236 OUTLINES OF BACTERIOLOGY 



2. The Sweating or Fermentation Process. Fermentation produces 

 further changes in the substances formed during the curing. This 

 process may be effected in either of two ways. According to one 

 method, the leaves are left hanging a long time, being then packed 

 closely in boxes in a very slightly damped condition. They are then 

 left to themselves for several months. Fermentation develops without 

 any further care being bestowed on them by the grower. The 

 boxes are finally opened, when the leaves will be ready for the manu- 

 facturer. The other method, which produces better tobacco, is fermen- 

 tation in open piles. It can be employed in temperate climates only 

 if artificial heat be used. A number of leaves are tied together at the 

 base, forming what is technically called a " hand." These " hands " 

 are well shaken to admit air to every part, moistened if necessary, and 

 then heaped together to form a large pile, each about four to five feet 

 wide and twelve to fifteen feet loiig. Each is made so that the butts 

 point to the outside. The surrounding atmosphere is kept warm and 

 steam passes freely into the air to secure uniform moisture. All this 

 results in a rise of the temperature of the leaves which, in three or four 

 days, reaches 52° C. (126° F.), or higher. Repacking becomes now 

 necessary to check the rise of temperature. A new pile is made, but 

 this time, to secure uniformity of treatment, the lower " hands " are 

 placed on the top and the outer ones in the centre. The temperature 

 will again rise, but this time more slowly, so that the next repacking 

 will not be necessary for about seven or eight days. Altogether the 

 piles are repacked some five to eight times. This process naturally 

 effects wide changes in the constitution of the leaves. There is a decrease 

 in the quantity of nicotine, tannin, and potassium nitrate, whilst the 

 sugar disappears altogether. These substances are oxidised, giving rise 

 to a number of other substances. The result of all these changes is 

 to cause the leaf to assume a darkish brown colour, when it is ready 

 for the manufacturer. 



Nature of this Fermentation. Diverse opinions exist with regard to 

 the nature of the changes that have taken place. Three points have 

 to be noted : 



1. The large rise in temperature when the leaves are packed. 



2. The oxidation of the nicotine, tannin, etc. 



3. The development of the aroma and flavour. 



According to one view the oxygen of the atmosphere is held to be 

 sufficient to explain the oxidations, whilst bacterial action is held 

 responsible for the development of heat and for the production of the 

 aroma and flavour. Another view makes bacteria responsible for all 



