Glesni MacLeod

Comparative assessment of the artefact background on thermal desorption of tenax GC and tenax TA

Abstract The artefact background on thermal desorption of pre-conditioned Tenax GC and Tenax TA is compared. Superior blank gas chromatograms were obtained from Tenax TA, and an efficient pre-conditioning procedure to minimise background on heat desorption is proposed. The pooling technique described is suitable for the analysis of trace components of food aromas, especially relatively high-boiling components. The majority of the volatiles identified by combined gas chromatography—mass spectrometry analysis of pooled blank tubes were aliphatic, alicyclic and aromatic hydrocarbons. Many are common food aroma components, and their existence in blank experiments must be monitored carefully.

Volatile aroma constituents of celery

Abstract The aroma volatiles of a local variety of celery from Libya were analysed using routine procedures. Nine of the identified components have not previously been reported as celery volatiles. Unusually, three constituents alone made up ca 70% of the total volatiles, 4,7-dimethoxy-5-(prop-2-enyl)benzo-1,3-dioxolan or apiole ( ca 23%), 3-butylphthalide ( ca 22%) and 3-butyltetrahydrophthalide or sedanolide ( ca 24%). The latter two compounds are known to possess strong characteristic celery aroma. Some of the relatively uncommon celery volatiles, including three newly identified, have also been detected in parsley leaves and may, therefore, be characteristic to some extent of the Umbelliferae.

Volatile components of starfruit.

Abstract Volatile components of starfruit (carambola) were analysed using routine procedures. In all, 178 components ( ca 95% ofthe isolate) were positively identified, of which 116 are reported as starfruit volatiles for the first time. A further 31 components ( ca 2%) were partially characterized. Esters (57) and lactones (9) were significant components of the aroma, together with several compounds deriving from carotenoid precursors, e.g. the four isomeric megastigma-4,6,8-trienes and megastigma-5,8( E )- and ( Z )-dien-4-one.

Volatile aroma constituents of mango (cv Kensington)

Abstract The aroma volatiles of the Kensington cultivar of mango were analysed using routine procedures, and results compared with those for other cultivars. In total, 58 constituents were positively identified, including 36 not previously reported for this cultivar, and seven not previously described for any cultivar of mango. Monoterpene hydrocarbons were the major group of volatiles (at ca 49% w/w of the total volatiles) with α-terpinolene as the most abundant single constituent ( ca 26%), but esters were unusually also major components (16 ca 33%). The latter probably contribute to the unique mango flavour of this cultivar, together with certain lactones important in peach flavour.

Volatile components of celery and celeriac

Abstract Volatile components of celery and celeriac were analysed using routine procedures. A high proportion of each isolate consisted of monoterpene hydrocarbons (46.0% celery; 24.8% celeriac) and phthalides (42.3% celery; 37.4% celeriac). Major components of both isolates were limonene and 3-butyl-4,5-dihydrophthalide (or sedanenolide). Celery volatiles contained higher concentrations of γ-terpinene and α-pinene, whereas those of celeriac had greater quantities of α-terpinene and β-pinene. A celery-like odour was associated during GC elution with each of the 16 phthalides reported, of which ( E )-3-butylidene-4,5-dihydrophthalide (or ( E )-ligustilide) and cis , syn -3-butyl-3a,4,5,7a-tetrahydrophthalide (or cnidilide) could not be detected in celeriac.

Volatile components of okra.

Abstract Valid aroma isolates were prepared from okra followed by analysis using established procedures. One hundred and forty-eight components were identified (ca 93% of the total isolate) in this first study of the volatile components of okra. Sixteen terpenes represented the most abundant chemical class (comprising 26.9% of the isolate), and this was largely due to five citronellyl esters at a combined level of 17.3%. The single most abundant component was 2-methoxy-4-vinylphenol at 9.3%. Other compounds of interest were 18 pyrroles, including four bicyclic derivatives and two bicyclic pyrazines.

The glucosinolates and aroma volatiles of green kohlrabi

Abstract The aroma volatiles of green kohlrabi were isolated and analysed by conventional procedures. Ca 190 μg of aroma components were obtained per gram fresh weight of kohlrabi. In all, 83 components (ca 96% w/w of the sample) were identified. Sulphur compounds. provided a high proportion of kohlrabi volatiles (ca 37% w/w), with dimethyl trisulphide (ca 25%) being the major component. Isothiocyanates, derived from glucosinolates, are also important aroma volatiles of kohlrabi. Eight glucosinolates were thus characterized in kohlrabi, the major ones being 4-(methylthio)butylglucosinolate, 3-(methylthio)propylglucosinolate and 2-phenethylglucosinolate. Two unusual sulphur-containing ketones were also identified, 4-methylthiobutan-2-one and 1-methylthiopentan-3-one.

Gas chromatography-mass spectrometry of the volatile components of cooked Scorzonera

Abstract Using established procedures, volatile components of cooked scorzonera were analysed for the first time. A total of 114 components ( ca 74% of the isolate) was positively identified, and a further 43 components ( ca 24%) were partially characterized. Eight aliphatic acids and 32 aliphatic hydrocarbons represented the two most abundant chemical classes, comprising 30.6 and 26.9% respectively of the isolate. The single most abundant component was hexadecanoic acid at 22.1%. Of greater relevance are the 40 sesquiterpenoids at a combined level of 20.3%, which included some furanoeremophilane derivatives.

Volatile aroma constituents of orange

Abstract The aroma volatiles from the peel of oranges cultivated in Libya were analysed using routine procedures. Sixteen of the identified components have not previously been reported as orange volatiles, including sabinol, 4-methylacetophenone, hexyl hexanonate, γ-selinene and bisabolene. Whilst limonene was the major volatile component ( ca 52% w/w of the total volatiles), this is a much lower concentration than is normally claimed for orange peel. However, other important aroma components were found at higher concentrations than usually reported, in particular, linalool (15.8%), geranial (3.5%), β-copaene (4.5%) and decanal (2.2%).

Combined gas chromatography-mass spectrometric analysis of the aroma components of cooked taro (Colocasia esculenta L.)

Abstract Using established procedures, volatile components of taro were analysed for the first time. A total of 62 components (c. 95% of the isolate) was positively identified, and a further component (c. 2·3%) was partially characterised. Many of the identified components were classic volatile products deriving from aspecific oxidation/degradation others were common volatiles deriving from the action of heat on amino acids and/or sugars. The most abundant component was octane (21·10%), and pyridine was present at the unusually high level of 18·60%.