Psychrometric parameters for accelerated yellowing of burley tobacco

The green-to-yellow phase of an accelerated cure of burley tobacco was examined on a laboratory scale. Nine curing cabinets for small samples (100 leaves) were especially designed for this experiment along with controls which maintained temperature within ± 0.5°F and relative humidity within ± 3 percent.

Nine combinations of temperature and relative humidity which covered the range of expected optimum combinations were examined in a 3x3 factorial experiment. Evaluation of each treatment was made after a 60-hour period by matching leaf color with preselected standard Munsell colors, including an optimum yellow. A regression equation was formulated that established a relationship among temperature, relative humidity and color. A curve of the temperature-relative humidity combination for the optimum color was presented. Four additional selected temperature-relative humidity combinations were used in a 60-hour cure to check the regression equation. The equation was found to closely predict the resultant color.

The results indicated that burley tobacco can be satisfactorily yellowed in an accelerated bulk cure with color comparable to that found in conventionally cured tobacco. However, an increase in temperature requires a corresponding increase in relative humidity for optimum yellowing. A maximum relative humidity for this phase of the cure appeared to be approximately 90 percent.