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Trente ans de travaux en technologie rhumière à l’Inra-Antilles-Guyane
This wonderful French paper came across my desk a while ago and it may finally be time to tackle it. It contains the history of the last thirty years of rum history (starting 1970) contributed by many great scientists.
Many times I’ve described rum history as starting with W.F. Whitehouse and then the torch being successively passed through the generations. The torch has wandered around a lot but basically for the last thirty or forty years been held by the French speaking parts of the tropics.
The paper summarizes their investigations and achievements and provides a stunning bibliography to pursue further (I’ve already dug into a lot of it over the years).
I’m going to try and translate it with Google to see if it can launch some ships. I’m going to take some liberties to smooth the translation so do not rely on it and please pursue the original work linked above.
Thirty years of work on rum technology at Inra Antilles-Guyane: Thirty years of research on rum technology
by Fahrasmane L., Parfait B.
Abstract: Thirty years of research on rum technology at INRA Antilles-Guyane. The rums produced in the French overseas Departments are marked by their strong and original aromatic character. Thirty years of research conducted at INRA Centre Antilles-Guyane allowed the inventory of the bacterial flora and the yeast strains involve in fermentation media, and get out of a manner of production mainly based on empirical practices. The collected data have contributed to control the vagaries of fermentation and at the same time to control the acidity of the distillates, resulting in better control of the regularity of rums quality. Among main results there were: a commercial yeast strain selected for the rum distillery, the first in the world for this purpose, and processes developed for waste waters remediation by anaerobic digestion producing also energy.
Keywords: rum, microbiology, sugarcane, fermentation, yeast, bacteria, waste waters, waste waters treatment, composition
I have heard of this Sacharomyces yeast, but was not aware it came from this French effort.
In the three islands French overseas departments, the production and processing of cane to sugar (Saccharum officinarum) remain a significant part of their respective economies, sugar production and the production of traditional rums.
The term “rum” is generic and refers to alcoholic distillates from the distillation of fermented must, prepared from sweet products derived exclusively from cane sugar: juice, syrup, molasses. Traditional type rums are characterized by their aroma. This type of production uses the empirical know-how of producers. To keep pace with the new patterns of consumption, changes in distribution and need to negotiate with the administrative and political structures involved in the environment of this sector, producers have had an urgent need for technical data and of production processes and products. This has resulted in a need for research that has been taken into account since 1970. Since 1972, INRA within its Center Antilles-Guyane has operational resources that enabled work to be carried out for this sector of activity.
Their idea of empirical parallels the idea of practical that we saw in American whiskey production. American whiskey got a little bit of help from the IRS’ excise officers, but the move to guided traditional processes did not exactly happen with government help. Here, private companies are given a very strong public foundation of basic science to advance on.
Sugar cane is an agricultural resource that, on a global scale, is subject to creation for a little more than a century. However, there has not been cane specially designed for the processing of rum.
A very interesting admission. When rum becomes more of a primary product and less of a byproduct it becomes possible to find out which varieties have the most extraordinary aromas. Cane varies in color a lot and there are a lot of unique aroma precursors correlated to skin color similar to wine.
The manufacture of traditional rum involves yeasts and bacteria that convert sugar into ethanol and co-produce compounds with aromatic properties. These strains are often genera and species identical to those found in other agro industrial fermentations (Saccharomyces, lactic acid bacteria). Schizosaccharomyces is a spontaneous genus, singular, and obligatory in the production of traditional rum of great aroma type. Ecosystems which constitute the fermentation media of rum production, have physicochemical conditions remarkably different from brewing, oenology or milk processing environments. The knowledge that could be generated on these micro-organisms, from tropical environments, is scientifically interesting for modern microbiology.
Extra fascinating and here we see strong language promoting Schizosaccharomyces for fine rums. The idea that this basic science could teach lessons to other biotech processes is very exciting.
Their diversity as well as historical, cultural and fiscal reasons make them appreciated. The dynamic stronger marketing of rums of all types makes the French aware that the road of rum goes around the world. As a result, traditional production will have more and more to face, in its markets of choice, to world production. Hence the need for it to produce knowledge in order to be able to value its products, to acquire new technical understanding making it possible to have marketing arguments, which guarantee the reputation of the most known.
