Manuel de Sucrerie de Cannes, Laguarigue de Survilliers, 1932

Laguarigue de Survilliers, J. de. Manuel de sucrerie de cannes, par J. de Laguarigue de Survilliers … Paris, Dunod, 1932 “La fabrication du rhum a partir des melasses” : p. 216-240. (Citation found here)

Marius Hayot

This lost text associated with Martinique’s Distillerie du Galion which still makes a grand arôme rum is a little bit of a smoking gun on the topic confirming suspicions. It says near nothing on making them, but it spells out the culture which is enduring:

e) Rum of high taste. – The rum of high taste or rum grand arôme is prepared by some factories. It has a special strong aromatic flavor and is a premium on the market because it supports better than ordinary rums cutting with neutral alcohol or other rums that are a little flat. As it is, it is a mediocre product of direct consumption.

The manufacturing process is secret, but from what we have said about the formation of impurities in rum, it is suggested that this rum is produced by a slow and acidic fermentation of highly concentrated musts. Moreover, there is a knack for the interested manufacturers to have just as little knowledge as possible.

So they are mediocre as a product of direct consumption. This is important backup to the enthusiasts that are coming across grand arômes from unique vendors like France’s Maison du Whiskey. As a vendor, they absolutely need to keep doing what they are doing, but we need to learn to pick up what they are putting down… and consume them appropriately. I could say much more if we ran some through the birectifier.

The next big thing to tackle is that all producers completely continue grand arôme culture and are oblivious to the extraordinary things they do and how it can help rum/rhum/ron culture as sugar declines in the region. Extraordinary value can be unlocked by these regions to sell product and support agro tourism. Certain categories of rum should return to being the most valued spirits of the world, beyond Cognac, beyond tequila, beyond anything else. So many things need to be reconciled from yeasts like Schizosaccharomyces Pombe to Rum Oil to exciting fermentation complications, etc.

Ancien Élève de l’Ecole Polytechnique.


The exhausted molasses, residues of the manufacture of the sugar, are used as raw material of the manufacture of the rum.

This production is based on the transformation of fermentable sugars into alcohol under the influence of ferments.

Total fermentable sugar of a molasses (or more generally of a sweet product) is the sum of the reducing sugars and the invert sugar that can be given by sucrose.

From this point of view the molasses are quite diverse. We have given to the “cooked and crystallized” chapter medium compositions of molasses which inform us about it. We repeat below the sucrose and reducing content of various molasses.

Either a sweet product containing a grams of sucrose c12H22O11 and b grams of reducing sugars C6H12O6.

We know that the transformation of sucrose into invert sugar is done according to the equation:

It is deduced that 342 grams of sucrose gives 360 grams of invert sugar or that 100 grams of sucrose gives:

about invert sugar.

The total fermentable sugar of the product studied is:

The theoretical transformation of fermentable sugar into alcohol is done according to the equation:

We deduce that 180 grams of fermentable sugar would give 92 grams of alcohol or that 100 grams of fermentable sugar would give:

But in reality the reaction (1) is more complex. It is also formed succinic acid, glycerin, higher alcohols, ethers, various acids, etc … and it is found that it takes about 105 grams of fermentable sugar to give 51 gr of pure alcohol.

In summary, 100 grams of a product containing a grams of sucrose and b of reducing agents will give:

Example – For 100 grams of molasses containing 35 grams of sucrose and 24 grams of reducing agents, by fermentation this molasses will give in admitting that all the fermentable sugar is transformed:

1° Alcoholimetry. – The richness of an alcohol solution in water is expressed in degrees. The measurement of this degree is done with the alcoholic alcohol meter of Gay-Lussac.

0 corresponds to pure water;
100 is pure alcohol.

If n is the division marked by the alcoholmeter, the degree of the alcohol is n and the solution contains n cubic centimeter of alcohol per 100 cubic centimeters of solution at 15 degrees centigrade.

If the temperature is different from 15°, it is necessary to make a correction.

