Comparison of microwave-assisted hydrodistillation withthe traditional hydrodistillation method in the extractionof essential oils from Thymus vulgaris L.

Microwave-assisted hydrodistillation (MAHD) is an advanced hydrodistillation (HD) technique utilizing a microwave oven in the extraction process. MAHD of essential oils from the aerial parts (tops) of Thymus vulgaris L. (common thyme) was studied and the results were compared with those of the conventional HD in terms of extraction time, extraction yield/efficiency, chemical composition, quality of the essential oils and cost of the operation. MAHD was superior in terms of saving energy and extraction time (75 min, compared to 4 h in HD). Scanning electron microscopy (SEM) of thyme leaves undergone HD and MAHD provided evidences as to a sudden rupture of essential oil glands with MAHD. Gas chromatography–mass spectrometry analysis of the extracted essential oils indicated that the use of microwave irradiation did not adversely influence the composition of the essential oils. MAHD was found to be a green technology.     

Hydrodistillation and in situ microwave‐generated hydrodistillation of fresh and dried mint leaves: a comparison study

BACKGROUND: Hydrodistillation (HD) has been used since ancient times for the extraction of essential oils (EO). Despite the intrinsic limitations of this technique, it remains the most common method both in the laboratory and on an industrial scale. The main drawbacks are the long extraction time involved and the risk of thermal degradation. Over the last decade, microwave‐assisted extraction (MAE) and in situ microwave‐generated hydrodistillation (MGH) have been shown to be the most promising techniques in improving plant extraction and hydrodistillation. RESULTS: In this study we compare HD with MGH in the extraction of several mint species cultivated in Piedmont: Mentha spicata L. var. rubra, Mentha spicata L. var. viridis and Mentha piperita L. MGH requires either fresh plant or rehydrated material, it is extremely fast and allows a reduction in energy consumption and overall cost. All the EO have been analyzed by gas chromatography‐mass spectrometry. A mechanism of microwave‐generated essential oil extraction has been proposed to explain the differences in the composition of the oil obtained from this environmentally friendly technique. CONCLUSIONS: The yields and composition percentages of the EO obtained by HD and in situ MGH of fresh and dried mint leaves lie in a relatively narrow range, although MGH is faster. MW polarization effects and the water solubility of the components influence extract composition Copyright © 2012 Society of Chemical Industry     

Effect of oregano and thyme essential oils on the microbiological and chemical quality of refrigerated (4 °C) ready‐to‐eat squid rings

The efficacy of oregano and thyme essential oils (OEO and TEO, respectively) in the quality retention of a refrigerated (4 °C) squid (Loligo vulgaris) ring ready‐to‐eat (RTE) product was studied. Essential oils were added at different concentrations to the coating medium during processing. An inhibitory (P < 0.05) effect of OEO on the microbial activity (aerobes, anaerobes, Enterobacteriaceae, psychrotrophs) of the squid rings was observed, with a more pronounced effect as OEO concentration increased. The addition of OEO also led to an inhibitory (P < 0.05) effect on lipid oxidation, as determined by peroxide, thiobarbituric acid‐reactive substance and interaction compound formation; however, no effect (P > 0.05) of the OEO concentrations on lipid oxidation development was detected. The addition of TEO did not lead to an inhibitory effect (P > 0.05) on the microbial activity of the refrigerated RTE squid, although a slight inhibitory (P < 0.05) effect on lipid oxidation was observed in the batches including the higher TEO concentrations.     

