No abstract

Analysis of volatile compounds and triacylglycerol composition of fatty seed oil gained from flax and false flaxLinseed (Linum usitatissimum, L.) and camelina (Camelina sativa, L.) are ancient crops containing seed oils with a high potential for nutritional, medicinal, pharmaceutical and technical applications. In the present study, linseed and camelina oils of plant varieties grown under Central European climate conditions were examined with respect to their volatile and triacylglycerol (TAG) components. Solid-phase microextraction was applied to the study of volatile compounds of several linseed and camelina oils, which have not been described prior to this publication. Hexanol (6.5-20.3% related to the total level of volatiles), trans-2-butenal (1.3-5.0%) and acetic acid (3.6-3.8%) could be identified as the main volatile compounds in the linseed oil samples. Trans-2-butenal (9.8%) and acetic acid (9.3%), accompanied by trans,trans-3,5-octadiene-2-one (3.8%) and trans,trans-2,4-heptadienal (3.6%), dominated the headspace of the examined camelina oil samples. TAG were analysed by MALDI-RTOF-MS and ESI-IT-MS, providing information about the total TAG composition of the oils as well as the fatty acid composition of the individual components. More than 20 TAG could be identified directly from whole linseed oil samples, mainly composed of linolenic (18:3), linoleic (18:2) and oleic (18:1) acid, and to a lesser degree of stearic (18:0) and palmitic (16:0) acid. While in linseed these TAG comprise more than 60% of the oils, Camelina sativa exhibited a wider range of more than 50 constituents, with a considerable amount (.35%) of TAG containing gadoleic (20:1) and eicosadienoic (20:2) acid.

The chemical composition of the essential oil from peppermint (Mentha x piperita L.) was analyzed by GC/FID and GC-MS. The main constituents were menthol (40.7%) and menthone (23.4%). Further components were (+/-)-menthyl acetate, 1,8-cineole, limonene, β-pinene and β-caryophyllene. Peppermint oil possessed antiradical activity with respect to DPPH (diphenyl picryl hydrazyl) and hydroxyl (OH•) radicals, exercising stronger antioxidant impact on the OH• radical. The concentrations required for 50% inhibition of the respective radical (IC 50 ) were 860 µg/mL for DPPH and 0.26 µg/mL for OH•. Peppermint essential oil demonstrated antioxidant activity in a model linoleic acid emulsion system in terms of inhibiting conjugated dienes formation by 52.4% and linoleic acid secondary oxidized products generation by 76.9% (at 0.1% concentration).

Several nut oil varieties mainly used as culinary and overall healthy food ingredients were subject of the present study. Headspace solid-phase microextraction combined with gas chromatography-mass spectrometry was employed in order to determine the qualitative composition of volatile compounds. Furthermore, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used in order to assess the profiles and relative composition of the prevalent triacylglycerols (TAG) within the oils. The headspace of the majority of oil samples was dominated by high contents of acetic acid (up to 42%) and hexanal (up to 32%). As nut oils are typically gained by cold-pressing from previously roasted nuts, characteristic pyrazine derivatives as well as degradation products of long-chain fatty acids were detected. TAG analysis of these oils revealed a quite homogeneous composition dominated by components of the C 52 and C 54 group composed mainly of oleic (18:1), linoleic (18:2), stearic (18:0) and palmitic (16:0) acid residues representing together between 65 and 95% of the investigated nut oils. The TAG profiles showed characteristic patterns which can be used as 'fingerprints' of the genuine oils. Nut oils exhibiting quite similar fatty acid composition (e.g. hazelnut, pistachio and beech oil) could be clearly discriminated based on TAG showing significant differences between the oils.

Commercially available aroma samples were evaluated for their olfactory quality by professional perfumers and tested for their antimicrobial activity. Agar diffusion and agar-dilution were used as test methods and a set of two Gram-positive (Staphylococcus aureus and Enterococcus faecalis) and four Gram-negative bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris G, Klebsiella pneumoniae and Salmonella abony) and a yeast, Candida albicans, were the test microorganisms. All the investigated compounds were active against Gram-positive bacteria, especially β-caryophyllene against Enterococcus faecalis (MIC 6 ppm), but only few substances showed activity towards Gram-negative bacteria, except for cinnamic acid, which was active against all (MIC 60 ppm) and Candida albicans, against which cinnamic acid and caryophyllene oxide showed high activity (MIC < 60 ppm).

Cumin oil samples (Cuminum cyminum L.) from four different geographical origins were analyzed using GC-MS and GC-FID for their qualitative and quantitative composition. The major compounds in all cumin oils were the monoterpenes β-pinene, p-cymene and γ-terpinene and the terpenoid aldehydes cuminic aldehyde and the isomeric menthadien carboxaldehydes. All essential oils, and cuminic aldehyde, were tested, using agar diffusion and serial dilution methods, against different Gram-positive and Gram-negative bacteria isolated from different sources of food (pork fillet, minced meat and sausages) and clinical isolates, as well as three different Candida albicans isolates. All cumin oils and cuminic aldehyde exhibited a considerable inhibitory effect against all the organisms tested, except Pseudomonas spp.

Although poppy seed oil is an expensive article of trade, no literature about identification methods for adulteration with cheaper vegetable oils, like sunflower oil, has been published. This kind of adulteration is a challenge for routine analytical methods, such as the determination of fatty acid composition, because of almost similar fatty acid ratios. The detection of adulteration of poppy seed oils with sunflower oils at different levels (5-40%, w/w) by using SPME-GC-MS and MALDI-ToF-MS is the subject of our investigation. With the mentioned SPME-GC-MS method, it was possible to detect an admixture of sunflower oils in all relevant (5-40%) amounts by using alpha-pinene as a marker compound. Admixture of sunflower oil with high levels of triolein (high-oleic acid type) could be undoubtedly detected by MALDI-MS down to the 5-10% level. In contrast, adulteration of pure poppy seed oil by "standard" sunflower oils remained indistinguishable using this MALDI-MS.

The oil of peppermint (Mentha x piperita L.) from the USA, a dementholized cornmint oil (M. canadensis L.), and a fraction of the dementholized cornmint oil were analyzed by GC-FID and GC/MS. The main constituents of the three samples analyzed were menthone (23.4%, 20.4% and 58.3%, respectively) and menthol (40.7%, 41.2% and 12.3%, respectively). The two oils, the cornmint oil fraction and seven mint oil compounds [(-)-menthol, (-)-menthone, (+/-)-menthyl acetate, 1,8-cineole, limonene, b-pinene and b-caryophyllene] were investigated for their antimicrobial effects against two Gram-positive bacteria (Staphylococcus aureus and Enterococcus faecalis), five Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, Klebsiella pneumoniae and Salmonella sp.) and the yeast Candida albicans using a modified agar dilution and agar diffusion method. Medium to high antimicrobial effects were found for both oils, the dementholized cornmint oil fraction, and the target-compounds against all Gram-positive bacteria, whereas against the Gram-negative bacteria and the yeast, one or more samples showed only weak or no activity.