by Louis Fahrasmane, Berthe Ganou-Parfait, Francius Bazile, Paul Bourgeois
Rum technology and typicality factors in the French West Indies L. Fahrasmane, B. Ganou-Parfait, F. Bazile, P. Bourgeois
Rum has been produced in the French West Indies since the 17th century. The changes in production since then have been influenced by technical, economic and qualitative factors. Rum must not only have its typical organoleptic qualities but also be competitive on the international market, and this requires technological progress. Through yeast-strain selection, we have contributed towards improving alcoholic fermentation in Cane-sugar-based media. Rum production in the French West Indies is typified by the raw materials (molasses, cane syrup or juice), the microbiology of the fermentation media allowing bacterial activity, and the distilllation equipment with its so-called a Creole columns ) producing a range of aromatic strengths. Until the end of the 19th century, slops and froth were used in making the musts. Following Pasteur’s work, a new understanding of hygiene led to these substances being replaced by Water, with the result that Saccharomyces yeasts replaced the Schizo saccharomyces as alcoholic fermentation agents. Distillation equipment has also progressed. That used today depends on the type of rum produced (figure 1).
A rum technology involves several unit operations (1): the preparation of the must (more singularly called “composition”), fermentation, distillation and maturation. In the 17th century, the control of alcoholic distillation as a production tool became a key factor in the emergence of rum production, which appeared as a way of using the by-products of the sugar factory, especially those derived from sugar byproducts.
In the middle of the nineteenth century, came the agricultural rum, whose particularity is the use of musts based on sugar cane juice. This type of rum became, in the French West Indies, an export product, a production in its own right, distinct from the sugar factory, keeping, in some aspects, an artisanal character and having markers of recognition of its typicality related to the practices and production conditions.
In Europe rum has been defined since 1989 by the Community Regulation on spirit drinks (R. (EEC) No 1 576/89): It is the spirit drink obtained exclusively by alcoholic fermentation and distillation either molasses or syrups derived from the manufacture of cane sugar, i.e. sugar cane juice itself, and distilled at less than 96% vol, so that the product of the distillation has a perceptible specific organoleptic characters of rum. The minimum acquired alcoholic strength by volume is fixed at 37,5% (vol.).
The French national regulation (Decree of 22 April 1988 on Appellation of Origin rums) distinguishes “agricultural rum” from cane juice, “traditional rum” from molasses and syrup, and “rum grand arôme” which is a variant of traditional rum, more loaded with aromatic substances (Table 1). “Light rum”, once defined by national regulations, is no longer so today . Distillates of different types can be delivered for consumption either in the form of untouched eau-de-vie or after ripening and dilution to the commercial level. They can also be matured longer or aged in wooden casks with a maximum capacity of 650 liters and for at least three years (Decree of 25 July 1963). Volatile elements other than ethanol must be at least 225 grams per hectolitre of pure alcohol.
Origins of rum production
The art of distillation dates back more than three thousand years, and it is thought that the Persians had discovered and implemented it to make rose water. The first stills were designed by Christians of Egypt, in 700 B.C.
The appearance of eaux-de-vie seems to have been preceded by that of alcoholic perfume, which began with the physician, philosopher and Arab alchemist, Rhases (864: 932). Around 1360, Hungarian water made from rosemary appeared. Perfumery developed later with Jean-Marie Farina (1685-1766), an Italian chemist who made the eau de Cologne created by his uncle Jean-Paul Feminis in 1690.
Wine brandy appeared in Europe, as medicine and the elixir of life, with Arnaud de Villeneuve (1235-1313) and Raymond de Lulle (1233-1315). Under the influence of the navies of Northern Europe (in particular Dutch), the distillation of white wines of the Charente became a common rural activity, leading to the development and marketing of Cognac and Armagnac in 1630 In 1624, the Corporation of Distillers was organized in France for the manufacture and sale of brandies. From the 18th century, the distillation of wine became a prosperous activity in France.
The appearance of rum production followed the development of cane-based sugar production (Saccharum officinarum L.) with natural hybrids on the American continent in the 17th century. The migration of sugar production from the Mediterranean area to the New World is linked to the capture of Constantinople by the Turks in 1453 and the expulsion of the Moors from Spain in 1492. There was a decline in the cultural influence of Arab origin and, with it, to that of cane, after about seven centuries of cultivation and sugar production in the islands and around the Mediterranean Sea [3, 4].
Holders of Genoese and Venetian capital, in search of new areas suitable for growing sugar cane, followed Christopher Columbus to the Americas. The expansion of sugar cane on the American continent triggered rum production as an annex to the sugar factory.