Essential oil composition and antibacterial activity of the grapefruit (Citrus Paradisi. L) peel essential oils obtained by solvent‐free microwave extraction: comparison with hydrodistillation

The chemical composition of the essential oil (EO) obtained by solvent‐free microwave extraction (SFME) and hydrodistillation (HD) from the peel of grapefruit (Citrus Paradisi. L) was analysed by gas chromatography/mass spectrometry (GC/MS). Totally, twenty‐five components were identified in the EO. Limonene was observed as dominant (91.5–88.6%) for two extraction methods, SFME and HD, respectively. β‐Pinene (0.8–1.2%), linalool (1.1–0.7%), α‐terpinene (0.7–1.0%) and the other minor components were also detected. Disc diffusion method was applied to determine the antibacterial properties of the EO. The results showed that the EO of grapefruit peel had a wide spectrum of antimicrobial activities against Staphylococcus aureus, Enterococcus faecalis, Staphylococcus epidermidis, Escherichia coli, Salmonella typhimurium, Serratia marcescens and Proteus vulgaris, with their inhibition zones ranging from 11 to 53 mm.     

Zataria multiflora Boiss essential oil and sodium acetate: how they affect shelf life of vacuum‐packaged trout burgers

The preservative effects of Zataria multiflora Boiss essential oil (ZEO) at 0.025%, 0.05% and 0.1%, sodium acetate (SA) at 2% and their combination on the quality changes of vacuum‐packaged trout burgers during 21‐day refrigerated storage (4 ± 1°C) were investigated. Results showed that control and ZEO‐treated samples reached undesirable levels of rancidity (P < 0.05) at 15th day, whereas samples with the combined effect of SA and ZEOs, especially at higher concentrations, proved to be more stable in sensory, biochemical (PV, TBA, FFA and pH) and microbiological analyses (P < 0.05). Therefore, ZEO+SA‐treated samples showed good overall acceptability even until 21st day. Regarding the results obtained from ZEO‐treated samples, it becomes apparent that combined application of SA and ZEO extended the shelf life of fish burgers during cold storage to 21 days, 1.4‐fold longer than other treatments, which indicates the potential application of synergistic activity of these agents in vacuum‐packaged fishburgers.     

1,3‐Dimethoxybenzene,a newly identified component of port wine

1,3‐Dimethoxybenzene was identified by GC–O, GC–MS and Kovats indices (polar Supelcowax, 1709; non‐polar Rtx‐5MS, 1158) as a new volatile component of port wine. Sensory evaluation described this compound as having a sweet medicinal odour with hazelnut, resinous and woody notes. Respective threshold limits in model wine and port wine were 21 and 47 µg l^?1. Quantitative analysis by GC–MS, using a selected characteristic ion (m/z 138), indicated that young port wines from the 1998 vintage contained up to 3 µg l^?1 whereas ports from the 1999 vintage contained up to 20 µg l^?1. © 2002 Society of Chemical Industry     

Chemical profiling of volatile compounds of various home‐made fruit spirits using headspace solid‐phase microextraction

Fruit spirits are typical alcoholic beverages in the Moravian region of the Czech Republic. The aim of this work was to find differences in chemical composition among volatile profiles of spirits produced from various kinds of fruits. Twenty‐four samples of seven kinds of fruit spirits (plum, apple, pear, cherry, mirabelle, apricot and raspberry spirits) were analysed for examination of their volatile profiles. The most abundant family of compounds was esters, particularly ethyl esters. Sesquiterpenes proved to be a significant group of volatile substances by observing the differences between pome and stone fruit spirits [by relative higher content of (E ,E )‐α‐farnesene and by presence of α‐zingiberene and (E )‐α‐bisabolene in volatile profiles of pome fruit spirits]. Only in stone fruit spirits were propyl decanoate and ethyl salicylate found. Some other compounds were observed as being characteristic for individual kinds of analysed fruit spirits, e.g. γ‐decalactone for apricot spirits, (E )‐β‐farnesene for apple spirits, (Z )‐9‐tetradecen‐1‐ol for mirabelle spirits or some apocarotenoids for raspberry spirits. This work could potentially be the basis for checking the fruit origin of these distillates, or a partial manual as to how to differentiate individual kinds of pome‐fruit spirits (pear and apple spirits) or stone‐fruit spirits (plum, mirabelle, apricot spirits). Copyright © 2017 The Institute of Brewing & Distilling     

