Arroyo 1941: Practical Results of Our Research in Manufacturing Rum

Arroyo R. Resultados Practicos de Nuestras Investigaciones en Manufactura de Ron. Revista de agricultura de Puerto Rico, Volume 33 (1941), 283-285.

Practical Results of Our Research in Rum Manufacturing
By Rafael Arroyo.
Jefe, División de Química Industrial, Estación Experimental Agriciola,
Universidad de Puerto Rico

Aware that the majority of the public is not interested in how results are achieved, as in the results themselves, we propose to relate in the simplest and least technical language possible, those practical results of our work, supposed to be of general public interest.

We will intentionally omit from this article those other results of a purely scientific nature; but in reality no less valuable than the others presented here.

In the course of our studies we have tried to foresee pitfalls that may arise in the way of our rum industry, and we have tried to find anticipated solutions to their appearance within the industry, so that, when confronted with the problem by the practical distiller, there is already experimental data that could serve at least as a starting point in the method to be followed for the solution of the personal and particular problem. We refer only and exclusively, of course, to problems of a technical nature.

Among the many and varied problems that the rum manufacturing distiller must necessarily find, we have observed the following most frequently and unfortunately:

1. Obtaining low fermentation efficiencies.
2. The problem of “Tufo” in raw rums.
3. Problems in the maturation of raw rum.
4. Creation of new types different from market currents.

1. Obtaining low fermentation efficiency means low alcohol content in the fermented batición in relation to the total available amount of sugars in the batición before being fermented.

According to data obtained by us, the fermentation efficiency varied greatly between one and another distilleries, reaching in some cases surprising disparities; except in the cases of two distilleries, the results obtained were generally too poor, fluctuating between 60 and 80 percent of the theoretically possible efficiency.

Obtaining this data, we immediately began to investigate all the factors that may be due to these low fermentation efficiencies. We soon came to the conclusion that this evil can be avoided by the following practices:

(a) Submitting the raw material to a pasteurization process before making the batición.
(b) Carrying out a complete analysis of the raw material, especially as regards deficiencies in phosphorus and nitrogen content, and remedying these deficiencies if necessary.
(c) Conducting a thorough study of the yeast used for fermentation, especially in terms of optimal pH values and concentration of sugars in the batición that best suite them; and applying this knowledge at the time of making the batición.
(d) Seeding this batición with sufficient amount of yeast to obtain high initial cell concentration.
(e) Maintaining, as much as possible during the fermentation period, optimal conditions of temperature and pH value.

All this has been widely discussed and published in local newspapers and magazines for information of the interested parties.

Soon we realized that following the instructions itself it was easy for us to obtain fermentative efficiencies of 93 to 95 percent of the theoretical according to Pasteur.

2. The problem of the elimination of the tufo in the crude distillate was another matter of great importance that it was our duty to address.

In practice we could observe that our distillers tried to eliminate the “tufo”, by producing alcohol instead of rum, that is, denaturing the product.

Not agreeing with such practice we strive to eliminate the “tufo” without harming or changing the inherent characteristics of a genuine rum; that is, without turning it into something that stops being rum.

Our studies in that sense led us to the conclusion that the so-called “tufo” of raw rum came from two different sources:

(a) That part of the smell inherent to the raw material itself, or formed during the fermentation period.
(b) That other part that is formed during the distillation of the batición.

Both forms are completely removable; but in a different way; the first by suitable fermentation methods, and the second by mechanical elimination methods.

By means of the suitable selection of raw material and water with which the batición is prepared, and following the rules already explained to obtain high fermentation efficiency, it is possible to eliminate the “tufo” cataloged under (a) above. As for the elimination of that part of the “tufo” that is formed in the alembic during distillation, it is easily eliminated if we consider the following two factors:

(a) Maintain the interior cleanliness of the still at all times.
(b) Separating by filtration all the solid matter contained in the fermented batición before proceeding with its distillation.

Following these practices we have been able to distill rums as low as 100 proof without suffering from the defect of the bad smell called “tufo”. On several occasions we have also written on this subject for the benefit of those interested.

3. The maturation of raw rum was one of the biggest problems since the beginning of the industry; this problem will be accentuated more every day, as the consuming public learns to differentiate, to judge and select commercial rums, not only in terms of taste and aroma, but also in terms of the more or less unpleasant and toxic effects that each brand produces.

At the beginning of the industry we observed that with very rare exceptions, all rum producers decided on artificial or accelerated maturation. We tried to dissuade them from this practice, because our experiments had indicated to us that it was not the safest nor the one that could offer permanent satisfaction neither to the industrialist nor to the consumer.

We were told that the classical method of aging in oak barrels was too slow, and even more expensive. We admit the objection; but immediately we are dedicated to the search of means to obtain the maturity of the raw rum by the classic method, but in a short time of aging, in months instead of years.

The final result has been more than satisfactory, as we have rums that have reached commercial maturity in the short period of six months of aging in oak barrels.

We have also exposed on several occasions what the technique is for obtaining these results.

4. We will mention, in the last analysis, the creation of two new types of rum in the native industry; the “Whiskey Rum” and the “Jamaican type rum”.

Using a special fermentation technique, we have managed to produce a rum with a “Scotch Whiskey” flavor and smell, but in fact it is superior to whiskey in aroma and flavor. The possibilities that a rum of these characteristics can have for the native industry remain to be known and they are a thing of the future, but we do not think it risky to suppose that it would make a decisive step in a market like the United States or England, where “whiskey” constitutes the national drink.

As for Jamaican-style rum, we wish to point out that it is not a cheap imitation of the excellent rums of the neighboring island, so famous and praised throughout the world; but it is a rum of quality and constitution exactly like the best products of Jamaica. Of this kind of rum we have made six different types.

German and Jamaican experts who have tasted them and put them to all kinds of tests, have declared them as good, and even better in some cases, than those made in Jamaica.

Up to here some of the most outstanding practical results of our research on manufacturing rum.