Marketing arguments is a much more important concept than anyone has realized at the moment. Lost Spirits jumped the gun and tried to make marketing arguments without doing any due diligence and though it worked out for them overall, it exposed them to a lot of weakness. A lot of my rum history explorations are based on collecting and exposing marketing arguments that can support a fine rum category.
Traditional production has long been characterized by the use of cane or molasses, without specification of the quality of these raw materials, as well as by the use of non-sanitized dilution water taken from the natural environment (watercourse, groundwater). The fermentation was often spontaneous. This resulted in a high variability of the quality of the products, some of which were characterized by high volatile acidity and off-flavor, abnormal tastes (acrolein, allylic alcohol, etc.). Production was thus confronted with the quality of raw materials, and of a random mixed fermentation.
I would love to learn more about the abnormal tastes so we can compare INRA influenced rums to those of Cape Verde.
Implementation of the research approach
French West Indies rum production has always been marked by the aromatic character of its products. At the beginning of the last century, attempts to integrate into the production new practices from industrial microbiology (pure culture, mother-cell, strain selected), had failed, as productivity gains had been favored. Products had become aromatically neutral. Most producers returned to 1920, to mixed fermentations. However, the passage from the still to the Creole column, with the aim of improving productivity gradually took place between 1818 and 1865 without any recognition that the products produced by the pot still are of better aromatic quality than those obtained with a distillation column.
Pure cultures are even plaguing other spirits and my hunch is that they’ve eroded the quality of tequila. I don’t know if 1920 is a significant date or just an expression here. And I’ve never heard of the column still referred to as a creole column. Very cool. We are seeing the return to guided to traditional processes.
The aromatic character of traditional rums is a determining factor in their culinary use. In France, in particular, nearly 2/3 of the rum is singularly used as an culinary ingredient. Within spirits, the extent of this form of use of traditional rum is singular. For the time being, in manufacturing and marketing, there has been no consideration for this specific type of use. It is interesting to note that approximately 10,000 hectoliters of pure alcohol of rum, a highly aromatic flavor, are marketed annually as a culinary ingredient, exclusively for culinary preparers, with particularly low taxation. This is a path that needs to be revitalized. To do this, there is an acquisition of knowledge to be carried out on the microbial ecology of the manufacturing rum of great aroma. It is a complex and spontaneous ecosystem that we hardly know how to reproduce. The failure many attempts to reproduce it bear witness.
I think by culinary use they mean bulk highly flavored rums for larger scale food production like making tons of pâté or flavoring tobacco. Potability parallels Angostura bitters so they are looking for the same tax break. It is admitted that they hardly know how to produce these high ester / grand arôme rums which are likely concentrates such as Jamaica used to make.
The need to control the quality of this aromatic production, and to objectify the descriptors of products, led the professional rum groupings, from Guadeloupe and Martinique, to research and development. It is in response to the expression of this need that INRA has put in place research work. P. Dupuy, Director of Research at INRA, created a two-week mission to the Caribbean in March 1970, with the main aim of a scientific orientation to a future INRA laboratory, working for the rum industry. In his mission report, he proposed a research program for “a study on the fermentation of rum”. The purpose of this was agricultural rum and industrial rum. The proposed objectives were:
• «… better know the flora responsible for fermentation and in particular the role of bacteria».
• determine «the conditions that will increase yield and esters, and decrease higher alcohols and aldehydes».
As early as 1972, A. Parfait began work at the Research Unit in Product Technology Plants of the INRA Antilles-Guyana Center.
It looks like they are creating an agricultural experiment state just like Jamaica had and just like the work of Arroyo. They were probably not exactly reinventing the wheel but seeing it first hand for themselves so they could consult. Tons of work was available such as Studies on Rum, but faith in it had likely eroded. It was also pre internet and hard to assemble materials. No French person wanted to create a million dollar company relying on a pamphlet of Puerto Rican science from the 1940’s.