Effect of various essential oils on Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Essential oils were extracted from four West African plant species [Tagetes minuta (Family Compositae), Hyptis suaveolens (Family Labiatae), white basil Ocimum canum (Family Labiatae), and sweet basil O. basilicum (Family Labiatae)] by steam distillation. The oil of the pepper Piper guineense (Family Piperaceae), was extracted from the fruits by hydro distillation and ethanol extraction. Mixed essential oil and total ethanol extract was used. Kaolin powder (clay) was mixed (aromatized) with these different oils. Cowpea weevils were reared on chickpeas and newly emerged males and females were deposited on uninfested seeds. Bioassays, i.e. fumigation with pure essential oils and aromatized kaolin powders, were carried out on adults and eggs. Twenty four hours after fumigation, 99 and 0% adult mortality were observed, respectively, as the result of treatments with Ocimum basilicum and the control. The application of powders aromatized with the same oils to weevil pairs resulted in a complete lack of oviposition, whereas 31, 56 and 76 eggs were laid in the controls after 24, 48 and 72 h, respectively. Application of aromatized powders did not have a significant effect on egg hatching (50 out of 110 with O. canum, 100 out of 115 with O. basilicum and 100 out of 130 in the control sample) but did have a significant impact on adult emergence: 0% for the two treatments compared with 100% in the controls. Our results suggest that plants of the genus Ocimum can be used as an alternative to synthetic insecticides.     

Ultrasound‐assisted extraction of quercetin from onion solid wastes

The extraction of quercetin with aqueous ethanol solutions from onion solid waste under sonication conditions was investigated using rational experimental design methodologies. It was found that the ethanol concentration (40–80%, v/v) and the temperature (40–60 °C) of extraction are the most influential parameters in the recovery yield, whereas pH (2–6), liquid/solid ratio (30–60 mL g^?1) and extraction time (15–35 min) do not significantly influence the completeness of the extraction. The optimal extraction conditions were determined to be an ethanol percentage of 59% and extraction temperature of 49 °C, yielding a total quercetin content of 11.08 mg per g dry weight of onion solid waste. An empirical relationship between extraction parameters and the extraction yield was suggested and verified.     

Chemistry and antioxidant activity of essential oil and oleoresins of black caraway (Carum bulbocastanum) fruits: Part 69

BACKGROUND: The present study describes the chemical analysis of the essential oil and oleoresins from caraway, which have been studied by using GC–MS. The paper also explains the importance of the extracted oil and oleoresins in the antioxidant activities of target plant species. RESULTS: GC–MS analysis of caraway essential oil showed 51 compounds representing about 96.6% of the total weight. The major components were dillapiole (44.6%), germacrene‐β (14.1%), nothoapiole (8.3%), and β‐selinene (6.8%), along with many other components in minor amounts. Major components in ethyl acetate and iso‐octane oleoresins are dillapiole, nothoapiole and germacrene‐β, whereas in ethanol oleoresin contains dillapiole (25%), sitosterol (21.3%) stigmasterol (9.5%) and nothoapiole (8.1%). The antioxidant activity was evaluated by various antioxidant assays such as peroxide, thiobarbituric acid and p‐anisidine values. These experiments were further supported by other complementary antioxidant assays such as ferric thiocyanate method in linoleic acid system, reducing power, and scavenging effects on 1,1′‐diphenyl‐2‐picrylhydrazyl (DPPH). Both the caraway volatile oil and its oleoresins showed strong antioxidant activity in comparison with butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). CONCLUSION: This study provides additional information about the chemistry and antioxidant activity of caraway. Hence, caraway may be used as natural food preservatives. Copyright © 2009 Society of Chemical Industry     

Formation of protein adducts of 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine in cooked foods