One of the first authors to talk about cane alcohol is the Father du Tertre who stayed in the Caribbean between 1640 and 1657. Father Labat, who arrived in the West Indies in 1694, describes at length the manufacture of the guildive in his New Journey to the Islands of America [title translated], The main characteristics of the rum production of the seventeenth and eighteenth centuries are:
– the use of byproducts, scums and molasses, resulting from crystallizing sugars (foams and deposits produced during the defecation of cane juice in sugar and syrupy residues of non-crystallizable sugar from the manufacture of sugar) as sources of fermentable sugar. The composition of musts at the beginning of the last century is shown in Table 2 ;
– the spontaneous alcoholic fermentation due to the microbial germs having withstood the various operations of candying (concentration, cooked syrups) and those provided by the wooden bins used for fermentation. Fermentation lasted one to two weeks in the presence of abundant bacterial flora associated with yeasts of the genus Schizosaccharomyces. This microbial complex, of low productivity and generating very tasty products, was favored by the supply of pre-fermented vinasses (residues of distillations) during the storage, which lasted several weeks, and during which acidifying bacterial fermentations took place. The musts thus obtained were acidic, with a high osmotic pressure. Only yeasts of the genus Schizosaccharomyces were active under such conditions of the medium.
The first distillation apparatuses installed were discontinuous stills operating by recycling [my interpretation of what they mean by “repasse”] (figure 1a). Most of them consisted of a copper boiler, surmounted by a head also of copper; the time under heat of the fermented musts was important, which favored esterification. These devices allowed the elimination of negative volatile compounds of “heads”, sulfur and amines, and some of the very heavy compounds constituting the “tails”. The quality of the products obtained was often mediocre or frankly bad, because of the inferior quality of the raw materials used, the little care given to the fermentations, the non-rectification of the distillates which would have been necessary to eliminate the substances responsible for bad tastes. The best quality rum “is the one made only with molasses; but not the one in whose fermentation one leaves the debris of the sugar cane, the foam, etc., always preserves an unpleasant acid point and often contracts the taste of empyreanism, which causes it to be rejected from commerce.  ” During the eighteenth century, devices were used to obtain a sellable eau-de-vie on the first pass. [I think the end of this paragraph is translated wrong.]
Rum technology, from the beginnings of the industrial era to today.
The first artificial hybrid was produced by Fairchild in 1708. In 1880, the rediscovery of cane fertility led to scientific initiatives, with Slotwedel in Java in 1888 and Harrison and Bovell in Barbados. 1889, through intra and inter-specific crossings. The success of cane hybridization in Java, Barbados and Demarara, Guyana, has led to the proliferation of hybrid breeding stations around the world. Modern varieties derived almost exclusively from hybridizations arrived at the commercial stage eight to twelve years later, with selection criteria including agronomic traits, sucrose richness, disease resistance, specific locality characteristics, and so on. In 1921, Jeswiet obtained a hybrid clone nicknamed “the marvelous” (POJ 2878), far superior to the natural hybrid noble canes by its resistance to pathogens and its agricultural and industrial yields.
Increasing alcohol consumption among the working classes, economic liberalism, and the phylloxera crises that hit the wine liquors catalyzed, during the nineteenth century, the important development of the rum industry. Production, which had remained relatively low until the beginning of the nineteenth century (an average of 3 to 4 million liters per year for Martinique, Guadeloupe and Guyana combined), exceeded 21 million liters in 1892. This increase brought profound changes affecting the structure of the rum industry and manufacturing techniques.
Sugar plants appeared from 1865 and annexed distilleries for the treatment of molasses. Price and quantity constraints led to the establishment, in 1818 in Saint-Pierre in Martinique, in addition to stills without iron, single columns (Figure 1b), Creole type, to increase productivity. The Creoles columns are used to distill wines, or fermented musts, containing 4 to 5% (vol.) of ethanol. Ordinarily, they comprise three to five trays in concentration, which makes it possible to obtain distillates at 60-70% (vol.) of ethanol. Rum that is distilled too high loses its aromatic qualities. The equipment must have at least fifteen trays so that there is no loss of alcohol in the vinasse [stillage / dunder]. All the equipment parts (basement, sections and trays) can be made of stainless steel but it is very important that the concentration parts (trays and Goose neck) are made of copper. The oxidative catalysis of copper with respect to sulfur products has been demonstrated. This type of distillation device became widespread in the French Antilles around 1880; it no longer allowed the extraction of heads and tails significantly. Thus, the resulting eau-de-vie reflected the quality of the fermented must, with no possibility of correcting organoleptic defects. Later improvements to the apparatus, in particular the optimization of fractionation, multi-column device (FIG. 1c), made it possible to obtain products of a light nature, free from bad tastes, but stripped of volatile esters of interest.