First Approach Work
These have been based on: esters which are deemed to be quality compounds of spirits, the problem of abnormal taste which existed on the products of the time, and the necessity of drawing up a state of art.
The composition of the traditional rums in volatile esters of higher fatty acids was the first published results (Parfait et al., 1972). Although the mixture of these compounds is not the complete characteristic aroma of rums, it participates in their qualities. The factors presented as distillation at a low rate of rectification, the addition of fermentation medium, the distillation of turbid musts and the use of selected strains of yeast.
I think the idea here was that if you targeted esters, you’d get the other stuff you wanted. Now, my hunch is that if you target rum oil, you’ll get all the esters you want when you consider how all the processes and consideration align. By turbid musts, I think they mean centrifuged and defecated cane juice such as Arroyo discussed and we can see in the comparisons of Martinique to Cape Verde.
The presence of acrolein derivatives in an abnormal flavor rum (Dubois et al., 1973) was the subject of which concluded that the observed bad taste was due to the presence of acrolein in fermented must. Parfait and Sabin (1975) gave an update on the main operating parameters of the technology ruminant, yeast flora, and the analytical composition of the main types of traditional rum that are: agricultural rum, industrial rum, grand arôme rum, and syrup rum. The authors concluded that «this traditional production of the French West Indies gives an important place to the art of the operator». These authors added that the determination of fermentation parameters (temperature, flora, distillation apparatus, complementation, etc.) did not guarantee obtaining a given product in conditions. So there was no control of the process.
I think this shows their complaint with the state of the industry they found. Distillers were too practical. They had no chemical or biological control so their products varied all over the place week to week. The acrolein idea is very important and I’m going to pursue it. It may plague some of the Jamaica rums or even be an unintended feature. It only becomes a flaw when we can attached regrets and miss opportunities to it.
In 1975, an international symposium on rums was organized by INRA and the Association for Promotion of Agricultural Industries was an opportunity to take stock of the skills available and the approaches developed in various parts of the globe in the area of rum technology. These first established milestones identified that traditional rum-problems of non-quality, which went beyond the problem of abnormal products of the time. It was clear that there was a lack of apprehension of health problems, raw materials, dilution water, and industrial facilities. Beyond elements that regulate rum, it was necessary to identify health data, microbiological and fermentation processes, which would make it possible to produce bad taste and off-flavor, while leaving room for diversity.
The symposiums is very interesting and I did a ton with it such as discovering Olbrich. By health problems I think they primarily refer to pollution and not copper poisoning or anything like that.
Research paths were then developed gradually with a view to identifying means of control, the sources of non-quality of traditional rums and control of the regularity of production. They concerned:
• the microbiology of fermentation media, both for yeasts and bacteria, rum chemistry and metabolic pathways,
• the operating conditions to control the appearance of off-flavors.
• processes for the treatment and valorisation of effluents from rum- land,
• the chemistry of rums in connection with the microbiology of fermentations and the maturation of distillates.
Metabolic pathways and microbiology become very important here. These people weren’t just biologists or chemists, they were microbiologists. They could ask and answer questions that even Arroyo could not. Arroyo suspected S. Pombe produced more rum oil, but microbiologists could actually tell us how which could be tied to more specific actions on the part of the distiller. They could even look closely enough to tease out the nature of complex off aromas.
Control of non-quality
Raw materials, molasses and sugar cane juice are not sterile and fermentation are neither sterilized nor pasteurized. With dilution water, raw materials host a bacterial flora that develops during the fermentation for rum production. The work in bacteriology have shown that in rum technology there is a varied bacterial flora (Fahrasmane and Ganou-Parfait, 1998).
In the aromatic character of traditional rums, the bacterial flora plays a decisive role; their elimination leads to neutral products, this is the case in the production of light rums. Beyond of a certain threshold, bacteria can be detrimental to the quality of the products. Without searching to eliminate bacteria, it will be interesting to identify the conditions, mechanisms of onset for negative factors to rum, resulting from bacterial activity, in order to propose solutions for control.