Heterocyclic amines (HCAs) are mutagenic and carcinogenic compounds found in cooked meat and fish. Although HCAs are known to form adducts with protein after metabolic activation, adduct formation during cooking has not been elucidated. In this study, we showed that 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) is released from high molecular weight compounds by acid or enzymatic hydrolysis of cooked foods. Formation of free and protein adduct forms of PhIP was dependent on cooking temperature and time, and PhIP–protein adducts were estimated to form after formation of free PhIP. We also demonstrated that PhIP–protein adduct is formed by heating of PhIP and albumin as a model protein. A new adduct peak including [M+H]⁺ (m/z=225) of PhIP as a fragment ion was detected in the high molecular weight fraction of heat‐treated protein by LC–MS analysis. From model experiments by heating of PhIP and amino acids, the adduct was estimated to be produced by condensation of the amino group of PhIP and the carboxyl group of protein. PhIP–protein adducts were detected in several cooked meat and fish at ng/g food level as PhIP content. These results suggest that food‐borne protein adducts of HCAs may influence human HCA exposure and carcinogenic risk.     

Microwave‐assisted extraction of bioactive saponins from chickpea (Cicer arietinum L)

Growing interest in plant secondary metabolites has brought with it the need for economical, rapid and efficient extraction protocols. Microwave‐assisted extraction (MAE) was used to extract saponins from chickpea (Cicer arietinum). Several MAE conditions were tested, and the method proved to be superior to Soxhlet extraction with regard to amounts of solvents required, time and energy expended. The use of a butanol/H₂O mixture showed selectivity towards saponin extraction. Using TLC, two distinct saponins were observed in the various chickpea extracts. The identification of the major saponin as a DDMP‐conjugated saponin was verified using ¹H and ¹³C NMR, for the first time in chickpea. The MAE procedure most likely contributed to the conservation of the heat‐sensitive DDMP moiety. The pure chickpea saponin exhibited significant inhibitory activity against Penicillium digitatum and additional filamentous fungi. Two Fusarium strains tested were highly tolerant to the saponin. The potential for using MAE for the efficient extraction of natural products may assist in expediting the chemical analysis and characterization of the biological activities of such compounds. Copyright © 2004 Society of Chemical Industry     

Volatile constituents of essential oils isolated from different parts of cinnamon (Cinnamomum zeylanicum Blume)

Cinnamon (Cinnamomum zeylanicum Blume, syn C verum JS Presl, family Lauraceae) is an important spice and aromatic tree cultivated in Sri Lanka and India. On steam distillation, different parts of cinnamon yield volatile oils of varying composition. In the present investigation the profiles of essential oils isolated from tender twigs bearing reproductive parts, from pedicels of buds and flowers, from buds and flowers, from pedicels of fruits and from fruits were analysed by gas chromatography (GC) and GC/mass spectrometry (GC/MS). The essential oil yields of the different plant parts were: tender twigs, 0.40%; pedicels of buds and flowers, 0.36%; buds and flowers, 0.04%; pedicels of fruits, 0.33%; fruits, 0.32%. The tender twig oil was richer in α‐phellandrene (3.4%), limonene (1.6%) and (E)‐cinnamaldehyde (4.0%). The volatile oils from pedicels were richer in neryl acetate (1.4–2.0%), (E)‐cinnamyl acetate (58.1–64.5%) and β‐caryophyllene (9.6–11.1%). Higher amounts of (Z)‐cinnamyl acetate (6.1%), α‐humulene (2.2%), δ‐cadinene (2.2%), humulene epoxide I (5.0%), α‐muurolol (4.9%) and α‐cadinol (2.4%) were observed in the oil of buds and flowers. The fruit oil showed greater concentrations of α‐pinene (4.2%), β‐pinene (1.9%) and linalool (27.4%). However, all the oils contained linalool (3.6–27.4%), (E)‐cinnamyl acetate (22.0–64.5%) and β‐caryophyllene (6.9–11.1%) as their major compounds. This is the first report on the oil profiles of pedicels and of buds and flowers of cinnamon. © 2002 Society of Chemical Industry