperatures above 40°C. ^[4ah]

Nutrients

Nutrients are added during fermentation because otherwise fermentation cannot proceed optimally. An environment with a high sugar content and few nutrients is very stressful for the yeasts and can create problems during fermentation. There should not be more sugar than the yeasts can convert into alcohol. If you dilute the sugar source accordingly, you also reduce the proportion of nutrients it contains. Therefore, to improve the fermentation quality, additional nutrients are usually added, such as nitrogen, vitamins and minerals. ^[4o]

The fermentation process

The basic ingredients for fermentation are – as already mentioned – sugar from sugar cane, water, yeast and nutrients. During fermentation, yeasts convert sugar into alcohol, carbon dioxide and heat. At the same time, aromatic substances are produced, which are concentrated and separated in the subsequent distillation. Depending on the yeast strain used in fermentation, different aromas are favoured. However, the character of the rum is also determined by the type of sugar source used. The most common sugar source is molasses or sugar cane juice. But the recipe of the mash also has an influence. ^{[4b] [4f] [4n] [5e]} An optimal mash should have a sugar content between 18 and 21 °brix, a pH value between 5 and 5.5. ^[4r]

Often the sugar source is partially or completely sterilised. With partial sterilisation, the microbiological flora is destroyed, with the exception of the heat-loving bacteria. The sterilisation temperature should not exceed 85 °C, otherwise the sugar begins to caramelise. Suitable fermentation conditions and the yeasts used displace the remaining microorganisms. ^[4q]

To obtain predictable fermentation results, the fermentation temperature should be controlled. This can also influence the amount of esters produced. ^[4t] It should also be noted that at temperatures above 40°C the yeast dies. ^[4ah] Since heat is generated during fermentation, cooling is necessary, especially if production takes place in warm climates. There are various methods for cooling and temperature control, for example cooling the fermentation vats, cooling the molasses, or delaying the addition of the molasses-water mixture so as not to provide too much sugar at once. Most often, fermentation takes place between 27°C and 32°C. ^{[4ah] [5e] [5f]}

In addition to the temperature, the duration of the fermentation also has an influence on the aroma profile. A fast fermentation reduces the number and type of aroma compounds that are produced. As a rule of thumb, a light and bright column-distilled rum is usually fermented for only a short time (24 to 26 hours). A full-bodied and strong pot-still rum ferments significantly longer, ^[5f] because the longer the fermentation lasts, the higher the acidity of the mash and the more esters are produced. ^[5g] The fermentation is usually completed after two to six days. The alcohol content should then be around 6.5 vol%. ^[4u] Fermentation can be done in batches or continuously, each of which has its own advantages. ^[4s]

Fermentation practices in Jamaica

For a typical full-bodied Jamaican rum, special fermentation conditions have to be observed. The fermentation is controlled in such a way that a high amount of congeners get into the distillate. For this purpose, bacteria and wild yeasts are used in the fermentation, which convert more sugar into esters, acids and fusel oils and less into ethyl alcohol. ^[4v] These bacteria and yeasts are specifically bred. ^{[4u] [4v]} To do this, molasses and sugar cane residues left over after squeezing the juice are mixed and left in pits called “muck pits” for six months, never being completely emptied. During this maturing period, bacteria and yeasts multiply. Small amounts of this mass are added to the diluted mixture of molasses, sugar cane juice and dunder at the beginning of fermentation. ^[4u] Dunder is the liquid left in the still after distilling. ^{[4ag] [5g]} It is used to optimally adjust the acidity. ^[4x]

Fermentation thus takes place without the addition of cultured yeasts and can last up to two weeks. During this time, a high concentration of esters is produced and a rum rich in esters can be made, containing up to 1600 g of esters per 100 litres of rum. ^[4u]

Jamaican rum is classified according to the concentration of esters. According to a list from 1947, a “Common Clean” contains 80 to 150 parts ester per 100000 parts alcohol, a “Plummer” 150 to 200 parts, a “Wedderburn” 200 to 300 parts, a “Continental Flavoured”, also called “German Flavoured”, 700 to 1600 parts. The gap between 300 and 700 parts ester is striking. This can be explained historically. The first three varieties were traditionally produced and also drunk neat. In 1887, however, the import duty into the German Reich on Jamaican rum was drastically increased by the Spirits Tax Act. As a solution to the problem, i.e. to save taxes, from then on highly concentrated rum was imported to Germany, mainly to Flensburg, to be blended with neutral alcohol. ^{[5g] [6] [7] [9] [10] [11]} In 1934, the upper limit of 1600 for the ester content was set by the Jamaican government. ^[6]