We give here a table that allows to make this correction:

Note that if an alcohol indicates to the alcohol a¹, and has a volume v¹ the volume v², that it will occupy when it indicates a² will be:

The latter formula is actually close, the mixtures of alcohol and water contract and the value of this contraction being variable with the proportion of the constituents of the mixture. However, it is sufficiently close to industrial practice when the variation in alcohol concentration is of the order of a few degrees.

Fermentation and bacteria. — the transformation of sugars into alcohol, is due to the presence of yeasts or ferments, lower organisms that can be classified into several groups, the two most important of which are:

Saccharomyces are small, round or oval yeasts with a size of 5 to 10 μ (Fig. 11); these are the most important ones.

Schizosaccharomyces are not found in all countries. They are long (up to 25μ).

They have been identified in the fermentation must of the Hawaiian Islands and the French West Indies, for example.

These yeasts require a temperature high enough to develop well: from 23° to 40°. Below 23° they hardly act. Above 40° they are destroyed or nearly ineffective. The optimum temperature is about 30°-35°.

Yeasts that are living, breathe, feed and eliminate waste from their physiological activity.

When they have a lot of oxygen at their disposal (aerobic yeasts), they develop a lot but do not attack little or no sugars, When they have little oxygen at their disposal (anaerobic yeasts), they develop little, but attack the sugars they break down as we have seen.

The best yeast food is in fact sugar. It should be noted, however, that not all sugars are attacked. The ones that ferment the most easily are the sugars in C6. C12 sugars only ferment after transformation into hexose sugars. For this purpose the yeasts secrete a diastase called invertine or sucrase which causes the transformation of sucrose (C12 sugar) into glucose and levulose (C6 sugar). These C6 sugars are in turn transformed, as we have seen, by a diastase secreted by yeast, zymase, into alcohol, carbon dioxide, and various other by-products.

In addition, the yeast needs nitrogen (ammonium salts, nitrates, etc …), potash and phosphoric acid like all plants.

Finally, with regard to the influence of the products of fermentation on the yeast itself, it has been found that the carbon dioxide evolved had no appreciable influence on the activity of the yeast, but that ethyl alcohol, the concentration of which increases as fermentation occurs, slows down the activity of the yeast.

We have seen that in addition to the normal production of ethyl alcohol and carbonic gas, fermentation produces various bodies. Among these bodies, some such as glycerine and succinic acid being fixed do not pass into the products of distillation and therefore have no effect on the taste of the rum. Other bodies are volatile, distill at the same time as the alcohol and consequently have a direct influence on the aroma of the product of the distillation.

It is therefore very important to know as precisely as possible the nature and origin of impurities in rum. The question is very complex, in short little studied and in the current state of the question, we do not believe it is possible to conduct a molasses fermentation with the certainty of obtaining a rum with such a taste that we desire a priori. At most, in a few factories, we know how to make rum of high taste, of which we shall say a word later.

Among the volatile impurities mentioned may be made of higher alcohols, certain acids, aldehydes and ethers.

The higher alcohols, propyl CH3CH2CH2OH, isobutyl CH3CH(CH3)CH2OH and amino CH3CH(CH3) CH2CH2OH depend, according to Ehrlich, on the nitrogen supply of the yeast, which decomposes certain nitrogenous bodies by freeing alcohols and absorbing the ammonia produced.

Volatile acids such as C2H4O2, acetic acid, are formed by the action of a ferment (acetic fermentation) or by the consumption of ethyl alcohol itself by the yeasts.

It is the same for aldehydes, ethyl aldehyde for example. Finally, ethers, ethyl acetate, ethyl isobutyrate, amyl acetate, etc., come from the action of acids on alcohols.

The impurities of which we have just spoken are formed in every fermentation, even perfectly pure. But it is quite certain that, especially in tropical countries where there is always a moist heat, molasses, cell walls, etc., are environments in which numerous bacteria grow at the same time as good yeasts. These bacteria have various actions, sometimes happy. (According to Deer, the Jamaican aroma is attributed to the presence in musts of bacillus mesentericus) and most often harmful. (Bacillus levaniformans is a great destructor of sugar, the leuconostoc mesenteroid makes viscous molasses and hinders the action of yeasts.) It is especially important to avoid lactic fermentation (lactic ferment).

But it is enough to acidify the musts to prevent the development of these lactic ferments.