Bacteriology of dilution water
For the composition of the musts, water is supplied. The volumes used represent between half and 4/5 of the production. It comes from rivers or groundwater. A study on the bacteriology of distillery production waters in Guadeloupe was carried out (Ganou-Parfait et al., 1991). The bacteria of dilution waters are anaerotolerant germs (106 cfu / ml): coliforms, fecal streptococci, Clostridium, sulfato-reducing bacteria (BSR) (103 c.f.u./ml). Their number increases with the rate of mineralization of these waters. The flora of the waters, particularly rivers, grows seriously in bad weather. Increasingly, distilleries are equipped as a water treatment plant; it is a necessity to manage the health risk from the dilution water, in particular with strongly water mineralized or in rainy weather. The health status of manufacturing waters has improved.
This reminds me when I covered Scotch, pond water, and floaties.
The volatile acidity of wines and rums.
Three main factors affect the nature and quantities of volatile acidity of rums (Fahrasmane et al., 1983):
• fermentation agents,
• the temperature of fermentation whose rise increases the volatile acidity,
• the degree of distillation.
The volatile acidity of fermented media and distillates is related to the activity of the yeast that occurs during alcoholic fermentation. The bacteria present in the media fermentation contribute to the volatile acidity pool; in particular during fermentation accidents, the volatile acidity of these media is increased. The slowing down of the fermentation rate, which may result in a cessation of fermentation (Ganou-Parfait et al., 1991).
The consumption rums usually have a volatile acidity which varies between 1 and 5 ml/l (ml/ l). This parameter doubles in aged products. In acidic rums, the volatile acidity varies between 10 and 20 (ml/l).
The level of volatile acidity and the proportions of its components appear as indicators the presence of bacteria and their activity during rum fermentation.
So when fermentation is temperature controlled to ideals, volatile acidity implies flavor and implies contribution of bacteria to aroma.
The bacteriology of musts.
Sugar cane juice, which is the raw material of agricultural distilleries, contains germs (Ganou-Parfait et al., 1991). Micrococcus, Corynebacterium, Bacillus are the most common assets. They come from soil, sugar cane stalks, air and installations. We find there also aerotolerant anaerobes, capable of using the lactate produced by Leuconostoc, Lactobacillus and anaerobic Clostridia. Lactic acid bacteria dominate.
In molasses, mainly lactic bacteria and sporulates (Bacillus) are found.
The populations of distillery musts are very varied. We find there:
• Micrococcus in sugar cane juice (Ganou-Parfait et al., 1988). These are bacteria of the soil, which is also found on sugar cane stalks, in distillery wort; they can be divided into three types. They are preferential: whereas anaerobiosis is not yet established, their populations reach 105 cf. / ml in musts. Their activity is detrimental to the quality products because they produce acrylic acid and allyl alcohol in rums based on cane juice.
• Bacillus in sugar cane juice musts (Ganou-Parfait et al., 1987). They come from canes attacked by rodents (rats), and dug by galleries by insects borers. The strains remain anaerobic. They produce volatile fatty acids from the lactate. They have the characteristic of forming sails at the surface of the tanks at the end of the alcoholic fermentation. These sails seem to protect open-pit tanks from the development of bacteria.
• Corynebacterium (Lencerot et al., 1984) and Clavibacter. They come from the sugar, especially when its health status deteriorates. These bacteria degrade glycerol, which produces secondary alcoholic fermentation by yeast, acrolein (2-propenal) and 2-propenol. These reactions give rums with a pungent taste.
• Clostridium which are anaerobic germs. The improvement of the sanitary quality of manufacture has made it possible to decrease the population of Clostridium telluric. Clostridia play an important role in the manufacture of rum great aroma, with in particular Clostridium saccharobutyricum. Sugar cane juice media frequently contain Clostridium butyricum and Clostridium bifermentans. In molasses based media, also some species of clostridia.
• Lactic bacteria, the number of which varies between 107 and 108 c.f.u./ml, at the beginning of fermentation, whether in musts based on cane juice or molasses. 80 to 90% of strains have anaerobic behavior. It contains homofermentary bacteria and heterofermentative. Their activity generates lactic acid and polysaccharides. Bacteria lactic acid constitute the bulk of the bacterial flora of molasses-based musts; while is more varied in those based on cane juice.
