Evaluation of Electrical Conductivity as a Quality Parameter of Lemongrass Leaves (Cymbopogon citratus Stapf) Submitted to Drying Process

Abstract

This study aims to evaluate the quality of lemongrass plants after drying at different speeds (1.0, 1.5, 2.0 m s⁻¹), temperatures (40, 50, 60, and 70°C), and drying air control systems (manual and automatic) using electrical conductivity as a parameter for evaluation. Firstly, we evaluated the time necessary for imbibitions of material in deionized water after drying for different air speeds and control systems. Secondly, the effect of temperature in fresh and dry plants was evaluated, comparing them with contents of essential oils and the quantity of ions leached by the electrical conductivity test. According to the results, the value of liquid diffusion increased with the increase of drying air temperature, and the value of activation energy was 62.84 kJ mol⁻¹. The quality of lemongrass plants evaluated by the electrical conductivity test was inversely proportional to the increase in drying air temperature, and the levels of essential oils were higher in dry plants with lower drying air temperatures. The adaptation of the electrical conductivity methodology to lemongrass plants was effective. A period of 33 h of imbibitions of the material in deionized water was necessary to obtain consistent results from leaching of potassium ions. The electrical conductivity can be used as a quality parameter for drying of medicinal plants.

Keywords:

• Air
• Control
• Plant
• Speed
• Temperature

Notes

Means followed by the same letter do not differ at a 5% probability.

Means followed by capital letters for each type of velocity of the drying air and lowercase for each type of speed control of the drying air do not differ at a 5% probability.

Means followed by capital letters for each type of velocity of the drying air and lowercase for each type of speed control of the drying air do not differ at a 5% probability.

T = tendentious, R = randomized.

^a All estimated coefficients were significant at 5% probability by t test.

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