The ester content of the rum is essentially determined by the fermentation time. The longer the fermentation lasts, the higher the ester content. A “Plummer” ferments for 48 hours, a “Wedderburn” longer, a “Continental Flavoured” between five days and two weeks. Since esters are formed from acids and alcohols, the ester content can be increased by adding (acid-rich) dunder. ^{[4n] [5g]}

To reduce the ash content, up to 50% sugar cane juice can be added to the molasses in distilleries where sugar cane juice is available. Fresh sugar cane juice also contains wild yeasts that contribute to the production of the ester profile. ^[4v]

However, cultured yeasts are also used for less full-bodied styles of rum. ^[4v]

The distillation

Distillation is used to separate alcohol and aromas from the fermented liquid. Distillation is carried out with different stills. Depending on the distillation apparatus and method, distillates of different characteristics result. ^{[4b] [4ai] [5i] [5j]}

The liquid that remains in the still after the first distillation is called dunder. For every litre of rum, up to 16 litres of dunder are produced. The dunder is often used to adjust the acidity before fermentation. It also provides concentrated rum flavours. ^[4aj] If the distillery produces a lot of dunder, it can also be used to produce methane, which makes it possible to produce some of the energy needed. However, dunder can also be used as fertiliser. ^[4aj]

After fermentation, many congeners have been created, all of which have a different boiling point. The art of distilling is now to include the desired congeners in the spirit, but exclude the undesired ones. The lightest ones, i.e. those with the lowest boiling point, must be removed as they are harmful. As the boiling point rises, however, delicate ones with a fine scent of flowers and apples follow. As distillation continues, the heavier congeners are increasingly released. The aroma is no longer delicate and floral, but fruity. Finally, there are oily aromas that are very strong and unpleasant. These heavy alcohols are called fusel oils. These harmful, heavy congeners must also be removed. ^[5h]

Depending on which congeners are to be transferred to the spirit, the distiller sets the beginning and the end of the middle run. For a heavy Wedderburn rum, for example, one does not collect the stronger-smelling congeners at the beginning of the run, but the stronger flavours from the middle and the end of the run. If you want a lighter distillate, you leave out the heavier congeners. In principle, these points of separation can be set very precisely in a pot-still rum, and one obtains a greater depth and fullness than rums produced by the column distillation process can exhibit. ^[5h]

The ageing

The ageing of the distillate was already known in the 16th century, when rum was carried in wooden barrels on long ship voyages and it was noticed that it improved as a result. Distilleries then also began to age their rum in barrels. ^[4b] From 1660 onwards, rum was always barrel-aged. ^[8]

Normally rum is stored in oak barrels. This often applies to white rums as well, but they are filtered afterwards to remove any colouring and to make them lighter in flavour. The chemical processes that take place in the barrel are not fully understood. However, there are three main processes that can be distinguished. First, the extraction of wood components that contribute colour and flavour. Then the oxidation of the congeners present in the distillate by the porous wood. And finally, the reaction between the different congeners present in the distillate with the wood components. ^[4b]

Ageing is a complex chemical process that takes place during the storage of a spirit in a wooden barrel. During this ageing, alcohol, esters and oils of the distillate oxidise with components of the wood and new molecules are formed. Colour, aroma and body are thus added to the distillate. The degree of maturation depends on a few factors. One is the size of the barrel, because with smaller barrels the ratio between wood surface and volume is greater and the ageing is accelerated. Temperature fluctuations also have an influence, because higher temperature fluctuations cause liquid to expand into and out of the wood more quickly, which accelerates the maturation. Humidity is also a parameter, because high humidity causes the barrels to emit ethanol, while low humidity causes water to evaporate. Air pressure also seems to play a role, although its role is not yet well understood. ^{[4d] [4e] [4y]} he loss of volume during maturation, the so-called “angel’s share”, can be considerable. In the cool Scottish climate it averages 2% per year. In the Caribbean it can be between 6% and 8%. ^[5l]

