1. General

1.1 Compounds

Volatiles reported to be present in a product have only been tabulated if the validity of identification could be judged. For example, compounds whose identification was based on retention time on one gas chromatographic column or on a mass spectrum only, have not been included. Compounds reported to be artefacts have been omitted. These artefacts originate from extraction solvents (e.g. low-boiling hydrocarbons, chloro compounds and phthalates) or from plasticizers used in packaging material (e.g. phthalates). Compounds that are presumably artefacts but have not been indicated as such by the author(s), have been included in the compilation. It is left to the reader to decide whether such a compound should be considered an artefact.

1.2 Products/Product Groups

To make the search easier, also product groups are given. The product groups have been chosen as simple and logical as possible. To get an overview of all products also the option ‘all product groups’ can be chosen. The products are listed in alphabetical order.

For some very similar products specific product groups with a combined list of references are formed. For example ‘Allium species’: When you choose ‘Allium species’ in the product group vegetables you will only get a list with literature references covering all references from the products onion, garlic, shallot, leek, chive etc. When you choose the product onion, you will get the options ‘all literature of product Allium species’ and ‘details of product onion’. The latter option will show only the literature references from onions.

The compounds are only given per product such as onion, etc. and not under ‘Allium species’.

2. Details of product

2.1 References

Reference(s) which contain qualitative data for compounds in a particular product are left blank after the literature number. Sources also containing quantitative data are marked after this number by an asterisk: *. When the quantitative information has not yet been used or when only relative concentrations are reported the asterisk is given in parenthesis: (*) behind the reference.

Two asterisks (**) are used for the following articles:

Review articles which are of interest, but have not been used as a source of information, and articles used as a source of information in earlier editions, which information has now been deleted because of insufficient confirmation of the identity of the compounds.

The abbreviations of the titles of periodicals are those of the Chemical Abstracts Service Source Index (CASSI).

For the sake of simplicity, only the surname of the first author is mentioned.

The references are listed in alphabetical order.

When you choose the option product, two options are obtained: ‘Details of product’ and ‘All literature of product’. In the first option only those references with qualitative or quantitative data are given. In the second option also the ‘review’ references are given.

2.2 Compounds

When you have chosen a specific product you can get the composition of the product by choosing ‘Details of product’,

Then you can go to ‘compounds’ by choosing the option ‘compounds’ or by scrolling via ‘literature’ references to compounds.

The various compounds, if present, are arranged under the following headings:

• Hydrocarbons
• Alcohols
• Carbonyls, aldehydes
• Carbonyls, ketones
• Acids
• Esters
• Esters, lactones
• Bases
• Sulfur compounds
• Acetals
• Ethers
• Halogens
• Nitriles and amides including oximes and nitroso compounds
• Phenol including phenol ethers
• Furans including furan alcohols, furan aldehydes, furanones, furan acids, furan esters and furan ethers
• (Ep)oxides, pyrans, coumarins
• Oxazol(in)es
• Anhydrides and phthalides

Principles of arrangement under each heading are:

• Aliphatic compounds precede cyclics
• Cyclic 5 rings precede cyclic 6 rings
• Aromatic compounds precede heterocyclics
• Heterocyclic 5 rings precede heterocyclic 6 rings
• Compounds with few C atoms precede compounds with more C atoms
• Simple compounds precede complex compounds
• Esters are classified primarily by their acid moiety
• Unsaturated lactones are arranged under furans
• Dihydro-2-furanones are arranged under lactones
• Aliphatic sulfur compounds are arranged by the number of S atoms

If a compound could be arranged under more than one heading, the suffix generally determines its arrangement, for example, 3-hydroxybutan-2-one (acetoin) will be found under carbonyls, while 2-aminoethanol will be found under alcohols.

The main exceptions to this rule are:

1. Sulfur-containing compounds are always arranged under S-compounds, irrespective of their suffix.
2. Halogen compounds are arranged in a separate group.

2.3 Quantitative Data

When you click on a specific compound in the list mentioned in 2.2, detailed information such as synonyms, CAS registration numbers, etc. of that compound will be shown. In the headings of this tabel also minimum and maximum levels of that compound, as given in all literature for that specific product, are shown. Quantities are in ppm (mg/kg or mg/l) sometimes followed by a specification (for instance: ‘ppm in oil’ for spices).

When quantitative data are present, these are given before the literature reference in which this information is given. Also trace amounts are indicated. This is illustrated with the following examples:

Quantity

10-25	Means a concentration range between 10 and 25 ppm.
Trace-0.01	Means a concentration range between trace amounts and 0.01 ppm. This figure is usually the detection limit of the method applied.
Trace	Means that a certain compound is present in a concentration at the level of the detection limit of the method applied.