There is just so much in here. First we find that rat eaten canes pick up rodent bacteria that may be aroma beneficial. It is also an ancient European invasive species influence on the terroir. The protective nature of lactic bacteria also makes rum seem more like sour mash whiskey and we get more explanation of surface films and how they protect fermentations. Basically I’m going to get Boston wharf rats to eat cane and infect it with their bacteria for my New England rum.
An approach to the dynamics of the various bacterial species during the fermentation cycle it can be concluded that, in particular, sugar cane juice lactic preference of musts, before the alcoholic fermentation takes place (Ganou-Parfait et al., 1989). Work in progress aims to model this “co-culture”, in order to enhance it technologically. Indeed, the current practice is to acidify the musts at the beginning of fermentation by supply of sulfuric acid. By directing microbial ecology, it could be lactic acidification which would then allow alcoholic fermentation by yeast, in the usual pH range which protects the environment from the development of bacteria damaging.
Here I think they are proposing trading sulfuric acid which eventually became traditional for dropping pH for lactic acid which can better protect a ferment from bacteria without dropping the pH as low. Definitely need that paper.
Alcoholic fermentation of rum
The main unit operations carried out during the production of rum are the extraction, fermentation and distillation. There are losses at all these stages. Losses during the fermentation are the most important. Measurements of fermentation yield in fermentation (Fahrasmane, 1991).
The results are as follows:
– Yield Gay-Lussac 0.67 l AP / kg glucose,
– Pasteur yield 0.61 l AP / kg glucose,
– Optimal theoretical efficiency 0.59 l AP / kg glucose,
– Yield on molasses 0.52 l AP / kg glucose,
– Yield on cane juice 0.47 l AP / kg glucose,
– Yield on syrup 0.40 l AP / kg glucose.
In a beet molasses distillery, with a yeast per stock, the fermentation yield is of 0.58 l AP / kg glucose (from Miniac, 1988). While improved performance was not a priority, after the problems of non-quality had been resolved, the professionals improvements in performance. One of the pathways explored is the search for yeast strains selected, adapted to the fermentation of sugar cane products (Fahrasmane et al., 1986)
I think the measure meant there is liters of pure alcohol produced (AP) per kilo gram of sugars as glucose.
Schizosaccharomyces of rum distilleries have been isolated and collected in our Unit (Fahrasmane et al., 1988). Their taxonomic study showed that there were essentially Schizosaccharomyces pombe (90%), some S. malidevorans (8%), and S. japonicus (2%). A study on their use in rum technology was carried out (Ganou-Parfait and Parfait, 1980). This type of yeast may under certain technological conditions, have a productivity in alcoholic fermentation, equivalent to Saccharomyces cerevisiae. The aromatic profile of secondary compounds products is very different from that of Saccharomyces.
Schizosaccharomyces and the bacterial complex, rich in Clostridium, which accompanies it in the fermentation of the flavoring rum constitute for the moment an ecosystem, giving products singularly rich in aromatic properties. Producers know at best how to reproduce ecosystem without controlling it. There is knowledge to generate, in order to master it and better value.
I think what he means at the end of this passage, is that they know how to start the ferment but not exactly how to control it. In the days of the Jamaican experiment station, it wasn’t confidently even known how to start these ferments.
A collection of strains of Saccharomycetaceae of rum distilleries was constituted (Parfait and Sabin, 1975; Fahrasmane and Ganou-Parfait, 1998). From this collection, a study was undertaken in to select yeasts for the rum. This work culminated in 1997 in the selection, world, of the first commercial strain of rum distillery yeast: DANSTIL EDV 493 (Vidal and Parfait, 1994), a Saccharomyces cerevisiae marketed, in the form of active dry yeasts, by Lallemand. This selected yeast allows an improvement of the fermentation yields and of the productivity, by means of a seeding arrangement, in relation to the usual conditions cutting. One of its peculiarities is not to be as affected as the other strains of yeast, used as make-up yeast, at temperatures around 35 ° C which can be measured in the vats of rum distillery.
