علی رضوانی اقدم

Pre-drying operations and drying methods have a significant effect on the quantity and quality of plants essential oils.

In this study, the effect of pre-drying operation and vacuum oven-drying was investigated on the essential oil content and composition of Lippia citriodora.

This research was conducted as a factorial experiment in a completely randomized design (CRD) with three replications. The two studied factors were (1) pre-drying operations in two levels including pre-drying and without pre-drying operation, and also (2) drying methods in 5 levels including fresh plant, shade drying and vacuum oven-drying at 35, 45 and 55°C at 0.5 bar atmospheric pressure.  In this study, the amount of pigments and essential oil content and composition were measured.

The results indicated that the highest chlorophyll content was related to treatment of vacuum oven-drying at 55 °C with a pre-drying treatment, while the highest amount of essential oil was obtained by vacuum oven-drying at 45 °C without a pre-drying operation. The highest amounts of monoterpene hydrocarbons, oxygenated monoterpenes, and geranial were obtained by drying at 55 °C, while the highest content of sesquiterpene hydrocarbons, oxygenated sesquiterpenes and neral were observed in Low-temperature drying.

In general, this study indicated that vacuum oven-drying at 45 °C was the best drying method for obtaining maximum content of essential oil and active components.

Aromatic herbs are considered the most valuable antioxidant source in nature. In this research, 3 different ecotypes of Oliveria decumbens vent. were collected from three important regions in Khuzestan province, including Behbahan, Shushtar and Masjed Soleyman in flowering stage. Essential oils were extracted by hydrodistillation method (Clevenger apparatus) and d were analyzed by GC /Mass and the antioxidant activities were specified by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Results were showed that the highest thymol (29.67) and carvacrol (27.88%) were dominanted in Behbahan region oil. The percentage of degradation of DPPH free radicals in different concentrations of essential oil including 50, 100, 200, 300, and 400 μl were calculated to determine the antioxidant activity of the essential oil. The IC50 values were calculated 34.21, 26.85 and 21.23, respectively from Shushtar, Masjed Soleyman and Behbahan regions. Finally, Behbahan ecotype with the highest source of thymol, carvacrol and antioxidant properties can be considered as a new best natural source of antioxidant supply.

Dried garlic with various nutritional and medicinal values is used in food industry as flakes or powder. The nutritional and medicinal properties of garlic are attributed to Allicin. This substance (a compound of Tyosulfinates) is produced enzymatically after crushing. Since the temperature affects the enzymatic action that results in pirovic acid and allicin. The size and temperature are two critical factors to prevent color change and reduce allicin and pirovic acid present in garlic during drying process.
This study investigated the effects of sample size and temperature on qualitative characteristics such as color of powder and pirovic acid and alicin retention in a convective hot-air dryer. For this reason whole and half and minced Shushtar garlics (Allium sativum L.) were dried at air temperatures of 50 and 70°C with the relative humidity of 22%.
According to the obtained results by increasing the temperature from 50 to 70 C the color of half garlic have changed and allicin and pirovic acid have been increased. The quantity of pirovic acid and color of the minced samples were not affected significantly by the temperature of drier but allicin content of minced samples were reduced by increased temperature. Whole garlic dried at 70 °C was not affected by change in color but the quantities of present allicin and pirovic acid were reduced considerably.
According to the findings in this research work the condition that the halved samples were dried at 70 °C could be regarded as the best condition for producing garlic powder.