Alongside the sugar plants, distilleries called “agricultural” were developed in the French West Indies and French Guiana, whose products became quite important from 1883 onwards. Some owners of old homes far from the sugar plants, rather than sell them their cannes, burdened with high transport costs or trying to obtain substandard sugar, found it more advantageous to turn their crops into rum by fermenting the juice either directly or after concentrating, which gave birth to agricultural rum.
The post-Pasteurian hygienist wave of the beginning of the century also concerned the rum industry and caused a stir. The need to replace spontaneous fermentations with pure fermentations  was concluded, and in 1913 a detailed study of rum yeasts  led to the promotion of pure fermentation with selected yeasts. The concern to improve productivity was decisive for researchers who thought that bacterial flora was detrimental to rum fermentation, whereas chemists attributed to bacteria an important part in the formation of the bouquet of high-flavored rums [9, 10].
The application of pure fermentations led to changes in conduct. First of all, the operating conditions of the spontaneous yeasts were reduced by lowering the density of the must and adding Sulfuric acid to lower the pH in order to limit the bacterial activity, and ammonium sulphate to complement the nutrient nitrogen medium. Then, the use of yeasts acclimated to certain antiseptics spread. Yield improvements were obtained, but the aromatic quality of the products was significantly reduced as they became more and more neutral. Most of the producers subsequently gave up the use of the selected yeasts and concluded, around 1920, the superiority of mixed spontaneous fermentations which made it possible to obtain rums that were more full-bodied, with a more intense and characteristic bouquet.
The use of scums and vinasse [dunder/stillage] in the composition of musts was gradually abandoned and replaced by water as a means of dilution. Currently, the vinasse is no longer used, except in the preparation of musts for the manufacture of rums of the high flavor type. For about fifteen years, the new element in rum technology is a supplement of the yeast flora of alcoholic fermentation, by supply of baker’s dry yeast, cheap and very available. We selected a strain of yeast for rum (Box I).
Saccharomyces cerevisiae var. cerevisiae 493 EDV, a rum specific yeast.
The main technical characteristics of this strain are:
– optimal pH = 4.5; | – optimum temperature = 33° C;
– yield of alcoholic fermentation = 0.595 liters of alcohol pure / kg glucose equivalent (1 ap / kg glucose);
– ethanol productivity = 3.0 g / l / h.
This yeast improves the productivity and fermentative yield, compared to spontaneous fermentations and those carried out with supplemental yeast or bakery yeast supply and shows, with respect to this, a good occupation of the environment and a better rate of living cells. Possessing the “Killer” character, it inhibits certain types of yeasts. It keeps a good activity at a temperature of 36° C and does not cause the appearance of bad tastes in the products.
Yields of sugar-alcohol processing | usually obtained in distillery are relatively low (0.52 || ap / kg glucose on molasses and 0.47 || ap / kg glucose on cane juice), while the optimum yield is of the order of 0.60 | | ap / kg glucose.
We are working to improve the fermentative efficiency of yeast, by adding sterol extracts and candy defecation mud to the must .
Yeasts constitute above all a factor of technical efficiency of the sugar-alcohol transformation while having a part in the synthesis of the components and the precursors of aromas. This is the case, for example, in the formation of volatile fatty acids, the synthesis of which is modulated, depending on the strain, by the citric acid content of the raw material .
Saccharomyces cerevisiae var. cerevisiae 493 EDV, a rum yeast
Elements of typicity
White rums are presented under four types, three of which are defined in French regulations, by their non-alcohol content (or TNA) and the type of raw material used (table 1). If typicity is what characterizes a product and allows us to recognize it, we must look for elements of the typicality of rums in non-alcohol, or all compounds other than the water and ethanol that constitute it. The TNA of the aromatic rums of the French West Indies is generally higher than that of the light rum, the last of the four types, where the bacterial presence and activity are weak or non-existent. This parameter, however, remains lower than that of the rum aroma which is an archetype where the bacterial activity reaches a high level.
The bacterial flora is at the origin of the production of volatile acidity and precursors of aromatic compounds such as esters. Rums from environments where bacterial activity exceeds acceptable product quality limits have a high volatile acidity (> 15 mEg/l)  and contain undesirable substances such as acrolein  and butanol-2, markers of bacterial problems. The level of formic acid in rums can also be an element of appreciation of possible bacterial problems and, therefore, of quality .