So it has heat tolerance and “killer yeast” characteristics that prevent the growth of wild yeasts.
The sugarcane stem is wrapped with a cuticular layer of wax. The wax is concentrated in the defecation sludge from the sugar. A fractionation of these sludge was undertaken. Steroids, including stigmasterol and sitosterol have been isolated. These have been added to media fermentation in order to study their action on the fermentation behavior of yeasts. when the addition of these steroids results in an increase in ethanol production, compared with a control medium without the addition of steroids. Bakery yeast already relatively rich in sterols is much less sensitive to the intake of steroids (Bourgeois and Fahrasmane, 1988).
I don’t completely understand what is happening here.
Secondary products of alcoholic fermentation
Glycerol is a by-product of alcoholic fermentation, frequently present in quantities, in the rum fermentation medium. It has the particularity of being consumed by bacteria (Fahrasmane and Ganou-Parfait, 1998) (Micrococcus, Bacillus, Lactobacillus, Leuconostoc, Clostridium) by producing compounds related to the bad tastes of rums: acrolein, propenol 2 and sometimes acrylic acid. These compounds are indicators of disorders bacteria, which must be remedied, for example in molasses-based production, avoiding fermenting conditions which are favorable to the formation of glycerol (18), and by working in sanitary conditions which inhibit the action of an overabundant contaminating bacterial flora.
At the end of a thesis work on «the formation of short fatty acids and higher alcohols by of yeasts of a rum distillery», Parfait and Jouret (1980) showed that the choice of the species and of the strain of yeast is crucial in the quantitative and qualitative control of the production of short fatty acids and higher alcohols. It appears that in the cane juice medium there is formation of propionic acid; the composition of organic acids (citric, aconitic and malic) of the juice appears production. It is necessary to put this result in conjunction with the singular wealth of traditional rums to propionic acid in particular, and more generally to short fatty acids.
From a methodological point of view, we have been interested in ethyl 2-methyl-butyric acid, identified by some authors as a characteristic of rums (Fahrasmane et al., 1985). This work showed that it is more the quantities of this acid of bacterial origin which are singular, because in the end it is found in other stuff as well.
Some translation errors obscure the specific significance here. I’ll have to track down those papers. A lot of this considers what specific fatty acids and esters most characterize rums.
The work carried out in chemistry of rums, beyond the esters, involved chemical compounds or chemical families that are major in non-alcohol (higher alcohols), or that are sensitive in terms of product quality.
Rum contains a greater variety and greater amounts of organo-sulfur compounds than other spirits (Fahrasmane et al., 1989). According to Leppanen et al. (1979), rum is the only spirits containing dimethyl sulphide. The activity of sulfate-reducing bacteria in the media fermentation would be partly at the origin of all these compounds. The composition of sulfur-containing elements in sugar cane and the addition of ammonium sulphate and sulfuric acid, would provide a substrate for sulfate-reducing bacteria in musts.
I definitely need this paper because I’ve heard anecdotal stories about cane high in sulfur that I’ve never been able to make sense of.
Downstream of the distillery, the methanisation of effluents poses the problem of a precarious balance between methanogenic and sulfato reducing flora. The organo-sulfur fraction of rums deserves a thorough and systematic study, because it has an analytical and organoleptic interest for the characterization of rums.
The dosage of formic acid in aged or non-aged rums shows that the level of formic acid in of traditional rums is within the range of figures found for other spirits. Also, the intervention of bacteria leads to a significant increase in the level of formic acid in rums (Jouret et al., 1990a). This acid is quantitatively more important in molasses rums than in those based on sugar cane juice.
Some alkylpyrazines of rums appear to be able to differentiate molasses based white rums from those of cane juice. Indeed, 2 methyl pyrazine, 2 – 5 methyl pyrazine and 2 – 6 dimethyl pyrazine are absent from agricultural rums, although they are clearly present in those based on molasses (Jouret et al., 1990b).
