Green tea composition, consumption, and polyphenol chemistry.

This review surveys the occurrence, analysis, and properties of glucosinolates and derived compounds in plants and products intended for humans and animal consumption. The paper, which includes references published in 1981, is also intended to compliment existing reviews on the chemistry of these sulfur‐containing natural products. Particular emphasis is placed upon members of the Brassica family because of their importance as vegetables, condiments, oilseeds, and animal feedingstuffs. Since much of the work considered here relates to glucosinolate decomposition products, biochemical information concerning the nature, occurrence, and properties of the glucosinolate‐degrading enzyme, myrosinase, is considered in Section III. The methods available for the chemical analysis of glucosinolates and their various breakdown products are discussed critically. Factors affecting the glucosinolate content of plants and plant products arc outlined in Section VII. Particular emphasis is placed upon the effect of proces...

Glucosinolates and their breakdown products in food and food plants

Two-dimensionally extended, polycyclic heteroaromatic molecules (heterocyclic nanographenes) are a highly versatile class of organic materials, applicable as functional chromophores and organic semiconductors. In this Review, we discuss the rich chemistry of large heteroaromatics, focusing on their synthesis, electronic properties, and applications in materials science. This Review summarizes the historical development and current state of the art in this rapidly expanding field of research, which has become one of the key exploration areas of modern heterocyclic chemistry.

Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds: Synthetic Routes, Properties, and Applications

Control of soil-borne plant pests using glucosinolate-containing plants

Value-added products from beekeeping , Value-added products from beekeeping , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Value-added products from beekeeping

Extracts of the steam volatiles of cooked potatoes and of a dehydrated, granular potato product have been prepared. High-boiling fatty acids preponderated and were removed prior to concentration and examination of the resulting essences by combined gas chromatography-mass spectrometry-odour assessment. Thirty-five components were identified in potato essences and 20 in a potato granule essence. Chemical and retention data indicated that 2-methoxy-3-ethylpyrazine1 was present in potato volatiles and mass spectral evidence was obtained of its presence in potato sprout essence. Synthetic work confirmed the known characteristic raw potato odour of 2-methoxy-3-ethylpyrazine and demonstrated that isomers do not possess it. Lack of volatiles rather than off-flavour is believed to account for the differences between the flavour of cooked potatoes and of the potato product examined.

Volatile flavour components of cooked potato

Essences of the volatile components of five samples of horseradish root, three fresh and two of dried flakes, have been prepared and examined by gas chromatography (g.c.) and combined gas chromatography-mass spectrometry (g.c.-m.s.). At least 17 compounds are involved. Five of these have been rigorously identified by comparison with authentic compounds, synthesised where necessary, through mass spectra and retention data and the identities of three others have been tentatively established. The compounds concerned are methyl, ethyl, isopropyl, 2-butyl, allyl, 4-pentenyl and 2-phenethyl isothiocyanate and allyl thiocyanate. The constituents of the five essences were assessed semi-quantitatively by g.c. and definite differences found. These were reinforced by examination of the headspace vapours over the coarsely grated root.

Additional attention was devoted to the allyl isothiocyanate-thiocyanate interconversion and to the odour assessment of the volatile horseradish components.

Volatile constituents of horseradish roots

Sixteen basic heterocyclic compounds have been identified by g.c.-m.s. after careful extraction of a flavour essence from an English beer. They include the following that have not previously been reported as beer constituents: pyridine, 2-acetylpyridine, 3-acetylpyridine, pyrazine, methylpyrazine, 2,3-dimethylpyrazine, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, 2-ethyl-5- (and/or 6-) methylpyrazine, trimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine, 2-ethyl-5,6-dimethylpyrazine, 6,7-dihydro-5H-cyclopentapyrazine, 2-methyl-6,7-dihydro-5H-cyclopentapyrazine, and thiazole. The minimum total concentration of basic compounds in the beer was estimated to be 10 mg/kg.

Basic compounds contributing to beer flavour

Norfolk beeswax with a good honey aroma was used as a source of honey volatiles. Low- and medium-boiling volatiles of beeswax were studied using combined gas chromatography-mass spectrometry-odour assessment, 28 compounds being conclusively identified and a further 20 tentatively.

The aroma of beeswax

An efficient, yet relatively inexpensive combined gas chromatography-mass spectrometry-odour port unit has been used to follow the changes in the volatiles of cooking apples during cooking. Since headspace samples contained insufficient volatiles for mass spectrometric identification, they were isolated by a Likens and Nickerson extractor, the pentane extract being concentrated before examination. The volatiles were collected during successive intervals from the same cooking sample. Alcohols were prominent throughout the exaggerated cooking time of 6.5 h and were accompanied by varying amounts of hexanal, phenylacetaldehyde, damascenone and farnesenes. In the early stages, several esters were present in amounts sufficient for identification, but no evidence of their later evolution and of the accompanying apple odours was obtained. 2-Furfural, benzaldehyde. 5-methyl-2-furfural and 2,4-decadienal were not detected initially, but contributed increasingly later, 2-furfural finally becoming the predominant volatile.



A taste panel established a highly significant difference between cooked apple prepared fresh from Bramley's stored at +5 °C for 5 months and blast-frozen precooked apple, stored for 5 months at −20 °C and made originally from the same batch of Bramley's. The former was preferred as being less acid and having more apple flavour. Instrumental comparison of extracts prepared by the above methods showed that precooked frozen apple stored for only 1 week contains relatively higher concentrations of esters and of n-hexanal than after 5-months' storage, when traces of the decadienal were found. The sensory and instrumental evaluations thus accord with one another.

An examination of the volatile compounds present in cooked bramley's seedling apples and the changes they undergo on processing

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