3. Rational fermentation. – From the short study that precedes, we can deduce the following conclusions:

1° To obtain the best alcohol yield, the development of the bacteria must be prevented as much as possible, and the action of the good yeasts must be encouraged;
2° The good yeasts working in the air (aerobic yeasts) develop enormously without producing an appreciable quantity of alcohol;
3° The good, yeasts working away from the air (anaerobic yeasts) develop little but vigorously transform the sugar into alcohol;
4° The taste of rum is linked to the impurities it contains (higher alcohols, volatile acids, aldehydes, ethers). The nitrogenous diet of yeast certainly has an influence in this respect;
5° It is in the interest to work with acidic musts to avoid the development of harmful bacteria.

a) Choice of yeasts. – The most important problem is the mode of action of the good yeasts. The leavening process has been almost abandoned, and the technique currently in use consists of the use of yeast accustomed to various antiseptics, which introduced at high doses into the fermentation tanks will prevent the development of harmful bacteria.

The main antiseptics used are sulfuric acid, formalin, sodium hydrofluoride. The proportions of these different antiseptics to use are approximately:

The industrialist will generally be interested in buying his yeasts from organizations specialized in their breeding and will not seek to procure them himself.

b) Seeding of musts. — One first forms a cuve-mère [mother vat] which is sown with the yeasts accustomed to antiseptics whose names we have just spoken.

The antiseptic is introduced into this mother vat at the appropriate doses, and when it is in full activity, its contents are distributed between the vats of the rhummerie which are fed with the must and into which the antiseptic is also added.

By successive samplings on these vats, the subsequent fermentation is started.

However every 8 or 15 days it is advisable to reform a mother vat with a different antiseptic, harmful bacteria getting used to the first antiseptic used in the long run.

This results in fermentation times of thirty-six to forty-eight hours and industrial yields of 80 to 85 percent. 100.

c) Composition of musts. — The composition of musts is quite variable.
Here is one:
Mêlasse . . . . . . . . . . . . 13 litres.
Vinasse . . . . . . . . . . . . .60 —
Eau . . . . . . . . . . . . . . . . 27 —

The density is of the order of 1.080 to 1.060.

The vinasse employed is, as we shall see, the residue of the manufacture of rum. It is a colored liquid of about 1.050 density and acid reaction (about 10 grams per liter expressed as SO4H2). It contains little alcohol (0.2%), a little sugar and a fairly high proportion of nitrogenous materials.

A small amount of sulphate of ammonia (200 grams per 1000 liters) is useful as a nitrogenous food yeast. If sulfuric acid is added to the must, it is sufficient to add a little ammonia. The role of the acid is not to cause the inversion of sucrose. This role is filled by the yeast secretion of sucrase as and when needed. This sucrase causes the inversion of sucrose as we have seen.

d) Duration and conduct of the fermentation. — The duration of the fermentation is normally forty-eight hours. The initial density of the mixture is 1.060 to 1.080 and the temperature is 30 to 35°.

It must be avoided that the departure temperature is too high. (In no case should it exceed 40°.) The good yeasts, indeed, develop well only between relatively narrow limits of temperature, while the temperatures of 40° to 45° favor certain bacteria to the detriment of the rum fermentation. Care must therefore be taken to ensure that the vinasse is not used too hot, and it is often necessary to cool it in tanks containing cold water circulation coils or by the use of trickle coolers.

During fermentation the temperature tends to rise: so it is good to have in the tanks a coil with cold water circulation. The temperature should be maintained at 32-35°.

When the fermentation is over the density has dropped to 1.030 to 1.040.

Here is an example of molasses fermentation according to Pairault and he does not quote any more as a model.

e) Rum of high taste. – The rum of high taste or rum grand arôme is prepared by some factories. It has a special strong aromatic flavor and is a premium on the market because it supports better than ordinary rums cutting with neutral alcohol or other rums that are a little flat. As it is, it is a mediocre product of direct consumption.

The manufacturing process is secret, but from what we have said about the formation of impurities in rum, it is suggested that this rum is produced by a slow and acidic fermentation of highly concentrated musts. Moreover, there is a knack for the interested manufacturers to have just as little knowledge as possible.

a) Generalities. – The study of the distillation of musts fermented molasses escapes a little theory due to the complexity of the products involved.

