Steam Hydrodistillation Research Articles

Effect of Harvesting Treatments and Distillation Methods on the Essential Oil of Lemon Balm and Apple Geranium Plants

The effects of harvesting treatments and / or distillation methods (hydrodistillation, hydro-steam distillation and steam distillation) on the essential oil content and composition of Pelargonium odoratissimum L. and Melissa officinalis L. plants were carried out in a greenhouse at Shanghai Institute of Plant Physiology and Ecology (SIPPE), Shanghai, China, during the years of 2007 and 2008. The highest oil yield of P. odoratissimum L. and M. officinalis L. was obtained by hydrodistillation and the lowest by steam distillation. The essential oil was significantly decreased towards the second harvesting. The main component of P. odoratissimum essential oil extracted by hydrodistillation was methyl eugenol (25.9 % - 30.4 %), while the main component of hydro-steam distilled or steam distilled oil was limonene (30.5 % - 32.4 % for hydro-steam distilled oil and 38.8 % - 49.4 % for steam distilled oil). The most abundant compound of M. officinalis oil extracted by hydrodistillation or hydro- steam distillation was citronellal (36.1 % - 37.8 % for hydrodistillation and 27.3 % - 29.8 % for hydro- steam distillation ), whereas αthe essential oil content and co-terpinene (20.2 % - 21.9 %) was the main component with steam distillation. The oxygenated compounds and hydrocarbon compounds were changed according to the distillation methods and / or harvesting number for both P. odoratissimum and M. officinalis. plants.

Studies on the effects of microwave drying and cabinet tray drying on the chemical composition of volatile oils of garlic powders

Garlic cloves in the form of bits were dried in a cabinet tray dryer and a microwave dryer, and pulverized to obtain free flowing powder. The volatile oil was obtained by hydro-steam distillation method. Fresh cloves and the powders resulting from the two drying methods were used for obtaining the volatile oil, which was analyzed by GC-MS. The studies were mainly restricted to comparing the effect of drying methods on the volatile oil composition of the powders. Although the drying time was reduced considerably from 8 h in a cabinet dryer to 0.25 h in a microwave dryer, essential oil yield and color values were lower, and flavor quality varied considerably. The relative concentrations of major peaks such as diallyl disulfide, diallyl tetrasulfide increased in both the drying methods, and it was more so in microwave-dried samples. However, the concentrations of the other two major peaks, diallyl trisulfide and allyl methyl trisulfide, decreased in both drying methods, and they were lower in microwave-dried samples. Hunter values of L and b were lower for samples obtained by microwave drying as compared to those of cabinet-dried samples.

Characterization of the Volatile Pattern and Antioxidant Capacity of Essential Oils from Different Species of the Genus Ocimum

The antioxidant capacity of essential oils obtained by steam hydrodistillation from five species of the genus Ocimum, namely Ocimum basilicum var. purpurascens, Ocimum basilicum, Ocimum gratissimum, Ocimum micranthum, and Ocimum tenuiflorum (syn. O. sanctum), were evaluated using a high-performance liquid chromatography-based hypoxanthine/xanthine oxidase and the DPPH assays. The yield of oils from the leaves of the five species was variable with the greater amount obtained from Ocimum gratissimum (3.5%) and the least from Ocimum basilicum var. purpurascens (0.5%). In the hypoxanthine/xanthine oxidase assay, strong antioxidant capacity was evident in all the oils but the greater was shown by that obtained from Ocimum tenuiflorum (syn. O. sanctum) (IC50 = 0.46 microL/mL) compared to Ocimum basilicum var. purpurascens (IC50 = 1.84 microL/mL). Antioxidant capacity was positively correlated (r = 0.92, p < 0.05) with a high proportion of compounds possessing a phenolic ring such as eugenol, while a strong negative correlation (r = -0.77, p > 0.1) with other major volatiles was observed. These correlations were confirmed to a large extent in the DPPH assay. The results of a 24 h experiment with Ocimum tenuiflorum (syn. O. sanctum) shows that the antioxidant capacity factor (amount of essential oil obtained x free radical scavenging capacity; mg x %/100) reaches a threshold between 10 and 12.00 h, corresponding to maximum sunlight intensity in Brasil and furthermore exhibits a clear diurnal variation. The data generated with Ocimum species indicates that essential oils obtained from various herbs and spices may have an important role to play in cancer chemoprevention, functional foods, and in the preservation of pharmacologic products.

Determination of 2-Hydroxy-4-Methoxybenzaldehyde in Roots of Decalepis hamiltonii (Wight &amp; Arn.) and Hemidesmus indicus R.Br.

The roots of Decalepis hamiltonii and Hemidesmus indicus are aromatic and possess the crystalline compound 2-hydroxy-4-methoxybenzaldehyde as the major compound (> 90%) in their volatile oils. A gas chromatographic procedure was developed for the assay of 2-hydroxy-4-methoxybenzaldehyde in both fresh and dried roots of different origin. Benzyl butyrate was used as the internal standard. Among the methods tried, steam hydrodistillation was suitable for extraction of the volatile oils. The quantity of this aromatic compound varied from 0.03 to 0.54%.

Chemical Composition of the Essential Oil and Headspace Solid-Phase Microextraction of the Guava Fruit (Psidium guajava L.)

The oil and headspace of fresh white flesh guava fruits (Psidium guajava L.) from trees grown in Reunion island were obtained by steam hydrodistillation and headspace solid-phase microextraction (SPME), respectively. The chemical composition of the extract was investigated by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). A total of 73 compounds were identified, of which 61 by hydrodistillation and 24 by headspace SPME. In the headspace, the major constituents were: hexanal (65.9%), γ-butyrolactone (7.6%), (E)-2-hexenal (7.4%), (E,E)-2,4-hexadienal (2.2%), (Z)-3-hexenal (2.0%), (Z)-2-hexenal (1.0%), (Z)-3-hexenyl acetate (1.3%) and phenol (1.6%), while β-caryophyllene (24.1%), nerolidol (17.3%), 3-phenylpropyl acetate (5.3%) and caryophyllene oxide (5.1%) were the major volatile constituents present in the hydrodistilled oil. Many compounds were identified for the first time in the guava fruit such as γ-butyrolactone (7.6%) in the headspace SPME and nerolidol (17.6%) in the oil. In addition some compounds such as (Z)-3-hexenal, (E,E)-2,4-hexadienal, γ-butyrolactone, borneol, phenol, cuminyl alcohol could be identified only by the headspace method (SPME).