Evaluation of Electrical Conductivity as a Quality Parameter of Lemongrass Leaves (Cymbopogon citratusStapf) 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 À1 ), 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 À1 . 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.

Physical quality of grains subjected to moistening and drying processes for marketing

“…Increasing the drying temperature and time led to greater cell damage to the grain tissues, according to results reported by other authors (Oliveira et al, 2013;Coradi et al, 2014). However, the wetting was not an intensive increase in electrical conductivity.…”

“…The loss of grain quality due to the leaching of ions was verified through the electrical conductivity, that is, the rewetting of the grains contributed to the reduction in quality, in proportions similar to those in the drying. However, higher electrical conductivity values coincided with the higher temperature treatments, because these conditions promoted largest amount of leached ions, i.e., greater disruption of cell membranes of the tissues that make up the grains (Vieira, 2008;Siqueira et al, 2011;Coradi et al, 2014). Thus, it can be seen that increased water content in the grains for the allowed marketing conditions (13.5% w.b.)…”

“…Ambiental, v.20, n.9, p.847-855, 2016. time and temperature to which the grains were subjected during the drying step. These events occur because the water potential is much changed, especially in the early imbibing, influencing the water absorption and may derail the sequence of events related to the process (Vieira, 2008;Coradi et al, 2014).…”

Effects of drying air temperature and grain initial moisture content on soybean quality (Glycine Max (L.) Merrill)

“…), causing a chain of random undesirable reactions. According to CORADI et al (2014a), once cell disruption is observed, those reactions become irreversible, resulting in a product of poorer quality at the end of the process.…”

“…For storing and selling, moisture content of soybeans must not exceed 14%, or even 12%, because it would improve storage quality. Therefore, drying process is extremely important; however, it may damage grains for changing their physical properties or even causing direct damage thereto NIAMNUY et al, 2011;SOUSA et al, 2011;CORADI et al 2014a). Even though the mechanical drying of soybeans can anticipate harvest, the high air temperatures involved in such process may cause biochemical changes in the product, affecting its quality.…”