Or a compound must as follows:
Mêlasse . . . . . . . . . . . . 13 litres.
Vinasse . . . . . . . . . . . . .60 —
Eau . . . . . . . . . . . . . . . . 27 —

It is easy, knowing the composition of molasses and vinasse and knowing that fermentable sugars give about 51 p. 100 alcohol, to know the proportion of alcohol in fermented musts. We thus arrive at:
Alcohol . . . . . . . . . . . . 4 p. 100
Eau . . . . . . . . . . . . . . .  74 —
Other bodies . . . . . . . 22 —

In the heading “other bodies” are products that are more or less volatile and may be distilled. The main ones are in order of decreasing volatility:

If we also consider that the fermented musts contain many other fixed or nearly fixed bodies, such as glycerine, under the practical conditions of distillation, we come to the conclusion that the fermented must is a complex mixture of fixed bodies or volatile, miscible or not with ethyl alcohol.

We know that theoretical studies on distillation have focused only on mixtures of two immiscible liquids (Gay Lussac) or two miscible liquids (Duclaux, Groening, Sorel), three miscible liquids, one of them not entering the mixture at very low dose that is to say the state of impurity (Sorel).

The conclusions to which these various authors are united are summarized as follows:

1st CAS: 2 immiscible liquids. – Whatever the proportion of the constituents, the boiling point remains fixed and the composition of the vapors constant.

2nd CAS: 2 miscible liquids. – The steam is richer in the most volatile product than the generating liquid. As the distillation progresses, the generating liquid becomes poorer, in that of the products which is the most volatile, and the boiling temperature rises. Moreover, the enrichment of the vapors depends on the initial proportion of the two liquids.

Aυ being the p. 100 of the volatile product in the vapor.
Aι being the p. 100 of the volatile product in the liquid.
According to Sorel, the coefficient K has the following values:

3rd CAS: 3 miscible liquids. – In this case we define the coefficient:

Iν being the p. 100 of the impurity in the steam.
Iι being the p. 100 of the impurity in the liquid.
Or what is more interesting when one seeks to realize the p. 100 impurity with respect to alcohol, the coefficient is defined:

called purification coefficient, K having the meaning seen in the second case. It is easy to understand that the knowledge of λ only concerns distillation processes tending to purify the phlegms obtained in the distillation of must, that is to say the rectification of alcohols.

We reproduce below a short table according to Groening, giving the boiling temperatures of the mixture of water, ethyl alcohol, under atmospheric pressure, for different contents of alcohol:

As a conclusion of this study, we will remember that:

the vapors from the distillation of the fermented must will be richer in volatile products, in particular in ethyl alcohol, which is the most abundant volatile substance in musts, than the generating liquid. We can even say from Sorel’s table that, given the alcoholic richness of the liquid, we will have an order of magnitude of the alcoholic richness of the vapors.

(b) Continuous distillation. – For the treatment of fermented molasses musts or grappe [fresh juice], only the process of continuous distillation, the principle of which is the

The liquid to be distilled falls by gravity on a succession of trays placed one above the other in a column, where it is brought to a boil, the vapors produced successively bubbling in the liquid which is on all the trays placed at above it. The steam produced on any plate, thus has a tension equal to the sum of the pressures represented by the layers of liquid which are on the upper plates. This tension therefore decreases as one goes up the column; the boiling temperature of the liquid decreases at the same time. A state of equilibrium thus tends to be established such that the alcoholic richness of the liquids increases from bottom to top in the various trays. The same is true of the vapors produced and the final vapors escaping at the top of the column are the result of this action.

It is quite obvious that the alcoholic richness of the final vapors depends on the number of trays.

Without going into a complete study of the phenomena that are going on, a study that would otherwise be uncertain given the complexity of these phenomena, we can see approximately the number of trays necessary to obtain rum at 60 degrees which is the rule in the French West Indies.

The liquid that reaches the top of the column contains for example 5 p. 100 of alcohol approximately. The exhausted vinasse escaping at the bottom of the column contains about 0.2% p. 100 of alcohol.