Rum straight from the still often tastes rough and spicy, so it is aged for a few years. This makes the rum milder and gives it additional character. Barrels with a volume of 180 litres are often used. The most common are once-used, decanted American bourbon barrels made of American white oak (Quercus alba), as these may only be used once in bourbon ageing due to legal regulations and are thus easily available. ^{[4d] [4z] [5k]} Each wood contributes characteristic aromas, and in the case of American white oak, vanilla, coconut and a spicy sweetness are prominent. ^[5k] In addition to American white oak, other woods are also used as barrels. Rhum agricole, for example, is often matured in barrels from cognac production. The French oak (Quercus petraea) has a higher tannin content and more obvious spicy notes than the American. ^[5n] Former European oak sherry casks are also used. This wood has a high tannin content and is characterised by notes such as clove, dried fruit and resin. ^[5n] Other barrels, for example from port or Madeira production, are also experimented with. ^[5n] Basically, it can be stated that a large part of the final taste of a matured rum is due to the reactions between the barrel and the distillate. ^[5k]

An older rum is more expensive because volume losses occur during the maturation period, depending on the storage conditions (heat, humidity, air pressure). In tropical areas, rum matures faster than in temperate climates. For example, a rum that has been aged for 30 years in the UK will have similar characteristics to a rum that has been aged for 10 years in the tropics. ^[4z] The barrels can be used several times, but their lifespan is shorter in tropical climates than in temperate climates, where a barrel can be used for up to 80 years. Three times use is normal. ^[4z] When it comes to ageing, it is also important to take into account how many times a barrel has been filled after it has been burnt out. If it is filled for the first time after being burnt out, it can still release many aroma compounds. If it has already been filled several times, it releases fewer compounds. ^[5m]

A special feature of the ageing process is the solera method. It originates from sherry production and is used by some rum producers. In this process, rows of barrels are used. The fully matured distillate is bottled from the oldest row of barrels, the so-called “solera”. Only a part of the matured rum is taken from the barrels of the solera, usually 1/3 to 1/2 of the contents. The solera is then filled up with rum from the second oldest row of casks, whose casks are also only partially emptied. This procedure is continued through all the rows of barrels until the row of barrels with the youngest rum. The important thing about this process is that none of the barrels are completely emptied, so that the aromas can blend between the different vintages. ^{[4ad] [5n] [5o]}

Barrel ageing gives the initially colourless rum a colour. Some white rums are barrel-aged for a few years to make them milder, and then charcoal flitted to remove the colouring. However, there are also many white rums that are sold unaged. ^[4z]

With regard to maturation, two essential things need to be clarified: “age” refers to a number of years, while “maturity” refers to a taste. Consumers have long been persuaded that older (and therefore more expensive) products are automatically the better ones. But this is not true at all. It is better to focus on maturity than on the age of a product. ^[4y]

Depending on the country, labels must contain different information. In the USA, rum does not have to have an age statement. However, if an age is indicated, the age of the youngest rum contained in the product must be stated. In all French islands and in Guyana, the age indicated always corresponds to the youngest rum contained. In other countries, however, including Central and South America, the average age is indicated. For example, a bottle of ten-year-old and four-year-old rum is shown as seven years old, regardless of the proportion used in each case. ^{[4z] [5p]}

Blending & vatting

Once maturation is complete, vatting or blending usually takes place. ^[4b] It is important to understand the differences between blending and vatting, because colloquially the term blending is often used incorrectly. Vatting is when a distillery blends different batches of its own products of the same type. Blending is when products from different producers are mixed, which may be of different types, for example, neutral alcohol, other distillates or infusions may also be used. In concrete terms, this means that a mixture of rum and neutral alcohol is created by blending, while a mixture of different rum batches from only one distillery is created by vatting. ^[4aa]

Vatting and blending is used because it allows products with a consistent flavour profile to be produced. Furthermore, by blending different types of distillates – which can be, for example, matured, un-matured, full-bodied or light – different flavour profiles can be created. ^{[4aa] [5o]}

To adjust the colour of the product, either sugar couleur can be added to increase the colouring, or the rum is filtered to remove colouring agents. ^{[4b] [4p]}