Ethyl carbamate or urethane is a molecule known to be carcinogenic that can be found in rums. The North American market has adopted an upper limit for the presence of this compound in the rums, which is 125 μg / l. This substance may originate from fermentation, particularly in urea-containing media, which is not the case for distillery media, but it can also be formed by purely chemical reaction during and after distillation.
Rums have never been known to be particularly rich in ethyl carbamate. Its presence, beyond the defined threshold, is a concern for producers who want to export, in particular, to North America; some rums are exempt but others are not, can now have explanation. The quantities measured are up to 2,500 μg / l. There is therefore knowledge to be generated on the determinism of the appearance of ethyl carbamate.
I don’t think I’ve ever posted on ethyl carbamate though I’ve read quite a few papers. My theory is that it is a chemical trade barrier. It might technically be toxic, but because the enforcement is so selective it can effectively become a trade barrier. U.S. compliance is voluntary which shows just how toxic it is. Ethyl carbamate is produced by exotic copper reactions and is reduced by using stills that are combinations of copper and stainless to reduce the reactions. Substrate is also a factor and I’m under the impression that the Scots bread new generations of malt to reduce ethyl carbamate. Even post bottling it can form from UV reactions and it increases in fruit eau-de-vies that have sat on a store shelf.
The raw material sugar cane
The production of traditional rums combines the production of ethanol with the production of ethanol aromatic or non alcoholic compounds, during the fermentation. This production depends on the suitability of the must, and therefore of the raw material, to meet the needs of the yeast and the co-fermentation agents are the bacteria. We are interested in sugar cane as a plant resource, (Célestine-Myrtil-Marlin and Ouensanga, 1988), its contents, and that of molasses (Célestine-Myrtil-Marlin and Parfait, 1988) into organic acids. Measures have also been of the age of sugar cane (Célestine-Myrtil-Marlin, 1990). The organic acids act on the metabolic behavior of yeast, during fermentation (Fahrasmane et al., 1985).
Work has begun on methods of processing sugarcane associated with a method of sugars (Célestine-Myrtil-Marlin and Parfait, 1987). We needed precise and reliable methods for measuring sugars and monitoring their evolution during bio transformations (Célestine-Myrtil-Marlin, 1991).
Their involvement has deepened so much that they’ve worked backwards into investigating and developing more suitable substrates. Arroyo never got that far.
Treatment and recovery of effluents
The distillation of fermented rum media produces discharges, waste water, vinasse, which contains a polluting charge. Programs in our Unit have contributed to the characterization of the vinasses and propose processes of depollution and valorisation, by digestion to form methane.
The pollution flows generated by the distillation of cane molasses alcohol are particularly high: 950 to 1900 kg DCO / m³ of pure alcohol (A.P.) produced, i.e. a polluting load of 13 to 26,000 equivalent per day / m³ A.P. product. The distillation of agricultural rum represents pollution is six times lower: 250 kg / COD / m³ A.P., i.e. 3000 equivalent inhabitants day / m³ A.P. product (Bories et al., 1994). Where the organic load of waste water from the agro-food industries, such as distillery, is discharged without precaution into the natural environment, it causes different forms of disadvantages, the most characteristic being water pollution and odor pollution accompanied by the nuisances they induce.
Various channels have been proposed for the elimination or treatment of vinasses: evaporation incineration, irrigation, anaerobic lagooning, microbial biomass production, digestion anaerobic digestion or methane digestion. The latter is a natural biological process consuming and reducing organic pollution. Its application in sewage treatment plants, effluents and at the same time the production of combustible biogas.
In Guadeloupe, in a major distillery, the molasses vinasse is digested anaerobic, according to a process sized by an INRA study. This process makes it possible to under normal operating conditions:
• decontamination with 60% of DCO eliminated,
• energy production: biogas representing 60% of the energy needs of the distillery (Bories et al., 1988).
Pilot trials result in more than 95% removal of DCO from juice
of cane by anaerobic digestion (Bories et al., 1994). The biogas produced is of very limited interest for the agricultural distillery, as it has bagasse as fuel.