Assuming that the alcoholic degrees vary in a regular way in the liquids of the trays from bottom to top, one deduces approximately the alcoholic richness of the liquids of each plate. For example, a column with 10 trays. The alcoholic wealth of the various plateaus will be about p. 100.

0.2  0.7  1.3  1.9  2.4  2.9  3.5  4.0  4.5  5.0

According to Sorel’s table, we can deduce from it the richness of the vapors of alcohol emanating from p. 100.

2.4  7.7  12.5  16.8  20.5  24.2  28.0  31.4  33.9  35.7

It is concluded that in the first plate 2.4 alcohol and 97.6 steam are released. In the second it emerges:

97.6 X 7.7 / 100 = 7.5 alcohol and 92.9 water vapor, etc.

By repeating the same reasoning for a plate, we come to the conclusion that at the top of the column 172 alcohol and 73 water are disengaged, which represents an alcoholic vapor at the rate of about 70.

It would take a little less than 10 trays to get a rum to the degree desired.

In practice the condensation of water vapor is not complete in the trays, a little alcohol is retained in each tray. In addition some of the heat is lost in the column for various reasons (radiation, etc.)

Also the columns producing rum at 60 degrees commonly have 15, 20 trays and even more. We will see later how these trays are made to ensure a good bubbling vapors.

The required steam consumption is 350 to 400 kilograms of steam per hectolitre of alcohol produced.

e) Economic distillation. – In order to minimize the consumption of heating steam, the calories contained in the vinasse and in the alcoholic vapors with preliminary reheating of the fermented must.

For this purpose it is passed in tubular heaters or coil called wine heaters, analyzer or recuperator which are heated by the boiling vinasse out of the device or by alcoholic vapors. In the latter case, a certain condensation takes place which, by a phenomenon opposite to that which we have seen with regard to distillation, produces a liquid whose alcoholic strength is lower than that of the generating vapor. This liquid can be reintegrated into the column and the vapors which have not been condensed are thus richer in alcohol than at the end of the column.

Thanks to the use of the heaters, the fermented must arrives in the column at approximately boiling point.

Devices. Description. Operation. – Appliances include wholesale, the winery and distillers.

a) The winery. — The vat room is the place where the fermentation takes place. Its essential elements are:
1 ° Covered molasses tubs, where the molasses of the plant is put in depot before use. It is important for the reasons that we said above that these tanks are also protected from dust as possible.

A composition pit in which is made the mixture of molasses of water and vinasse in proportion wanted. This pit, which must be waterproof, will be frequently cleaned with lime milk (every week).

The composition can be done in the same tanks, but it is better to make the mixtures in a special container.

3° Serpentine tanks where cooling water can circulate (Fig. 113). A good capacity of the tanks is about 10,000 to 12,000 liters which corresponds to admitting an alcohol yield in volume of 4.5 to 5.0 p. 100 to 450 to 500 liters of pure alcohol per tank:

450 x 100 / 55 = 800 and 600 x 100 / 55 = 1,100 liters of rhum at 55°

If the fermentation lasts two days, it will take two vats for a production of 800 to 1,100 liters of rum per day, (not counting the mother vat). It will be good to increase the number of tanks found this way, in order to have a steering wheel allowing the cleaning or the repair of some tanks.

The tanks are filled with vinasse, water and molasses pumps.

(b) Apparatus for distillation. — The grappe falls first by gravity into a tray B (Fig. 114) and from there is taken by a pump P which sends it into a food tray located at the top of the rhummerie.

Tracking the grappe. – We will follow the path of the grappe in the different devices (Fig. 115).

At the end of the food tray A, it enters a constant level float tank F which aims to regulate the pressure at the start. Leaving F it passes through a flow control valve r then enters a first heater C1 called wine heater, tube or coil, where it is carried by the alcoholic vapors from the 65-75 ° column. The heating area is 4.5 to 5 square meters for a production of 100 liters of rum per hour.

At the end of the wine heaters, the grappe passes through a second heater C² where it is carried by the boiler out of the appliance at 90-95°. The heating area is also 4.5 to 5 square meters for a production of 100 liters of rum per hour.

