Technological and Technical Development of Tobacco Drying
Technological and Technical Development of Tobacco Drying
Technological and Technical Development of Tobacco Drying
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Every year we emphasize to do topping <strong>and</strong> sucker control in an early time, because these technology<br />
elements have a large influence for the quality <strong>and</strong> ripening time.<br />
Last <strong>and</strong> this year some trials were made to evaluate the influence <strong>of</strong> the ripeness. The experience was,<br />
that the degree <strong>of</strong> maturity had a considerable influence on the yield <strong>and</strong> quality <strong>of</strong> tobacco (Kerekes,<br />
1999).<br />
The Table 1. shows the effect <strong>of</strong> degree <strong>of</strong> maturity at harvest on yield, quality category, nicotine content,<br />
carbohydrate <strong>and</strong> income.<br />
Table 1. Influence <strong>of</strong> maturity on some features<br />
Treatment Yield<br />
t/ha<br />
Quality<br />
category<br />
(Class)<br />
Unriped 2,13 2 nd , 3 rd<br />
Riped 2,04 1 st<br />
Overriped 1,93 1 st , 2 nd<br />
Nicotine<br />
content<br />
%<br />
Carbohydrate<br />
%<br />
Income<br />
%<br />
3,63 15,94 83<br />
1,21 29,86 100<br />
2,55 15,17 91<br />
In these tests the unriped tobacco lacked about one week <strong>of</strong> being as ripe as the growers prefer for<br />
harvesting. The overriped tobacco stayed in the field about 7 days longer than usual.<br />
These data showed a reduction in yield with a delay in harvest. The quality <strong>of</strong> the cured tobacco was<br />
worse, when the tobacco differed from the ripped condition. The nicotine content considerably high,<br />
when the tobacco unriped or overriped, comparing with the optimum harvesting. The amount <strong>of</strong> the<br />
carbohydrate was half <strong>of</strong> the required rate.<br />
The income was increased from unriped to ripped, but was decreased when the tobacco became<br />
overriped.<br />
In Hungary the racks are sometimes loaded at the barns <strong>and</strong> not directly on the field. It means more<br />
working time <strong>and</strong> labour, as well as the leaves sustain a loss.<br />
The <strong>Tobacco</strong> Processing Corporation - with my cooperation - elaborated a proposal for h<strong>and</strong>-harvesting:<br />
the farmers can gather the tobacco leaves directly into the racks placed on a special vehicle, which are<br />
transported immediately to the barns.<br />
In some cases it was used bins instead <strong>of</strong> racks, but it was found, that the loading never was perfect so<br />
that the curing was not so successful. The quality <strong>of</strong> the dried leaves was poor <strong>and</strong> the curing time<br />
increased significantly.<br />
In the tobacco farms the workers strive to load full one barn during a day. But sometimes it happens, they<br />
load the racks unevenly so that it does not develop a uniform air-circulation through the racks.<br />
In loading bulk kilns, it must be pushed the racks tightly together to ensure, that the air will move through<br />
the leaves rather than between the racks. Also, it has to be closed <strong>of</strong>f any space between the racks <strong>and</strong><br />
loading doors with fiberboard or other material.<br />
Despite the technical development, the purpose was to improve the quality <strong>of</strong> the cured tobacco <strong>and</strong><br />
decrease the energy dem<strong>and</strong> by working out a modified drying technology.<br />
During application <strong>of</strong> the conventional curing process, the cure man has to strive for that the wet-bulb<br />
temperature remains at about 30-35 o C, disregarding the start <strong>and</strong> finish phases. The relative humidity in<br />
the barn is lower <strong>and</strong> decreases rapidly.<br />
The degree <strong>of</strong> air changing is determined by this rule. It means that we have to open the external air<br />
louver <strong>of</strong> the barn too <strong>of</strong>ten <strong>and</strong> for a longer time. This conventional technology requires much more<br />
energy for curing <strong>and</strong> disadvantageous for the chemical components <strong>of</strong> the end-product (Kerekes, 1996).<br />
The developed experimental curing features are demonstrated in the following figures. The change <strong>of</strong><br />
temperature <strong>and</strong> relative humidity are shown in Figure 1. <strong>and</strong> 2.