Dr. Oscar Loew of the United States Department of Agriculture’s Division of Vegetable Physiology and Pathology wrote Curing and Fermentation of Cigar Leaf Tobacco in 1899 after doing his own research and exploring the research of others. It dives deep into what happens to tobacco during the chemical processes of curing and fermenting. If you’re interested in the changes that happen to leaves after they are taken from the field, this is a fascinating resource.

After going through the various changes that leaves undergo in the curing process, Loew summarizes by saying: “The principal changes in the curing process may be summed up as follows:

  1. Disappearance of starch
  2. Formation of sugar and its partial disappearance by respiration
  3. Decomposition of protein with formation of amido compounds
  4. Decrease of fatty matter
  5. Decrease of tannin
  6. Change of color and flavor”1

After examining the changes that occur during fermentation, Loew summarizes again: “The principal changes which take place during the sweating or fermentation process, as found by various investigators, may be summed up as follows:

  1. Decrease of nicotine
  2. Increase of ammonia
  3. Increase of alkaline reaction
  4. Disappearance of sugar
  5. Decrease of nitrate
  6. Improvement of flavor and aroma”2

Loew also describes a process called ‘petuning’, which “consists in spraying a liquid on the leaves during or after the sweating process. The fillers only, and not the wrappers, are petuned, the intention being to give them a darker color, an improved flavor, and the appearance and character of a strong tobacco.”3 The petuning liquid mixtures are kept secret by those who use them, though “it is generally believed that one method of preparing the petuning fluid is by pouring organic fluids yielding ammonium carbonate over crushed tobacco stems, and letting this mixture digest.”3 He goes on to describe how leaves that have been ‘petuned’ often grow undesirable bacteria, and he advises against smoking such leaves.

Curing and Fermentation of Cigar Leaf Tobacco is in the public domain and can be read for free on Google Books.

  1. Dr. Oscar Loew, Curing and Fermentation of Cigar Leaf Tobacco, 1899, pg. 13 [↩]
  2. Dr. Oscar Loew, Curing and Fermentation of Cigar Leaf Tobacco, 1899, pg. 18 [↩]
  3. Dr. Oscar Loew, Curing and Fermentation of Cigar Leaf Tobacco, 1899, pg. 19 [↩] [↩]