The chemistry of the rums reveals propionic acid as singularizing the rum within the eaux-de-vie, because of the relatively high contents observed . The level of propionic acid formation is related to fermentation yeast activity, which appears to be specific in cane-derived media . Bacteria inventoried in distillery media contribute to the formation of propionic acid. They are Propionibacterium, Bacillus and Clostridium.
The alkylpyrazines seem to be of interest for the analytical differentiation between white and agricultural white rum. Given the thresholds of perception of these compounds, we think that they participate in the aroma of some rums with olfactory notes of brulee, caramel and leather .
The use of the Creole distillation column, determines the quantitative level of the TNA (it decreases when the degree of alcohol rises) by the low number of trays in concentration (three to ten ) which, itself, affects the degree of proof of the distillate by limiting it (60 to 80% (vol.) of ethanol); regulations allow distilling up to 96% (vol.) of ethanol.
Damascenone is present in molasses . It has been shown that an isomer of this compound, at the same mass spectrum, has a characteristic odor of rum . This ketone and its presumed isomer, identified in other products of plant origin, could, on the basis of quantitative considerations, be a differentiating factor of rums within eaux-de-vie.
The production conditions of rums (fermentation microbiology and distillation) as well as the raw material thus contribute to the development of their analytical typicity. There is a sensory analysis work to do to describe this typicity, by characterizing the components that will have to be looked after to improve the competitiveness of rums.
Perspectives and conclusion
In the French West Indies, rum production must, in order to remain competitive, adopt fermentation methods that leave no room for spontaneous fermentations. The aim of producing aromatic rums, whether from molasses or cane juice, is to follow rigorous protocols that take into account the following aspects: use of selected yeasts, control of the bacterial flora, rational choice of distillation parameters, quality management of raw materials, products and by-products (Box 2).
The reasoned conduct of fermentations by acidification of the musts (in order to contain, within appropriate limits, the presence and the activity of the bacterial flora), the control of the temperature and the use of selected yeasts for the rum production allow an active fermentation with a reduced latency. This way of operating gives way to a positive bacterial expression with regard to the quality and authenticity of the products.
The potential evolution of separation techniques – increasing the number of trays (twenty to thirty) in the Column Concentration, use of vacuum distillation, pervaporation and reverse osmosis – should allow the selective extraction of certain volatile compounds which, present in too large quantity, mask the expression of the notes of typicity. In this way, the latter could be better expressed, despite the decrease in TNA, according to pre-established product profiles in which ethanol becomes more and more a vector of aromas [22,23].
We must, moreover, seek to make the most of the quality signs (AOC, label …) related to the regulations. Although the rum was originally an annex to the sugar refinery, the same is not true of the agricultural distillery in the French West Indies, which is a full-fledged production structure whose qualitative requirements for raw materials could be considered in a specific way, depending on fermentation considerations and the aromatic properties of the products. Indeed, the production of agricultural rum could benefit from a raw material better adapted to its peculiarities than the hybrids used in sucrose production, by selection of varieties richer in non-sugar (nitrogen, phosphorus, magnesium …) and in aromatic precursors, in order to better meet the nutritional needs of fermentation agents and to reinforce the typicity associated with the raw material.
They are addressed to R. Pichy, M.L. Saint-Marc and C. Galas, from INRA Pointe-à-Pître, whose technical collaboration has been invaluable
Wastewater treatment and environmental protection in the rum
The rum production generates residues (vinasse) with a high pollutant load (250 kg of COD / m * of pure alcohol in agricultural distillery, 1500 to 1900 kg of COD / mol of pure alcohol in molasses distillery). This sector of activity is more and more likely to integrate, downstream of its work plans, measures for the protection of the environment. To treat wastewater from rum, various methods can be used: evaporation-incineration, irrigation-spreading, anaerobic lagooning, biomass production and anaerobic digestion. The latter way, while reducing the organic pollutant load, produces combustible biogas. It allows, in the case of a molasses rum production unit, to decontaminate the effluent to 65% with biogas production, providing 60% of the energy necessary for the operation of the distillery. The wastewater treatment of the agricultural distillery, whose COD varies from 15 to 25 g / l with a BOD / COD ratio of 0.5, is easier than that of the waters of the molasses distillery, whose COD varies from 90 at 120 g / l with a BOD / COD ratio of 0.2 to 0.4 (21). Indeed, purification rates of the organic load of more than 90% are obtained.
Treatment of wastewater and environmental protection
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