The rum styles

In the past, the distinction was simple. There were the English, Spanish and French styles. Rum from the British colonies such as Jamaica, Barbados, Trinidad or Guyana was known for being full-bodied and highly aromatic, made from molasses and using the pot-still method. Rum from Spanish colonies such as Cuba, Puerto Rico, Nicaragua and the Dominican Republic was known for being light-bodied, made from molasses, either continuously or repeatedly distilled in a pot still. Rums from the French West Indian colonies such as Martinique and Guadeloupe were known for a style called rhum agricole, a dense aromatic rum made from freshly pressed sugar cane juice. However, this clear distinction changed with Prohibition. During Prohibition, rum became popular with US Americans, and they preferred the light Cuban style. This became so popular that Jamaica, as well as other countries that produced full-bodied rum, began to change their products accordingly in order to survive. They produced less full-bodied rums blended from pot still distillates and distillates from continuous distillation. Then in the 1980s, spiced rum was added as a separate category. ^[4ab]

So today it is no longer possible to classify a rum according to the old classification. On the one hand, because the molasses used comes from numerous countries other than the country where the rum is produced. So you can no longer taste a terroir, as is only possible with rhum agricole. On the other hand, there are now so many different types of rum resulting from blending and vatting that they go beyond the scope of the old classification. ^[4ac]

Sources

1. http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CONSLEG:2008R0110:20090120:EN:PDF: REGULATION (EC) No 110/2008 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 15 January 2008 on the definition, description, presentation, labelling and the protection of geographical indications of spirit drinks and repealing Council Regulation (EEC) No 1576/89
2. http://bar-vademecum.de/chronologie-rum-rhum_agricole-cachaca/: Chronologie des Rums, Rhum Agricoles und Cachaças.
3. https://de.wikipedia.org/wiki/Zuckerrohr: Zuckerrohr
4. Ian Smiley, Eric Watson & Michael Delevante: The Distiller’s Guide to Rum. ISBN 978-0-9910436-0-6. Hayward, White Mule Press, 2013. 4a = page xii, 4b = page xiii, 4c = page 7, 4d = page 38, 4e = page 39, 4f = page 41, 4g = page 42, 4h = page 43, 4i = page 44, 4j = page 45, 4k = page 46, 4l = page 47, 4m = page 48, 4n = page 49, 4o = page 50, 4p = page 51, 4q = page 53, 4r = page 56, 4s = page 57, 4t = page 59, 4u = page 60, 4v = page 61, 4w = page 62, 4x = page 63, 4y = page 81, 4z = page 82, 4aa = page 83, 4ab = page 95, 4ac = page 96, 4ad = page 100, 4ae = page 137, 4af = page 138, 4ag = page 139, 4ah = page 37, 4ai = page 67, 4aj page 71.
5. Helmut Adam, Jens Hasenbein, Bastian Heuser: Cocktailian 2, Rum und Ca­cha­ça. 1. Auflage. ISBN 978-3-941641-41-9. Wiesbaden, Tre Torri Verlag, 2011. 5a = page 68, 5b = page 69, 5c = page 70, 5d = page 71, 5e = page 72, 5f = page 73, 5g = page 74, 5h = page 75, 5i = page 77, 5j = page 78, 5k = page 88, 5l = page 90, 5m = page 91, 5n = page 92, 5o = page 93, 5p = page 95.
6. http://barrel-aged-mind.blogspot.de/p/jamaican-rum-2.html: Jamaican Rum.
7. http://barrel-aged-mind.blogspot.de/2015/09/berry-bros-rudd-finest-jamaica-rum.html: Berry Bros & Rudd Finest Jamaica Rum Hampden Distillery 1990 17 YO. By Marco, 20. September 2015.
8. Edward Hamilton: Das Rum-Buch. ISBN 3-7852-8432-2. München, Lichtenberg Verlag, 1998. Page 28.
9. http://www.eyeforspirits.com/2015/10/21/was-du-ueber-klassischen-deutschen-rum-wissen-solltest/: Was du über klassischen, deutschen Rum wissen solltest. By Andre Demin, 21. October 2015.
10. https://de.wikipedia.org/wiki/Branntweinsteuer: Branntweinsteuer.
11. http://www.retrobibliothek.de/retrobib/seite.html?id=117325&textview=true. Branntweinsteuer. Faksimile von Meyers Konversationslexikon, Verlag des Bibliographischen Instituts, Leipzig und Wien, Vierte Auflage, 1885-1892. 17. (Ergänzungs-)Band.

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