The grappe then falls on the first trays of column C. The trays are schematically represented opposite fig. 116). The grappe arrives in 1 on the board, follows the path indicated by arrows and leaves by 2 from where it falls on the lower board after having come into contact with a number of boilers and where the steam comes from the lower board.

The total surface area of the trays, which varies with the system of used boilers, is 3.5 to 7 meters squares for a production of 100 liters of rum per hour.

At the bottom of the column comes the vinasse. As we have said, the vinasse is acidic (about 10 grammes of sulfuric acid per liter). It contains little alcohol (0.2% on average) and a certain amount of sugar. In addition, it contains nitrogen, potash, and phosphoric acid, on an average per cent of vinasse.

Azote . . . . . . . . . . . . . . . . . .  0.6
Acide phosphorique. . . . . . 0.06
Potasse . . . . . . . . . . . . . . . . . 1.0

Hence its value as fertilizer.

The vinasse that comes out hot from the C² heater is cooled in tanks or by runoff.

Steam path. The heating vapor returns to the base of the column at a higher pressure, as we have said, to the sum of the pressures represented by the liquid layers which are on the different plates. In general, a pressure of 100 to 200 grams above atmospheric pressure is adopted, which is sufficient.

It is very important for the proper running of the column, to have a perfectly regular pressure, pressure also related to the flow of the grappe and that we settle once and for all. This result is obtained by means of a pressure regulator, the sketch of which is shown opposite (Fig. 117).

This apparatus comprises two reservoirs 1 and 2 partially filled with liquid and communicating as shown in the figure by a pipe.

The tank 1 communicates by its upper part with the bottom of the column and is thus always at the same pressure as this column. This pressure pushes the liquid through the communication tube in the tank 2 where a float acts by an appropriate linkage on a steam control valve P. The distance of the tanks 1 and 2 can be varied and thus act on the pressure of the steam.

The steam used is exhaust steam at 1kg, 500 which is stored in a balloon. This balloon carries a lively steam intake valve that opens automatically when the pressure falls below 1kg, 500.

The heating steam works in the column as we explained. At the end of this column, the alcohol vapor passes into the wine heater C1. Partial condensation occurs as we say and the formed liquid can be returned to the column. The alcoholic vapors then enter a refrigerant R where they condense. The condensation is done by coil where cold water circulates. The cooling surface is about 3.5 to 4.0 square meters for a production of 100 liters of rum per hour.

The rum passes through a test tube with overflow E or dives an alcoholometer which allows the permanent control of its degree, then flows in a gauge (fig, 118) carrying externally a graduated tube in liters. Then it is put in casks. Rum can also be preserved in oak or vitrified steel casks.

In the French colonies the rum comes out as we have said from the apparatus at 60° apparent, which corresponds according to the tables given at the beginning of this chapter to about 55° real. In the British Colonies, St. Lucia, Trinidad, English Guiana, Jamaica, rum flows at 78° and even 80-85°. It is reduced to about 45 degrees for consumption.

As an indication, here are some digital information on two devices to be distilled in service in Martinique:

Composition of the rums. Coefficient of Impurities (from F. Annotel, Chemical Engineering, ICA – As we have said, rum, like all distilled alcohols, contains mainly ethyl alcohol C2H5OH and water, and contains a certain number of impurities which give it also its characteristic aroma, impurities which come from the raw materials but also from fermentation and distillation.

During the fermentation, not only ethyl alcohol and carbonic gas are formed, but also succinic acid and glycerine (Pasteur), fatty acids, volatile acids, higher alcohols, ethers, and the like. The composition of the must, its temperature, its degree of acidity, the nature of the yeast, influence the formation of these products and consequently have a direct action on the aroma of the rum.

During the distillation, furfurol is mainly formed. This furfurol comes from the action of heat on cellulosic materials and the action of acids on starchy materials.

The weight in grams of the non-alcohols contained in one hectolitre of alcohol at 100° centesimal is called the impurity coefficient.

According to Annotel, here are some analyzes of rums and the corresponding impurity coefficients.