Arroyo never really got into effluence disposal but it was the main subject of the rum pilot plant. What is interesting is that its less useful for agricole distilleries because they already have tons of bagasse to use for fuel. Distilleries have gone to more extensive efforts to be green than you’d think without consumers even noticing.
Two symposia on the traditional rums of the French Overseas Departments were held, in 1994 and 1996 respectively in Guadeloupe and Réunion. They were an opportunity for meetings between professionals, technical institutes, administrations, institutes of research. These events resulted in the publication of Acts which provided an update on the problems and questions of the production of traditional rums.
I was not aware of these. Will have to track down any special papers.
The work carried out on the manufacture of traditional rums, over the last thirty years, knowledge and understanding of bacterial flora and its products, the mechanisms of quality in these products, and to suggest ways of remedying them. The products of bad qualities are now much less frequent than thirty years ago. The medals won by the distillers of the French West Indies, to the agricultural competitions are more and more numerous.
When it is noted that problems are less frequent, it makes me wonder if we are seeing flaws marketed as features coming back to the market such as with natural wines. New producers (and bottlers) are coming online that are wading into this ambitious grand arôme territory and are not technically versed enough to see what should be regrets and missed opportunities. We do not understand enough of beauty and sauvity or what is possible to make all the connections. I’ve tasted a number of acrid spirits that are raising flags in my mind (not from the French!).
Work on yeast strains collected in rum distilleries has made it possible to select a strain which constitutes a tool to contribute to the conduct of the fermentation. There are fewer knowledge on the functioning and bacterial dynamics of distillery ecosystems, marked by a great biodiversity. There is phylogenetic proximity between the lactic bacteria of fermentations and corynebacteria, some of which are sugar cane pathogens.
I don’t completely understand the bacteria being described here and I think it might just be microbiologists nerding out and pushing the boundaries of what can be investigated.
On the raw material, there is the need to define a technical itinerary of agricultural production and post-harvest treatment, suitable for processing by rum, taking into consideration other organic acids, aroma precursors, markers, tracers, etc. cane juice, sterile, stabilized by tangential microfiltration, which we have developed, we have a study environment of behavior, in pure culture, of microbial agents.
Things get really interesting here and I just know rules of thumb for dealing with fresh cane and haven’t actually read anything too aroma centric. Cane degrades rapidly and the recoverable sugars changes, but if your objective isn’t sucrose recovery, what can be said specifically about aroma? Filtration or centrifuging becomes significant here, either for logistics of large productions or for optimizing aromas. “Undefecated” fresh sugar cane juice rums are very different as noted by Arroyo, but I’ve never read exactly from a microbiologist.
Most of the work was carried out on a laboratory scale. Consideration of the matter and co-cultures requires the addition of a pilot-scale device to the laboratory scale, and also to carry out operations on industrial sites.
We have not developed any distillation activities. This manufacturing step is also significant to the development of product quality.
The maturation of rums is a stage on which we have for the moment only done preliminary exploration, through the use of woodlands and red woods of Guyana.
Very exciting! Tropical cooperage!
The singular aromatic character of traditional rums has received little attention. It has the advantage to be outside the field of alcoholism. There is potential for innovation to formulate products of the rum distillery, responding in a targeted way to these aromatic uses.
Treatment and recovery of effluents benefit from the results obtained, both on effluents from molasses than on sugar cane juice effluents. On the former, there are treatments of upstream or secondary of different types to be studied or to be dimensioned: plowing, spreading, lagooning …
The traditional rum model is relatively complex, because it involves:
• treatment of raw materials: molasses and cane juice (biochemistry, physiology …),
• complex bioconversions: alcoholic fermentation, bacterial co fermentation, methane fermentation of downstream effluents,
• unit operations in process engineering: grinding, extraction, distillation ….
• maturation treatments of distillates, varying in length, to develop various qualities of products.
The different tools and itineraries mastered and the achievements of the research and development in the sector cane-sugar-rum can find applications in the agro-processing of tropical plant resources.
In summary, the work will benefit many, even beyond rum!
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