Arroyo Valdespino, Rafael (1892–1949), has arguably had a greater influence on modern rum production than any other figure. As head of the Agricultural Experiment Station of Puerto Rico in the 1940s, Arroyo made significant advances that are still the backbone of the industry today. Cuban born but educated in Louisiana, Arroyo was best known for his seminal 1945 text, Studies on Rum, as well as for patents held for heavy rum production.
Arroyo’s Studies sought to reveal the mysteries of distillation of both commodity rums and fine rums at every stage of production. Commodity rums benefited from his examination of molasses pretreatment techniques to prevent detrimental scaling of continuous column equipment, which at the time created maintenance problems that frequently shut down operations. Fine rums benefited from his explorations of (and possible experimentations with) the yeast The progressive process of slow, meticulous advancement was expounded by Arroyo, and he illustrated methods for homing in on optimal production parameters. Much success was attributed to the use of novel micro-distillation analysis techniques in the laboratory, and Arroyo was among the first to put significant emphasis on rum oil as a congener class while others were focused primarily on esters. Rum oil, to which Arroyo attributed the “suavity” of great rum, was only maximized by careful attention to every stage of production and integrated into decisions regarding every other congener class. Arroyo’s efforts to improve the art of rum distilling were cut short by his untimely death in 1949 at the age of fifty-seven while still completing his ambitious work. Arroyo, Rafael. Studies on Rum. Rio Piedras: University of Puerto Rico, Agricultural Experiment Station, 1945. “Necrology.” Chemical and Engineering News 27 (1949): 3643. By: Stephen Shellenberger