Components
	Updated 2020-10-27

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Components in Food Composition Databases

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The components in food composition databases are the descriptors (identifiers) that are used to identify the chemical sustances, compounds or physico-chemical properties to which the reported values relate.
The components are typically defined with a more or less complete description and are typically held in a simple list or in a more complex thesaurus (or ontology) in a database or printed form.

The list or thesaurus entry normally includes the descriptor and its corresponding component name, a scope note to define usage of the term and additional information.

A few typical examples of these lists or thesauri ("systems") are in non-prioritised order

• the CAS register (numbers unique numerical identifiers assigned by the Chemical Abstracts Service to every chemical described in the open scientific literature)
   
• the ChEBI ontology (EBI Chemical Entities of Biological Interest database and ontology of molecular entities focused on 'small' chemical compounds, that is part of the Open Biomedical Ontologies effort )
   
• IUPAC Rules for nomenclature (inorganic, organic nomenclature defined by the IUPAC Committes, e.g. IUPAC-IUB Commission on Biochemical Nomenclature (CBN))
   
• the FAO INFOODS food component identifier (also named tagnames)
   
• the EuroFIR Component thesaurus (maintained by the EuroFIR consortium)
   
• European Food Safety Authority's parameter codes (included in EFSA's Standard Sample Description)
   
• descriptors/codes defined in regional and international regulations (e.g. pesticide regulations, food additive regulations and standards: European Directive on food additives (E numbers), Codex Alimentarius General Standard for Food Additives (INS Numbers))
   
• and many more

Several of the listed examples cross-link to other component lists, e.g. ChEBI links to CAS Numbers and IUPAC names, the EuroFIR Thesaurus link to ChEBI identifiers and INFOODS food component identifiers, etc.

Although there is an ongoing discussion of which system is best or to use, it is evident the use of a "system" must match its purpose. As the different "systems" are constructed for specific and/or different purposes, the food composition data compiler is often in the situation that there is a need for applying several of the systems in parallel. This is especially the cases when the food composition database contains information from several different component groups, e.g. nutrient, heavy metals, pesticides, food additives, etc., which is most likely the case in modern laboratory information management systems (LIMS).

The typical component thesaurus is organised into a hierarchy that uses group headings that are not used to identify components for individual compositional values. A term or group heading may be linked to more than one parent term in the hierarchy (a poly-hierarchy), e.g. L-Ascorbic acid can be both a naturally occuring nutient (vitamin) and a food additive (antioxidant).

A component thesaurus also includes descriptors for measurable properties such as density, pH, edible proportion, etc. so that their values can also be reported using the Value entity.

For an in depth description of nutrients and their roles, see the excellent accumulated set of nutrient information articles from the American Society of Nutrition's review journal, Advances in Nutrition.