Oregano in European food market: Botanical identification and quality control in the light of Codex Alimentarius standard

Abstract

Oregano is a very popular herb widely used worldwide for food flavoring in a number of recipes and dishes. European consumers usually buy dried oregano in various packages with crushed of rubbed leaves and flowering tops. The aim of this study was threefold: (i) to find out the botanical identity of the plant material used in the oregano packages sold in the European food market (ii) to measure the density (number/mm2) and size (diameter) of leaf sessile glands, and (iii) finally, to look for any relation between glandsʼ size and density and the total essential oil (EO) content. Commercial samples of oregano were purchased from supermarkets and local food stores of southern, central and northern European countries. The botanical identification of plant material was based to the key-characters (calyx-form, bracts, size and density of leaf sessile glands) [1], [2], [3], [4]. Three taxa of the genus Origanum were intentified to sold as oregano, viz. O. onites, O. vulgare subsp. hirtum and O. vulgare subsp. vulgare. A wide range of the glandsʼ density and size as well as of the total EO content was found. On the basis of their EO content (mL/100 g D. W.) the oregano samples are grouped in three quality-categories, as given in Codex Alimentarius [5]: Extra: oil content > 2.5%, Class I: oil content 2.4 – 1.6, and Class II: oil content < 1.5. Finally, the correlation found between the glandsʼ size with the EO content may lead to a rapid and economical assessment of the commercial oregano quality.