Composition of Oregano Essential Oil (Origanum vulgare) as Affected by the Use of Winery-Distillery Composts

Abstract

Three different winery-distillery composts were used as binary components with peat-perlite mix (PP) in growing media for oregano cultivation. These composts were prepared using exhausted grape marc as principal component combined with several co-composting wastes, such as citrus juice waste (C1), tomato soup waste (C2) and cattle manure (C3). Three treatments were established for each compost type, with increasing compost quantities to traditional PP mix (0%, 25% and 50%). Physical and physico-chemical analyses of the different mixtures of winery-distillery composts and PP were carried out. The volatile compounds of oregano samples were extracted by steam-hydrodistillation and analyzed by GC/MS. Twenty-seven compounds were tentatively identified, with terpinen-4-ol, carvacrol, thymol and γ-terpinene being the major compounds. The total yield of volatile compounds (mg plant−1) was always increased by the use of the compost materials as ingredients of the growing media. However, the total volatile concentration of control samples, 16.3 g kg−1, was only increased by the compost-mixtures containing 50% of C1 and 25% of C2 or C3. The final recommendation is to use grape marc together with citrus juice or tomato soup wastes at ratios of 1:1 as growing media for the cultivation of aromatic herbs, including oregano