The impurity coefficients resulting from the above analyzes are very high. Today, much lower levels of impurities, 200 to 300, are commonly obtained. The difference between natural rums and industrial alcohols in this respect is decreasing and the protective measure for natural alcohols, which consisted in requiring a high impurity coefficient had to be modified. Nowadays we only need an impurity coefficient of 200 (and in some cases 150).

Aging rum. — The rum ages like all eaux-de-vie and thus acquires with the years a fine taste that brings it much closer to old Cognac.

The aging is due in particular to the etherification of the acids and to the oxidation by the air, the rum is aged in barrels or in oak casks and with the time it evaporates very appreciably.

Currently few rums of molasses are aged, The old rums are almost exclusively rums from agricultural distilleries where they ferment and distilled the vesou.

The molasses rum is used to make cuts or is consumed before aging as we have seen. The rums with a grand arôme, which are more advantageous from this point of view, are more important than the others.

The export of industrial rum is made in the year following its manufacture in new oak casks of 250-260 liters and sometimes when it is intended for rectification, in iron barrels.

Control of the manufacture. — This control relates to two points:
1° Determination of the theoretical quantity of alcohol that can be obtained and the quantity practically obtained.
2° Assessment of the impurity coefficient.
a) Determination of alcohol yield. — The raw material being the must, the first thing to do is the dosage of the total reductants in this must.

Determination of total reductants in the musts. — We have said that total reducers include natural reducing sugars and reducing sugars from sucrose reversal. We saw in the sugar house how these reducers were determined.

We know that if a is sucrose for 100 and b direct reducers for 100, the total reductants T are:

and that the yield of absolute alcohol will theoretically be:

In volume the theoretical output will be:

0.79 being the density of the absolute alcohol at 15° centigrade, the theoretical yield in rum at 55° will thus be:

Analysis of fermented musts. — The statement will cover the quantity of reducers not processed into alcohol. We will operate as follows:

The alcohol will be removed by boiling. Acidify with HCL, invert and reduce the reducers after inversion.

Analysis of the vinasses. — The vinasses will be used for alcohol lost during distillation. For this purpose, one liter of vinasse will be collected, which will be neutralized and distilled slowly. In this way, a certain amount of alcohol will be collected and titrated with alcohol.

We will be after these analyzes able to know:
A) The theoretical amount of alcohol that should be obtained A;
B) The actual amount collected (by direct measurement) A¹;
C) The origin and the value of the losses, by non-fermentation of a certain quantity of reducing agents in the musts and by loss of alcohol in the A² vinasse.

We will have:
A = A¹+A²+X

X representing indeterminate losses.

We have already said that industrial output is between 70% and 85%. 100.

b) Evaluation of the impurity coefficient (according to F. Annotel). Let us first remark that rhummeries rarely have a laboratory well equipped to be able to make the determinations which lead to the evaluation of the impurity coefficient which is, as we have said, in direct relation with the aroma, and the quality rum.

Volatile acids, aldehydes, ethers, higher alcohols, furfurol will be tested.

1° The volatile acids easily measured by difference between the total acids titrated with a solution of soda and the fixed acids titrated in the same way after evaporation in vacuo.

2° The determination of the aldehydes will be by colorimetric method. A typical solution of ethyl aldehyde and a solution of fuchsin will be prepared. The standard solution and the solution studied will be stained with fuchsin in the same proportion. We will compare the two colors and by means of special tables we will deduce the desired content of aldehyde. It should also be noted that the coloring is not proportional to this content;

3° The ethers are dosed with a titrated SO4H2 liquor;

4° The higher alcohols are dosed using the fact that SO4H2 browns the higher alcohols and does not stain the ethyl alcohol; it is necessary to eliminate before operating the aldehydes which give the same coloring. They will be removed for example by means of the acid phosphate of aniline. The higher alcohols are then calorimetrically measured using a standard solution of isobutyl alcohol dissolved in alcohol.

(5) Furfurol will also be measured by colorimetric method using a standard solution of furfurol and mixed with the two solutions of pure aniline and glacial acetic acid.

For example, the following result can be found:

The impurity coefficient will be 326.7:

We have been content with very basic indications. It is easy to see that the measure of the impurity coefficient escapes a little the normal means of an industrial distillery.


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